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#173629 01/14/08 11:47 PM
Joined: Aug 2006
Posts: 356
Niko Offline OP
Member
I think i am right on this but i need your thoughts as well.

The client has the portable gas powered generator hooked up with an extention cord through the outside wall to a independant duplex receptacle and has marked it generator.
This receptacle is not part of the existing circuitry.

I told the client first the SJTW extension cord has to get protected and second she can not have a permanent connection to the building.

I recommended to have the permanent SJTW cord removed. Install a flanged inlet at the outside of the building and during a black out use a generator cord to power the inlet which will power the inside receptacle.

Am I right on this and what is the NEC section?
I could not find anyhting about a portable unit permanently connected to the building in 445, 702, 705


Thank you for your input.



Be kind to your neighbor, he knows where you live

Joined: Dec 2001
Posts: 2,492
T
Member
Sounds good, but a transfer switch is definitely needed.

Joined: Mar 2005
Posts: 1,213
S
Member
The generator provides its own protection, beit with a breaker or mechanical limiting. The temp cord must be sized to the generator and use an appropriate plug.

Also, I'm a bit confused when you say "independant"- do you mean this receptacle is not connected to the electrical system in the house, it's simply providing a pass-through so they can leave the generator outside yet plug stuff in, inside?

Oooh, that sounds fuzzy NEC-wise, as it would count as a 2nd service to the building which is a no-no. Also, the ground wire must be grounded. Honestly, though, if the cabling is sized to the outlet (20A cabling for a 15A or 20A duplex receptacle), I don't see a problem electrically/fire-wise. I don't like the idea of backfeeding a receptacle, though, as that would leave the generator cord with energized prongs and a potential shock hazard- the exterior outlet should either be a male socket, or a permanant connection. I see no issues with leaving it permanantly connected, though it's probably not advisable to leave a portable generator out in the weather like that.

If the HO is going to this trouble, why not do it right and give them a full-up transfer switch?

Joined: Jan 2005
Posts: 5,316
Cat Servant
Member
I recently had a job where the purpose was to upgrade just such a system. While I give praise that this customer decided to invest in a proper generator, transfer switch, etc .... I could not fault their earlier practices; they had done the best the could.

That is, every time the power went out, they trundled out the portable generator, and manually transferred the cord & plug connections of critical equipment from their 'normal' receptacles to a generator-only connected receptacle. The 'critical' loads were even within the capacity of the little genny!

Now, of course, they have plenty of power. With the auto transfer, they may not even notice when the power goes off. Is the new arrangement better? Sure it is. Was the former arrangement safe? I'd say "yes." .... Just not very 'user friendly.'

Joined: Jun 2007
Posts: 301
J
Member
Texas Ranger,
Automatic transfer switches are not required for portable generators. An inexpensive interlock kit will serve the purpose just fine. The one I will provide a link to is UL approved. However, you can find them for less money.
www.interlockkit.com
It is not advisable to tap into branch circuits. Take the generator power to a breaker in the main or sub panel and use the interlock, or take the power to the transfer switch.

Joined: Mar 2007
Posts: 404
Member
Or, bust out the tin snips and some scrap from an old can. Be sure to grind off/bend the edges for safety's sake. :P

Last edited by noderaser; 01/16/08 12:19 AM.
Joined: Aug 2006
Posts: 356
Niko Offline OP
Member
Thanks for all of your input.

Edward



Be kind to your neighbor, he knows where you live

Joined: Dec 2001
Posts: 2,492
T
Member
Quote
Automatic transfer switches are not required for portable generators. An inexpensive interlock kit will serve the purpose just fine. The one I will provide a link to is UL approved. However, you can find them for less money.

No need for an automatic one for sure, but some kind of interlocking emchanical switch will be required to prevent the generator from backfeeding the grid under all circumstances.

The other method mentioned, basically a permanent extension cord inside the wall, is indeed safe but not very user friendly. It's most definitely cheap though.

Joined: Jun 2007
Posts: 301
J
Member
Thats what the interlock kit does. Prevents backfeeding to the power grid and keeps the generator from blowing to bits when the power is restored.
"basically a permanent extension cord inside the wall" NEC violation. No cords permitted inside walls, for permanent use and not accesible. I assume you mean permitted cable or conduit?

Joined: Dec 2005
Posts: 152
A
Member
This application note from Schneider is very straight forward http://members.rennlist.org/warren/Gen_Panels_Appl_Note_EN.pdf
I often use it to explain errors people make.

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