dig out your books for this one

[t sharp]

is it possable? i told them no, they made me do it anyway.

think modular/or closed construction type of building.

170 feet of #4/3 so under the gooseneck of the trailer hooked to a 3 phase disconect modified
to single phase. this feeder supply is of temp. nature but here's the catch it will supply 480v single phase and or 120v single phase. from the disconnect that has 60a fuses. to a double pole double throw manual transfer switch.this is where it gets interesting. up on the trans sw sends 480v single phase to a 15kw transformer(that produces no nutural) then on to the only 120v panel on board the trailer.no type of protection
other than the 60a fuses. now flip the transfer switch down then you feed straight to the same 120v panel as above.

we electricans in the shop decided to size the wire according to the transformer input and output
the main breaker on the only panel is a 60a
but we are still concerned as to where our nutural
will be dirived from when this system is in 480v opperation. oh yeah they also wanted it all wired in so cable like the other 3. but i forgot
and they got rigid/thhn/liquidtight.art.400.
but then friday i found out that this would be heading to an industrial chemical plant????

i need lots of ammo. will take all the help i can get. thanks

 

[physis]

Re: dig out your books for this one

Ed Mclaren (I hope I spelled his name right) can post schematics. I'd be interested in seeing this in schematic form.

 

[bphgravity]

Re: dig out your books for this one

Originally posted by t sharp:
is it possable? i told them no, they made me do it anyway.

As an electrician, you are ethically bonded to uphold the code standards and safety requirements of any and all electrical installations. I promise you that "they made me do it" does not hold up in a court of law.

170 feet of #4/3 so under the gooseneck of the trailer hooked to a 3 phase disconect modified
to single phase.

What do you mean by "modified"? This sounds like a 110.3(B) vilation.


As far as the rest of the stuff goes, I cant follow it. Can you explain it again or reword it another way. No offense but, it sounds like a real mess!!!

480-volt Single Phase????

 

[jim dungar]

Re: dig out your books for this one

I can't follow this.

Have you really modified the 3 phase disconnect (not allowed), or are you only using 2 of the poles (which is allowed).

Your description says that the manual two-position transfer device switches both 480 and 120V. How can you switch two different voltages to a common feed? Are you using a 4 pole switch?
I would have no problems with a 2 pole set up that fed the 480V directly to the transformer and then switched the panel to the 120V transformer output or to the 120V line.

If you do manage to get the transfer switch working like you described then, it appears the transformer secondary will be connected directly to the panel. This connection will cause the transformer to be back-fed (with a resulting "live" 480V side) when the panel is fed from the 120V source.

You can establish a "neutral" (actually a grounded conductor) on the secondary of your transformer simply by identifing one and then bonding it to the trailer frame and other metallic surfaces. Typically the X2 terminal is chosen for this purpose. This new neutral should also be bonded to the grounding conductor that is part of the supply system regardless of whether it is the 480V or the 120V source.

Summary:
Wire the 480V to the transformer.
Wire the 120V source and the transformer output to the transfer switch line terminals.
Wire the panel to the transfer switch load terminals.
Follow the NEC installation of transformers and seperately derived systems.

 

[frenchelectrican]

Re: dig out your books for this one

c'est un desordre ( it is a mess) anyway i really can't get this crazy layout what you try to describe it . but what jim is saying about using the transfer switch i did make my own drawing but i am little annoying about using the transfer switch at 120 volt source i know you saying about 480 volts going to transformer then go to transfer switch but set the transfer switch little diffrent and put a interlocking device or shunt trip in case if turn on the 480 source then the transfer switch can go ahead go with 120 from transformer if hook up from 120 volts source then should have transfer switch locking device or something prevent unexpecting engerized it by ran backward to transformer but for 3 pole disconnet switch i think it is a wise idea put interlocking device but i am sure few other members can help here too

merci marc

 

[hurk27]

Re: dig out your books for this one

This sounds like a disaster wating to happen.
Guess what would happen if this trailer is hooked up to 480 and someone decides to throw the transfer switch. and there is computers and other expensive office equipment in it. guess whos going to go after your company for repairs or someone getting hurt or even killed?
Someone just posted an artical about an electrican getting 5 years in jail for the death of a 12 year old boy! It is not worth jeperdizing your life to put others in danger. Don't do it!!!

 

[hurk27]

Re: dig out your books for this one

Tell them that the only code compliant way to do this would be to install two diffrent male receptacles on the outside of the trailer one for 480v one for 120 have the 480v feed the transformer then like Jim said have the 120v from transformer with X2 bonded as the neutral feed line 1 on the transfer switch and the 120v receptacle feed line 2 on the transfer switch.
The load from the transfer switch goes to the panel.
Then make up two power cords one for each and this way the two can never get mixed up