Flashlights are still handy- but I was glad there was a plug in shoplight right by my panel when I jury rigged mine up last Saturday. Just got power back last night. Felt kinda weird working in the entrance panel box with 120 light from the generator.
Another caution that I might have skimmed over as I've read this thread--- [and why the double pole double throw switch is a good idea. Make damn sure you don't leave any connection back to the grid. Not only will it fry your generator if the power comes back- it creates a dangerous situation for the guys working on the lines.
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.)
The NEC calls for the furnace to be hard wired to the circuit panel. That said, it's physically possible to use a 110 volt plug and socket along the line some where. Wire the furnace to a cord and plug. Plug that into a powered socket. In time of power cut, plug the furnace into your extension cord. Your refrigerator runs for twenty years with a plug and socket. Why not the furnace? Furnace probably draws 5 to 7 amps, much less than the fridge, or window air conditioner.
I wired up my oil burning furnace with an in-line 110 volt plug and socket 9 years ago for Y2K (remember that?). Havn't used it since, but its still there in the rafters of my laundry room. Did our well pump too with a 220 volt plug and socket. Tested them both out with a generator and they both worked great. If nothing else, its good peace of mind. My only mistake was reversing the plug and socket. Be sure you put the plug end on the furnace side and the socket on the line side, otherwise you will have a live plug (with the bare prongs hanging out) if you ever disconnect.
I don't know if my generator (Honda EB3000) would run mine (no need for heat here when Ike hit), but the refrigerator worked fine (drawing about 6A when running the compressor, less than 1A otherwise).
Probably not with NEC but I dont see anything wrong with it. We use a similar NEC approved setup at work to connect a backup-backup generator. Adding a properly sized fused disconnect on the furnace side may make it more kosher.
Furnaces need regular maintenance. All of mine were installed by a professional company, and he installs all furnances with a plug in cord. He's a stickler for detail on code, so i'm sure that cord and plugs are acceptable.
Cord and plug connection may be appropriate when you may have to remove equipment to service it. For example a dishwasher, trash compactor or oven. All are explicitly allowed to have cord and plug connection. You don't remove a furnace for maintenance or repair.
Furnaces have a switch or disconnect installed by the electrician for servicing.
I doubt you will find many inspectors that agree if they are enforcing the NEC.
From NEC 400 - flexible cords and cables:
400.7 Uses Permitted. (A) Uses. Flexible cords and cables shall be used only for the following (6) Connection of utilization equipment to facilitate frequent interchange (7) Prevention of the transmission of noise or vibration (8) Appliances where the fastening means and mechanical connections are specifically designed to permit ready removal for maintenance and repair, and the appliance is intended or identified for flexible cord connection end quote
And:
422.16 Flexible Cords. (A) General. Flexible cord shall be permitted (1) for the connection of appliances to facilitate their frequent interchange or to prevent the transmission of noise or vibration or (2) to facilitate the removal or disconnection of appliances that are fastened in place, where the fastening means and mechanical connections are specifically designed to permit ready removal for maintenance or repair and the appliance is intended or identified for flexible cord connection. end quote
(A furnace is not likely an appliance.)
Where do the quotes allow a furnace to be cord connected? Or cite another NEC section.
In the case of the OP, an inspector may, at their discretion, allow the short cord connector for generator backup. I don?t see where the code allows it. (Disconnecting the furnace with a plug should not break the connection to the system ground.)
That's simple - I want to prevent the noise from the furnace from being transmitted through the solid wire connection.
As long as I use that as my reason for using the flexible cord, it meets the code.
It's mabee stupid - but the way it is written they have no leg to stand on - particularly if you also have a soft cuff on both the cold air return and the hot air duct, for the same reason (which many furnaces DO have)
A few years ago I had to go back on a furnace installation we had done that failed inspection. (I didn't personally install it). It was in a real tight closet and the gas pipe was a couple of inches in front of the furnace on the left side of it. The red tag said it had to be moved to fascilitate removal of the equipment. With a number of fittings I was able to get it far enough over but it was a PITA. Even the customer, a real nice lady, said it was the stupidest thing she had ever heard of. I told her "the guys who installed it must have thought it would it was going to stay in there for 15- 20 years. What dummies Most people just have us replace their furnace every few months when the filter gets dirty" Larry
I've connected lots of furnaces with EMT (which is rigid) with no noise or vibration problems (often Romex in an EMT sleeve). MC/AC is probably common. How do you transmit noise/vibration with MC/AC? I would expect that in addition to saying there is a noise problem, there has to be a problem.
I think an inspector would likely look at cord as a substitute for "fixed wiring", which is not permitted.
What inspector? If it was my house and I had frequent need to run heat with a generator, I'd just go ahead and do it. I'd be sure that it was done with proper material and equipment and safe.
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