AC Evaporator wire Corrosion – Think a Freon Leak Is the Cause?
Corroded wire, huh? Freon itself wouldn’t do that. It would quickly evaporate in your air and be gone. When corrosion’s the problem, it can be a associate different situations. If air flow is for some reason very high, already for a short time, condensation gets blown everywhere in a spray instead of dripping into the drip pan and safely disposing outside by a pipe. however, sometimes the manufacturer of a wire is not very reputable, or accidentally produces a form in which the copper tubing and fins are in contact without any inner of protection between them, so dissimilar metals are in contact, which causes bad rust. Sometimes the screws can be a third different metal, and it compounds the problem.
I visited Johnson Controls, in Wichita, KS, and they told and showed my tour group that figuring out the best alloys to use on all the parts of evaporators and condensers is a pretty competitive thing. Carrier, Trane, HEIL, all of ’em are buying units from each other and trying to reverse-engineer what each other are doing so they can get an edge in producing coils that don’t erode. It’s important stuff.
TXV problems do sometimes happen, and they are expensive. Each one has to exactly match the size of your lineset, size of your coils, air flow (which should be 900 CFM for residential in spite of according to Manual J, but maybe not), and pounds of refrigerant, and kind of refrigerant.
And because of the way furnaces, fan blowers, and evaporators are set up to work, it really is a big pain in the butt to get up in there and change it out. Just physically getting to it, can be frustratingly cramped. Before your technician can already do that, he has to evacuate and recycle the refrigerant in your system. If your evaporator is leaking and corroding, then air and moisture have gotten in. Now that water has mixed with your oil, and produced acid. If it’s a 410A system, the acid can be literally 100x more corrosive than in most other systems. So here’s what all they’re going to be doing if that’s a big issue:
Most people do not know at all that oil is indeed flowing with your refrigerant. Refrigerant passes by the compressor shell, over the gears (whether pistons or a scroll), and over the electrical windings, to cool down the compressor. The refrigerant and oil do mix, and both must cycle by the system within a flexible range of velocities to make sure the oil level inside the compressor is consistent.
Hook up gauges and additional tubes to your condensing unit outside, with a recovery cylinder, a good evacuation machine with hopefully a filter drier in good condition, and a vacuum pump. You’ve got acid, so just removing moisture from the system is not enough. Your refrigerant’s polluted and it’s going to have to be sent back to its manufacturer for disposal, which is pricey. This is a big chunk of the $1,300, because now he has to sell you new freon, too. Oil doesn’t come out of the system during this course of action because it does not evaporate at the pressure and temperature that the freon does.
Once the system is in a vacuum, they’ll disconnect that stuff and set it aside. They’ll use an acetylene torch to unsweat (undo the soldering) the connections holding your evaporator to the lineset. They’ll be able to inspect how bad the acid situation from there. If your linesets need to be replaced, that’s another thing. Right now I don’t think they truly know. The acid problem may not be bad at all if you haven’t lost too much refrigerant. The pressure of the system may nevertheless be enough to keep most moisture out.
If acid is a meaningful problem, they’ll have to inspect the compressor, which method cutting the linesets from it, too. Because of oil, they will not use a torch their, just this little cutting tool, so that’s not expensive or dangerous. It’s basically just a clamp, a roller, and a blade wheel. I am guessing since they didn’t mention compressor substitute, they do not think it will need replacing, but hopefully they look at it anyways, it can’t hurt.
They have to recycle your freon and then put it back in in spite of of whether or not acid is an issue. You can’t vent it into the air because all the fluorine in it destroys a helluva lot of ozone, it’s very flammable and many refrigerants produce nerve gas when it’s burned, and it’s an oxygen displacer. already if it doesn’t poison you, all the oxygen will just be pushed away in a room until just the freon is left, then you can’t breathe.
What may be a really giant pain about your system is that the worse the leak, the longer it takes to pull a vacuum. They already have to use a bigger, more powerful pump. Hopefully while that pump is running, your technician(s) have something else to do to occupy their hands. If you catch ’em just sittin on their butts, call their boss. If they need to let the pump run for like 2 hours or something, they can take off and work on a simpler problem somewhere else in the neighborhood while it’s doing its thing.
While they’re soldering the new evaporator in, they should also be running some nitrogen into the system. They do this because it keeps oxygen, air and water out of the system while it’s open, and consequently out of the solder and torch flame. It ensures a strong joint, and when they remove the nitrogen, it will go quick b/c there’s no moisture to remove.
When it comes time to put freon back into your system, they’ll need the cylinder of new refrigerant, a extent, their gauges, and temperature probes. Your compressor will be running as they put it back in. They should charge it to exactly what your condensing unit says, then making sure the pressures and temperatures are also correct while it runs for at the minimum 10 minutes.