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Posted By: Niko Portable generator hookup. - 01/15/08 03:47 AM
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.

Posted By: Texas_Ranger Re: Portable generator hookup. - 01/15/08 11:03 AM
Sounds good, but a transfer switch is definitely needed.
Posted By: SteveFehr Re: Portable generator hookup. - 01/15/08 11:48 AM
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?
Posted By: renosteinke Re: Portable generator hookup. - 01/15/08 03:23 PM
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.'
Posted By: JValdes Re: Portable generator hookup. - 01/15/08 05:39 PM
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.
Posted By: noderaser Re: Portable generator hookup. - 01/16/08 04:18 AM
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
Posted By: Niko Re: Portable generator hookup. - 01/16/08 06:30 AM
Thanks for all of your input.

Edward

Posted By: Texas_Ranger Re: Portable generator hookup. - 01/16/08 08:43 AM
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.
Posted By: JValdes Re: Portable generator hookup. - 01/17/08 04:44 PM
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?
Posted By: Ann Brush Re: Portable generator hookup. - 01/17/08 08:15 PM
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.
Posted By: Texas_Ranger Re: Portable generator hookup. - 01/18/08 10:50 AM
"Permanent extension cord" was an attempt to put "flanged inlet + cable + interior receptacle" in short words. It is permanently installed with suitable wiring materials but basically serves the same purpose as an extension cord threaded through a hole in the wall.
Posted By: JValdes Re: Portable generator hookup. - 01/18/08 03:53 PM
Got it Ranger. Sometimes I cannot read between the lines.

Ann, Since I do not plan to read the whole story you posted from Schnieder, could you make your point for us.

Posted By: gfretwell Re: Portable generator hookup. - 01/18/08 06:03 PM
How do you run a "cord" through a hole in a wall and stay legal? 400.8(2)
Posted By: Ann Brush Re: Portable generator hookup. - 01/18/08 09:52 PM
JValdes - the application note explains with great clarity the most frequent code compliant and non-compliant set-ups w.r.t. bonded and floating neutral configurations that involve a 2 or three leg transfer switch. I often see three pole x-fer switches used erroneously because the client believes that neutral MUST be switched.
Posted By: Ann Brush Re: Portable generator hookup. - 01/18/08 09:53 PM
"How do you run a "cord" through a hole in a wall and stay legal? 400.8(2)" - By having the hole double as a door. Thats a joke by the way.
Posted By: JValdes Re: Portable generator hookup. - 01/19/08 03:52 PM
Thanks Ann
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