Correct piston size or TXV - http://www.hvacmechanic.com/ Forums
Original message
| tcerbo
 |  "Correct piston size or TXV"
, posted Thu 16 Aug 15:52  
I have a 12 Seer Goodman heatpump CPK24-1 (24,000 Btu) and mated to a new Goodman ARUF3030 1 (30,000 Btu).
My question is the NEW Goodman air-handler initially had a .065 pistion and that would not cool properly, both lines at air handler were cool to the touch and gave about a 10 degree differential between inlet air to ourlet air. The piston was replaced with a .059 and that seemed better with a 12 degree difference. Now a piston between of .059 to .065 is being considered. I believe it should be a bit smaller than .059. Others people are saying it should be larger than .059. Or should the best solution be to install a TXV (Goodman TX3N2)valve. Thanks Tom Cerbo
Thomas A. Cerbo
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Replies:
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| yuri
| "Re(1):Correct piston size or TXV" , posted Thu 16 Aug 17:26
I would use the TXV valve recommended for it by Goodman only. It gives you much better control and more SEER rating. They have to match it to their system so make sure they supply the correct one for 24,000 BTU's, cannot mix and match them. Make sure the installer weighs in the refrig charge with an electronic scale. Heat pumps are critically/exact charge only.
Yuri
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| | tcerbo
| "Re(2):Correct piston size or TXV" , posted Thu 23 Aug 14:40
Ok, today the .061 piston was installed & tested and proved worst than the .059. Would it now be recommended to go with a piston slight smaller than the .059 or just "bite the bullet" and have a Goodman TXV installed. Since this is a brand new Goodman air handle, I wonder if that would void the warranty.
Any help would greatly be appreciated. Incidently the D/T temp difference between inlet & outlet is 14 degrees with the .059 piston. I recall with the older components that being > 17.
Thanks
Tom Cerbo
Thomas A. Cerbo
Thomas A. Cerbo
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| | tcerbo
| "Re(2):Correct piston size or TXV" , posted Fri 17 Aug 16:00
I am being told that a TXV valve will not physically fit and that the correct piston is the only way to go to correct. Right now it has a .059 and my question is in order to get better a better differential from input temp to dicharge temp should a larger or smaller piston from the .059 be used. The return compressed line is only slightly warm to the touch. I recall it was quite a bit warmer (or hotter) when the old Air Handler was used. The compressor is only drawing about 8.3A (at 240 VAC) and seems not to working very hard. Right now with the .059 there is only a 13 degree difference from in to out of duct and it use to be 17 degrees.
Thanks
Tom
Thomas A. Cerbo
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| | dapster1
| "Re(3):Correct piston size or TXV" , posted Fri 17 Aug 18:23
Tom
I too have a goodman (3 ton system )matched coil and gas furnace. In my user manual of my cased evaporator coil it gives all the Goodman piston sizes from the factory by model/series type.
If you could give me model of condensor and coil I will look it up for you on my install manual and give the piston size
Think....work smart not hard!!
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| | tcerbo
| "Re(4):Correct piston size or TXV" , posted Sat 18 Aug 11:37
OK,
1) The Goodman (12 SEER compressor) is Model CPKJ24-1B (several years old now)
2)The brand new Goodman Air Handler is Model ARUF303016AA, S/N 0707436440.
Any help would greatly be appreciated.
Tom
Thomas A. Cerbo
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| | dapster1
| "Re(4):Correct piston size or TXV" , posted Fri 17 Aug 18:29
Think....work smart not hard!!
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| | dapster1
| "Re(5):Correct piston size or TXV" , posted Fri 17 Aug 18:36
I just looked it up ...I dont know if this helps but Goodman chart shows .065-.059 on several models- all 2-ton w/ 2.5 ton coil.
By rule and looking at this chart, the larger the coil the the higher the piston size. Example 4 ton systems that are matched are .082-.090
Think....work smart not hard!!
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| | tcerbo
| "Re(6):Correct piston size or TXV" , posted Sat 18 Aug 12:11
Yes, I agree with you in general about orifice sizes. Are there any adverse affects to go smaller than the .059 since that is what is installed there now and much better than the .065 previously installed. What is the next size down from .059. Are these pistons unique to a specific manufacturer or available from other Mfgs as well that would work in a Goodman system. Unfortunately Goodman will only speak to LIC contractors even though I am an Engineer.
Agin thanks for the help..
Tom
Thomas A. Cerbo
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| | dapster1
| "Re(7):Correct piston size or TXV" , posted Sun 19 Aug 16:07
As per the chart ....it looks like the next smaller size is a .052. This oriface size is only listed on 1.5 to 2 ton Evap coils. I would think that you would have TOO much restriction on this one. And also all the oriface part numbers are Goodman numbers so if you experiment I would get the Goodman replacement so all the fittings and seal washer fit.
JUST A THOUGHT: Have you looked at your charge rate by superheat method? If it not charged correctly this could make a BIG difference.
Think....work smart not hard!!
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| | tcerbo
| "Re(8):Correct piston size or TXV" , posted Mon 20 Aug 10:37
Ok, again thanks for the tips, we wil try .061 to see if there is an improvement in cooling and possibly the charging method. I will know by the middle of this week and report the results to you.
Tom
Thomas A. Cerbo
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| | tcerbo
| "Re(9):Correct piston size or TXV" , posted Wed 22 Aug 15:33
Ok, today the .061 piston was installed & tested and proved worst than the .059. Would it now be recommended to go with a piston slight smaller than the .059 or just "bite the bullet" and have a Goodman TXV installed. Since this is a brand new Goodman air handle, I wonder if that would void the warranty.
Any help would greatly be appreciated. Incidently the D/T temp difference between inlet & outlet is 14 degrees with the .059 piston. I recall with the older components that being > 17.
Thanks
Tom Cerbo
Thomas A. Cerbo
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