Panelboard in -50F Weather

[deb4523]

How much of a concern should it be about breakers functioning correctly in a panelboard in -50F weather?

I have a new project where I was also originally planning on installing the panelboard outside. We have several panelboards installed outdoors on the facility, but I am concerned about the breakers not being rated for temperatures that low. I spoke with an Eaton rep up here in Alaska. He told me I could install outside in this area if I put a heater unit in the panelboard enclosure. He said that the breakers don't open like they should at extremely cold temperatures. We are regularly below -30F throughout the winter and I've seen it drop to below -60F, but only once. We usually require things installed outdoors to be rated to -40F or -50F depending on the importance of it functioning year round.

What are your thoughts/experiences? Should I push to start modifying the panelboards that are currently installed outside for safety's sake or leave them as is. To my knowledge, there hasn't been a problem to date. :blink:

Thanks,
Debbie

 

[Jraef]

How much of a concern should it be about breakers functioning correctly in a panelboard in -50F weather?

I have a new project where I was also originally planning on installing the panelboard outside. We have several panelboards installed outdoors on the facility, but I am concerned about the breakers not being rated for temperatures that low. I spoke with an Eaton rep up here in Alaska. He told me I could install outside in this area if I put a heater unit in the panelboard enclosure. He said that the breakers don't open like they should at extremely cold temperatures. We are regularly below -30F throughout the winter and I've seen it drop to below -60F, but only once. We usually require things installed outdoors to be rated to -40F or -50F depending on the importance of it functioning year round.

What are your thoughts/experiences? Should I push to start modifying the panelboards that are currently installed outside for safety's sake or leave them as is. To my knowledge, there hasn't been a problem to date. :blink:

Thanks,
Debbie

The conventional wisdom is to use panel heaters. Most commercially available panelboards are going to be designed for -10 through 60 deg. C operation, so that's +14 to 140F. Below -10C, the breaker may not trip when it is supposed to, meaning the protection it provides may not be there. You can get special breakers rated for low temperature operation, usually -40C (which is coincidentally also -40F) and for lower than that, a few mfrs offer "ultra-low temperature" rated breakers that go down to -50C (-58F). But these are not going to be for panelboards, they are stand-alone, and they are VERY expensive. Below that and you run into issues with lubrication of the mechanical parts freezing up and the plastic insulators fracturing.

Side note; assuming these are outdoor CIRCUITS fed by the panel and might require GFCI protection, the UL standard for GFCIs is only down to -35C (-31F) so you are pretty much screwed there.

 

[don_resqcapt19]

Even though the breakers can operate at -10C, there is a major change in the tripping point. Squared has a chart that shows a 125 amp breaker will trip at about 175 amps in a -10C ambient.

 

[JFletcher]

Even though the breakers can operate at -10C, there is a major change in the tripping point. Squared has a chart that shows a 125 amp breaker will trip at about 175 amps in a -10C ambient.

:happyyes:

The trip curves get even more seriously skewed at the temperatures the original poster is talking about... At minus 50 degrees, a 20 amp breaker could carry somewhere in the neighborhood of 70 amps indefinitely... Tho number 12 wire in an ambient temperature of -50 would be able to carry roughly the same load without melting.

It seems to me that if practical, locating panels inside would be a better solution than panel heaters which are always drawing current, and subject to failure.

Do any manufacturers make like a double-walled enclosure with insulation between the two for extreme cold or hot applications?

 

[rlundsrud]

:happyyes:

The trip curves get even more seriously skewed at the temperatures the original poster is talking about... At minus 50 degrees, a 20 amp breaker could carry somewhere in the neighborhood of 70 amps indefinitely... Tho number 12 wire in an ambient temperature of -50 would be able to carry roughly the same load without melting.

It seems to me that if practical, locating panels inside would be a better solution than panel heaters which are always drawing current, and subject to failure.

Do any manufacturers make like a double-walled enclosure with insulation between the two for extreme cold or hot applications?

Without something to heat the space up like a panel heater, no matter how well you insulated it will eventually reach whatever the ambient temperature is outside of it.

 

[augie47]

when (if) it does trip, who is going to draw the short straw and go outside to reset it

 

[deb4523]

It is mainly for a new small booth. The wall space on the inside of the booth is quite limited, but I don't think I have an option here. Something will have to get mounted on the ceiling or something so the panel can be installed indoors...

Thanks everyone for the feedback!