Transformer mounting...

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L

lady sparks lover

Senior Member
i have more questions...

Q: I would like to mount two transformers in the same room. Would you prefer for them to be a)floor mounted side by side, b)stack one on top of the other, or c) both mounted above the ceiling if conditions are adequate or premissible??

Please give pros and cons of each conditon.... :)

[ October 14, 2003, 10:49 AM: Message edited by: lady sparks lover ]
 
Re: Transformer mounting...

Patty,
If you stack them, you need to take a good look at the temperature issue. The upper one will be getting the hot air from the lower one. If I'm the electrician, I prefer them side by side on the floor for an easy installation, but this takes a lot more floor space. If I'm the building owner, I would want them above the ceiling to free up more profit making floor space.
Don
 
Re: Transformer mounting...

You could stack one above the other if they were the same depth per 110.26 (actually within 6").
It would also depend on the size. some transformers are easily wall mounted, some get pretty heavy and are easier to locate on the floor.
I prefer floor mounted large transformers, in the winter they are nice and toasty warm to sit on while eating lunch.
 
Re: Transformer mounting...

Well, what do you think is the largest size to be mounted above the ceiling...

maybe a 112.5kva or 75kva or larger??

Lady :)
 
Re: Transformer mounting...

Patty, I have a job we did last year with (3) 150's above the ceiling. We had to have a seismic engineer approve the mounting method down to every bolt, this varies with local.


Roger
 
Re: Transformer mounting...

Roger I was going to bring up the seismic issue but I thought it was just a local thing.

Where we would have hung from the ceiling before, we now stack them with uni-strut racks.

The racks also let us comply with 110.26 if the transformers are different depths.
 
Re: Transformer mounting...

Bob, the seismic issue is growing to everywhere it seems. I don't know if it is merited in every situation but it is another requirement we have to consider and learn now.

Roger
 
Re: Transformer mounting...

I think that 450.13(B) limits the installation of transformers above ceilings to 50 kva or less.
Don
 
Re: Transformer mounting...

Don,

50KVA, I know that article limits because of combustible materials, but is there any other reason??

Also, my sup tells me if the length between the transformer and the OCP is over 10' on the primary you need a disconnect on the secondary in addition to or a breaker panel... Huh??

Why have the breaker in the panel, why not just have a disconnect. :)
 
Re: Transformer mounting...

Patty,
I don't know of the reason for 450.13(B). The 10' rule is from 240.21(C)(2). You may be able to go to 25' using 240.21(C)(6). The rules in 240.21 do not require a disconnect for the secondary of the transformer, but rather require overcurrent protection for the secondary conductors. Remember that the lengths in 240.21 are the actual end to end conductor lengths.
Don
 
Re: Transformer mounting...

Don, out of curiosity where is "Hollow Space" formally defined.

The installation in my post above is drop ceiling (atleast 12' from ceiling to structure) with cat walks and platforms where starters, amplifiers, security componets, and assorted mechanical items are installed. Some items are supported on the platforms and others along with our transformers have their on supports.

Regardless of the cat walks and platforms this is still above a ceiling.


Roger
 
Re: Transformer mounting...

Roger,
I don't know where "hollow space" is defined. As I recall the information in the ROPs and ROCs indicated that the space above a ceiling is a "hollow space". All I can say is check with the AHJ before putting them above the ceiling. I assume in your case the AHJ had no objections.
Don
 
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