Flex entering Transformer?

Status
Not open for further replies.
A

Alfont1120

Member
Location
Dighton, MA
Occupation
Electrical Project Manager/Journeyman Electrician
Does it specify anywhere in the code that you need some type of non-rigid (FMC for example) type of conduit to enter and/or exit a transformer. I've read through the whole transformer article and can't seem to find it. Is it actually a building code issue? I've always used it, but I was curious if there was a minimum length of FMC needed in-between the transformer and EMT feeding it. Thank you
 
Just installed a 75 KVA

Just installed a 75 KVA

Just install a 75KVA xformer and installition instructions said SHOULD be hooked up with flex but didn't say it SHALL be.
 
just the cowboy said:
Just install a 75KVA xformer and installition instructions said SHOULD be hooked up with flex but didn't say it SHALL be.
Click to expand...
Which is perfectly consistent with it being a design recommendation related to vibration.
For example, for a pad mount transformer outdoors with UG feeders, where the vibration will not be going anywhere of consequence, it is normal not to use flex.
 
Flex

Flex

If it is possible to use FMC or the
coated, it definitely cuts down on
vibration. The 60 Hz can be a
cause of damage to the attached
equipment.

When I worked as an electrician, there
was only one project that called for RMC
on everything. And it is still doing fine
after many years of full load. So it really
is probably ok if the transformer pads in the
bottom support are allowed to absorb the
vibration.

I know this doesn't really answer the question
but if installed correctly it makes little difference

(Just my opinion, but the flex is probably the way
to go-if possible)


JR
 
Last edited:
The concern about transformer vibration is due to noise transmission being annoying. There's no mechanical risk from hard-piping transformers.

When I have a choice in it, it's often my preferred method: It makes the install and pull easier when you don't have to play with a flex transition.
 
Status
Not open for further replies.
Top