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Old 08-27-15, 07:51 AM   #1
stevehull
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Default GT heat pump - evap coil pinhole leaks

I just got a functioning closed loop GT heat pump for $100. But here's the catch . . .

Leaking gas from somewhere and the HVAC guys think it is in the evaporator coil. Apparently this particular unit has tiny "bubbles" in the coil that are attacked from the inside (that is what I was told). They suggested some kind of liquid that can be put into the system that "plugs" tiny pinhole leaks. Not a great solution (reminds me of using that crud in car radiators . . . ).

The unit is a 2.5 ton, single stage Florida counterflow unit. It was set up for closed loop, so I got the circulation pump as well. A beautiful coaxial coil inside and the scroll compressor works great. I saw it working.

The owner got tired of putting in a couple lbs of R22 every six months and the unit is about 15 years old.

Ideas on plugging leaks? The alternative is to go with a generic coil as the specific OEM replacement from Florida is almost $1000.

TIA.

Steve

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Old 08-27-15, 10:54 AM   #2
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What is the unit configuration, water to water, or water to air, or water to line set? Pics would be awesome.

If the compressor and/or water pump work, you got your money's worth. Everything else that works is a bonus.
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Old 08-27-15, 12:55 PM   #3
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Jeff,

Water source to air with desuperheater for hot water tank.

Steve
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Old 08-27-15, 04:39 PM   #4
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Quote:
Originally Posted by stevehull View Post
Leaking gas from somewhere and the HVAC guys think it is in the evaporator coil. Apparently this particular unit has tiny "bubbles" in the coil that are attacked from the inside (that is what I was told).
That sounds like formicary corrosion. It is a big problem with R410 systems. I've never heard of it on an R22 system. About the time manufacturers switched to higher pressure R410 they also started using thinner wall tubing to increase EER (and profit margin). It didn't work. The HVAC industry is still in plausible denial.

You are right that goop in the coil is not a solution. I suggest finding another coil - if that is indeed the problem. It might be a slow leak around the glass seal on the compressor. I've seen a few of these.
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Old 08-27-15, 06:00 PM   #5
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Quote:
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Ideas on plugging leaks?
Does it have any R22 in it?

If yes, salvage the R22, vacuum it down to a deep vacuum, then fill it with R290, and do the flame test.

If no R22, vacuum it down to a deep vacuum, then fill it with R290, and do the flame test.

Once you know where the leak(s) can be found, use your well-honed brazing skills and braze up the leak(s).

If Xringer can do it, maybe you can too.

Otherwise, call a local HVAC tech to come out and fix it for you.

-AC
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Old 08-27-15, 07:12 PM   #6
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Why not just use an R22 "sniffer" to detect the leak right now? And yes, it has R22 in it right now as I saw it running before it was taken out. I think I can borrow one. Or, I could put in fluorescent dye and look for leaks.

I actually helped with the labor of getting this 200+ lb thing out of the closet . . .

I need to call as the HVAC guys may have used a "sniffer" as they kept talking of pinhole leaks in the evaporator coil.

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Old 08-27-15, 08:19 PM   #7
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With a sniffer, you can recover down to atmosphere or less, recharge with nitrogen or argon, and the small fraction of refrigerant can Still be easily detected. Propane will not reach a high psig reading at room temp, it starts to condense. Same with R22.

The flame test will work, though. If you use BBQ gas, you can also smell it when it leaks out, as long as you leave the compressor shut off. If it circulates much, the filter dryer will catch the stink oil, and it will lose its smell. I still like the soap bubble solutions myself. Spray or glop on some Scooby doo juice and watch for foam. Patience helps a lot.
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Old 08-27-15, 08:32 PM   #8
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Jeff, the unit still has a charge of R22 in it so I don't need to further charge with argon. Or are we talking "past" each other.

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Old 08-27-15, 08:59 PM   #9
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If it is a teeny tiny little leak, a normal charge may not leak enough to detect. If you have a really sensitive sniffer, your luck increases. By stuffing in non-condensible gas, the pressure can be raised so the gas leaks out faster. Once in a while, the seal will fail when the pressure is raised, so having something benign inside is a definite plus. Usually raising the pressure close to the labeled design will reveal the problem.

Also, having non condensing gas in the system will tell you how bad your leak really is. Charge to a target psi, and the gauge pressure will decrease steadily as gas leaks out. With pure Freon inside, the condensed gas will boil off and maintain gauge pressure.

Of course, a good sniffer wand or thick bubble soap solutions will increase your luck. But once you find the source of the leak, then what? The gas has to come out anyway.
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Old 08-28-15, 09:22 AM   #10
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SH,

Do you actually have the tools to do HVAC work?

Tools like:
  • Refrigerant Extracting machine
  • HVAC grade Vacuum pump
  • Micron gauge
  • Nitrogen tank
  • Brazing equipment (& experience)
  • Manifold gauge set
  • etc.

You're going to need to assemble (at least) this set of tools to solve your problem.

Also, if you want to keep this beast in the R22 world, you're gonna need a HVAC ticket to get any more R22.

Do you really intend to do all that?

-AC

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