I just had a my condenser and evaporator coil replaced. The system appears to be cooling fine. But I noticed some water collecting just below the valve where the copper lines connect to the condenser unit outside. When I wiped it up, it felt oily. Is this an indication of a leak?
Yes it can be; oil will also escape with the freon if leaking. You can check for leaks your self by simply spraying some dishsoap on the area in question.
If you just recently as you stated had the unit worked on there can be oil on the valves from removing the gages if the service Tech did not use gages with check valves on the end of his hoses as required by the EPA.
Oily residue on lines can come from a couple of different things. The question I have is on what line did you find this stuff or was it on both? An oily residue on a suction line could be a leak that is drawing compressor oil through a pin hole leak. Why did you have to replace the condensing unit an the evaperator coils? If it was because of a burn out…there could have been compressor oil that leaked out and the tech might have just reused the existing lines. If that is the case…you should have an acid check done to make sure the lines were properly evaporated. The other thing I can think that would cause an oily residue would be residual soldering flux. HVAC lines should be silver soldered which is a little different from the kind of solder that most people are used to seeing in plumbing applications. Residual silver solder flux (if done correctly) usually dries to a hard finish that almost looks like shalac. If the tech was inpatient and didn’t wait for the different phases for the flux to change colors and soldered the joint too soon…I could see that the flux would be a little oily if it got wet from condensation on the lines. There could be a lot of different things oil could come from on an AC compressor. Could even be something as simple as WD 40 from the tech trying to unscrew a valve stem cap (BIG NO NO). Best thing to do is call the company back up and request for a different tech than the one who installed the unit. The EPA has some pretty strict guidelines as to what needs to be done when a system has major service work like that done and if a tech screwed up…he’s not going to admit it most of the time since they can be fined pretty harsh.
Hope I could shed a little light on your question.