Portable Generator - Commercial

[Npstewart]

Im working on a office going into a existing strip mall with a centralized electric room. It is fairly vital for this office to have power during a power outage, and they originally wanted a back-up generator for all their computers, phone & AC etc. After visiting the site, and speaking with the landlord, they said it is impossible to install a generator on the site, and the municipality would not allow them to do so.

The adjacent tenant discovered this early while the building was being built and had a 240V receptacle added so he could bring in a portable generator, plug it in to that receptacle which I took a picture of (See attached).

If I put a few lights, receptacles and but no AC on a separate sub-panel and fed it with a manual transfer, would I be able to power the transfer switch with the 240V receptacle and the generator? Is a set-up like this legal?

 

[cpinetree]

Where to start?

Where to start?

Not Legal !!
Use a generator inlet to feed the subpanel.

What size generator?
What is your calculated load?

 

[Npstewart]

I am not sure yet on the size of generator required because this is just theoretical at this point.

I saw a Q&A about grounding portable generators in EC&M magazine. It says a portable generator is not required to be grounded if it only supplies the receptacles mounted on the side in accordance with NEC 250.34(A). Which would mean the portable generator would have to be permanently grounded correct?

What did you mean about a "generator inlet"? You mean like a pin & sleeve connection? When you say it isn't legal, do you mean the entire idea is not legal, or the receptacle on the building isn't legal?

 

[cpinetree]

Google is your friend

Google is your friend

The receptacle needs to be an inlet.

Try this: http://www.google.com/#hl=en&sugexp=bvie&cp=15&gs_id=1l&xhr=t&q=generator+inlet&pf=p&sclient=psy&source=hp&pbx=1&oq=generator+inlet&aq=0&aqi=g2g-v3&aql=f&gs_sm=&gs_upl=&bav=on.2,or.r_gc.r_pw.&fp=b1f2da363eba176a&biw=1024&bih=632


Just imagine you have the cord plugged into the generator, the generator running (why you would do it this way I don't know, but I am sure people do) and you try to push the male cord cap into the receptacle mounted on the building, but you slip and are now holding the male end of a cord cap in your hand. Voltage courses through your body instead of the receptacle.

Note excerpt from pg78 of Mike Holt's grounding vs. bonding 2011

A portable or vehicle-mounted generator supplying fixed wiring for a premises must be grounded(connected to the earth) and bonded in accordance with 250.30 for seperately derived systems and 250.35 for nonseperately derived systems.

 

[qcroanoke]

I am not sure yet on the size of generator required because this is just theoretical at this point.

I saw a Q&A about grounding portable generators in EC&M magazine. It says a portable generator is not required to be grounded if it only supplies the receptacles mounted on the side in accordance with NEC 250.34(A). Which would mean the portable generator would have to be permanently grounded correct?

What did you mean about a "generator inlet"? You mean like a pin & sleeve connection? When you say it isn't legal, do you mean the entire idea is not legal, or the receptacle on the building isn't legal?

The inlet needs to be a male plug what you have is a female receptacle.
Think of it this way you would need a cord with male plugs on both ends. And if you plugged into the generator first and it was running the other end that you are holding in your hand would be hot and the pins are exposed. Now try plugging it in without touching it to yourself or something else. Very dangerous!

 

[Npstewart]

So if I did the generator inlet plug, then would it be legal to feed a manual transfer switch that feeds a small sub panel, or would I not be meeting the grounding requirements?

 

[augie47]

Does your theoretical transfer switch also switch the neutral ?
(It will make a difference in grounding)

 

[jumper]

The inlet needs to be a male plug what you have is a female receptacle.
Think of it this way you would need a cord with male plugs on both ends. And if you plugged into the generator first and it was running the other end that you are holding in your hand would be hot and the pins are exposed. Now try plugging it in without touching it to yourself or something else. Very dangerous!

I think you meant a male plug, for the female generator outlet receptacle, and a female plug, for the male inlet receptacle to the panel/transfer switch, on the cord.

A double ended cord with male plugs on both is a suicide cord, which I know is what your are saying is to be avoided.

 

[qcroanoke]

I think you meant a male plug, for the female generator outlet receptacle, and a female plug, for the male inlet receptacle to the panel/transfer switch, on the cord.

A double ended cord with male plugs on both is a suicide cord, which I know is what your are saying is to be avoided.

yeah, that's what I meant.
I was trying to say in order for what he was planning he would need a suicide cord.
Not what he would need to be compliant.