Disconnect on HV side of Transformer

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kingpb

kingpb

Senior Member
Location
SE USA as far as you can go
Occupation
Engineer, Registered
MV breaker feeding a HV-LV transformer at a parking garage with the LV equipment directly coupled to the transformer.

In my opinion a separate disconnect on the HV side of the transformer as it enters the garage is not required.

Thoughts/Opinions/ Code References.
 
We are the Owner's Engineer and the design engineer who works for contractor was trying to say it was required. Thought I would get a second opinion. It would have been a huge change order.
 
Do you have a long run of cable before you get to the transformer? It should be under concrete until it gets to the transformer. There is no definition for "nearest the point of entrance for the conductors", but in my region, under six feet counts as "nearest".
 
JoeStillman said:
Do you have a long run of cable before you get to the transformer? It should be under concrete until it gets to the transformer. There is no definition for "nearest the point of entrance for the conductors", but in my region, under six feet counts as "nearest".
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The MV feeder is in duct bank, and about 200ft away from MV breaker.
 
I guess this is an installation I would call "Code Minimum". It's really a question of how much you can rely on your personnel to be available if the need to throw the switch should arise.

To be fair, they are probably better qualified for MV operations than the first responders. I was at a construction site yesterday where they told me the fire department immediately started hooking up their hoses to fight a fire in a transformer vault. An electrician interrupted them and they went in with dry chemical extinguishers instead.
 
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