-40F electrical installations

[jchayes123]

I occasionally build water delivery systems for areas that are very cold like -40F/-40C. These systems include electrical equipment like disconnects, relays, circuit breakers, etc. Often the electrical systems are installed external to the building. How do you handle these cold environments as it relates to the selection of the electrical components, short of placing them indoors where it is warmer. Which is not always possible.

Thanks for your help

 

[waross]

A small 240 Volt strip heater connected to 120 Volts will keep the panel dry, combat condensation and last for years. No thermostat, on 24/7.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[Mbrooke]

I second the strip heater idea. Best and most simplest option IMO for nearly all applications.

 

[DanEE]

Certainly not enough heat for a -40deg environment, but a known side effect with panels loaded with a considerable compliment of AFCI and/or GFCI type breakers is panel temperature rise from the heat generated by the internal power supplies inside these type breakers.

Dew point condensation in "blade" style backplane panels can lead to corrosion and eventual arcing that burns the blade off the backplane. For this reason in addition to the heater suggested above, would recommend using only panels where the breakers use a bolted connection to the backplane, rather than the blade style backplane relying on breaker contact spring force to maintain an adequate connection.

Have also experienced copper creep leading to loosened connections with certain types of wire lugs found on breakers. If your -40 environment also includes major temperature swings, would expect you might see connections loosen over time.

 

[racookpe1978]

Tension/loosening of the copper lugs clamped by steel/brass bolts over time as temperature swings from ambient -40 deg C/F up to +40 C/+120 F?

Copper resistance heat load increases as well as current flows in summer? The box won't always be outside in the very cold.

 

[cuky2000]

The strategy to deal with severe cold weather may change from equipment to equipment. Relay panels and equipment enclosed in a cabinet could be easily compensated with heat tracing or space heaters as suggested above. Wind barrier could also be helpful.
Transformers could be designed by the manufacturer to keep the oil without getting freeze or consider additional space heaters.
Gas insulated circuit breakers or insulated with SF6 could used heated blankets for dead-tank design. For live tank design or dead- tank without heaters, breakers could work satisfactorily at -50C With a gas mixt of SF6 and Nitrogen or a mixt with SF4. For low temperature cycle test IEC std 56 could be used as reference.

Air disconnect switches should be mechanically design for ice break at operating temperature.

Gas insulated substation could be an option for outdoor application with a combination of heater and gas mixt and pressure increase.

 

[rkvbobby123]

There is a mil Standard on this.DO-160-D thru G I believe. These can be certfied to honor these extreme temperatures. Aircraft group tests their cabling and other electronics for these extreme Temeratures.
Thanks.

 

[unclebob]

SF6 gas will turn liquid around -40 C, don't plan using this.

 

[jchayes123]

Really appreciate all the great feedback. Let me throw a bit of a wrench in the spokes. These systems often need to be certified by a 3rd party agency like CSA or UL. Especially going into Canada. Hence the -40F. We are being told that the components must be rated for -40F. Most parts either don't have a rating this low or no rating at all. Should we be looking at a particular type of component rating?

Again thanks for all the guidance.

 

[cuky2000]

There is good experience in Canada using mixt with SF6 gas for operation without heaters up to -50C.
Check with manitoba Hydro or the local utility in Canada to see if any reference or standard that could be used safe for your application.

 

[tinfoil]

Is this gear going to Ontario in particular?
They have unique Approval processes that you may want to use some 'local expert' to help you.

But we use thermostatically-controlled strip heaters at my utility here in Canada, sometimes more than one stage with different temperature set-points.

An adequate amount of heating for 0°C (32F) may be too little for -40°C/F, and will be way too much for +40°C (104F).
It does get kinda hot in Canada too, sometimes.
In addition, running heaters 24/7/365 wastes power if they are not needed all of the time.

In my metal-clad substation buildings, I have heaters, automatic ventilation louvers, and forced-air cooling (all connected to thermostats) to cover the ambient temperature variations.

 

[jchayes123]

One last wrench in the spokes. Many of these installations are in an explosive area. I would guess putting in strip heaters my use of hermetically sealed components used in a NEMA 4 box. Would guess my best bet is to place all electrical inside my enclosure that is heated. Would also think the electrical disconnect needs to be outdoors however. Specific to the 40 amp disconnect switch are there switched rated this low in temp? How do you do this in Canada?

As always thanks for the help.

 

[mgtrp]

There are disconnect switches rated this low. Our company, located in Northern Canada, uses this type normally -

http://www.schneider-electric.ca/documents/electrical-distribution/en/shared/catalogue/DE2.pdf

- but there are others. Note the low temperature grease option. I can't help you much with the hazardous area aspect, that's not something we need to deal with.

 

[low1]

There is good experience in Canada using mixt with SF6 gas for operation without heaters up to -50C.
Check with manitoba Hydro or the local utility in Canada to see if any reference or standard that could be used safe for your application.

When I was in Apparatus Maintenance in southern Manitoba, we used a 50/50 mix of sf6 and cf4. I'm not sure if that has changed though, I've been in Generation North for a little more than a decade now.

 

[racookpe1978]

Look up the specifications for the Antarctic research domes and building power supplies down there. Gov. contracts -> They ought to be available.