This question comes from Don J. Gilbert. "Can I use a 2.5 to 3 ton MrCool evaporator coil with an older 2 ton Goodman heat pump if I changed the piston?" That's a good question. A good technician can make different brand manufacturing equipment work with other brands. They can take older units and make them work with newer units. A good technician can do a lot of things. I don't really know from your question how old your Goodman unit is, so the answer is "maybe". There are, however, a few reasons you might not want to do it. The first reason is that you might be voiding the warranty. Probably no manufacturer is going to let the warranty carry over if you mismatch equipment. Even if the technician could get the evaporator coil to work with the Goodman unit, that's going to void the warranty on the MrCool and the Goodman unit if it's still under warranty. The next problem you may run into is that there won't be an AHRI listing for your combination. AHRI is the industry entity that does all the efficiency standards. So, if you're trying to get incentives or rebates based off of an efficiency rating, you will have no proof of efficiency from your units. So, you wouldn't get the incentives. But, if you don't care about that, then maybe it could work for you. Have more questions? Just ask them in the comments below or on Facebook or on Twitter.