Attacting two much tranformers to a circuit can make void time you spend on the repairing. How much you save by reparing your water warmer ? Water warmers are mostly shows an unexpected shut down due to the problem of pressure valave and controllor. By changing transformers again and again you can damage the board.
szyhxc, you may even find that a nontraditional approach will provide you with much better functionality, and longevity of some parts. One little known fact is that the multi-speed blower motor, the kind with one lead for each speed, acts like an autotransformer when energized. When you apply 120 volts to the high speed connection you have a lot more than 120 volts at the low speed connection. And intermaediate voltages, all above 120, at the other speed connections. So a transformer connected across the low speed terminals to power a water valve for a humidifier during the heating season will fail within a few minutes when the airconditioning mode is selected and running.
The copper water pipe ground is intended as a safety ground only, not as part of a circuit ground.
The use of multiple transformers in a interconnected circuit is poor workmanship, no excuses. The reason is because of potential problems such as you experienced.
Yes, it is possible to isolate the power in complex systems and make it work with multile transformers, but it is always a poor practice, because it also makes servicing the system more difficult, as you have probably discovered.
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.)
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.
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).
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.
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