Space heaters in low voltage motor conduit box

[JBUDA54]

I have a client that has requested that the low voltage Motor manufacturer provide bus terminations for 200HP LV Motors instead of using motor leads. Now they are concerned that the motor connections will require a space heater to remove condensation. I have never put space heaters in low voltage motor conduit boxes, but I haven't requested that bus connections be used either. Is this a waste of money or is there some merit to this request.

 

[electricpete]

For LV motors, both items sound excessive to me (bus bar connections and term box space heaters).

I'm not sure what is the connection between bus bar connections that would increase necessity for space heaters..
1 - Insulator which may become damp? I wouldn't think at 480vac that would be a big problem.
2 - Larger term box?
In any case I'd think the motor space heaters do a good job of helping keep the term box warm to avoid condensation with machine shut down.

All of our 460vac motors have no bus connections and no term box space heaters. We have a bunch of them including many outdoors and have had no failures attributable to condensation in term boxes for that configuration that I've heard of. I do remember two that had abrasion in term box which caused a problem.

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(2B)+(2B)' ?

 

[electricpete]

My vote would be do away with the bus connections and make sure the motor space heater is sized adequately.

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(2B)+(2B)' ?

 

[electricpete]

... because I was just remembering we did have one failure where a contributor was moisture in term box but the motor space heater was way undersized. It was a dc 100hp motor with a puny 40w space heater.

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(2B)+(2B)' ?

 

[7anoter4]

I agree with electricpete the motor anti condensation heater could keep the conduit box warm enough.
[Let say for a 200 hp motor a heater of 240 w will be usually good.]
I had a similar problem with a 200 hp motor located far from the MCC and I had to triple the cable in order to overcome the voltage drop and the conduit box was not able to accommodate all these cables. So, instead a junction box outdoor of motor I used a Burndy Mole. See:

http://portal.fciconnect.com/Comergent/fci/documentation/2007 Burndy Underground_4-10-08.pdf

You don't need heaters.
If, however, you have to use the conduit box as a junction box see:

http://www.ingramproducts.com/Panel_Heaters-15W_Anti_condensation_Heater.html

 

[potteryshard]

Bus duct would seem to be much more open to longitudinal air circulation than would cable in conduit... Where that internal air flow and consequent heat transfer can occur, bus duct would seem to be more vulnerable to moisture drop out at the cold end.

If the motor is installed outside, or is attached to something like a cold water pump that would serve as a heat sink, I'd tend to think that heaters in the bus duct and the motor connection box might not be a bad investment.

 

[electricpete]

I didn't take it to mean bus duct. I took it to mean that there were 3 standoff-insulated buses inside an oversized terminal box. We have that configuration on some of our MV motors but no LV motors. Maybe the OP can clarify what is meant by "requested that the low voltage Motor manufacturer provide bus terminations for 200HP LV Motors instead of using motor leads"

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(2B)+(2B)' ?

 

[JBUDA54]

Sorry for the confusion. The owner has had problems with the vibrations of motor T-Lead type connections for larger LV motors so he had me request bus terminations in the motor conduit box. The motor would be cabled to the MCC.

Thanks for everyone responses.