Generator

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I want to get a generator just to run my furnace fan if the power goes out during the winter. We are in the Boston area, and the snowstorms are pretty fierce. I know that 3750kw will be plenty of power for what I need, but is this as simple as running the generator outside, running an extension cord into the basement and plugging my furnace fan into it. Or I guess, plugging everything in, and then starting teh generator.
Does the generator run even when no power is being drawn from it. Also, would the thermostat work without power? What about the furnace itself?
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I don't think the furnace would work without power.
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Maybe it will if the thermostat has a battery
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wrote:

If a thermostat has a battery, it's probably a small one that provides enough current for the thermostat to maintain electronic memory (and possibly run a clock). It would be much less than is required to run the fan. Also, an electronic thermostat is often electrically isolated from the furnace.
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That would be some kind of battery!
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Christopher A. Young
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Last month we bought a generator and had a 10 circuit Transfer Switch Panel installed (about $600). If we lose power, the generator cord plugs into the Transfer Panel and we can choose which circuit(s) and how many of them we want to run at the same time. This type of set up was the safest and easiest for us to operate. The size of the generator depends on how many circuits you want to run at one time. The Honda web page has some good information on it. We were told that Honda was the quietest generator made, but it is very expensive (we bought a Briggs & Stratton) and our needs didn't justify the high cost. The generator directions recommend that the owner provide protection for three sides of the generator while it runs to protect it from the weather elements.

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Of course the generator runs even when no power is being drawn from it; does your car motor run at traffic lights? The thermostat normally draws power from the furnace, so if you hook it up properly there should be no problem. Furnaces can be forced to run without power, but without the fan running you will trash it pretty fast. Running an extension cord is certainly the cheapest and most idiot proof way to go, but also the most clumsy. Your furnace probably doesn't have a plug on it; you will have to do something about that, and I suspect you are not the person to do it. My furnace will run on a 500w generator; yours might not. Investigate that before buying one. Furnaces have been ruined by poor quality electricity coming off cheap generators; but a lot of people do it without any problems. A judgement call.
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What kind of furnace are we talking about? No one has said.
Maybe gas will burn without electricity--I don't know-- but oil won't.

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Gas will burn, but most furnaces today have electronic ignition and electronically operated gas valves. Of course even if you defeat all of that, the limit switches won't be working.
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wrote:

How much power does the gas valve need? Perhaps something could be arranged, like on a gas water heater?
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wrote:

Sure. He just needs to power the whole furnace and not just the fan. Powering just the furnace fan is a bit like toasting marshmallows over a campfire that isn't burning.
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If oil won't burn without electricity, what are they doing at the refinery in England, at the moment? And how many watts did it take for Sadaam to burn his oil wells?
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Your furnace will run just like it normally does. You need to have an electrician install a male plug at the furnace, connected to a single pole double throw switch. In one position the furnace gets its power from your electrical system, and in the other position it will get its power from an extension cord plugged into your generator.

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RBM wrote: > Your furnace will run just like it normally does. You need to have an > electrician install a male plug at the furnace, connected to a single > pole double throw switch. In one position the furnace gets its power > from your electrical system, and in the other position it will get its > power from an extension cord plugged into your generator.
That male plug is called a flanged inlet. Best practice is to use a double pole double throw switch that switches the neutral as well as the hot conductor. That avoids grounding the neutral on the load side of the service disconnecting means. While your running off of the generator the Service disconnecting means is the generators main breaker. The generator will be grounded through the Equipment Grounding Conductor of the cord.
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wrote (with possible editing):

Yes.
Doesn't matter - if it's really a furnace, it needs power to run the fan. If you meant a boiler, it still needs power to run the circulator. Both need power if you're burning oil; most need power if you're burning gas. A thermostat is essentially a single pole, single throw switch. If it's programmable, it might have a battery.
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TheMightyAtlas wrote:

Sure. Figure a gallon of gasoline per hour. Plan on getting up in the middle of the night to re-fuel.
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My generator will go 8 hours on a gallon with just the furnace on it.
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wrote:

Yes, but more slowly, right. Don't they have speed regulators that somewhat depend on the load. Cars use far less at idle than they do when moving the car.

If he says so, I'm sure heybub is right. All the more reason to conserve on heat use Close vents and doors to unused rooms, etc. (although I'm told there is a limit to that.) Turn down the heat. Use an electric blanket. And maybe your wife will only have to fill the tank once during the night.
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wrote (with possible editing):

Actually that would be very rare. I've never seen one that does that, and I've used many of them. They usually run constantly at one of two speeds: 1800 rpm or 3600 rpm. That is necessary to maintain the 60 hz that they produce. They certainly use less fuel when no load is being drawn, but the speed remains the same. An alternator designed to run at 1800 rpm is more expensive than one designed to run at 3600, but typically the engine will last longer due to reduced wear.
We have an automatic 18kw diesel for backup here and I own a gas driven Honda used for construction. I've also used two Generacs and a few other gas driven models.
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... : >Yes, but more slowly, right. Don't they have speed regulators that : >somewhat depend on the load. Cars use far less at idle than they do : >when moving the car. : : Actually that would be very rare. I've never seen one that does that, : and I've used many of them. They usually run constantly at one of two : speeds: 1800 rpm or 3600 rpm. That is necessary to maintain the 60 hz ...
No, not so rare. MANY generators idle during periods of no-load. Most generators around here do, including mine. If there is ANY load though, it jumps up to speed incredibly fast.
So, it depends on the particular generator design. A 5 gallon tank of gas can last me a day during power-outages IFF I only power the furnace & fridge. When they're all off, the generator drops to a fast idle and stays there. It still puts out 130Vac, but I have nothing to see the frequency with because my test equipment triggers it up to speed. Too lazy to drag out my scope to look at it. Just a 4W nightlight is enough to cause it to spring up to speed. As long as they're supplying any current though, they will definitely be at speed, and that speed is usually governed in some way to remain pretty stable; that's how they get the 60Hz frequency.
I've no experience with generators that vary motor speed with load, but I do know there are some - they've been discussed on various groups. So I don't know how those work. I suspect they're more DC systems than anything else.
HTH,
Pop
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