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When power is out, how do you hook the furnace to the generator?

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Dick in Wisconsin

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If the power goes out and you don't have a whole house cut over switch on the main panel, how do you get power to the gas furnace?

Open up the conduct box on the furnace, put a plug on wires going into the furnace, and plug the plug into an extension cord?

I can see when the power comes back on to leave the plug in place, put an outlet in the box that is fed from the furnace circuit, and put the plug into that outlet. The one can easily switch from main line feed to generator and back by simply moving the plug.

How do you guys do this?
 
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oilslick

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I have a plug on my furnace and normally it is plugged into an outlet but when no power I switch it to a drop cord.
 
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ddawg16

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Depends.....gas or electric? If electric...I would find another way to heat the house.

Gas....easy....you should have a bypass switch at your load center. On bypass, your disconnected from your main and your generator is tied to all of your home wireing....hence, your furnace is ready to go. The only thing the generator is really running is the fan....not that much of a draw.
 
OP
D

Dick in Wisconsin

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ddawg16 said:
Gas....easy....you should have a bypass switch at your load center. On bypass, your disconnected from your main and your generator is tied to all of your home wireing....hence, your furnace is ready to go. The only thing the generator is really running is the fan....not that much of a draw.
Click to expand...

Gas, no bypass switch ... yet. Asking what to do if you don't have a bypass switch set up and are running extension and drop cords.
 
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SeattleKent

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My gas furnace is hardwired to the panel. I asked an electrician about changing it to a plug into a socket. Turns out that is against the electrical code. Not sure why.
 
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ersatzs2

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Mercer County, New Jersey
Yes it is against code, but what I did was wire an extension cord with a male end into the on/off switch of the furnace. On the 'switched' pole, I wired it to the 'on' side of the switch. That way, when the switch is in the 'off' position, there is no way if the power suddnely comes back on that the motor will be seeing power from both generator and the panel.
The reason it is against code is that once the power does return, and you throw the switch to the 'on' position, you now have an extension cord with two exposed hot prongs (well one hot prong) My solution was to plug the male end into a female cord receptacle. Then I used a label printer to print some instructions so if I'm not around, someone else knows what to do. The solution worked fine all during the blackout but it isn't something an electrician will ever do for you.
 
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Charles (in GA)

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SeattleKent said:
My gas furnace is hardwired to the panel. I asked an electrician about changing it to a plug into a socket. Turns out that is against the electrical code. Not sure why.
Click to expand...

Because NEC 400.8 says what Flex Cord cannot be used for and "As a substitute for the fixed wiring of a structure" is one of the reasons.

You could install a Double pole, double throw switch rated for the current involved (usually not a lot if just a gas furnace with blower and control circuits) and route the hot and neutral of the house thru it to the furnace and have a suitable pigtail cord from the box connected to the other side of the switch. This way, throwing the switch takes the POCO/house wiring off the furnace and allows the generator to supply the furnace, throwing it the other way removes the genny and puts the house back to supplying the furnace. No way the two power sources can both be applied at once and has the house wiring properly hardwired to the furnace (thru the switch).

Charles
 
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malibu101

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Charles (in GA) said:
Because NEC 400.8 says what Flex Cord cannot be used for and "As a substitute for the fixed wiring of a structure" is one of the reasons.

You could install a Double pole, double throw switch rated for the current involved (usually not a lot if just a gas furnace with blower and control circuits) and route the hot and neutral of the house thru it to the furnace and have a suitable pigtail cord from the box connected to the other side of the switch. This way, throwing the switch takes the POCO/house wiring off the furnace and allows the generator to supply the furnace, throwing it the other way removes the genny and puts the house back to supplying the furnace. No way the two power sources can both be applied at once and has the house wiring properly hardwired to the furnace (thru the switch).

Charles
Click to expand...
What you described is almost exactly what my mom and dad have to power their furnace with a generator.
Same switch setup and it has a center off position, but, instead of a cord dangling out they have an inlet wired in and placed by the cellar window.
An inlet is the exact opposite of an outlet. ;) :lol_hitti

Just run a cord from the generator to the inlet, throw the switch to the other side and the house goes warm. Safely.
Power comes back, throw the switch back agin, unplug the cord. Simple and safe.

Although VERY simple and VERY safe for very cheap- Does this setup violate any NEC codes?
 
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malibu101

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Charles (in GA)

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Wow, kinda pricey, but that would do the job. Never seen it in a HD before but they have lots of items that don't make it to the stores, and not all stores have the same stuff. Was in one today about 70 miles away from the house, and it had quite a few items I don't find in the store 15 mi from the house. Different store "buyers", which are the people in cubicles responsible for what each store stocks. Each store has several "buyers" who only work one or two stores.

A 20 amp DPDT switch is about $50 (I bought three of them from Fruitridgetools.com last year) (and you need the DP to transfer both the neutral and the hot of the 120v) and a decent cord and plug or the flanged, recessed inlet plug like the Reliance box uses, is another $20, then add a box to mount all of this in, faceplate, etc, you are not far from the price of the Reliance box.

Code issue with the homebrew one?,I don't know of any, but I'm not a professional electrician either. (not that they know the code any better.... many don't)

Charles
 
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justsam

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lametec

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The NEC article 422.16 says:

NEC 422.16 Flexible Cords said:
(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.
Click to expand...

So unless you have a furnace that's designed in such a way that it's meant to be removed for maint. or repair, it doesn't meet the requirements of the code.
 
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MrMark

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I think all the CA furnaces I have seen must be under #2 above. We just had one installed and it has a cord and plug. The tracts I have seen are built with a receptical for this purpose
 
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HouseDadLife

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Oct 20, 2020
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Location
Manitoba
I recently got tired of having my power drop every winter. I know I'm late to the party but maybe my video can help someone else come up with a solution for their furnace. I hooked up an old APC battery backup with some new automotive batteries. I figure it should give me 3 to 4 hours of continuous heat, and something that switches itself when I'm not at home for the family.

Sorry guys, can't post the link, I'm new. hxxps://youtu.be/ESiBomY1h0o

Good luck with your projects.
 
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Zmann

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Almost 8 years late lol
ps that link is no good even dropping it into a browser
 
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LS6 Tommy

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Northern NJ
oilslick said:
I have a plug on my furnace and normally it is plugged into an outlet but when no power I switch it to a drop cord.
Click to expand...

**** in Wisconsin said:
That is what I figured.
Click to expand...

SeattleKent said:
My gas furnace is hardwired to the panel. I asked an electrician about changing it to a plug into a socket. Turns out that is against the electrical code. Not sure why.
Click to expand...

NEC doesn't allow cords on permanent appliances and equipment.


EDIT. As usual, I posted before reading the entire thread. Can't delete anymore.

Tommy
 
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Spareparts

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Lansing Ks.
NEC has not been in my basement, mine is plugged into a dedicated plug and when needed it gets pluged into my generator.
 
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Denwood

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Thunder Bay, Ontario, Canada
Just a heads up that if you have a newer high efficiency furnace with electronic control, your generator will likely not run it. Mine does not like our generator, but is quite happy being fed by the new 120v inverter generator.
 
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theoldwizard1

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SE MI
Extension cord and

41XkFYfnCkL._AC_.jpg


Reliance Control TF151W Generator-to-Furnace Transfer Switch
 
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evh

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Nov 20, 2018
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Midwest
Here is my solution. I did this at my previous house and will do it it in the next few weeks at my new home. See the attached two pictures. Photo A shows what I bet most of us have on our furnaces. The standard on/off switch with a fuse tied into it. Photo B shows what I changed. You can replace the on/off fuse setup with a fused plug. Cost is roughly $11. In photo B you see the plug coming out of the side of the fused plug. That is wired directly to the furnace. None of the wires on the plug are connected to anything inside the fused plug. They just happen to run through it. So easy to use. When I want to hook it to the generator, simply unplug it and plug the generator extension cord into it. When done, plug it back into the fused outlet. I was a little bummed to see earlier in this thread someone said this was against code. O well, it works and is mistake proof.
 

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jtsboss

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ohio
I use a standard outlet that is on my deck. Its on the same side of the box my furnace is on. Shut down the main and back feed into the house. When I see the neighbors lights on I shut down the gen and go flip the main back on. Simple. Run the fridge and freezer the same way.
 
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Jackfre

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N CA
homebuilt burner said:
My intention is, when needed I will cut the end off of an extension cord and wire my furnace to the generator.
Click to expand...

Yes, they are called a "suicide cord". When using them as I did last year, prior to getting my proper generator installed I made up a suicide cord from the generator to the 50 amp plug I run my welding machine off and backfed the shop and house.
THE ESSENTIAL STEP IN DOING THIS IS TO KILL THE MAIN BREAKER AT THE PANEL FIRST SO YOU DO NOT KILL A LINEMAN ON A BACKFEED.
Yes it is illegal, but it falls in the any port in a storm category.
 
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nadogail

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Coronado, CA
Jackfre said:
Yes, they are called a "suicide cord". When using them as I did last year, prior to getting my proper generator installed I made up a suicide cord from the generator to the 50 amp plug I run my welding machine off and backfed the shop and house.
THE ESSENTIAL STEP IN DOING THIS IS TO KILL THE MAIN BREAKER AT THE PANEL FIRST SO YOU DO NOT KILL A LINEMAN ON A BACKFEED.
Yes it is illegal, but it falls in the any port in a storm category.
Click to expand...

If you run an extension cord directly from the generator to the location of the furnace, and plug the furnace into the extension cord, the furnace will then be on a dedicated power supply and there will not need to be an interconnection between your generator and the grid.

No interconnection prevents your back feeding the grid.
 
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Skiff Builder

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Southern NJ Coast
I have a 5 yr old Nat Gas , Baxi Luna 3 Combi boiler and DHW- factory made with a cord which goes to a 15 amp outlet. Inspected yes, legal - I don't know or really care.
 
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HouseDadLife

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Manitoba
You know, I've been thinking more about this whole legal ****. I'm not an electrician, so I have to ask the question what's unsafe about the plug idea? If it must be hard wired, I could always put the guts of the APC in a metal enclosure box, mount everything and wire it all up.

For the generator people, wouldn't a relay switched by the hot wire from the other phase? Would work for 110v, not sure what to do to isolate flow from a 220v so there is no backfeeding.
 
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Jackfre

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N CA
Yes, Nadogal, if it is a simple line cord to an isolated appliance there is no need to worry about backfeed as that appliance is not connected to the system. HDL, to isolate the power you go out to your main electrical panel and turn your 100 or 200 amp service off.
We cope with the PSPS, Public Safety Power Shutdown, our new acronym, by PG&E. They shut down the power to most of N CA at 3pm Sunday and expect to bring it back on late this PM. High winds, up to 90mph over in Calistoga, and 5 mos without a drop of rain and a utility which took good care of the stockholders and poor care of the infrastructure require it. Last year I ran the place on a 5500w gas powered generator with no problems. With the Generac and the transfer switch it is seamless. Only problem is the way the place is wired, the generator only runs the house/well and not my shop.
 
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