How to heat an electrical enclosure with -35 degree ambient temps?!?

[emiller233]

I could use some help...!
I've never had to use a heater on an enclosure, so this is all new territory for me... and this project is going to Russie so we have to deal with -35 degree temperatures. It is a motor starter enclosure with some terminal blocks inside of it. It will be mounted on a hydraulic pump unit.

I tried a few online calculators to even see what ballpark this was even en for requirements, and they're all 'no solutions'. I thought about using a heat exchanger to use some of the heat from the hydraulic oil. Some kind of heating jacket to put over the enclosure. but no reasonable solutions yet, other than put a bunch of electrical heaters inside the enclosure.

Anyone have some good ideas/guidance for me..?

 

[retirede]

We always used Hoffman enclosures and (when necessary) their heaters.
It’s been a few years ( before nVent bought them) but they used to have really good application Engineering support. We’d send them the conditions and they’d size everything.

 

[cpickett]

Will the pump unit be on a skid exposed or in a building? May be worth making a small insulated building to house everything, the heat from the hydraulics would warm the building and reduce the heater requirements for your cabinet. I like the idea of the hydraulic heat exchanger, other than that electric heaters is all I've seen for an electric cabinet. Only time I've had to add them is for condensation prevention when equipment is not running, usually the rejected heat from transformers, drives, etc was enough to keep the cabinet warm. At -35F (or C for that matter) a heat pump won't work, and probably not a good idea to put a fuel (propane, oil, etc) heater in an electrical cabinet.

When you say motor starter, is it just a contactor/overload? Does that even need heating? Other than maybe a small electric heater to prevent condensation?

Try the thermal calculator from SCE, Saginaw Control. It's geared towards enclosures.

 

[petersonra]

insulation is your friend.

 

[Jraef]

insulation is your friend.

LOTs of insulation. I used to do projects in Alaska, same issue. We would over size the box, then use 2" thick rigid PIR* foil faced foam insulation blocks glued to the interior walls. It meant adapting the back panel mounting because the insulation had to be on the back wall too, so it involved some creative sheet metal work. Then you want a fan forced heater mounted to the back pan (not to the foam directly as one of my guys learned the hard way), because a strip heater gets too hot in small areas and melts the foam board.

*PIR = Polyisocyanurate closed cell foam, you need that because you will need fire retardancy for an electrical enclosure. Polyurethane foam can work too, but you have to get the ones that have a fire retardant added to them.

To select the heater wattage, use this (you may have to blow it up to read it).


So assuming you need the starter to be at least 40F, and the ambient is -35F, that is a 75F temperature rise over ambient. So using the 80 degree column, you calculate the total surface area of the box in square ft., then from the left hand column, move across to the 80F column (white because it's insulated) to get your minimum heater wattage. If it is exposed to the wind (probably yes in Russia), then double it.

So let's say it is a 12 x 24 x 10 enclosure. Total surface area is 12 x 24 x 2 (front and back) + 12 x 10 x 2 (top and bottom) + 24 x 10 x 2 (right and left sides) = 576 + 240 + 480 = 1296 sq. in. / 144 = 9 sq. ft. So you need 230W of heat minimum (115 x 2 because of wind)

 

[emiller233]

We always used Hoffman enclosures and (when necessary) their heaters.
It’s been a few years ( before nVent bought them) but they used to have really good application Engineering support. We’d send them the conditions and they’d size everything.

I put a call into them looking for help. they're not a primary vendor for us but i used to use them at my previous company, they are very good with that stuff. hopefully they are this time to!

Will the pump unit be on a skid exposed or in a building? May be worth making a small insulated building to house everything, the heat from the hydraulics would warm the building and reduce the heater requirements for your cabinet. I like the idea of the hydraulic heat exchanger, other than that electric heaters is all I've seen for an electric cabinet. Only time I've had to add them is for condensation prevention when equipment is not running, usually the rejected heat from transformers, drives, etc was enough to keep the cabinet warm. At -35F (or C for that matter) a heat pump won't work, and probably not a good idea to put a fuel (propane, oil, etc) heater in an electrical cabinet.

When you say motor starter, is it just a contactor/overload? Does that even need heating? Other than maybe a small electric heater to prevent condensation?

Try the thermal calculator from SCE, Saginaw Control. It's geared towards enclosures.

It will be exposed, and typically wont be in use, (OFF), so putting an enclosure wouldn't do much of anything. I liked that idea tho.
But yea our mechanical engineers shut me down real fast on the heat exchanger idea anyways haha.
this is only going to have a tiny control transformer in it and maybe a small 24VDC power supply. so they might give me what, about 100Watts heat?
I haven't picked all of the components out yet, but i do have one that has a -5 degree minimum ambient temp. so i at least will have to keep the cabinet at least that warm when it's -35 outside. But something above freezing point would be more desirable....

Humidity seems high for this area to 56-82%. I just got this info, so i didn't include it in the original post unfortunately. I did see that Hoffman has a dehumidifier to put in an enclosure also that just has a tube to a drain on the enclosure floor

it will have a fused disconnect switch (100A), 1 MCP, 2 contactors, 1 control transformer, possibly a 24VDC power supply, and terminal blocks. no pilots devices on the door (yet)

LOTs of insulation. I used to do projects in Alaska, same issue. We would over size the box, then use 2" thick rigid PIR* foil faced foam insulation blocks glued to the interior walls. It meant adapting the back panel mounting because the insulation had to be on the back wall too, so it involved some creative sheet metal work. Then you want a fan forced heater mounted to the back pan (not to the foam directly as one of my guys learned the hard way), because a strip heater gets too hot in small areas and melts the foam board.

*PIR = Polyisocyanurate closed cell foam, you need that because you will need fire retardancy for an electrical enclosure. Polyurethane foam can work too, but you have to get the ones that have a fire retardant added to them.

To select the heater wattage, use this (you may have to blow it up to read it).
View attachment 2554287

So assuming you need the starter to be at least 40F, and the ambient is -35F, that is a 75F temperature rise over ambient. So using the 80 degree column, you calculate the total surface area of the box in square ft., then from the left hand column, move across to the 80F column (white because it's insulated) to get your minimum heater wattage. If it is exposed to the wind (probably yes in Russia), then double it.

So let's say it is a 12 x 24 x 10 enclosure. Total surface area is 12 x 24 x 2 (front and back) + 12 x 10 x 2 (top and bottom) + 24 x 10 x 2 (right and left sides) = 576 + 240 + 480 = 1296 sq. in. / 144 = 9 sq. ft. So you need 230W of heat minimum (115 x 2 because of wind)

this is incredible! i gave them a large enclosure size hoping i could add insulation. but i didn't know if i could or not. Or what type of material it had to be...
i was wondering about the subpanel tho, how did you handle that? just make extensions for the standoff bolts that it normally mounts onto?

I never thought about the wind... glad you threw that out there!

i think i told them a 36x36x8 enclosure to ballpark the size so i should be ok there. I just found a 950W heater on Automation direct that i was hoping would be big enough. could always do multiple i guess...

 

[Jraef]

If you have too much heat, but you have a thermostat, it will just cycle the heater on and off.

 

[Besoeker3]

I'm a bit surprised that its in Russia if it's in degF.

 

[winnie]

I'm a bit surprised that its in Russia if it's in degF.

In Soviet Russia SI convert you!

Seriously though -40 is the point where C and F match, so if the temp scale got lost in translation it makes little difference in this case.

I would think that a thermostat is required in this installation because so much heat is required on the coldest day. You don't want to overheat during the summer.

Though if the humidity is really high then perhaps something self regulating but always on would be best.

Jon

 

[Besoeker3]

In Soviet Russia SI convert you!

Seriously though -40 is the point where C and F match, so if the temp scale got lost in translation it makes little difference in this case.

I would think that a thermostat is required in this installation because so much heat is required on the coldest day. You don't want to overheat during the summer.

Though if the humidity is really high then perhaps something self regulating but always on would be best.

Jon

Yes, I recollect the -40F/-40C conversion from school days - a long time ago..........)
Move in Siberia which is pretty cold and you get average January of −25 °C or −13 °F.
I haven't experienced Siberia but on the Canadian great lakes I had it frozen at about -20 °C/-4 °F
It's cold!

 

[emiller233]

If you have too much heat, but you have a thermostat, it will just cycle the heater on and off.

very true. is it worse to have the heater cycling or not have enough heat tho (theoretically).
haven't actually done the calculation you sent me yet... i'll get a smaller one if needed. that's just what i stuck on there at first (to cover costs)

I'm a bit surprised that its in Russia if it's in degF.

The spec was in C, I just changed it to F. figured I'd make it easier for people to help me
see attached picture (it's dual language)

I would think that a thermostat is required in this installation because so much heat is required on the coldest day. You don't want to overheat during the summer.

Though if the humidity is really high then perhaps something self regulating but always on would be best.

i have a thermostat on the BOM. and the heater i was looking at also had one built onto it. so it will be regulated. i think the lowest setpoint on it was 40 F

I never used a dehumidifier either, but i stuck one of those in there as well. it drains out the bottom of enclosure

 

[GeorgeB]

I've never had to use a heater on an enclosure, so this is all new territory for me... and this project is going to Russie so we have to deal with -35 degree temperatures. It is a motor starter enclosure with some terminal blocks inside of it. It will be mounted on a hydraulic pump unit.

I'm going to ASSUME the reservoir is heated, starting a pump with common industrial or mobile fluids at those temperatures invites pump destruction in short order. If so, can you perhaps be thermally coupled to the reservoir?

The summer days would make this less attractive when the fluid is 55C (131F) or higher.

 

[xformer]

In Soviet Russia SI convert you!

Seriously though -40 is the point where C and F match, so if the temp scale got lost in translation it makes little difference in this case.

I would think that a thermostat is required in this installation because so much heat is required on the coldest day. You don't want to overheat during the summer.

Though if the humidity is really high then perhaps something self regulating but always on would be best.

Jon

I also remember this temperature at which the hot water from a coffee mug thrown into the air will turn to snow and freeze before it hits the ground.

 

[Jraef]

One thing I have experienced and learned from (the hard way)...

Investigate WHERE the power for the heaters is coming from! If it is on-site generators, and they shut them down at times, keep in mind that if you allow the equipment inside of the enclosure to operate BEFORE the heater has a chance to warm it up, there may be problems. You said it is a "starter" so they are fairly robust when it comes to cold, but still, all of the plastic parts can become extremely brittle at -30F and might shatter if the coil is energized. I would put a "freeze-stat" in the control circuit, which is a thermostat that closes on temperature rise above freezing, i.e. the type of thing used to bring on the compressor in a freezer.

 

[emiller233]

I'm going to ASSUME the reservoir is heated, starting a pump with common industrial or mobile fluids at those temperatures invites pump destruction in short order. If so, can you perhaps be thermally coupled to the reservoir?

yea there's a recirc pump on it to that we'll kick on before the main pump

I also remember this temperature at which the hot water from a coffee mug thrown into the air will turn to snow and freeze before it hits the ground.

video, or it didn't happen...!!

One thing I have experienced and learned from (the hard way)...

Investigate WHERE the power for the heaters is coming from! If it is on-site generators, and they shut them down at times, keep in mind that if you allow the equipment inside of the enclosure to operate BEFORE the heater has a chance to warm it up, there may be problems. You said it is a "starter" so they are fairly robust when it comes to cold, but still, all of the plastic parts can become extremely brittle at -30F and might shatter if the coil is energized. I would put a "freeze-stat" in the control circuit, which is a thermostat that closes on temperature rise above freezing, i.e. the type of thing used to bring on the compressor in a freezer.

never even heard of a freeze-stat, but you bet your ass I'm going to put one in there now I have no idea what they're powering it with yet? but that's definitely great insight! i have a thermostat with an output contact on it as well. Maybe i'll use that latching relay and the freeze-stat as a failsafe,

Thanks!

 

[Jraef]

never even heard of a freeze-stat, but you bet your ass I'm going to put one in there now I have no idea what they're powering it with yet? but that's definitely great insight! i have a thermostat with an output contact on it as well. Maybe i'll use that latching relay and the freeze-stat as a failsafe,

Thanks!

You can get freeze-stats at places like RSD (Refrigeration Supply Distributing, they are a nationwide chain) or similar refrigeration component distributors.

 

[kwired]

Will the pump unit be on a skid exposed or in a building? May be worth making a small insulated building to house everything, the heat from the hydraulics would warm the building and reduce the heater requirements for your cabinet. I like the idea of the hydraulic heat exchanger, other than that electric heaters is all I've seen for an electric cabinet. Only time I've had to add them is for condensation prevention when equipment is not running, usually the rejected heat from transformers, drives, etc was enough to keep the cabinet warm. At -35F (or C for that matter) a heat pump won't work, and probably not a good idea to put a fuel (propane, oil, etc) heater in an electrical cabinet.

When you say motor starter, is it just a contactor/overload? Does that even need heating? Other than maybe a small electric heater to prevent condensation?

Try the thermal calculator from SCE, Saginaw Control. It's geared towards enclosures.

That is the million dollar question. It don't take a lot of heat if all that is needed is to prevent condensation.

If something needs to be kept at a certain minimum it gets more complicated, plus you possibly even need to consider cooling abilities if there is a wide enough ambient temp swing.

 

[kwired]

yea there's a recirc pump on it to that we'll kick on before the main pump


video, or it didn't happen...!!



never even heard of a freeze-stat, but you bet your ass I'm going to put one in there now I have no idea what they're powering it with yet? but that's definitely great insight! i have a thermostat with an output contact on it as well. Maybe i'll use that latching relay and the freeze-stat as a failsafe,

Thanks!

Wouldn't need to be anything marketed for that purpose, just a general use thermostat that can operate a contact at the desired temperature and configurable for close on temp fall.... and I guess designed to withstand that sort of temp.

 

[retirede]

That is the million dollar question. It don't take a lot of heat if all that is needed is to prevent condensation.

If something needs to be kept at a certain minimum it gets more complicated, plus you possibly even need to consider cooling abilities if there is a wide enough ambient temp swing.

Condensation is not likely to be an issue at -35F. Air holds very little moisture at that temperature.

 

[Eddie702]

LOL, if it's going to Russia just ship it and let Putin figure it out