Control circuit fuse sizing

[nizak]

How does one go about determining the fuse size required for protecting control circuit wiring?

I have A vendor supplied contactor with a 460V coil. Coil gets its power from the line side of the but has no protection.

Only protection in the entire circuit is a 25 amp breaker 400 ft from the equipment.

Thanks

 

[petersonra]

How does one go about determining the fuse size required for protecting control circuit wiring?

I have A vendor supplied contactor with a 460V coil. Coil gets its power from the line side of the but has no protection.

Only protection in the entire circuit is a 25 amp breaker 400 ft from the equipment.

Thanks

if the wire is #10 than a 25 Amp breaker is sufficient to protect the wiring.

 

[SceneryDriver]

How does one go about determining the fuse size required for protecting control circuit wiring?

I have A vendor supplied contactor with a 460V coil. Coil gets its power from the line side of the but has no protection.

Only protection in the entire circuit is a 25 amp breaker 400 ft from the equipment.

Thanks

What size is the control wiring?


SceneryDriver

 

[nizak]

The control wiring in the assembled enclosure is 16 gauge Cu.
Input power from disconnect for motor is #10thhn.

Push button control and associated wiring for indicator lights etc is all 16

 

[david luchini]

The control wiring in the assembled enclosure is 16 gauge Cu.
Input power from disconnect for motor is #10thhn.

Push button control and associated wiring for indicator lights etc is all 16

That seems like it complies with T430.72, Column B.

 

[ptonsparky]

Compliant or not, we always add fusing to the control circuit wiring. Class CC fuses.

It prevents damage to the PBs and holding contacts when the coil takes a dive.

 

[Jraef]

Compliant or not, we always add fusing to the control circuit wiring. Class CC fuses.

It prevents damage to the PBs and holding contacts when the coil takes a dive.

And to that point, most control circuit devices are going to be rated for 10A continuous, which is why I usually use a 10A CC time delay fuse. That’s not a guarantee though, you really need to double check. Some cheaper stuff is rated for less.

 

[petersonra]

using an OCPD to protect a PB or other device is not a code requirement though.

 

[ptonsparky]

using an OCPD to protect a PB or other device is not a code requirement though.

Sure isn’t and I certainly do make more money replacing those parts.

 

[SceneryDriver]

using an OCPD to protect a PB or other device is not a code requirement though.

"Not all good ideas are code-enforceable." The fuses are cheap insurance, code-required or not. I'd certainly put them in.



SceneryDriver