First off, let me say that motors are my personal area of weakness.
Knowing that they are my area of weakness, I’ve tended to try to avoid them.
However, I have a small job now for an existing customer, that I think would be a good job to review motor basics as covered by the CEC.
The customer has a small shop and wants to hook up a compressor.
The compressor is 240V and the nameplate says 15A.
The compressor has a thermally protected motor and an on/ off switch.
The panel feeding power is an old one with plug fuses and is within M of the compressor.
Because the compressor has a switch and is thermally protected, I can just feed it with 12/2 and fuse it between 20A up to a max. of 45A.
Correct?
See 14-510 and 28-200 to 28-204
Now some confirmations please relating to motors.
If the compressor didn’t have a switch, then I would need a disconnect switch. A 20A DPST switch would work for this purpose. Correct?
Sorry, see 14-510 and maybe it does
If the compressor didn’t have a switch but the circuit was fed through a breaker panel, then would the circuit breaker count as the disconnect switch?
Yes per 28-600 to 28-604
If the compressor motor wasn’t thermally protected, what would be the most cost effective method of providing this?
A manual motor switch with integral overloads might do it but be careful about whether it will restart automatically.
Thanks in advance. Sorry for the long post.
Bruce
Bruce we never get better when we avoid particular work because we don't know the answer. Glad to see you are trying.
If it were not for the danger presented by moving parts and the need to up size the over current devices then motors would be easy. BTW the on off switch might serve as a disconnecting means. Good luck and stop letting your current abilities determine your future abilities. These are opportunities to expand your competencies. Time to open section 28 and get comfortable but not too comfortable as that can lead to complacency.
