Wiring a furnace to run off an extension cord.

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My gas furnace is hard wired to the main panel. In the event of an extended power outage in winter, I'd like to have the option to run it off my small Honda generator. The only real electrical draw is the small 110V blower motor.
If we were in for an extended outage right now, I would probably just jury-rig it with wire nuts and a sacrificed 12ga extension cord. I'd like something a little more... sophisticated, something that is ready on a moment's notice.
What if I: 1. Cut the existing hard line above the furnace and install a box with an L5-20 twistlock socket. 2. Continue the hard line to the furnace from a second box adjacent to the first. 3. Bug a short piece of 12-3 flexible cord to the hard line in the second box. 4. Terminate the flexible cord with an L5-20 twistlock plug.
Is this kosher with NEC? Would running flex cable from the socket clear to the furnace be a more acceptable solution?
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snipped-for-privacy@rochester.rr.com wrote:

Don't think so.
The suggestion I have seen is put a double pole double throw switch on the H and N wires and switch them to a male socket to which you attach an extension cord when necessary.
--
bud--


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wrote:

Any reason it needs to be that complicated? No need for a switch at all, just put a regular plug on the wires going to the furnace and move it to either a regular receptacle or an extension cords.
--
10 days until the winter solstice celebration

Mark Lloyd
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Use a single outlet, not a duplex. And a nice armored plug. Keep everything short and neat.
Bob
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zxcvbob wrote:

And check local codes. It should be perfectly safe, but code is not always logical, and just because it is safe does not mean it is legal. That naturally doesn't stop a lot of people, but I like to keep things up to code whenever possible, reduces the chance of liability.
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James Sweet wrote:

I think the key is make it such a neat and tidy and well-thought-out installation that the inspector will *want* to pass it. He has great latitude to overlook minor technical violations if they are safe and for a good reason. [I think you could make an argument that cord-and-plug is allowed (barely) by section 400-7(a)(6) "connection of stationary equipment to facilitate their frequent interchange"]
OTOH, if your work is sloppy, it's not going to pass muster even if you do things right (don't ask me how I learned that one.)
Bob
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Mark Lloyd wrote:

A switch and an "inlet" isn't much more complicated.
The NEC limits the use of cords to connect equipment (422.16 is relevant). Cord and plug connection is permitted for maintenance and repair or frequent interchange. (Specifically alloweded are garbage disposers, range hoods and wall mounted ovens.) If boilers and furnaces were allowed to be cord and plug connected you would probably have receptacles provided, and boilers and furnaces would come with cords the HVAC installer would plug-in. (Would there be an electrical inspection? If there was no furnace circuit outlet would someone connect to a general use outlet with an extension cord?) IMHO hard wired is more reliable for an essential function.
As I said in another post "aside from the code, the plan sounds practical and safe."
--
bud--

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A better way is using a flanged inlet such as this: http://www.leviton.com/OA_HTML/ibeCCtpItmDspRte.jsp?sitex021:22372:US&item358 and the double pole double throw switch that Bud suggested: http://www.leviton.com/OA_HTML/ibeCCtpItmDspRte.jsp?sitex021:22372:US&item)67
The flanged inlets are also available in twistlock if you prefer. Mount the flanged inlet in a box right on the furnace and change your existing shut off switch to the double throw.
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most importantly.. do not even THINK of running the generator in the basement or near an open window...or anyplace the CO can get sucked into the furnace.
How will you route the cable in but keep the CO out?
Mark
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wrote:

You make the modification you proposed at the panel - if the panel is in the garage, and run the genny on the driveway or out back of the garage.
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Mark1 wrote:

That part is easy, the generator should be outside, period. Run the cord in under a door, through a window, and use a strip of tape to seal the rest of the gap from drafts, through a pet door, etc.
The furnace won't suck in CO, the air it sucks comes from the return duct.
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Mark1 wrote:

Here's what I do:
1. Remove the spline in order to open up a small (1 inch is adequate) corner of the screen on a window ~12 ft. from the EU2000i generator which sits outside, on a deck, with exhaust pointing into open air.
2. Open the storm window and the inner window to run the two 12 gauge extension cords (one 50 ft., one 75 ft.) from the generator inside.
3. Shut the storm window so it rests on the cords and put foam backer rod under the small remaining open space to "seal" it.
4. Do the same with the inner window.
5. Run the 75 ft. extension cord (with an added 1 ft. 12 gauge 3-outlet extension) upstairs for refrigerator-freezer, radio.
6. Run the 50 ft. extension cord (with an added 1 ft. 12 gauge 3-outlet extension) to the basement for furnace transfer switch, small chest freezer, sump pump.
7. Use 25 ft. 12 gauge extension cords, where necessary (for example, to the furnace transfer switch), to run power from the 3-outlet extensions to whatever I want to power up in the basement. So nothing is farther than 76 ft. of 12 gauge extension cord from the generator.
8. Keep battery-operated CO detector in room with window through which the extension cords from the generator are run. So far ZERO CO level has been measured in 80 hrs (~20 episodes) of running.
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snipped-for-privacy@rochester.rr.com wrote:

I'd tap into the works at the circuit breaker box. No "wiring," just some plugs and boxes.
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snipped-for-privacy@rochester.rr.com wrote:

This is the transfer switch I use with my Honda EU2000i:
http://www.generators.us.com/TF151W-Easy-Tran-TF-Furnace-Transfer-Switch.html
Reliance Controls 15 amp TF151W Easy/Tran TF Furnace Transfer Switch. It's sold by lots of places.
There is also a 20 amp version:
http://www.generators.us.com/TF201W-Easy-Tran-TF-Furnace-Transfer-Switch.html
Reliance Controls 20 amp TF201W Easy/Tran TF Furnace Transfer Switch
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wrote:

*This is a much better solution. You can just wire it into your circuit breaker panel onto the furnace circuit.
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On Dec 12, 9:46am, snipped-for-privacy@rochester.rr.com wrote:

Is that the 1000w honda, without knowing how big the blower is just remember on startup a blower motor surge will pull more, it might be all the unit can take. Have your extension cord so the gen is far away from the house, I got Co in mine being 10 ft away.
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On Fri, 12 Dec 2008 09:51:04 -0800 (PST), ransley

DC blower motor solves that problem - soft start.
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On Fri, 12 Dec 2008 07:46:12 -0800 (PST), snipped-for-privacy@rochester.rr.com wrote:

JUst make sure you have a non-corroded flashlight and batteries, because you're going to be finishing this job when there is no electricity. At least I would be.
I've found that alkaline batteries and even carbon-zinc flashlight batteries last for years when I don't use them, or only use them when I'm actually looking at something. But 2 or 3 years stretches into 5 years pretty easily. And I don't think my flashlight batteries have ever lasted longer than 5 or 6 years.
I keep my batteries, film, long candles, drugs, and paint dispensers** in my fridge. **They have those paint brushes and rollers that suck the paint into the handle. I used to clean every night, but I found I could just put the thing in the refrigerator and it was good the next day, even several days later.
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mm wrote:

I've sure had a lot of alkaline batteries leak, seems worse in the last several years. Have had several Maglites ruined by leaks, if you can get the batteries out the manufacture will usually pay for the damaged item. I'm hoping the eneloop rechargeables I use now will hold up better. Lithium is a good option for emergency flashlights too, they rarely leak.
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About 99+% of gas furnaces in my area , with the exception of manufacuted houses aka mobile homes, are hooked up with a regular cord and receptacle. Of course they are located either in the attic or a closet in the house or garage--basements are VERY rare here. Don't know about code, but that's the way it is done here and has been that way for decades. Larry
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