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Old 05-20-2014, 07:21 PM   #16
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In Layman Terms, Explain the Necessity for Superheat & Subcooling Calculations


Remember a year ago when I told you to document the Freon pressures on different SEER machines at different outdoor temps and humidities and indoor/outdoor temps. That is the only real way to get good at this biz. Once you know what a properly charged machine is doing you have a reference point.

There is a LOT to it but you can learn a lot by having some reference points to start with.

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Old 05-20-2014, 07:47 PM   #17
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In Layman Terms, Explain the Necessity for Superheat & Subcooling Calculations


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Originally Posted by yuri View Post
Remember a year ago when I told you to document the Freon pressures on different SEER machines at different outdoor temps and humidities and indoor/outdoor temps. That is the only real way to get good at this biz. Once you know what a properly charged machine is doing you have a reference point.

There is a LOT to it but you can learn a lot by having some reference points to start with.

Yes I remember and I'm all for it. In fact, I just recently did a rough draft (don't mean to make it sound complex and difficult) of a checklist of items to record on first visit. Well aware of a having a Baseline for comparison. I'll add the temps and humidities to the checklist. Know of a better one online?

My problem is... I do so few of these a season - it will be slow going I'm afraid.
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Old 05-20-2014, 08:13 PM   #18
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In Layman Terms, Explain the Necessity for Superheat & Subcooling Calculations


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Originally Posted by digitalplumber View Post
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.


I seldom actually get to talk to the guy that works on my truck. He's in the bay with my van, and I'm out working. I really did't get to talk to him to find out if he is worth what the garage charges me for his work the first time I took it there. But if it hadn't been good the first time, I would not have taken it back the next time it needed work.

So my question to you is how long do you think I or any HVAC tech should spend explaining something like SH and SC to the customer.
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Old 05-21-2014, 06:49 AM   #19
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In Layman Terms, Explain the Necessity for Superheat & Subcooling Calculations


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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.
"Beer can cold always works if the owner is a beer drinker"

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