ECN Forum Forums General Topics of the Trade General Discussion Area Dry Transformer Primary & Secondary Conduits

Tell me if there is any problem with the following methods of running conduit to a dry type transformer.

Transformer is sitting on a concrete floor. The primary and secondary conduits are brought directly up into the bottom of the transformer using the proper box connector.

Same situation but stubbing PVC in to the bottom of the transformer with no connector.

Transformer is sitting on floor or hung. A small section of trough or a properly sized pull box is mounted to the side of the transformer where the conductors enter the transformer via chase nipples. The primary and secondary conduits are directly connected to the trough or pull box with no flex. (I know flex is not required)

We were discussing these methods at work today and I'm not sure if there is anything wrong with any of the above methods or not.

They all seem OK although I'm not crazy about stubbing the PVC into the transformer without a connector.

I've always fed the transformer via flex. Just seemed like the easiest way but it can get expensive.

What do you guys think?

PVC with no connector would violate 300.4(F), if the conductors are 4 AWG or larger.

You could stub up with pvc and put a coupling so that the top is flush with the bottom of the transformer. Then you could use an adapter like the one pictured on page 15. You would not have to lift over threads and risk damaging them. Just shimmy the unit to line up the knock-out that you had made and slide the adapter on. Low profile and allows immediate bending if conductors.
http://www.beckmfg.com/pricesheets/pvc082.pdf

Ryan,

I was always under the impression that bushings were not required with PVC conduit.

Trust me, they are #4 and larger.

I was too. In fact, I couldn't tell you how many times I've installed like this into the bottom of an MDP or MCC.

I hate to say it, but there is no exception for RNC to that rule.

.

[This message has been edited by Ryan_J (edited 05-20-2004).]

OK, I understand the bushing issue but what about the methods that I described?

As long as you get some bushings on the PVC method all of the ways you describe are fine.

I have come up in the bottom, used flex, trough, EMT, etc.

As long as you come in where the instructions allow, usually below the terminals.