Question:

• Can you use a 3 pole L9 breaker on a 1 or 2 pole load?
• Can you use a 3 pole L8 breaker on a 1 or 2 pole load?
• Can I use just 2 of 3 poles from L9-10/3/C (2 phases from 3phase lines) 1st and second pole?

Answer:

You can use a 3 pole device on a 1 or 2 pole load or a 2 pole device on a 1 pole load but the following should be noted:

• This will not affect the short circuit tripping functionality of the device.
• This will affect the thermal calibration of the device. The device is calibrated with power on all of the available poles. Not having all the poles powered will result in less heat in the breaker. This lower heat level will result in the pole(s) being used to allow for higher current levels (more heat) before thermally tripping
• A 3 pole device will not have the DC ratings that many of the 1 or 2 pole devices may have. If the 1 or 2 pole version of the 3 pole device is rated for DC, the poles in the 3-phase device can be used on the same voltage DC loads, but will not be labeled with any DC voltages.