[SLO-BOB]

Definitely not an EE question. Any good electrician can figure this out.

The heating elements should be connected in parallel to a voltage source. Therefore, whatever you did to the last element would have no influence on the other two.....probably. There may be some interlocks, but I seriously doubt it.

You say that the heaters each have 120 v going to them but no heat. You also say that 230v is going to the contactor and then to the heaters. So it sounds like the heating elements require 230 volts to work, correct? I also assume that there are two leads going to two connections on the heating element correct? If so, you need to measure the voltage across those two leads and not to ground. You should have 230 volts if I'm understanding your scenario.

The boxes should have nothing to do with the return path.

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