# School Temp Bldg with transformer



## amcdv (Sep 21, 2012)

hey guys...im purchasing a 2 room temporary shack type of building from a school that has closed down....the side of the building has the breaker box and a transformer attached to it....it looks like the power goes thru the transformer and then to the breaker box....im curious as to why the transformer...i was hoping to just connect the power pole to the breaker box...and flip on the light switch...any ideas....im sure ill have a electrician do the work....but for now im just looking for any unexpected surprises...such as having to re-wire the whole building type of thing...thanks in advance.... amcdv in texas


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## Marcus (May 13, 2012)

http://en.wikipedia.org/wiki/Three-phase_electric_power


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## webeable (Aug 29, 2012)

It is set up to handle POLE power. All you need to do is disconnect the power at breaker box then make sure everything is set for single phase 220.


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## Marcus (May 13, 2012)

webeable said:


> It is set up to handle POLE power.


That was the way I was leaning too, but I wasn't sure. It wouldn't hurt to google the transformer model number and make sure.


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## amcdv (Sep 21, 2012)

thanks guys...ill see if i can find a number on the tranformer box next time im there...amcdv


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## Kenny78 (Jul 12, 2011)

Like said, get the model number or snap a picture of the data plate on the transformer. Most if not all job/temp trailers I have hooked up were 120/240 1ph. Same as houses. It's likely that the service feeding the building was 480 or 240 with no neutral, hence the reason for the xformer.


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## willysman (Nov 3, 2010)

Are you sure it is a transformer and not a meter base? You can have a meter base with no meter mounted in it.


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## amcdv (Sep 21, 2012)

Kenny78 said:


> Like said, get the model number or snap a picture of the data plate on the transformer. Most if not all job/temp trailers I have hooked up were 120/240 1ph. Same as houses. It's likely that the service feeding the building was 480 or 240 with no neutral, hence the reason for the xformer.


i spoke with 1 of the school maintainence guys yesterday...he was explaining that the school district can buy electricity cheaper if they provide transformers on the temp buildings...i guess what kenny78 posted makes sense...the buildings have 16- 110v outlets and 8-220v outlets and flourscent lighting...he suggest just by-pass the transformer and hook up directly to the fuse box...and i should be good to go... amcdv


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## Kenny78 (Jul 12, 2011)

Just as FYI xformers are very expensive to buy new. Though it might be an odd duck, throw it on craigslist to recoup some money. Btw the weight of them is the steel core and the majority of windings are aluminum, so scrap price is very low. Good luck


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## Jimmy24 (Apr 20, 2011)

If you know what the imput voltage is/was and what the output voltage is/was, you can calculate the stepdown ratio. You could use it for other projects. Is it a dry cell transformer? 

Don't know the exact number, but I hung over a thousand pots in a 30 year career with the power company here. Been on ice storms and hurricanes in a lot of places and never saw what you are talking about. What is the KVA rating on it?

Very interesting.

Jimmy


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## Jimmy24 (Apr 20, 2011)

Oh, what are you calling "pole power"? I assume primary voltage correct?

Jimmy


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## LincTex (Apr 1, 2011)

Jimmy24 said:


> Oh, what are you calling "pole power"? I assume primary voltage correct?


God, I sure hope not! I think primary around here is in the 1000's.
I can see 240...even 460 MAX (but unlikely?) at the wall of the building.


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## Tex (Oct 31, 2008)

I think Kenny78 nailed it. Most residential power comes in as 220, which can be split into 110/110 single phase. Commercial sites (including large school buildings) are wired with 3 phase 480 or 460 depending where you are. The building you bought is most likely single phase 220 or 240, which can be split up to feed 110/120V wall outlets. Because the school had 480 3 phase, they needed a transformer to tap into 2 legs of the 480 and step it down to a usable 240 or 220. I suspect you will bypass the transformer and recycle (reuse) or trash it. If you bypass it, make sure to completely disconnect the XFMR, otherwise it will put out 480 on it's input side and be a safety issue.


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## Jimmy24 (Apr 20, 2011)

Hmmmm never saw or had a school with 480. All schools I've had dealings with, are 120/240 delta or as most are now a days 120/208. I still don't see the reason for a transformer. You want single phase 120/240, you just have the utility company use the two lighting legs and the neutral and you’re in business. Done it many times. No need for a transformer. Now if the building was being served from a bank of transformers that fed a large well, it might have a corner ground 480. I that case a transformer would be needed. 

I do realize that this may be some old oddball type of setup. But I would say it would be the exception rather than the rule.

And LincTex, that's why I was asking. There are three types of voltage out there on the wires. Transmission, primary and secondary. Poles have all three types of voltage.

And yes you’re correct about in the thousands. The most common primary voltages, phase to phase are 4 KV, 12 KV, 14 KV and 23 KV. 

Jimmy


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## LincTex (Apr 1, 2011)

Tex said:


> Commercial sites (including large school buildings) are wired with 3 phase ... I suspect you will bypass the transformer and recycle (reuse) or trash it. If you bypass it, make sure to completely disconnect the XFMR, otherwise it will put out 480 on it's input side and be a safety issue.


This sounds like the most plausible scenario.


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## Kenny78 (Jul 12, 2011)

I am a commercial electrician, every school I have been to that's been built since the 50's has 480 v 3 phase as the primary source coming from the power company. It will get broken down as needed in the school or utilize 480 for anything of size,ac electric heat lighting boilers etc.

Btw I hate corner ground. People don't understand it, some vfds don't wanna run and I have argued with inspectors about grounding. Better than 240 high leg ex: my new water fountain quit; that's because you we're running a 120. Appliance on ~208. The empty breaker spaces on high leg is like a flame to moths


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