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Old 07-26-15, 01:34 PM   #1
NeilTheCop
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Default AC leak

Need some advice.
I fitted a Goodman 2 ton AC unit last year. Filled the system with nitrogen before brazing with oxy-acetylene and a 15% silver filler rod. Pulled a vacuum with a good vacuum pump overnight, held at 5 Pascals for another 24 hours. Using subcooling (TVX fitted) I charged the system with R410A and it worked wonderfully.
Checking it out yesterday and I found compressor oil on the low pressure line where I brazed it to the condenser unit, so I have a refrigerant leak
Now the question.
Can I evacuate the system, fill it with nitrogen and simply re-braze the leaking fitting, or will the oil that will undoubtedly be present in the fitting be a problem requiring that I un-braze, solvent clean and re-braze?

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Old 07-26-15, 04:24 PM   #2
jeff5may
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Quote:
Originally Posted by NeilTheCop View Post
Need some advice.
I fitted a Goodman 2 ton AC unit last year. Filled the system with nitrogen before brazing with oxy-acetylene and a 15% silver filler rod. Pulled a vacuum with a good vacuum pump overnight, held at 5 Pascals for another 24 hours. Using subcooling (TVX fitted) I charged the system with R410A and it worked wonderfully.
Checking it out yesterday and I found compressor oil on the low pressure line where I brazed it to the condenser unit, so I have a refrigerant leak
Now the question.
Can I evacuate the system, fill it with nitrogen and simply re-braze the leaking fitting, or will the oil that will undoubtedly be present in the fitting be a problem requiring that I un-braze, solvent clean and re-braze?
The second option is prudent, and may never cause trouble again. Worth the extra time to remove all doubt. A visiting tech on a service call would probably just pull the refrigerant back into the outdoor unit, shut off the valves, purge with nitro and re-braze. This option might also be fixed forever. It's your time, not his. Depends on your confidence or gambler factor.
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Old 07-28-15, 10:37 AM   #3
NeilTheCop
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The thing is, I thought I brazed it properly the first time. May have a crack in the pipe, so off it all comes
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Old 07-28-15, 04:59 PM   #4
Elcam84
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What Jeff said is exactly what a service call would be. Just close the high side valve and hold the contactor in while watching the low side gauge and when all the refrigerant is back in the condenser close the suction valve and then release the contactor. Rebraze and open the valves back up (after the usual line purging).
It's recommended to replace the desiccant filter but on a system that's not open its not worth it.



Also check your nut fitting on the txv they are known to leak as well. I really hope the replacement for 410a is a lower operating pressure gas as leaking evap coils are still a very common problem. Thin tubes and high pressures especially in heat pump mode are a recipe for leaks.
I still prefer the old refrigerants for practicality and imo less of an impact on the environment but... Still have r12 for automotive but used my last r22 in the house unit this year.
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Old 07-29-15, 10:40 AM   #5
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Quote:
Originally Posted by Elcam84 View Post
What Jeff said is exactly what a service call would be. Just close the high side valve and hold the contactor in while watching the low side gauge and when all the refrigerant is back in the condenser close the suction valve and then release the contactor. Rebraze and open the valves back up (after the usual line purging).
I'll give that a try, but why hold the contactor in, is it to bypass a pressure cutoff switch?
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Old 07-29-15, 01:12 PM   #6
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Correct. The switch won't let it go into a vacuum on the low side like you need it to when pumping down a system. In fact walk in freezers have a solenoid that closes the high side at the evaporator at the end of the cooling cycle and the compressor pumps all the refrigerant against it. That way when he system has to cool again it instantly cools instead of having to wait for the liquid to get up to flow and pressure.

The 19 seer ish and up of most brands you can't do this method and you have to use a recovery machine. They also have a small computer you hook up on the super high seer units that has lots of info including telling you if it needs more or less refrigerant. That's the only benefit to the super high seer units.
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Old 08-04-15, 12:16 PM   #7
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Mine is a 13 Seer so I should be able to use your contactor method.
Many thanks I'll let you know how it worked later in the year. They forecast over 100 degrees for at least the next week, so I'm leaving everything well alone
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Old 08-04-15, 03:36 PM   #8
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That's every day weather here in tx. I just hope we don't sit at 115* for weeks like we have the last couple years.

Those goodman units aren't bad either. Best bang for the buck. They were recently bought by daikin which has been trying to get into the us market for years. Some of the other brands that are made by goodman have gotten really cheapened since the buyout though. Flimsy cases etc.
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Old 08-05-15, 01:14 PM   #9
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Agreed about Goodman products. With the AC I also installed one of their variable speed 95% furnaces, and our gas bill dropped by about 40% last winter. My biggest problem now is overcoming the wife's genetic female problem, that is, it can never be the correct temperature, she's either too warm or she's chilled no matter what the thermostat says
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Old 08-06-15, 04:46 PM   #10
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I'm going to use one of their 95% furnaces bit not the variable one. We aren't going to be here much longer so it isn't worth the extra cost and high efficiency units don't increase resale value here. However an oversized ac does as man j figures aren't correct for the weather here. I did the man j and it came up with a 3.5 ton unit. Well man j shows 99* which is below what it should be especially when right now we sit at 104* for around 4 hrs a day and the heat isn't even here yet. Ac will basically run about 20 hrs a day or more and when it gets up to 115* you won't be comfortable. The only way I get ours to cycle at all when it's over 100* is to reduce airflow to parts of the house. The laundry room has no air going to it and the kitchen is always warm but bearable.
Luckily many hvac contractors are now sizing systems for 105* extra and 70* inside. Some will size for 68* as allot of people like it that cool. I prefer 72* which is also what is recommended for commercial buildings as that's where most people are comfortable.



Not sure if I'm going 3.5 or 4 ton yet. Furnace size is typically always oversized here as you need the larger furnace because of the larger ac we need here. The current furnace is an 80% Lennox and the blowers in them are very loud (slow start as well)and use more electricity than other brands. The Rheem I put in my parents house same size is so much quieter pulls less watts and actually moves more air.

Never have liked the idea of having to build a sealed room for the hvac in which you provide a vent to the outside for combustion air. Or it sucking conditioned air out of the house and pulling air through all the small leaks in he walls etc.

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