I have been doing mostly residential HVAC installs this past year. One of the dealers asked me to go look at a precharged AC system that had been installed by the homeowner. I was to be paid under the warranty plan if it was a mfg. defect so I agreed.

The homeowner had installed the A-coil in the RETURN.... sideways.... because it wouldn't fit into the supply plenum. To top that.... he FOLDED the A-coil to "make it fit in the return!" LOL! AND he wired the fan control backwards..... LOL! I told him what was wrong and that I could repair it.... he said "No, he would fix it." So as I was leaving I asked for payment... he had the nerve to suggest that I bill it to warranty! Of course, I collected my pay and thanked him when I left..... hehehehheheh!

With more precharged AC systems becoming available to homeowners I can see this happening more often.