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Old 01-14-2011, 10:15 PM   #16
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Temperature at Refrigerant line too low?


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I have had some work done to my HVAC system, which consists of two Goodman air handlers and two 13 seer goodman heat pumps. There were apparently leaks in one of the systems' refrigerant circuits and those were repaired, but I am seeing some behavior that worries me and that the HVAC techs haven't been able to give me a good explanation for.

The temperatures, when read with an IR thermometer, at the outlets of the two heat pumps are 87 and 113 degrees, typically. It seems to me that since these units are identical, they should be putting out refrigerant that is heated to the same temperature! The only differeing factor that I can think of is that the circuit is physically longer to the upstairs zone since the handler is in my attic.

I contacted the HVAC service company about this, and they came out to check it out. They told me that I need a new PCB because my heat pump was stuck in defrost mode! Well, that's not the issue that I called about, nor is it an issue that I have before or since witnessed. I pressed them on this and they claim that there are "too many factors" that could cause the discrepancy in heating ability between the units?!?! The way I see it is this:

Refrigerant coming in at X degrees -> black box heating magic -> refrigerant out at Y degrees

The return lines are approximately the same temperature going into both units, so I don't see how there could be a 20 degree discrepancy between the two!


As a disclaimer, I should note that I have little experience working with HVAC systems (so far!), but I'm hoping that you resident experts can point me in the right direction.

Thanks in advance,

Russell
What resulted in the defrost stuck thing?
Is the fan on the outside unit running?

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Old 01-14-2011, 10:54 PM   #17
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Temperature at Refrigerant line too low?


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What resulted in the defrost stuck thing?
Is the fan on the outside unit running?
They said it was a faulty circuit board, but I am skeptical, as I have never seen that happen. I think the guy just didn't wait long enough for the defrost cycle to end and probably walked in thinking that was the problem. The fan is running so I know it isn't stuck right now, at least.
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Old 01-14-2011, 11:03 PM   #18
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Temperature at Refrigerant line too low?


87 degrees on the discharge line means that it is not picking up any heat. Could be charge is short or compressor is not pumping right. Need some pressure readings along with temp readings.
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Old 01-15-2011, 03:35 AM   #19
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Temperature at Refrigerant line too low?


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They said it was a faulty circuit board, but I am skeptical, as I have never seen that happen. I think the guy just didn't wait long enough for the defrost cycle to end and probably walked in thinking that was the problem. The fan is running so I know it isn't stuck right now, at least.
Defrost boards going bad, are a common problem.

IR thermometers aren't accurate enough to take line temps of heat pumps or A/Cs.

The attic unit could be moving more air then the downstairs unit, and that will change the liquid line temp.
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Old 01-15-2011, 07:39 AM   #20
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Temperature at Refrigerant line too low?


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Defrost boards going bad, are a common problem.

IR thermometers aren't accurate enough to take line temps of heat pumps or A/Cs.

The attic unit could be moving more air then the downstairs unit, and that will change the liquid line temp.
What I mean was that I have never seen MY unit stuck in defrost mode. Both of my air handlers are the same, with the same size air inlet. I'm thinking that since the handlers are the same they should be pulling in close to the same amount of air, right?
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Old 01-15-2011, 08:31 AM   #21
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Temperature at Refrigerant line too low?


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What I mean was that I have never seen MY unit stuck in defrost mode. Both of my air handlers are the same, with the same size air inlet. I'm thinking that since the handlers are the same they should be pulling in close to the same amount of air, right?
Only if the return duct and supply duct are both the same. Which since one is an attic install and the other is a basement install, the duct work isn't the same for both of them.

Very easy to have one moving a good amount of more air then the other. The attic install will also have a lower return air temp,which will cool the refrigerant more then the basement one. The longer line set to the attic one wil also have some effect.

While it may be under charged/low on charge. The temp check you did isn't enough to know if it is or not.
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Old 01-15-2011, 08:34 AM   #22
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Temperature at Refrigerant line too low?


Yeah, I'm trying to figure out if my r134a gauges will work with R22 and if not, I'll have to order a gauge set or get one from craigslist or something.
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Old 01-15-2011, 01:46 PM   #23
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Temperature at Refrigerant line too low?


IMO....With all do resppect.....If you dont know the difference between Supply and Return air, delta T, sub cooling, super heat, actual cfm, or static pressure, Please God do not attempt to attach a manifold. Do you have low loss fittings, Do you know which refrigerant you have? One mistake could end up adding non-condensibles into the system......If you are not satisfied with the answers from your HVAC company please call them back and speak with the owner, tell him you are not satisfied in a calm manor, and have their lead tech and himself come out....
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Old 01-15-2011, 02:20 PM   #24
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IMO....With all do resppect.....If you dont know the difference between Supply and Return air, delta T, sub cooling, super heat, actual cfm, or static pressure, Please God do not attempt to attach a manifold. Do you have low loss fittings, Do you know which refrigerant you have? One mistake could end up adding non-condensibles into the system......If you are not satisfied with the answers from your HVAC company please call them back and speak with the owner, tell him you are not satisfied in a calm manor, and have their lead tech and himself come out....
Believe me, I tried not doing this myself. I patted myself on the back when I called a tech instead of learning how to do it myself as I usually do. What did that get me? Frustrated! Saying to someone "if you don't know this, don't do that" isn't very helpful. Perhaps what you meant is "if you don't know this, learn it before you do that"? Better yet, feel free to educate me!

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