Working Space

[Glenn Becnel]

We are in the starting phase (fondations will be poured mid-November) of a new control building in our refinery. The proposed location of the building's 500kva transformer (along with a 500kw generator) will be set on a dedicated area outside of the building. This area is at the same elevation as the fondation of the control building. However, the access to the transformer's termination chamber (4160v/480v)is 18" from the outside edge of this slab. This area will have a handrail around the edge due to grade at this location will be 3 feet 6 inches lower than the top of the building floor & the bottom of the transformer.
Per NEC's Article 110.26, the mininum working space for equipment (depending on the voltage) is 30" wide or the width of the equipment with a mininum depth in front of the equipment of 36". Engineering is proposing to delete the handrail in the area of the termination compartment to comply with 110.26 & the 90 degree rule for electrical equipment doors (the doors open toward the handrail).
Engineering's position is, removal of the handrail will comply with the NEC's requirements. The equipment is low maintenance & the transformer can be serviced with scaffold erection each time.
Is there anything in the NEC requiring this maintenance work space to be 30" X 36" at the same elevation?

 

[petersonra]

Re: Working Space

I don't recall that there is any requirement that the working space have specific access requirements. otherwise you could not put transformers on walls.

OTOH, there are more stringent requirements for equipment over 600V and since I rarely work with voltages over 600V I am not real conversant with them.

I do seem to recall there is a requirement that access be limited to authroized personnel. I would think you would need a fence around the whole thing to comply with such a requirement.

[ October 28, 2004, 02:28 PM: Message edited by: petersonra ]

 

[russ]

Re: Working Space

I think article 450.13 would require a transformer larger than 600 volts, to be readily accessible. There are specific rules for 600 volt and less, to be installed where they are not readily accessible, but no exceptions mentioned for more than 600 volts.