Air Conditioning Plumbing Question


Hello,
Have a forced hot air heating system, where the duct work is also used for the house air conditioning. Pretty typical setup: Condenser is outside the house, of course, and has two pipes running to the furnace where the Evaporator section of the A/C is. Furnace blower then bolws air thru the evap. section into the ductwork.
"Plumbing" from the outside Condenser to the Evaporator is run thru the ceiling and walls.
Might be a leak somewhere.
It's not a very long run, but I really don't want to rip away part of the ceiling and wall to try and find.
Thinking of having the A/C guy, or a Plumber just run new tubing on the bottom of the existing ceiling. Tubing would be exposed, but would paint.
Question: good idea or approach ?
Would this new tubing have to be insulated ? How ?
BTW: are leaks in the connecting tubing fairly common after 20 years or so, or is nearly "always" a leak in the compressor or elsewhere in the actual A/C unit ?
Thanks, Bob
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On Sun, 18 Jul 2010 11:36:40 -0400, Bob wrote:

The tubing leak is not common. More likely a leak in the A coil, the connections, or the condensing unit. Any competent tech can find a leak with today's tools of the trade.
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wrote:

Why do you suspect a leak? What are the symptoms?

The are typically three pipes leaving the evap coils.
1. Refrigerant in 2. Refrigerant out 3. Condensation drain
If you're loosing refrigerant pressure, the problem could lie in pipes 1 or 2, but most often leaks arise at the compressor or evap coils, or the couplings to same. These pipes would be copper.
The condensation drain is typically a gravity drain and not under any pressure. Pipe is probably half inch copper if very old, and simple PVC if a newer installation.
You would definitely need to insulate pipe 1 for reasons of efficiency and to prevent horrible condensation problems.
I think you need a better diagnosis of the problem before prescribing any specific solution.
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Not a good idea. Have an AC tech come out and find the leak, if that is the problem. It is not a simple matter of a plumber running new tubing as you would for water. He will have a leak detector and can probably pin-point the leak in a short time. Lines have to be evacuated and charged and must be done by a licensed operator.
It may be something simple like a loose compression fitting and it is repaired and the system re-charged. Figure any house call is going to be $100 minimum though.
Some jobs are best left to a pro. This is one of them.
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AC refrigerant lines are some what different than water lines. For example, refrigerant lines don't use compression fittings. You may have been thinking "flare" fittings. Easy misteak to mayk.
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I guess from what little you said it aint coolin good, have you looked at the interior coil to see if its dirty. If its clean get a pro out to find the leak. Has it ever been recharged is it old.
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Bob wrote:

Hmmm, Why play with unqualified guess work. Call for service. They have leak sniffer. Don't assume anything.
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Leaking freon, or water?
The suction tube (large one) needs to be insulated, as it gets cold. It will condense water and drip.
We need more information.
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On Jul 18, 6:00pm, "Stormin Mormon"

If the tubing in question is part of a 20+ year old system that isn't working right, I'd say it's time to evaluate getting a whole new system. Between Fed tax credit of 30%, various state, utility and or manufacturer rebates, plus savings on energy, it could be better than putting money into an old inefficient unit who;s days are numbered.
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