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#201522 - 06/06/11 12:55 PM Another HO generator question.  
gfretwell  Offline


Member
Joined: Jul 2004
Posts: 9,069
Estero,Fl,usa
As I said earlier I am being inundated with generator questions here lately.

Here is an interesting one. Can a snap switch be "transfer equipment" as in, can they have a box on a piece of equipment with a double throw switch that switches the load between the generator, via an inlet for a temporary cord and the utility? I don't see a safety issue but there might be a code/listing issue.

I already said no on simply pig tailing out a cord and cap from the box.

Is this switch still a disconnect? (with no cord plugged in)


Greg Fretwell

2017 / 2014 NEC & Related Books and Study Guides

#201524 - 06/06/11 01:23 PM Re: Another HO generator question. [Re: gfretwell]  
LarryC  Offline
Member
Joined: Jul 2004
Posts: 783
Winchester, NH, US
Greg,

Are you talking about a 3 position disconnect that is set up for Utility, OFF, and Generator? I have seen that setup in a former dairy barn.


#201527 - 06/06/11 02:47 PM Re: Another HO generator question. [Re: gfretwell]  
gfretwell  Offline


Member
Joined: Jul 2004
Posts: 9,069
Estero,Fl,usa
Nope they are asking about using a box with a 5-15 inlet connector and a SPDT snap switch to switch a 120v line.
The generator is set up as an SDS (neutral bonded)

Single family dwelling if that matters.

They assume most of the loads will be C&P connected. This is for a well pump but I did have the same question asked from someone up in the frozen north who wanted to do the same thing with a (gas) furnace blower.

I suppose if you used a center off snap switch it solves the disconnect problem but is it legally "transfer equipment"


Greg Fretwell

#201531 - 06/06/11 08:41 PM Re: Another HO generator question. [Re: gfretwell]  
Tom  Offline
Member
Joined: Jan 2001
Posts: 1,044
Shinnston, WV USA
Greg,

Snap switches are not listed by UL for the use that you describe. See SNAP SWITCHES (WJQR) in your White Book. "Snap switches have not been investigated for switching a load between two alternate sources of supply."

Tom



Few things are harder to put up with than the annoyance of a good example.

#201532 - 06/06/11 09:38 PM Re: Another HO generator question. [Re: gfretwell]  
gfretwell  Offline


Member
Joined: Jul 2004
Posts: 9,069
Estero,Fl,usa
Thanks Tom. That is the answer I needed.
I am still having trouble explaining why back feeding the dryer outlet is not the way to go so this is an up hill climb.

It is not surprising that more people get killed and injured after a storm than in it.


Greg Fretwell

#201534 - 06/07/11 12:20 AM Re: Another HO generator question. [Re: gfretwell]  
LarryC  Offline
Member
Joined: Jul 2004
Posts: 783
Winchester, NH, US
How about a suitably rated DPDT relay that is powered by the back up power source? PoCo power thru the NC contacts and back up power thru the NO contacts.


#201536 - 06/07/11 02:23 AM Re: Another HO generator question. [Re: gfretwell]  
gfretwell  Offline


Member
Joined: Jul 2004
Posts: 9,069
Estero,Fl,usa
That was another idea that floated around the beer soaked brain storming session.

You still end up with how the relay in question was listed.




Greg Fretwell

#201537 - 06/07/11 02:56 AM Re: Another HO generator question. [Re: gfretwell]  
gfretwell  Offline


Member
Joined: Jul 2004
Posts: 9,069
Estero,Fl,usa
I found a likely suspect for the relay but I am not sure where to find the listing data for these approval numbers

UL E22575; CSA LR15734

There is a Russian site that pops on a google but I am not really interested in downloading anything from Russia.


Greg Fretwell

#201541 - 06/07/11 10:35 AM Re: Another HO generator question. [Re: gfretwell]  
Tom  Offline
Member
Joined: Jan 2001
Posts: 1,044
Shinnston, WV USA
Greg,

I, too, dealt with these questions two winters ago when there were widespread power outages & downed service entrances. I went out to do service inspections where the generator was hooked up to the new service & running. I advised these folks that our local POCO had the right to refuse service or disconnect the service, without notice, for improperly connected generators. This generally produced the desired result of them disconnecting the generator



The explanation to the wannabe electrician is that proper transfer equipment removes human error from the process. It seems that every hurricane season, I hear of at least one lineman killed by a generator that has been incorrectly connected (via the dryer outlet or other means) and someone forgetting to turn off the main breaker.

You might stress that intelligent people do idiotic things during an emergency, such as firing up the generator before inserting the plug in the receptacle. Also, the plug could be yanked out accidently or by a child.

Perhaps a proposal for the 2014 NEC should include mandatory jail time for anyone proposing this type of installation. :-')


Few things are harder to put up with than the annoyance of a good example.

#201563 - 06/09/11 09:41 PM Re: Another HO generator question. [Re: gfretwell]  
gfretwell  Offline


Member
Joined: Jul 2004
Posts: 9,069
Estero,Fl,usa
I am still not sure what my neighbors are going to do. I think I have them thinking the right way. The snap switch/relay guy is still hanging on but at least he is not back feeding the dryer plug and trying to remember to turn off the main. The solution is elegant, if not totally legal. The only questionable thing is the listing of the relay he chooses. Since we shot down the snap switch idea, he is looking at a motor rated, 30a DPDT Potter Brumfield unit.

It turns out I will end up with a generator out of this whole mess when the dust settles. One of the guys is upgrading from a 5500w Briggs machine and he made me an offer I can't refuse. I am converting it to propane.

I am taking the easy way out with my transfer problem. My main panel is a natural for the main breaker interlock kit and I have always had a generator in the back of my mind so all of my critical circuits are grouped. I can turn off all but 6 breakers and have everything I need covered. I will still need to do some load management but I think I will survive.
My heavy hitters are still my well and house pumps.


Greg Fretwell

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