A number of the HVAC installers that I've known never had any formal training at all. One guy in particular was a friend of mine and after only a couple weeks on the job he was made the job site foreman. His crew thought that he was the smartest boss they ever had, and I wouldn't let the guy wire a string a Christmas lights.
When I saw the subject line as "Smartest Ever" I thought it was going to be a political joke about the current POTUS.
I have to agree, I have had HVAC guys come over to repair the AC and am amazed at their lack of electrical skills. I had a blower motor go bad and even told the technician how I checked it and know it is bad. But he insisted in was a control board and the caps. After wasting an hour, then he replaced the motor. Funny thing is he charged me for the wasted hour and the new board and caps! Now I do my own repair unless it is specifically related to a freon charge (or loss of charge).
By the way, being a maintenance manager during a past job, I had to deal with the industrial HVAC guys. They seem to be better trained, but more expensive (and most do not service residential units).
Every one of the Industrial HVAC guys I have met were very knowledgeable. The only debate I ever get into with them is that there is some sort of law (so I was told) about how much fresh air needs to be pumped into a room. My office would go through these crazy thermal cycles in the Winter because the system pulls in fresh, Chicago, Winter air from the outside and then heats everything back up again. The HVAC company cut the fresh air flow down to the minimum, but it was still like opening a window for three minutes, then opening a blast furnace for three, rinse and repeat. I finally got a ladder and cut the flow down myself.
I do not know about training anywhere else, but here in St. Louis many, if not most, of the HVAC guys are in the Sheet Metal Workers Union. They pretty much keep them separated into groups. There are industrial, residential, service and new installation groups. While there is much cross training, there is also specialized field training. After taking the appropriate classes, each apprentice is tested in that field before he/she is licensed to work in it. The penalties within the union for using unqualified help are pretty steep. Even if that help is a card carrying member, but has not passed the required exams.
There is also a bit of a rivalry between the various groups, even if they work for the same contractor, but that would require another posting sometime. Unions may be a pain to deal with, but the good ones do keep their members well trained.
You need an air to air heat exchanger which for industrial means lots of bucks. My sister had problems with one bath next to the laundry. She correctly diagnosed the need for an air to air heat exchanger. Problem solved. In Mn you do not just want to vent to the out side. Heat costs money.
Even if the installer had provided a diagram, can one trust it after knowing what the installer did? Part of the solution here was to essentially trace (physically!) all the wiring to be sure none of it landed in a surprising place (like the copper plumbing).
It really does not matter if the installers were union members and union trained, or if they had just walked in from the last job of selling burgers and fries. Most of the trades folks don't trace out circuits, they follow the manufacturers book, or else they just go by the "standard" installation procedures and connections and many times never think about anything else being present.
In this case the smart move would have been to go to one transformer of adequate rating, which would assure that all of the voltages were correct. Sneak paths do appear. Besides that, using copper plumbing in a hot wtaer system for part of the controls circuits is a very bad choice, since it is not isolated from real ground, except for sometimes.
The copper ground is a given in any plumbing system. Code (and prudence) requires the power box be tied to it. The installers did not intentionally use it as part of the system but crossed the transformer circuits such that transformers were in series instead of parallel. The transformers really need to be isolated from each other which could easilly be done with the right thermostat and proper wiring. Using one wire to connect two transformers from within the attic to the thermostat made this very diificult to do. (The systems are still not isolated, but I may get to it this fall.)
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