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Pierre Rattini
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Why Have a Service Agreement for Your Air Conditioner?

Many of you think that a service agreement contract is just a scheme for heating and air conditioning contractors to generate excessive profits. If TIME translates to the COST to SERVE (which should impact the PRICE of service)…

HVAC Service Agreement

I ask you to apply your logic to the following…

How much PROFIT does a heating and air conditioning contractor make with each service agreement?

How LONG will it take someone to drive to your home to provide service? 15 minutes? 30 minutes?

How much does it cost to STOCK A VEHICLE with the tools, supplies, and a basic inventory of parts to perform “common” repairs, should any be discovered during an inspection? (Remember that since the system IS running there is NOT an expectation that repairs are needed.) The business owner MUST pay for the cost of the providing the vehicle to provide the service.

How much does it cost to pay a SKILLED TECHNICIAN to drive the vehicle and provide the service? The business owner MUST pay labor cost that are above and beyond the hourly pay of the employee (payroll taxes, unemployment, workman’s compensation, vehicle insurance and possibly a portion of health insurance premiums).

How many trips per year are included with the service agreement?  2?  I suggest doing some quick arithmetic. Divide the PRICE of the service agreement by 2. Now divide that amount by the number of systems to be serviced. Do you think there could be much profit is performing this service? Sure, the service representative should make more than 1 call per day and there are some economies of scale involved, but even so, does this service appear to you to be a real profit maker for the owner?

High Power Bills!!!

If a customer pays for the service and doesn’t receive the service, it may be a profit maker for the owner because he/she got by getting paid for a VALUE that wasn’t delivered! (How many times should a service provider get away with this?)

If a service agreement provides very low profits (if any) for an air conditioning contractor, why would any air conditioning contractor sell service agreements?   Is this type of service NEEDED?

My response is YES. We live in a highly-specialized world. No one grows their own food anymore – not even farmers.  Without specialized computers, no one can repair their vehicles anymore.  Home remedies are not sufficient to ensure a healthy life expectancy.  Neither can one prevent a virus on their computer without a specialized application.  In today’s world, no one can be expected to know enough to prevent the need for assistance in just about every facet of life.

Heating and air conditioning systems are dependent on the operation of electrical and mechanical components. They must have a stable supply of refrigerant to enable the pressure differences that generate heat transfer to perform properly. (Do you ever have to put air in your vehicle tires?) An HVAC system is NOT an appliance that can be replaced by “plugging it in” with a new one purchased from Lowe's or Home Depot. Heating and air conditioning systems require a professional installation so that they supply indoor comfort. Since statistics reveal that people are spending more time indoors, indoor air quality is becoming more of a concern. HVAC systems can have a huge impact to indoor air quality.

Is COMFORT to a HOME Similar to the Heartbeat of the Body?

Now consider YOUR expenditures - mortgage, health, kids, vehicles, college, entertainment, comfort… COMFORT may not be the highest expenditure, but it’s in the list. How important is your comfort when it is MISSING?  We consider your comfort as the heart-beat of your home!  What if someone living in your home has health issues that make comfort even more important? (My mother, who is now deceased, had COPD. She experienced greatly restricted breathing capacity if the indoor temperature was not maintained at or below 70 degrees during the summer.)

I think it is safe to say that service provided to any mechanical device helps ensure continued performance and longevity of that device.  And I think that it is safe to say the mechanical devices lose efficiency, will fail and the failure probability is higher without maintenance.  Does this remind you of your vehicle?

If maintenance is NEEDED, why do we offer Service Agreements with such little expectation of PROFIT?

HVAC technology has been around for many years. Heating and air conditioning pioneers first began developing systems during the beginning of the 20th century.  And regardless of what manufacturers would want us to believe, I don’t foresee any significant spikes to technology in the coming years. In a mature market such as heating and air conditioning, those  heating and air conditioning service companies that continue year after year, must do so on the SERVICE LEVEL provided.

If our PRICE exceeds the VALUE of the services provided, you will not be our customer very long.

  • If we don’t show up as expected, we don’t exhibit the VALUE the we expect to deliver;
  • If we were to arrive in poorly identified and maintained vehicles with minimal parts to repair common problems, our VALUE is negatively impacted;
  • If we don’t exhibit the knowledge and experience that YOU would expect our VALUE is diminished;
  • If we exhibit inconsiderate behavior that you deem inappropriate for YOUR service provider, then our VALUE is diminished.

I suggest that the PRICE of the SERVICE reflects the EXPECTED VALUE of the service to be received. When you evaluate products or services, is PRICE the only variable that is predictive of the VALUE of the service/product to be received?

Competitive quotes from respected heating and air conditioning contractors establish “market” prices for services rendered. Competitive quotes from other contractors that are less than respected and less skilled CONFUSE “market” prices with the implication that equivalent VALUE is consistent among ALL contractors.

Our PLEDGE, if you select us to be your heating and air conditioning service provider… "Professional service through values of HONESTY, TRUST, and INTEGRITY

Our SERVICE AGREEMENTS include… (in everyday language, without an attempt to impress you with technical jargon, or the NUMBER of steps performed);

  1. A REVIEW of repairs since the last check-up as compared to the current operation of the system(s). (INCLUDES energy cost since the last check-up.)
  2. COMPLETE and THOROUGH TESTING of mechanical systems based on quality testing procedures as recommended by manufacturers and engineers in the HVAC industry;
  3. OPTIMAL maintenance of the INSTALLED EFFICIENCY of your systems. Please note that the efficiency rate of your systems is likely to diminish with age. The corrosive environment (depending on how far your location is from the ocean) in our geography has a negative impact to manufacturer’s expected life cycles. Your systems contain metal and moving parts. Our salt-laden environment increases the corrosion rate of metal components. Moving parts wear out. Even plastic deteriorates at the beach!
  4. Experienced and Knowledgeable recommendations to replace PARTS, if COMFORT is likely to be compromised before the next check-up.
  5. IDENTIFICATION of systems that should be replaced BEFORE they fail. Our staff has the knowledge of guiding you with replacement options, and there are many. Options for replacement include precise temperature and humidity control that can result in optimum COMFORT and ENERGY SAVINGS. Options for the replacement of a heating and air conditioning system can be compared to the options of replacing your vehicle…will a KIA do or are you interested in learning about the BMW/Mercedes models?
  6. PRIORITY SCHEDULING should an un-expected disruption to your COMFORT occurs.

If you are like many of those who take for granted the COMFORT provided by your heating and air conditioning systems, and our services do include those items in 1 – 6 above, there is a good chance we could minimize the occurrence of a “LACK OF COMFORT” event. If we do that, then there is an additional "priceless" VALUE in our service.

WE think we can!

Maybe your COMFORT is on your worry-free list of objectives yet to be accomplished...

WE wish we could guarantee that too… but heating and air conditioning systems can “jump-off-the-tracks” at times and at the most inconvenient times. If this weren’t the case, there wouldn’t be much of a demand for heating and air conditioning service providers. When YOU have done all YOU can do to minimize an unwanted occurrence, isn’t that all you CAN do?

And if we didn’t live in a “corrosive” environment (near the beach), expected life cycles of heating and air conditioning systems wouldn’t be what they are.

Doctor of COMFORT

In CONCLUSION, I want to leave you with 1 last analogy. If you happen to be one of the lucky ones who have discovered a doctor and have utilized his/her services for a number of years, then you have identified a VALUED service...

  1. When you go to your doctor, do you think he/she is QUALIFIED to make observations from his knowledge, access to testing devices, and your medical history that best maintain your health? 
  2. Do you think he/she could also detect an unknown concern that could be detrimental to your health? And if you haven’t discovered such a doctor, aren’t you searching for one or hoping that you will discover one?

I suggest that if you select the “right” heating and air conditioning contractor, he/she can provide a similar type of service that best maintains your COMFORT.

Tri-County Mechanical IS the RIGHT Choice!

You can click on the PDF image (on right) and get a copy of our Service Agreement.  We highly recommend signing it and sending the executed version back to us.  ( Send to: [email protected] )

Or you could go here and get more details regarding our Energy Savings Agreement Program.

Energy Savings Participation Agreement

If you SEE something that looks like a duck, walks like a duck and sounds like a duck, it’s probably a duck…

Getting Closer…To Moving In – Part II

What better time to illustrate that you believe in the products and services that you promote than when you have the opportunity to practice what you preach?

We are also using 3 Ruud Variable Speed (inverter) systems for 3 of 5 systems for our new office.  These Ruud variable speed systems are what we consider to be the “value” choice for variable speed (inverter) systems.  Click here to preview the components of these systems

They too will operate somewhere between 30% to 100% capacity. Ditto for COMFORT and HUMIDITY REDUCTION as compared to other manufacturers’ variable speed models.  Click here to learn about the types of heating and air conditioning systems.

Click here to discover what 360 is all about…

Ruud Spring Promotion

But few consumers even KNOW that Ruud has a line-up of Variable Speed heating and air conditioning systems.  In the past few years, Ruud has re-designed its complete product line.

They use components (compressors, valves, protective devices and coil designs) that are common to the leading HVAC manufacturers.  Their controls (thermostats) monitor the performance of the systems to ensure that they are running as efficiently are similar to the other leading manufacturers.

If we install our InfiniGard treatment on Ruud systems, our customers/clients receive a 10-Year warranty on the outdoor coil even in CORROSIVE environments.  Click here to learn more about our InfiniGard treatment.

 So what is missing?

Ruud products do not contain the consumer advertising $$$ that are contained in other brand offerings.  If it is plausible to believe what I have written so far, and we think it is…now you understand why we call it our VALUE OPTION.

I have compared three models of variable speed heating and air conditioning systems.  For this comparison, I used models with 3 tons of cooling capacity.  The dimensions that are common to all three comparisons : 20 SEER efficiency ratings and rated cooling capacity.

The “dimensions” that were different are noted below.  Note that my scale is Best, Better, Great.  (Typically I would use “Best, Better and Good”), but all of these choices are GREAT choices.  BEST and BETTER choices as compared to Great Choices!







Brand A

Brand B


Great Choice




Great Choice



Great Choice

Great Choice




Efficiency and sound ratings are based on AHRI Certified Ratings.  Go here to learn about AHRI ratings.

For an understanding of what a SEER rating is go here.

For an understanding of what a HSPF rating is go here.

For an understanding of what a EER rating is go here.

Thanks to Wikipedia, one of my favorite online information sources

Duct systems were noted in PART I.  Same duct system design as the 1st two systems.

If you are interested, click here to learn more about “why duct systems are important”.

You may say…”Well, you can purchase the systems a lot cheaper, because you are a heating and air conditioning dealer.”

I would respond that we chose to use the most efficient systems that we could.  We could  have also received  a deal on the lower efficiency systems. that would have required a lower investment .

We are “hunkering down” at the new location because we plan on being there a while…at least through the life cycle of these systems, 15 years?  Our plans should also illuminate they we plan on being around for a decade or two and continue providing our clients/customers with quality heating and air conditioning service with integrity.

Click here to view some pictures on our Facebook page with our new facility in various stages of completion.

If you are considering a replacement, you could click here to learn about rebate options for a Ruud system like the ones we are installing.  If you are a Santee Cooper customer, you can click here to get the information you need for Santee Cooper rebates (and apply for a Santee Cooper loan with a 1.5% interest rate to finance the replacement).

(I still haven’t forgotten about them…  There ARE “indoor” components of a heating and air conditioning system.  Those components will be described in the next article.)

Getting Closer…To Moving In – Part I

What better time to illustrate that you believe in the products and services that you promote than when you have the opportunity to practice what you preach?

We are using Bryant Extreme Evolution systems for two systems.  There are no heating and air conditioning systems more efficient than these.  In the industry, they are known as variable speed (inverter) heat pumps.

They will operate somewhere between 30% to 100% capacity providing the most comfortable indoor environments possible - perfectly tempered indoor air (temperature and comfort).  Click here to preview the components of each system.

Go here to see what the EXTREME graphic is all about...

The variable speed heat pumps do a superior job during the winter... they may never need to energize the electric heaters to keep the building comfortable, even at the coldest temperatures during the winter!  Interested in reading about the TYPES of heating and air conditioning systems?

Since the indoor blowers are "synched" with the speed of the outdoor system, we may not hear the system running while inside our office.  And if you were outside, you probably wouldn't notice the noise generated by the outdoor systems.  The sound levels produced will be  no more than the noise generated from a refrigerator!  (Do you have a noisy outdoor system near your pool or deck that is irritating?)

And since these systems will only be running at a capacity level to meet the thermostat setting inside the building, they will be using significantly less energy than traditional systems.

Since I mentioned the thermostat, did you know that the thermostats (controls) on these systems can be connected to home automation devices?  Interested in learning more?  Click here.

The picture at the beginning of this article illustrates that we take the systems apart to apply the treatment...then reassemble them before they get installed.

Before we install the outdoor systems., we do what we recommend to our clients...treat them with our InfiniGard treatment to extend the life of the systems and maintain the installed efficiency  as when they were new.  Learn more about our treatment here.

Let's change gears and focus on the duct systems.

Check out our duct systems.

Installing GREAT equipment alone doesn't mean that your SYSTEM will produce high efficiency results!.    They are comprised of round metal pipes as opposed to rectanglular, duct board systems.   Go here to read an article regarding the importance of duct systems.

The air flow requirements needed for each room in the office have been calculated.  The "pipes" have been sized to deliver the correct airflow to each room.​  Go here to learn more about load calculations.

And if by chance, the science of computing air flow requirements for each room prove in-correct, we have dampers installed so that air flows can be "manually" adjusted.​  (You will have to trust me on this one)..I neglected to take pictures of the dampers...they are not visible...but they are there, just in case!

​This is important for you to know.  We don't over-engineer our duct systems!  We don't have zoned duct systems.   What is a zoned duct system?  Click here.  Why don't we use them with our systems?

Answer: All of the rooms in our office ​have approximate equal heating and cooling requirements.  We don't have a "room over the garage" or a "Carolina room" that has different heating and cooling requirements than the rest of the house.

You may say..."Well, you can purchase the systems a lot cheaper, because you are a heating and air conditioning dealer."

I would respond that we chose to use the most efficient systems that we could.  We could  have also received  a deal on the lower efficiency systems. that would have required a lower investment​.

We are "hunkering down" at the new location because we plan on being there a least through the life cycle of these systems, 15 years?​  Our plans should also illuminate they we plan on being around for a decade or two and continue providing our clients/customers with quality heating and air conditioning service with integrity.  Want to see how the new office is progressing?  We have pictures posted on our Facebook page here.

If you are considering a replacement soon, if you act before July 15, 2017 you will receive significant rebates toward the purchase of a system like we are installing.  Go here to learn about available rebates.  If you are a Santee Cooper customer, you can get the information here to qualify for the rebates (and apply for their loan program with a 1.5% Interest rate).  Don't forget about the Santee Cooper THERMOSTAT rebate.  Bryant thermostats qualify! 

(I didn't forget about them...  There ARE "indoor" components of a heating and air conditioning system.  I will describe those components in an an another article soon.)

What Type of HVAC System Should I Buy?

Possibly because you have never experienced the dilemma of replacing a heating and air conditioning system and the “BIG EVENT” is likely to happen or has already happened you are not current with the choices that are available for replacement. Statistics indicate that more consumers have not experienced this scenario than those who have. And there is a whole industry out there waiting for this event to happen and you only have a short time (days?) to make an informed choice. And some of those in the industry will lead you to purchase the system that best suits them, not you. How will you know what you need or want without doing some homework first? Where do you go to get the best advice? Of course, we think that should be us.  If you are in learning mode, my advice is to enjoy the ride, if you can.

This article is about the types of heating and air conditioning systems available for replacement. And since you are making the effort to be informed, the experience can be a rather illuminating one before the purchase decision is installed. Afterwards, the chosen installation will impact approximately 30+% of your monthly power costs.   Maybe more!

Let’s see if I can help your “lights” come on. There are systems with 3 different types of compressors (the main component of the system). I will compare the versions with an analogy to light bulbs. There are “incandescent”, “compact fluorescent”, and “LED” versions of AC systems.

Incandescent versions of heating and cooling are known as single stage systems utilizing a compressor that has two states, OFF or ON. This “single-staged” compressor is designed to cool your home on the hottest day of the summer and the “not-so-hot” days of the summer with the same rate of capacity all of the time.

If the temperature is, say 80 degrees outside (note that it has the capacity to cool on a 95-degree day), the cooling cycles should be relatively short. The system utilizes the 95+ degree capacity and quickly cools your home. While the system is off, the heat indoors increases above the thermostat set-point and causing the system to start cooling again.

  • Did you know that the frequency of the start/stop cycles has a significant impact on the expected life cycle of the system?
  • Did you know that a single-stage heating and air conditioning system consumes more energy at start-up than it does while running?
  • Did you know that de-humidification is provided by air conditioning? Air that is cooled forces humidity out of the air when cooled. The removed humidity changes to water which is removed by the condensate lines that run from your indoor blower and carried outside. For an explanation of how a heat pump works go here.
  • Did you know that air conditioners require 3 – 5 minutes of run time before any humidity is removed from the air? Did you know that you could be just as comfortable indoors at a slightly higher temperate if more humidity was removed from the air?  You could save 1 - 3% for each degree the thermostat is raised above 72 degrees.
  • Have you thought about the performance of the air filters on the system when your system is turned off? While off, there is NO air is going through your system, so absolutely no air filtration is occurring.
  • Did you know that Santee Cooper’s utility rates have been increasing the past few years because of a mandated shift from producing coal-fired generation and shifting to higher cost solar powered alternatives and nuclear generation? Did you know that future cost increases are already approved? (Suggestion: Google this search string "santee cooper rate increase"). Even if you are not a Santee Cooper customer, your electric power supplier purchases power from Santee Cooper.
  • Not only is the compressor single-speed but the blower fans (outdoor and indoor) have one speed. Why is this significant? It takes some knowledge of chemistry to understand this, but the density of air decreases with the replacement of air molecules with water molecules (humidity). Humid air is the LIGHTER dry air. To me that seems to be the opposite of what I would deduce. On moist days (when the humidity is greater than 60%), since the wet air is lighter, the air passes through through the indoor blower and outdoor fan faster than dry air, the air flows are faster than the "rated condition" of the system and the cooling capacity is reduced. 

Even with all the short-comings of a heat pump system with single speed compressor and a single speed indoor blower, they are capable of sufficiently cooling indoor spaces. Are you starting to get the idea that there is a better method of air conditioning your home?

The better method of air conditioning your home is a cooling system that contains a compressor with 2-stages of capacity. I call it the “compact fluorescent” version of air conditioning. The fluorescent version contains a compressor with 2-stages of capacity and contains variable speed blowers for the indoor and outdoor fans. Unless the outdoor temperature is hot, the system cools your home while running at the lower speed. And many good results begin to occur!

  • The cycles are longer which reduce the number of starts and stops which should positively impact the expected life cycle of your system.
  • When the system starts, the system consumes less energy because it is starting at a lower capacity rating.
  • Significantly decreased sound levels (from the outdoor and indoor systems) when running at a lower capacity level. Do you have a system that runs at loud levels that is located near your pool, deck or bedroom window?
  • Since the cycles are longer, more dehumidification occurs with each cycle. Cycles are typically significantly longer than the systems with single stage compressors.
  • With a 2-stage system and because of the reduced humidity, a higher temperature setting will result in equivalent comfort. (Warning here… if energy savings is your objective, don’t lower the temperature below the temperature setting utilized on your old system because your power bill is lower and you can now afford more comfort!)
  • There is a chance that you may have to replace your ac filters a little more frequently because of the increased run time that provides better filtration of the indoor air. There may be a minimal increase in the number of filters you buy to provide a cleaner air space in your home.
  • You will not have to pay increased power costs on energy savings achieved by a more efficient system. I suspect you won’t mind if you are paying less to your power company for increased comfort.
  • The variable speed blowers (if properly installed) reduce the air flows from the fans to a rate that more closely match the “rated capacity” of your system.  You really ought to read this article about variable speed air handlers, the indoor component of a system.

Did you notice that I referenced a 2-stage system as a BETTER method of air conditioning? I am sure you noticed that. If a single-staged system is a good method, the 2-stage system as a better method, then there must be a BEST method of heating and air conditioning.   And there is!   I reference it as L-E-D version of comfort. In the industry, we reference this type system as an “inverter drive” system. This type of heating and cooling system is like getting out on the interstate and “setting” the cruise control on your car!

The inverter drive compressor is one that provides a real low stage of capacity (30 – 40%) and has the capability to increase or decrease its capacity on the need (demand) for cooling. And it is designed to run long periods of time at the capacity needed to provide the comfort and humidity level settings on the thermostat.

  • Very few cycles per hour… if starts and stops have been greatly reduced, do you think this feature should impact an expected life cycle of the system?
  • Because of starting at very low capacities, the electrical requirement for variable speed systems at startup is greatly reduced.
  • BEST humidity reduction possible is available from a system with an inverter drive… with variable speed blowers that are programmed to run at a matched speed based on the capacity of the inverter compressor.
  • Quietest possible system…Do you have a deck, pool, or bedroom that would provide more utility if the heating and air conditioning system contributed little, if any, objectionable sound levels?
  • Cleanest indoor air quality possible because of the long run times. With the addition of a whole house air cleaning system, your home could provide one of the most sterile environments that you frequent. 
  • Systems with an inverter drive provide the lowest monthly power costs available…at the highest possible level of comfort. Your power company may come to see you to see why your power costs decreased so dramatically!
  • You control the temperature and the humidity level inside your home. Just dial it in (like cruise control in your car) and let the variable speed compressor serve you, your way.
  • Inverter systems are the SMARTEST! They can communicate with humans to let humans know if they are running properly. If not properly operating, they can even communicate down to the component that isn’t functioning properly. They are even capable of reporting their “run-time” history to the internet to provide a technician what the problem is before he arrives to perform service. How smart is that?
  • Even though I haven’t mentioned heating yet, I will now. A system with an inverter drive doesn’t need supplemental heat to provide heat on the coldest days of our winter. Systems with inverter drives are the KINGS of heating with heat pumps.

Now let’s make some sense out of these type of systems, the “incandescent, fluorescent, and LED versions of heating and cooling.

Incandescent (single-staged) systems start at 14 SEER (the minimum standard) and can achieve up to a 16 SEER rating.

Some EXAMPLES of our Single Stage Systems

Fluorescent (2-staged) systems typically range from 16 SEER up to 18 SEER.

Some EXAMPLES of our 2-Stage Systems

LED (inverter drive) systems range from 18 SEER to 20+SEER. Their HSPF (heating) efficiency ratings are significantly higher than the other types of systems (they don’t need supplemental heating in the winter).

Some EXAMPLES of our Inverter Drive Systems

I went to purchase replacement light bulbs for a ceiling fan recently in Lowes. The light bulb that blew was an incandescent bulb. When I got to the light bulb replacement aisle in Lowes, I went directly to the LED section because they last longer, use less energy, and emit less heat. Sure, the LED model cost more but it didn’t matter because I have no desire to make frequent attempts to replace a “hard-to-get-to” light bulb. That’s when the thought occurred to me to make the analogy of light bulbs to heating and air conditioning systems. And yes, the LED version of heating and cooling requires a significantly larger initial cost but with a significant list of added features and benefits with substantial energy savings. The concepts of oldest, older, and relatively new also applies to light bulb and heating and air conditioning replacements.   I predict, as the year’s advance, the technology for heating and air conditioning systems will match the trends in indoor lighting.

If you are interested in getting a straight story about options to match your expectations, we do that with all of the customers we serve.  We won’t try to sell you anything. We promote Trane, Bryant, and Ruud systems. Each of these manufacturers have all types of models described in this article. We will consult with you to select the system that best fits the requirements of your home and your needs and desires.

How Air Conditioners Work

How Air Conditioners Work 2

Every time I ask someone to explain how the refrigerant cycle works, they begin with what’s going on with the COMPONENTS of the refrigerant cycle and I immediately am left with the “duh??” thought and I get frustrated because I get left behind. So here goes the way a commoner like myself comes to grip with understanding the refrigerant cycle.

I have been “thoroughly” educated but NOT in chemistry or physics. I am told it’s all about an evaporation process and immediately I start applying what I know about water. Big mistake… So how do you make something that doesn’t make sense to most of us easy to understand? I don’t think it is possible to make it easy to understand. I hope this article makes it EASIER to understand without delving into physics, thermodynamics, or an engineering appreciation of the components of the cycle.

How does the refrigerant cycle work?

So, let’s begin at a beginning:In a closed refrigerant circuit, there is a direct relationship between temperature and pressure. If temperature INCREASES, so does the pressure.  If the pressure DECREASES, so does the temperature.If there are any doubts about these two statements, you will have to go to a physics book or a very elementary book on thermodynamics.  Refer to the above paragraphs.  Please trust me on this beginning premise.

Air conditioning is all about increasing the pressure of a gas (the refrigerant, in this case R410a) and releasing the pressure at strategic places along a closed refrigerant circuit. Air conditioning is all about the pressure changes that are forced to occur within the refrigerant circuit.

The example I have chosen to illustrate is a split system air conditioner with the indoor component located in an attic and an outdoor system installed beside a house. I have chosen to identify the component located in the attic as the air handler.  The air handler contains two critical components of the refrigerant cycle, an evaporator coil and a blower/fan (Not shown). Refrigerant lines are connected from the outdoor system to the air handler.

Refrigeration System

However, with the typical refrigeration system diagrams I have seen, the diagrams assume the reader  knows where the components of the refrigerant cycle are actually located.

Don’t’ be concerned about the dashed line in the diagram YET. The top right portion of this diagram refers to those areas under “high” pressure. The bottom left portion of the diagram refers to those components with “low” pressure

The tx expansion valve, evaporator coil, and blower (or evaporator fan) are contained in the air handler and located in the attic,

Let’s start with the low-pressure portion of the circuit. There is a “ tx valve” that is connected to the small copper tube that connects to the evaporator contained in the component described as the “air handler”.

The valve causes a significant reduction (pressure drop) to the pressure contained in the small copper tubes that disperse the refrigerant through the coils of the evaporator. (Can you picture the effect of pressing the valve of an aerosol hair spray container?)

This forced pressure drop causes the temperature to cool the copper/aluminum coils contained in the evaporator coil. The fan (blower) propels air from the return air flows of the air conditioning system to pass through the coils of the evaporator. The air that passes through the evaporator (propelled by the fan) is significantly warmer than the copper/aluminum tubes. The heat transfer from the cool coils warms the gas that is in the cool coils. The heat transfer that results, forces the air to be significantly cooler than it was before the air entered the evaporator and the cooled air cools the conditioned space.

Now note the upper, right side of the diagram.  The compressor, condenser and the condenser fan is located in the outdoor system.

Now note the upper, right side of the diagram.  The compressor, condenser and the condenser fan is located in the outdoor system.

After the refrigerant is has passed through the evaporator the refrigerant flow is directed

Refrigeration System

back towards the compressor by a suction pressure in the larger of the 2 copper tubes. The compressor (the component of the system that produces high pressure compressed gas), contained in the outdoor system works to increase the pressure of the gas.

The highly-pressured gas enters the tubes in the condenser coils. The outdoor condenser fan forces air through the condenser coils and cools the high-pressured gas causing the high-pressure gas to become a lower pressured liquid. The heat that is transferred to the air stream created by the condenser fan blowing on the hot coils, decreasing the temperature of the refrigerant, is rejected into the outdoor air.

After the refrigerant travels through the condenser coil, the refrigerant leaves, but pressured as a lower pressured liquid. The refrigerant is now ready to make another pass the “tx valve”.

You may call this cruel and unjust punishment but now I am going to ask you to re-read the paragraphs again, but before you do, I am going to ask you to think about “what’s happening”. The air being “blown” by the fan in the air handler should be the approximate temperature as the desired temperature setting on your thermostat, somewhere between 70 and 78 degrees. So, the air being blown into the air handler is much warmer than the temperature that is produced on the copper/aluminum coils in the evaporator, cooled by the depressurized refrigerant.

As the air passes by the evaporator coil, heat is absorbed into the refrigerant and cools the air to a temperature much cooler than your desired temperature setting (approximately 60 degrees F). The conditioned air should be cooled sufficiently to satisfy the temperature setting on your thermostat so that your system will eventually “cut-off”

No, no, no … don’t stop reading yet!  Now consider what’s happening outside at the outdoor system. The outdoor temperature is cooler (even though it may be 95 degrees outside) than the temperature of the air that is being exhausted by the “condenser” fan. This outdoor temperature difference provides for the exhaustion of the heat in the refrigerant that was captured while the refrigerant was in the evaporator coil in the air handler located in the attic. Heat is being rejected (by the condenser fan blowing air through the aluminum/copper coils in the condenser) from the indoor air to outside air. Now go back and re-read the paragraphs explaining the refrigeration cycle:

The dashed line that is placed in the diagram is there to identify the “high” pressure areas of the circuit as opposed to the “low pressure areas of the circuit.

So far, I have made an attempt to explain the air conditioning (cooling) cycle.  Those of us in the industry may reference these types of systems as “air conditioners”, “air conditioning only”, “AC Only’, or “straight cooling systems”.  Because of where we live, if natural gas heating was more prevalent, you would hear “air conditioner” more frequently because heating could be supplied with a natural gas furnace. If we were to install a system that heats with gas, we would reference such a system as an “air conditioner with a gas furnace”.  Notice that none of these references include a “Heat Pump”?  Because of the limited availability of natural gas pipe lines, and the capability of heat pumps to heat very economically in most or our winter weather scenarios, homes in the Myrtle Beach area are heated with HEAT PUMPS.

Hopefully you have an “oh, now I understand what’s going on moment but I have no idea why this is occurring.”  Because I am attempting to explain at a simplistic level and keep the physics and thermodynamics out of my explanation, my explanation of the air conditioning (cooling) cycle concludes. After many years of selling and promoting heating and air conditioning systems, the light for me has now come on and I now possess a very basic understanding of air conditioning systems.  I strongly suggest letting the engineers and the technicians understand more about the “why’s” of the refrigeration cycle.  I don’t think there is many of us that feel the need to know more.   And there is only a few of us that care to know this much!

If you want to read about the differences contained in a HEAT PUMP, you will find those here.

I want to give credit where credit is due.  I had assistance writing my article.  I discovered a page from $mart Energy User that was used for me to gain the understanding of the condenser.  I actually “borrowed” the graphics, Typical Refrigeration System, from this article.  I also discovered another article that that was helpful to me in understanding the refrigeration circuit.

What is a Load Calculation?

What is a Load Calculation?

Residential Load Calculations

First, please allow me to begin with the things you should know if you don't read to the end of this article:

  • ​The size of a heating and air conditioning system has a direct impact on comfort, efficiency and the life cycle of your heating and air conditioning system. An accurate calculation is beneficial to the dwelling owner and the installing contractor. The homeowner should want one performed and the mechanical code states that the contractor is obligated to supply one. Having a load calculation performed is typically a free service when heating and air conditioning systems are replaced.  Just because the service is "free" doesn't mean there is no value.  Our "market" dictates that we do not charge a fee for the service.  Heating and air conditioning contractors wish we could charge a fee for the service, because of the training, knowledge, and time required to perform the procedure correctly.
  • The calculation procedure is a detailed calculation that accounts for many variables based on a scientific approach, utilizing some of the laws physics and thermodynamics. This procedure for the proper sizing of heating and air conditioning systems is endorsed by heating and air conditioning professionals and manufacturers across the nation and the world.
  • It is not a spreadsheet, nor a calculation that a heating and air conditioning representative developed. The calculation was developed by well-educated and informed engineers and is the procedure that is recognized in the industry as THE method of calculating properly sized systems. The calculation exists as a contractor software application that is purchased by most mechanical contractors. In my opinion, a software company named Wrightsoft is the most popular vendor for load calculation software.
  • Results from the calculation can have a wide variance. In my opinion, the accuracy of the output of the calculation depends on the accuracy of the inputs which Is influenced by the motivation and knowledge of the person performing the calculation.  Are the calculation results biased just to provide a result that the existing system was properly sized? Did the person that performed the calculation input the correct measurements, input the “as constructed” insulation values, fairly estimate duct system losses, and use the appropriate estimate for the infiltration for your home?  How would you know?
  • There are two methods of performing a calculation, a whole house or room by room calculation. If the duct system is NOT going to be replaced, the whole house method is the method utilized because this method is quicker to obtain a result. If the duct system is poorly performing or is to be replaced, a room by room calculation (which takes a little more time to measure and “input”) is the BEST method because it provides information for each room of the dwelling instead of a value for the “whole” house. The calculated heating and cooling requirements for each room are much more superior to “guesses” when it comes to duct system evaluations and or a replacement duct system.

Replacing your heating and air conditioning system will cost you thousands of $$$. If you think it’s worth 10 or 15 more minutes to assure that your heating and air conditioning contractor followed the correct steps when replacing your heating and air conditioning system, please continue reading. I am suggesting that this type of knowledge  IS worth your time investment! (At a minimum, heating and air conditioning professionals spend days learning how to collect the inputs for this calculation.) And if an air conditioning contractor is a true professional, and the professional’s interest is sufficient, he/she will continue to understand why the “inputs” of a calculation are important.

A load calculation is an industry wide method of estimating the required heating and cooling capacity of a dwelling. In my opinion, It is all about heat transfer that follows some fundamental laws of physics.

  1. The path of heat flow is from hot to cold. Translation: In the summer the path for heat flow is from the outside towards the inside, conditioned space of a dwelling. In the winter, the opposite direction applies, from indoors to outdoors.
  2. The greater the difference in temperatures (outdoor temperature versus indoor temperature), the greater the rate of heat flow.
  3. Cooling requires the removal of humidity for comfort. The path for humidity is from a wet to dry. Energy is required to remove water vapor from the air.
  4. Heat flow is measured in Btu’s per Sq. Ft. per hour –A Btu it is defined as the amount of heat required to raise the temperature of one pound of water by one degree Fahrenheit.

If one of the components is a temperature difference (TD or delta T). Well, what is that? Weather data has been collected for many years in many locations. The average lowest temperature (winter) and the average highest temperature (summer) is used for the design temperatures for heating and cooling. For load calculations, TD is the temperature difference between indoor and outdoor temperature on the hottest day of the summer or the coldest day of the winter.

Side note. The calculation procedure is a design calculation. “Design” calculations are configured so that they work a high percentage of the time, but not 100% of the time. Flood drain systems aren’t designed to work 100% of the time due to costs and the minute probability of needing a 100% design. The load calculation procedure contains a similar, built-in premise. Air conditioning systems (in cooling) become less efficient if over-sized. If a design is utilized that will be sufficient for days when the temperature is approaching 100 degrees (or more) which is greater than the “design” temperature for our location, the air conditioning systems will be grossly over-sized more than 95% of a typical summer. If you had a reason to look back at historical temperature information, and in our area and using the design criteria, heating and air conditioning systems are over-sized approximately 90% of the summer. Heating and air conditioning systems would be over-sized for a higher percentage of the summer if a summer design temperature of 100 degrees were used. And we do have some hours in some days during the summer that the outdoor temperature exceeds the design temperature used by the load calculation.

Now, let’s go to the components in your home that impact the rate of heat transfer and begin with the lights and appliances used in your home. Engineers have determined valid estimates of the amount of time lights and appliances are used in a typical home.  Manufacturers have determined the average amount of heat an appliance (or lights) create when used. Engineers have determined the average number of appliances contained in a typical home. And based on square feet, the calculation assumes the number of appliances and lights used in a home. When appliances are in use, they emit heat which helps contribute to heating your home. In the summer this “base load” is actually a portion of the total cooling requirement. The impact of lights and appliances are typically a minor portion of the total calculation. (Starting to see that the calculation is best described as an “estimate”? Hopefully, it is a scientifically based estimate? I refer to it as a SWAG in lieu of a WAG.)

An understanding of physics can be quite complicated.  I am going to keep this understanding of physics elementary because that's all that is needed to appreciate the calculation procedure.  (Which is the sum of all the physics I understand.)...

  •  Consider other components of a dwelling – the floors, walls, windows, doors, and ceilings. Remember that the objective is to estimate the rate of heat transfer. The rate of transfer is impacted on a temperature difference (outdoor versus indoor). But it is not that simple. The rate of heat transfer is impacted by radiant heat, conductive heat, and convective heat (Please remember that air is a type of "fluid" and is the carrier of heat.)  
  • To simplify, components like windows are significantly impacted by radiant heat, wood products have little impact (light from the sun doesn’t pass through) from radiant heat. For instance, components that contain metal (walls and or attics) or concrete (slab floors or walls) have a conductive value that impacts the time at which the heat received enters a conditioned space and even have the capacity to “store” heat. The convection heat transfer rate is simply the amount of heat that strikes one side of a component and emitted from the other side of the component.
  • Components that contain “dead air spaces” like insulation, retard the rate of heat transfer. Wood contains dead air spaces.  The air between 2 panes of glass in a window provide dead air spaces.  You may be familiar with R-values of insulation, the higher the “R”, the greater are its properties to retard heat flow. Engineers have calculated the values to be used for calculating the heat transfer rate based on the type of products used in each component (floors, walls, windows, and ceilings) of a dwelling and an estimate is derived based on the amount of square feet of each component. (Now, you may understand why measurements are required to perform a calculation.)

But dwellings have a 3rd dimension. There is the requirement for a volume calculation (length x width x height), which is supplied with an average ceiling height. Think about your home. Do all rooms have the same ceiling height? Do you have vaulted or cathedral type ceilings?

Included in the calculation is an input for the insulation value and leak rate of the duct system. All duct systems leak. Well-constructed duct systems have a significantly lower leak rate than poorly constructed duct systems. An observation of a duct system can supply the input required for an insulation value  The calculation uses an average leak rate based on prior test results and is used for duct losses.  Leak rates utilized are typically between 5 -30% of total system capacity. Another component is the age and location of the duct system. (Is the duct system located in the attic or crawl space?)  

And all homes are not constructed equally. Depending on how well-built they are, there is an infiltration rate (a path of airflow from inside you home to the outside or vice versa, depending on the season). Air leaks in (or out) of a home around windows and doors, poorly sealed light fixtures, air conditioning vents, electrical outlets, plumbing fixtures, and other penetrations. An estimate for infiltration is a judgment call based on appearance and the age of the dwelling. With proper equipment and testing, those that have the equipment and knowledge can obtain accurate measures for leakage rates.

The rate of heat flow is also impacted by orientation, the direction the dwelling is constructed in respect to the sun. The direction the sun strikes a dwelling impacts the estimated rate of heat transfer. The procedure has an input for the exposure of the dwelling to obtain the direction the front of the house is facing in respect to the sun.  (The impact of windows that face the sun.)

 Lastly, based on all the variables, a volume calculation determines the required air change rate needed to keep the air “fresh” based on engineering standards for different types of structures. In other words, how many times per hour does all the air in a dwelling pass through the air conditioning system?. The air change rate is used as a critical input in the blower size of the indoor system. In rare cases - “super-sealed, air tight homes, there may be a need to provide outside air to meet fresh air ventilation standards.

If you are skimming this article please STOP SKIMMING and
start reading from here to the end.

And there are still more inputs used by the calculation that can have an impact on the rate of heat transfer that I intentionally omitted in this article.  The point of this article is to illustrate that the calculation attempts to address all of the inputs that may impact the total heat transfer rate of a residential structure.

If you have read this far, hopefully you have an understanding of the “depth” of the calculation and why a load calculation is important. If a load calculation is included with your replacement, I don’t understand why you wouldn’t want one performed by a professional that performs this procedure correctly.

I am sure you have heard that the value of the inputs directly correspond to the value of the output.  Garbage in, garbage out...  If Santee Cooper requires a load calculation for compliance in their residential energy programs, they have determined that a load calculation has value. If reading this article peaked your interest, we can provide the time to go deeper into this subject. Or if you are ready to begin your replacement with a service provider that implements the procedure correctly and have sufficient interest, we would be delighted to have you help measure and learn more about the procedure.  This is one of many important steps of an installation that leads to optimal comfort and energy savings.

Maybe this IS the reason to call us to provide an estimate for replacement. A load calculation is just one of the reasons we install heating and air conditioning systems that provide optimal performance for our customers.

STAY TUNED.  We will continue to provide more informational articles similar to this one that addresses other subjects relating to heating and air conditioning.

If you liked this article and felt that the information was informative, would you please do me the favor of leaving a comment. Thanks.

Heating with Heat Pumps

It is FRIGID Outside!

It sure is cold outside this morning.  I know what the weather  forecast is…Colder!  I  am a little concerned about my heat pump.  So I thought I would post this thought.  If it stays WET and get’s as cold as predicted, you SHOULD KNOW THIS.

The way heat pumps work in the winter (during the heating cycle), the heat pump (the outdoor system) is attempting to extract heat out of the outdoor air to heat your home.  Because the ability to extract sufficient heat to heat your home is not available (somewhere around 35 degrees, + or – a couple of degrees), there is a possibility that your outdoor system could turn into a “block of ice”.  For heat to be extracted, the temperature of the coil (contained in the outdoor system) has to be lower than the temperature of the outside air.  Because of the cold rain/freezing rain or sleet, ice may build up on the outdoor coil.

The thing to remember before you read the next paragraphs, is that the heat pump is a SYSTEM with multiple components.  The outdoor system and the indoor system is synchronizing in different modes of operation simultaneously to provide heat.   This explanation may get a little complex, but hopefully you will understand.

A heat pump system contains a back-up heating capacity that is referenced as emergency heat, supplemental heat, or strip heating.  The heating elements are contained in the indoor system (air handler) of your heat pump system.  If the indoor temperature is more than a few degrees less than the thermostat setting, the supplemental heaters are energized to supply heat.  Your thermostat originates the signal to activate the supplemental heaters.  The supplemental heaters should provide sufficient heat to heat your home.

Now, let’s go to another standard component of a heat pump system.  All heat pumps (outdoor systems) contain a process called a DEFROST CYCLE.  If the temperature sensor on the outdoor system (coil) detects accumulation of ice, the heat pump reverses the refrigeration cycle (goes into cooling mode) which sends warm refrigerant to the outdoor coils. The “warmer” refrigerant should melt any ice that may have formed on the outdoor coils. Defrost cycles are utilized for short time intervals (usually in seconds), and then the cycle changes the refrigerant flow back the normal heating cycle.  If you have seen “steam” being emitted during the winter from an outdoor system, the steam was being emitted during the DEFROST cycle.  When an outdoor system activates the DEFROST cycle, the supplemental heaters receive a signal to activate, since heating is required to warm the indoor air in cooling mode to provide heat, and the supplemental heaters remain activated for the duration of the defrost cycle.  At the conclusion of the defrost cycle, the outdoor system initiates the signal to cut-off the supplemental heaters.

I attempted to describe the heating cycle of a heat pump in an elementary fashion.  (I don’t begin to claim that I can get any more technical than as written.)

But what happens if the ice accumulates faster on the outdoor system coil than the DEFROST cycle can eradicate the ice? Now refer to the picture.  Ice build up can happen in extreme conditions, even when a heat pump is operating as it should.

Now on days when the temperature is hovering around freezing or BELOW, AND it is precipitating in the form of rain, freezing rain, or sleet, your heat pump may become a block of ice.  When your outdoor system becomes a block of ice, the outdoor system fan may not have room to operate (due to the ice) and damages could occur to the fan motor and the fan contained in the outdoor system.

In conditions such as we are having today… close to freezing temperatures and rain… the safe course of action is to turn your thermostat on emergency heat until the temperature warms up or the precipitation has ended for a while.  For this unusual exception (we don’t get this kind of weather often), trying to heat in heat pump mode as opposed to heating with the higher cost form of heat (supplemental differences) will not provide significant spikes in energy costs that result from cold temperatures for short intervals of time.

And HOW DO I KNOW about such a possibility as I attempted to describe?  I will admit that this advice was NOT obtained by reading books NOR was the knowledge gained from someone else’s advice.

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