If , in fact, you do not have a reading between A and C, then you have an open fuse somewhere.Hello All,
I hired into a maintenance position last year and have a question in regards to 208v, 3 phase power as I'm not real familiar with such.
Anyhow we have pump, maintained by another company, that we are having issues with and it seems improperly wired to me as I research. BTW, they've sent two technicians out in the last month with the last stating the voltage is to low. He says it needs to be 240v to the pump....
Please confirm the following:
1) 208v 3 phase will show 120v on each leg (phase) but it will only read 208v across two legs; because the phases are never at peak power at the same time.
This seems correct but my Supervisor, who is intimately familiar with the system doesn't think so, and he spoke with an electrician who concluded the power company has a low voltage issue. That doesn't seem the case to me though.
I think they replaced the pump with an improper one or didn't wire it properly. I also noticed something "seemingly" odd with the electrical hookup for the pump.
The pump is protected by a breaker that has three hot wires (A, B, C). It is located in a panel which has various modules (contactors, float switches, timers). Each leg or phase on the breaker has 120v respectfully with A + B = 208 volts, B + C = 208 volts; However A + C = 0 volts.
That would indicate to me that A and C legs are the same phase. I would assume that breaker is meant to have three independent phases coming to it but I cannot say for certain because I don't know about the wiring requirements. I know the heat strip on my AC unit has a switch that separates two hot legs so they are used independently of each other.
2) I don't know if this breaker is serving some similar purpose but I cannot fathom why that would be the case? I cannot see any reason why you would have three legs on a breaker with two of them being the same? Maybe you can enlighten me.
3) How can you get 240v from 208v? Does the motor have to be wired for such or have a transformer of some sort? Otherwise, how can you get 240v as questioned above?
Thanks and Merry Christmas,
you need to trace back from the cabinet to the power source and see what is missing.
With your limited knowledge, this is really something you should not be messing with.