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Old 12-17-2012, 01:46 PM   #61
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Subcooling is way high -- Need Advice!


This is from left field and I know nothing compared to most of you, but could your LL be too small at 5/16" I lived in a neighborhood where many failures were occurring in heat pumps and the HVAC tech told me it was because of too small a liquid line, and he had replaced most with 3/8. Just wondered.
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Old 01-01-2013, 09:40 AM   #62
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That's a good idea. I think that I'll measure the temp. at both ends of that liq. line. If it is offering any restriction I believe it should show up as a temperature delta.

TODO:
- Reconnect TXV bulb properly
- Measure LL temps to verify no restriction
- Run system, taking subcooling measurement again with cardboard over condenser
I threw some plastic sheeting over the condenser because it was about 50 degrees outside today and these are my observations:

- LL temp differential is .8 degrees over the approx 20' line length from the condenser to the evaporator

- Pressure/Temperature readings at the condenser:
Suction - 139psi @ 42degrees -- -6 degrees superheat
LL - 420psi @ 56degrees -- 65 degrees subcooling

Obviously negative superheat is not possible so something was awry. I recalibrated the temp. and pressure on my manifold and will give it another go. Overall though, I am not very satisfied with my ability to get consistent readings. I'm going to take one last reading and if I can't make sense of things I am going to call a tech and just keep my fingers crossed that I get someone competent that cares about the quality of their work.

Question about blocking condenser airflow before I do this though; how much airflow should I block, and can I damage the condenser by doing this? I left a portion of the fins unblocked but I'm not sure if the refrigerant would pool up in one spot because of it or something like that.

Happy new year!
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Old 01-01-2013, 09:46 AM   #63
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Subcooling is way high -- Need Advice!


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Originally Posted by Ethereal View Post
I threw some plastic sheeting over the condenser because it was about 50 degrees outside today and these are my observations:

- LL temp differential is .8 degrees over the approx 20' line length from the condenser to the evaporator

- Pressure/Temperature readings at the condenser:
Suction - 139psi @ 42degrees -- -6 degrees superheat
LL - 420psi @ 56degrees -- 65 degrees subcooling

Obviously negative superheat is not possible so something was awry. I recalibrated the temp. and pressure on my manifold and will give it another go. Overall though, I am not very satisfied with my ability to get consistent readings. I'm going to take one last reading and if I can't make sense of things I am going to call a tech and just keep my fingers crossed that I get someone competent that cares about the quality of their work.

Question about blocking condenser airflow before I do this though; how much airflow should I block, and can I damage the condenser by doing this? I left a portion of the fins unblocked but I'm not sure if the refrigerant would pool up in one spot because of it or something like that.

Happy new year!
I would condenser at 110 degree saturation temp, don't have t/p chart handy.
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Old 01-01-2013, 09:50 AM   #64
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Subcooling is way high -- Need Advice!


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I would condenser at 110 degree saturation temp, don't have t/p chart handy.
That's about 365psi. Were you saying that would be your target temp or just the max you would go?
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Old 01-01-2013, 10:05 AM   #65
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Subcooling is way high -- Need Advice!


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That's about 365psi. Were you saying that would be your target temp or just the max you would go?
Target. Design temp is about 90 degree ambient. I would target a saturation temp at least 20 degrees above that for testing.
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Old 01-01-2013, 12:45 PM   #66
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Target. Design temp is about 90 degree ambient. I would target a saturation temp at least 20 degrees above that for testing.
Thanks, that helps a lot!
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Old 01-02-2013, 03:43 PM   #67
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I did another test. Got the tarp on, let it come to about 370psi and had approx. 12 degrees of subcooling which is in the realm of normal. Strange thing happened though, the temperature approached 100 degrees and then started backing off, down to around 80 degrees before I shut it off. This may have been going on for all my tests, as I usually let it run 15-20 minutes before taking readings but this time I waited only about 5 minutes. Almost seems like the indoor coil isn't pulling enough heat out of the indoor air? I heated the house up to 70 degrees before testing.

Does this give you guys any insight as to what's going on or is it time to call my greater area heating and air?
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Old 01-02-2013, 03:49 PM   #68
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Subcooling is way high -- Need Advice!


70 degees inside at what RH. You may have had virtually no latent load.
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Old 01-03-2013, 09:13 AM   #69
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70 degees inside at what RH. You may have had virtually no latent load.
Good question, I didn't get the idwb because one of my kids seems to have taken a liking to my wet bulb temp. probe. I suppose I could wrap the dry bulb probe in wet cotton or something. How does one determine what the latent load on a system is?

Edit: I noticed something, not sure if this is a symptom of anything though. At start-up, the compressor seems to "growl" for about a second before running smoothly. Not sure if that is normal, but wanted to put it out there just in case.

Last edited by Ethereal; 01-03-2013 at 09:33 AM.
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Old 01-03-2013, 09:47 AM   #70
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Subcooling is way high -- Need Advice!


Could be slugging, which is bad. Is there a crank case heater or single pole contactor for compressor?
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Old 01-03-2013, 11:00 AM   #71
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Could be slugging, which is bad. Is there a crank case heater or single pole contactor for compressor?
I'm not sure, what causes slugging? The condenser I have is this one: http://www.acwholesalers.com/Goodman...mp-p/11648.htm
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Old 01-08-2013, 08:31 AM   #72
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Subcooling is way high -- Need Advice!


A tech came out today to inspect my system. He told me that the growling on startup is something that is normal for Goodman units, and indicated that it is caused by the presence of a TXV in the indoor unit (and he might have connected that to the lack of TXV in the outdoor unit, I don't recall). He checked my unit's pressure, looked over everything, and told me that it all looks normal! He says that to get an accurate charge, I just need to wait until it gets above 75 degrees outside, otherwise there would be no way to get it spot on, especially since I have that 5/16" LL.

Although I may have spent a lot of time on this, I certainly learned way more than I could have just by reading a book about it. Thanks to all of you guys for helping me out, I really appreciate it. I will check the charge in the summer and post back here with the results. In the meantime, I'll continue to give others on this forum advice where I can to repay the kindness!
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Old 01-08-2013, 08:59 AM   #73
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Subcooling is way high -- Need Advice!


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Originally Posted by Ethereal View Post
A tech came out today to inspect my system. He told me that the growling on startup is something that is normal for Goodman units, and indicated that it is caused by the presence of a TXV in the indoor unit (and he might have connected that to the lack of TXV in the outdoor unit, I don't recall). He checked my unit's pressure, looked over everything, and told me that it all looks normal! He says that to get an accurate charge, I just need to wait until it gets above 75 degrees outside, otherwise there would be no way to get it spot on, especially since I have that 5/16" LL.

Although I may have spent a lot of time on this, I certainly learned way more than I could have just by reading a book about it. Thanks to all of you guys for helping me out, I really appreciate it. I will check the charge in the summer and post back here with the results. In the meantime, I'll continue to give others on this forum advice where I can to repay the kindness!
you'll be back...they always come back....it's like "Welcome to the Hotel California"....mmmhhaaahahahaha!


I think I said much earlier in the thread that "knowledge is not experience", well now you have tried to apply the textbook approach and found that it takes more that a bunch of facts and figures to find a solution, I think you understand where the experience part of the equation comes in.

Good luck.
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Old 09-02-2013, 08:02 PM   #74
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Subcooling is way high -- Need Advice!


To follow up on this, I read 20* subcooling this summer and had to spend some cash getting a proper setup to take some refer out... so all you guys that said it was overcharged, pat yourselves on the back!

I'm at 12* subcooling now, and the manual says to run at 7-9 so I might take a little more out. I'm at 12 because that was the most commonly quoted spec but I'll probably drop to 9 unless anyone has objections... I've seen people say to run at 12 regardless of what the mfr says but that really makes little to no sense to me; why would the manufacturer misquote their own hardware? Anyway, thanks again to all you guys that gave me feedback!
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Old 09-03-2013, 02:25 PM   #75
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Subcooling is way high -- Need Advice!


Assuming all else is correct, than either your SMAN 3 temp clamps are off or your TXV needs adjusting/replacement.

The SMAN 3 has been a "work in process" judging from personal experience ( had to exchamge mine 3 times. Still dont like it) and from what I read on PRO only sites.

Might want to use a diff digital temp tester to check your SC just tobe sure.

Last edited by hvac5646; 09-03-2013 at 02:34 PM.
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