View Full Version : Best way to wire furnace for generator use
11-06-2006, 06:34 PM
My electrician is coming over this week to wire the furnace in a way i can safely use my generator to heat the house. i live in buffalo, so all of you know the reason for this. i understand about turning off the breaker, and thought id check here for opinions before he does the wiring next week.
should i have him put a outlet in, and just unplug the furnace from outlet when power goes out, then make a male to male extension cord from the outlet to the generator ?
i have a homelite 4400 watt generator.
11-06-2006, 07:36 PM
Male to male is very dangerous
Put an outlet at the furnace, then make a plug from furnace to plug into outlet and then when power goes out plug furnace into gen.
If you do this the way your thinking you will kill the lineman:(
11-06-2006, 07:49 PM
no, lineman is still OK.
wire runs from main panel to outlet, outlet goes to on/off switch. unplug wire from main to outlet when power goes out. connected separate ext cord from outlet to genset.
11-06-2006, 08:10 PM
You don't make male to male extension cord EVER. You always want to prevent both sources interconnected at the same time.
Put a generator input connector on the outside of the house.
Best option with lots of flexibility.
A way is to use a manual transfer interlock which will prevent two breakers from being on at the same time. If the main panel permits, it can be placed to interlock with the main breaker. You could then turn off the main and turn off all other breakers but the heater or whatever circuit you want to use. An example is here:
Your panel has to be able to accept one. Your generator would have to be a 220/120 variety. Metering of the generator current on the inside of the house would be helpful.
Typical option with some flexibility.
The typical way is to install a special generator sub-panel for the critical loads. Fridges, sump pump, minimal lighting etc. You keep selecting loads such that you don't overload the genrator. Typically these panels have an ammeter.
Economy mode - no flexibility.
You might be able to get away with putting a breaker sized for the heater and a recepticle on the inside of the house for the generator power.
The house power source would need a disconnect and receptical as well. It would have it's breaker at the main panel.
You could, then put a plug on the furnace and switch from inside to outside power by turning off the breaker and disconnect. Switch the plug and turn on the appropriiate disconnect. You don't want to plug in anything when the furnace could be on.
In any event, install a generator connector on the outside of the house.
I remember trying to power 3 fridges for 3 days with extension cords. Don't do it. Engineer a solution.
FWIW. Automatic transfer switches do exist and the emergency circuits are placed in a sub-panel such that the generator won't be overloaded. An example of this might be a natural gas generator.
11-06-2006, 08:12 PM
I like the idea of having a dedicated outlet to your genset. If you are even remotely thinking of coming off your panel PLEASE use an isolation switch. This is an automatic device and doesn't require you having to remember to open any breaker. Linemen killed every year because of an uniformed homeowner or an electrician who won't follow the rules.
11-06-2006, 08:21 PM
Keep it simple.
Don't attach the generator to the house circuit at all.
Pick a safe, secure location for your generator.
Make sure you account for it's exhaust fumes.
Don't put it in the house or garage.
Run wires from the generator to the furnace.
An extension cord of proper size might work for this.
Unplug the furnace from the house circuit, and plug it into the generator.
This is provided code in your area will allow a plug on the furnace.
If not, use switchgear, but you MUST keep the generator isolated from the utilty company's wires.
Male to male is just wrong.
11-06-2006, 08:32 PM
there is a very easy way to do this:
Put a 220Volt twist lock outlet on the outside of the house and run the wire to a 60 amp DPST breaker to "backfeed" the panel box.
make up an extension cord to go from the Generator to the twist lock outlet on the outside of the house.
when the power goes out, turn off your main breaker, turn on your 60 amp "backfeed" breaker, turn off ALL the breakers you DON'T WANT TO RUN, leave on your furnace, refrigerators, freezer and TV ( and maybe a lamp or two )
when the power comes back on, there is nothing to worry about, your "main" is off. Turn everything off in the panel box, shut down the generator, turn off the 60 amp "backfeed" breaker and turn on the mains and all your other breakers.
I have been doing this for a few years. There is nothing "in the house" to change or re-wire, and it's perfectly safe ( as long as you remember to turn the "main" off )
11-06-2006, 08:45 PM
I agree with Mike. Make it fool proof. Things are at their absolute worst during a power outage and it's unwise/unsafe to have to remember sequences and things to do and not to do.
I used to backfeed all the time with a suicide cable but finally put in my own generator panel that prevents any possibility of the generator and utility grid to compete. Any good electrician should be able to get you set up safely.
11-06-2006, 09:35 PM
ya want fool proof, spend the money and put a whole house generator in.
done deal and you don't have to do a thing.......it's completely automatic, and expensive ( to install )
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