Heater sizing for stainless steel enclosure.

[kamikhan]

Hey guys!

I've just stepped into the field of engineering and am instantly faced with a problem that I'll need your help with:

Our electrical dept. has just bought a transformer that would be placed outside in the open. It has a relay(?) mounted on the outside that is subject to temperatures close to -40C in the winters. In order to maintain the temperature of the relay at around +20C, it has been decided that a stainless steel enclosure of 1m x 1m x 0.6m will be put around the relay on the outside of the transformer. The wall thickness of the enclosure is 1.5mm.

My task is to size a small heater that would enable the temperature inside the enclosure to be maintained at around +20C, to protect the relay.

I have tried to put some numbers together, but none of the results make much sense. My heater sizing appears to be way too big.

Please help me with this problem, as I have now almost given up hope trying to figure it out myself. Any help will be greatly appreciated.

Cheers

 

[DRWeig]

Are you getting about 3000 watts for an answer?

If so, you're pretty close, assuming the enclosure door is gasketed.

1) Is it really necessary to heat to +20C? Most of this stuff can work down to 0C at least, and often to -20C.

2) If you do need to maintain +20C at -40C outdoor, you should insulate the box well.

3) Will it be in the sun? It could get really hot in there too, in summer... Forced air ventilation with a backdraft damper might be needed too.

Let us know what you come up with!

Good on ya,

Goober Dave

 

[IRstuff]

Your mileage may vary. The answer depends greatly on the expect wind conditions, as well as ice/snow buildup.

For a strictly convection problem, with the surface of the box desired to be +20º, the power level can get as high as 5 kW, depending on the design point for wind. This level of power might also be required if the objective is also to maintain an ice-free surface.


TTFN

FAQ731-376

 

[corwil]

Is the relay weather proof by itself?