3 Phase breaker

[jim123]

I have a old motor starter feed from a 3 phase 208v, 70 amp breaker. I would like to use it for 2 single phase 208v,16 amp heaters. Using A/B for one heater and B/C for the other. Will the unbalance of these loads cause the 70 amp to trip. Thanks

 

[ptonsparky]

Breakers don’t trip on imbalanced loads, barring one isn’t 150 and the other two are 10. That is an overcurrent.

Newer motor starter overloads relays may have an imbalance option or phase loss detection.

 

[JFletcher]

I dont think you can use a 70A breaker to protect a 16A heater load unless the wires are sized for 70A. There's also the chance the breaker is not rated for more than one wire per lug (your B phase will have 2 conductors with what you propose).

 

[growler]

I dont think you can use a 70A breaker to protect a 16A heater load unless the wires are sized for 70A. There's also the chance the breaker is not rated for more than one wire per lug (your B phase will have 2 conductors with what you propose).

I would probably use the conductors (existing) to set up a little single phase sub panel and feed the heaters from that. The wires are big enough so the third conductor could be remarked as a neutral.

 

[JFletcher]

I would probably use the conductors (existing) to set up a little single phase sub panel and feed the heaters from that. The wires are big enough so the third conductor could be remarked as a neutral.

Good idea. I was taking the OP's post (probably too) literally, with no mention of a sub-panel.