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Old 03-08-2014, 06:19 PM   #31
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3 ton evap 2 ton compressor


Low load, gives a low super heat. The evap coil is being under fed. So you may have a blockage in the metering device.

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Old 03-08-2014, 06:21 PM   #32
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3 ton evap 2 ton compressor


Right, but wouldn't low ambient give me a high Subcool?

Last edited by wetbar; 03-08-2014 at 06:31 PM.
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Old 03-08-2014, 07:02 PM   #33
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Right, but wouldn't low ambient give me a high Subcool?
Yes it can. But it won't give you a high super heat. You have a restriction in the refrigerant circuit.
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Old 03-08-2014, 07:40 PM   #34
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3 ton evap 2 ton compressor


ok now I am in heat mode

ODDB drop to about 53 degrees (yes that fast)
INDB 71 degrees
LL 107.5 psig and 97.9 degrees
True suction 64 psig and 54.7 degrees
gives a super heat of 17.7 and a sub cool of . . . notta!
Vapor line temp 149 outside of cabinet
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Old 03-08-2014, 08:22 PM   #35
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3 ton evap 2 ton compressor


Did you look for a restriction at the indoor metering device yet.
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Old 03-10-2014, 09:24 AM   #36
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3 ton evap 2 ton compressor


I did check the piston and didn't find anything. When in heat mode that would take the inside piston out of play or maybe even unstop it, right? I did notice when I went to check the piston it was frosted up right were the piston is. fan seems to working, all filters are clean, and the coil is clean. The strange part is all is working fine in cool mode I am getting a delta T of 20 degrees and in head mode I am getting 30 degrees.
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Old 03-10-2014, 11:46 AM   #37
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3 ton evap 2 ton compressor


Wait a minute, I am getting loads subcool! Discharge minus the liquid line temp, right? 149 -97.9 is 51.1 I was using liquid pressure an liquid line temp, but I was in heat mode! So this thing is way over charged?
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Old 03-10-2014, 03:37 PM   #38
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Mismatch systems often are charge problems switching between heat and cool mode.

SC is liquid line saturation temp minus actual liquid line temp.
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Old 03-10-2014, 04:07 PM   #39
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oh I thought it was , Sub Cooling = Discharge Saturation F - Liquid Line F. If you are in heat mode.

I was going by this website -

http://hvacreducationtechtips.blogsp...t-pump-in.html
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Old 03-10-2014, 04:23 PM   #40
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oh I thought it was , Sub Cooling = Discharge Saturation F - Liquid Line F. If you are in heat mode.

I was going by this website -

http://hvacreducationtechtips.blogsp...t-pump-in.html
They word it poorly.

SC is the liquid saturation temp minus the liquid line temp.
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Old 03-11-2014, 03:35 PM   #41
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3 ton evap 2 ton compressor


ok pump down check piston again no problem found. Triple vac - same problem. How about noncodensables? It seems it is not flashing off or condensing would that give a high subcool?
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Old 03-11-2014, 04:39 PM   #42
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Non condensables would cause a high head pressure. but would cause it in both heating and cooling mode.

Okay. What size is the indoor coil, and what SEER was it intended for. What size is the condenser listed as on the data plate, and what SEER.

PS: You did check the strainer at the piston, if it has one.
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Old 03-11-2014, 07:27 PM   #43
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OK I recovered all R-22 vac down again and added fresh (new tank) R-22. Looking better but still kinda strange. here are the numbers:

In AC mode
Low side 48.2 and 48.4 degrees
High side 187.3 and 66.2 degrees
gives a super heat of 25.1
gives a subcool of 30.7

IDWB 58
ODDB 62
delta T 20 degres!

So I would expect a high super heat, I was shooting for 20, but look at subcool 30 degrees. Dont get me wrong subcool is my friend but freaking 30. Then look at delta T 20 degrees I love it.

. . but with a 3 ton outside unit and a 2 ton inside unit I would have high subcool right?
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Old 03-12-2014, 04:55 AM   #44
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Quote:
Originally Posted by subcool View Post
OK I recovered all R-22 vac down again and added fresh (new tank) R-22. Looking better but still kinda strange. here are the numbers:

In AC mode
Low side 48.2 and 48.4 degrees
High side 187.3 and 66.2 degrees
gives a super heat of 25.1
gives a subcool of 30.7

IDWB 58
ODDB 62
delta T 20 degres!

So I would expect a high super heat, I was shooting for 20, but look at subcool 30 degrees. Dont get me wrong subcool is my friend but freaking 30. Then look at delta T 20 degrees I love it.

. . but with a 3 ton outside unit and a 2 ton inside unit I would have high subcool right?
If you are using the piston for a 2 ton unit, yes.

When you have a 3 ton condenser on a 2 ton evap. You are suppose to use a TXV that is rated for 3 tons, and the blower should be moving 1200 CFM.

On a piston system with the IDWB and ODDB you posted. Target SH is 16F.

So what piston do you have in the piston holder, one for 2 tons, or one for 3 tons?

PS: Still won't have good readings in heat mode.
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Old 03-12-2014, 06:53 AM   #45
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3 ton evap 2 ton compressor


I think i remember the piston saying 59 on the side, when i pulled it out yesterday. Not sure if that is 2 or 3 tons.

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