Open the Walls?
OK, I would love some advice from you a/c heating gurus. We put in the “state of the art” mitsubishi city multi a/c system with heat coil. The problem, it has a small, very slow leak somewhere in the system that shows up abruptly, like last week, when the heat wouldn’t work, or at the…
OK, I would love some advice from you a/c heating gurus. We put in the “state of the art” mitsubishi city multi a/c system with heat coil. The problem, it has a small, very slow leak somewhere in the system that shows up abruptly, like last week, when the heat wouldn’t work, or at the height of the summer, when the a/c stopped cooling. The a/c guys come and put more refrigerant in, tighten everything, and hope it won’t happen again, but it did. What should we do? Do we really have to open the walls (this will kill us)? Is there any other way to find such a leak. Mitsubishi engineers say the system is working (when its working.) HELP!
Thanks everyone. This is really helpful.
Homey – The valves dont get “tightened” They are usually brazed on. My leak was at the packing of the valve itself. Also, if by chance your valves were installed by flare connections, those can not simply be tightened, a new connection must be made by cutting off an inch or two of pipe and starting with a fresh end.
As I said, at least one, but probably two of mine were deemed defective by my installer (Mitsubishi Trained and Certified). Thats a defect rate very uncharacteristic for Mitsubishi but may suggest a defective batch of valves due to handling. The ones I used were supplied by ABCO and my install was Feb/Mar 09.
Your equipment is comprised of (5) line sets from the outside condenser to the inside air handlers, right?
I am most familiar with Sanyo’s equipment, but assuming it is similar, here goes.
If there is no evidence of leakage at the outide unit and connections, and the system definitely was low on refrigerant, it has to be going somewhere.
The HVAC tech will have to evacuate the entire system, and separately high pressure check each line set. Except at the condenser there is no interconnection, so it should be possible to see which line set won’t hold pressure.
Obviously all simpler explanations should be eliminated, but knowing that the line sets are OK leaves only the condenser and the connections at the condenser.
If one zone won’t hold pressure, you can probably hear the leak while pressureized with nitrogen. No refrigerants into the atmosphere, and no air with moisture to contaminate the line sets.
A days labor by a tech isn’t cheap, but it beats tearing a house apart, not knowing what your looking for.
Bruceatjerseydata.net
They’re filling the system using freon with dye right? Using the leak detecting equipment can be difficult to pinpoint but maybe using a fiber optic camera inserted in 1/2″ holes at unseen places might turn up something.
There are many access panels for plumbing, but you can’t get to every part of the duct, or examine it all that well from them. It is a 5 story house, so we have 1 unit each on 4 floors and two on the fifth floor. But thank you HDL, I will definitely ask about those valves. However, I think that might be what they tightened last time.
Any other ideas?
Thanks
I also installed the City-multi. Before you rip open the walls have the installer check the disconnect valves at the indoor units. This summer I had a similar issue and it turned out that one, and maybe 2 of the 5 valves were defective. Since they were replaced there’s been no problem at all. Since there are no joints in the piping its unlikely to develop a leak unless your drywall guy was very careless. Besides, you’d notice that immediately.
Didn’t you install it with an access panel? Where is it located that you wouldn’t want a panel?