Heating or a/c loads

[KWH]

I have been on some jobs where there is a rattle/zinging sound from the conduits feeding electric heat,a/c's and once from a air compressor during start up. What would cause this.

 

[jumper]

Large starting inrush current perhaps.

 

[ptonsparky]

Large starting inrush current perhaps.

I agree. The wires rattle around in the conduit esp on startup. Normal.