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Old 05-19-2014, 12:04 PM   #1
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In Layman Terms, Explain the Necessity for Superheat & Subcooling Calculations


How do you all explain to homeowners, in layman terms, the necessity of superheat and subcooling calculations, for charging an A/C system.

I have EPA certification now, but will be relying on my partner to charge systems for the time being.

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Old 05-19-2014, 01:30 PM   #2
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In Layman Terms, Explain the Necessity for Superheat & Subcooling Calculations


I don't. No need to. All they care about is the bill and whether it works or not. They could not care at all or understand anything technical other than it needs the right amount of Freon to cool properly and efficiently. Use that if necessary.

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Old 05-19-2014, 04:02 PM   #3
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In Layman Terms, Explain the Necessity for Superheat & Subcooling Calculations


interesting question. I suspect that you want to inform the consumer of why your service is better than others, which is a sound business practice. In this day and age, with the internet etc, there is a percentage of consumers that want to fully understand what you are doing and why before you do it. I happen to be one of those people. If I had my choice between a tech who could explain, in laymans terms, what he was going to do and why, I would choose him over one who could not.
being a homeowner, not an expert in the field of HVACr, I have not been able to find a tech here in PHX who can explain subcool and superheat, much less perform the process. I have had contact with at least 20 companies and none have been able to convince me they know what subcool etc is. Now I will admit that the valley of the sun has a boat load of techs and companies and that I have not tried them all.

trying to find a way to explain what you are doing is a good thing!!!

try this???
Superheat refers to the number of degrees that refrigerant vapor is above its saturation temperature (boiling point) at a particular pressure. if the system is out of range, the efficiency will be poor.
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Old 05-19-2014, 05:25 PM   #4
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In Layman Terms, Explain the Necessity for Superheat & Subcooling Calculations


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Originally Posted by justplumducky View Post
How do you all explain to homeowners, in layman terms, the necessity of superheat and subcooling calculations, for charging an A/C system.
For the most part, I don't. They don't ask me, I don't tell them, cause they aren't really interested.

For the few that do. SH, tells me when I if liquid is getting back to the compressor or not, and how flooded the evap coil is or isn't.

SC tells me if I have enough liquid reaching the metering device or not.
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Old 05-19-2014, 07:24 PM   #5
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In Layman Terms, Explain the Necessity for Superheat & Subcooling Calculations


most homeowners could care less...for those that think they do after you start talking about s h ,s c they get really bored fast...
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Old 05-19-2014, 07:30 PM   #6
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In Layman Terms, Explain the Necessity for Superheat & Subcooling Calculations


then we HAVE to start talking about fan speeds, duct sizing , coil cleanliness. matched or mis-matched system and why the superheat, subcooling may be out and why we can or cannot do anything about it. about as interesting or exciting as watching paint dry IMO.

most people I talk to like it when it talk about their yard, pets, family photos not thermodynamics.
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Old 05-19-2014, 08:02 PM   #7
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In Layman Terms, Explain the Necessity for Superheat & Subcooling Calculations


may not be interesting to you, but as a consumer I can see where it allows the consumer to gain confidence in you.

Could be they know more than you think and they are testing you?

Just a thought
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Old 05-20-2014, 05:30 AM   #8
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In Layman Terms, Explain the Necessity for Superheat & Subcooling Calculations


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may not be interesting to you, but as a consumer I can see where it allows the consumer to gain confidence in you.

Could be they know more than you think and they are testing you?

Just a thought

At $145.00 an hour, most customers prefer not to slow me down.
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Old 05-20-2014, 07:19 AM   #9
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In Layman Terms, Explain the Necessity for Superheat & Subcooling Calculations


you hit the nail on the head beenthere...when they are paying 100.00 to 150.00 per hour shut the hell up and get your work done and get off the clock
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Old 05-20-2014, 06:00 PM   #10
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In Layman Terms, Explain the Necessity for Superheat & Subcooling Calculations


Thx to all for jumping in... Your responses are teaching me that I sometimes need to be more specific with my questions. First I'll rephrase the question (add to it just a little), then I'll explain a bit more of what I had in mind.

How do you all explain to homeowners, in layman terms, the necessity of superheat and subcooling calculations, for charging an A/C system, vs. charging a system without the Superheat and Subcooling method.

Well, instead of explaining more of what I had in mind, I went googling for SH & SC articles and came up with my own explanation. If I don't have it exactly correct, at least it should give you the idea of what I had in mind.

“An A/C system can only be tuned to maximum efficiency with the use of Superheat and Subcooling measurements, which are pressure and temperature measurements taken at strategic points in the system. Maximum efficiency also equates to maximum cooling, which results in a minimal amount of energy use (lower electric bills), because adjusting (charging) your system with the SH & SC method, will enable cooling your home with a minimal amount of system run time. In comparison, improperly adjusted (charged) systems (without using the SH & SC method) are inefficient and notorious for longer run times (higher electric bills), in order to maintain a comfortable temperature.”

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Old 05-20-2014, 06:06 PM   #11
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In Layman Terms, Explain the Necessity for Superheat & Subcooling Calculations


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Originally Posted by beenthere View Post
At $145.00 an hour, most customers prefer not to slow me down.

I understand and agree, but "picking your brain" lets me know that you are worth what you charge and you know what you are doing.

I see it all the time on these boards where pros chastise consumers for not asking questions.

I don't think the OP meant finite detail of superheat and super cool, but in general why it is used and why it is important.

if a tech cannot take the time to explain that to me, he does not need to be on my property.

You talk about the 145 and getting the work done and gone, some are not as diligent as you are.


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Old 05-20-2014, 06:10 PM   #12
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In Layman Terms, Explain the Necessity for Superheat & Subcooling Calculations


Thx to all for jumping in... Your responses are teaching me that I sometimes need to be more specific with my questions. First I'll rephrase the question (add to it just a little), then I'll explain a bit more of what I had in mind.

How do you all explain to homeowners, in layman terms, the necessity of superheat and subcooling calculations, for charging an A/C system, vs. charging a system without the Superheat and Subcooling method.

Well, instead of explaining more of what I had in mind, I went googling for SH & SC articles and came up with my own explanation. If I don't have it exactly correct, at least it should give you the idea of what I had in mind.

“An A/C system can only be tuned to maximum efficiency with the use of Superheat and Subcooling measurements, which are pressure and temperature measurements taken at strategic points in the system. Maximum efficiency also equates to maximum cooling, which results in a minimal amount of energy use (lower electric bills), because adjusting (charging) your system with the SH & SC method, will enable cooling your home with a minimal amount of system run time. In comparison, improperly adjusted (charged) systems (without using the SH & SC method) are inefficient and notorious for longer run times (higher electric bills), in order to maintain a comfortable temperature.”

I wouldn't bring this up with a homeowner unless responding to something he said or asked, but I have a competitor who services without the SH & SC method. I don't even know how to do this yet, but my partner does.

DigitalPluimber, you hit the nail on the head, thx. Other did as well, considering my slightly vague question.

Last edited by justplumducky; 05-20-2014 at 06:18 PM.
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Old 05-20-2014, 06:43 PM   #13
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In Layman Terms, Explain the Necessity for Superheat & Subcooling Calculations


Technically you don't want liquid refrigerant leaving the evaporator and getting into the compressor and smashing the valves, diluting and washing out the oil and doing damage. Therefore you want it to absorb a couple degrees F past it's saturation temp ( superheat or add extra heat ) so it guarantees 100% vapor to the compressor. It is also more efficient. Subcooling means that the bottom 2 rows of copper in the condenser are full of liquid refrigerant. The air passing over them "subcools" or cools it down another couple deg F so the liquid entering the TX valve is cooler and you can absorb more heat which adds to efficiency.

Your competitor is using the old school "beer can cold" method where you add Freon until the suction line at the comp is "beer can cold". Used for many years but after we got to 10 SEER that method went out the door. We also used to be able to get 20 deg F Delta T /temp dfiff between the supply and return air and a lot of the time "beer can cold" got you very close. Nowadays 20 is not the norm and 16 can be OK. All depends on the SEER and the manufacturers charts.

Tell your customer you are using the "proper method" with the manufacturers charts for setting up the system with modern instruments. Make sure you have both and know how to use them.
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Last edited by yuri; 05-20-2014 at 06:53 PM.
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Old 05-20-2014, 06:52 PM   #14
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In Layman Terms, Explain the Necessity for Superheat & Subcooling Calculations


I think this is a pretty good write up on it....

http://www.achrnews.com/articles/sup...ng-made-simple

I was having to explain something similar a few weeks ago. A customer was wondering why the nitrogen going into his autoclave at 70 deg was causing the temp to rise to over 130 deg. Conversely, when they cooled it down to about 90 deg with 200 PSI in it and then vented it, wanted to know why the inside was ice.
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Old 05-20-2014, 07:04 PM   #15
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In Layman Terms, Explain the Necessity for Superheat & Subcooling Calculations


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Originally Posted by yuri View Post
Technically you don't want liquid refrigerant leaving the evaporator and getting into the compressor and smashing the valves, diluting and washing out the oil and doing damage. Therefore you want it to absorb a couple degrees F past it's saturation temp ( superheat or add extra heat ) so it guarantees 100% vapor to the compressor. It is also more efficient. Subcooling means that the bottom 2 rows of copper in the condenser are full of liquid refrigerant. The air passing over them "subcools" or cools it down another couple deg F so the liquid entering the TX valve is cooler and you can absorb more heat which adds to efficiency.

Your competitor is using the old school "beer can cold" method where you add Freon until the suction line at the comp is "beer can cold". Used for many years but after we got to 10 SEER that method went out the door. We also used to be able to get 20 deg F Delta T /temp dfiff between the supply and return air and a lot of the time "beer can cold" got you very close. Nowadays 20 is not the norm and 16 can be OK. All depends on the SEER and the manufacturers charts.
.
Thx - that kind of explanation will help me a lot toward learning the technical end of it.

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