Furnace question

Anybody happen to know how much initial startup amperage is used for a furnace just coming on, starting its vent motor, and running the glow starter for a gas furnace? I'm needing to know what a reasonable generator capacity would be without overdoing it. Thanks.

Reply to
Michael B
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What you really need to know, is the voltage and amperage of the blower

Reply to
RBM

Not really. The glow ignitor can draw a few amps from the 120 volts.

Reply to
Art Todesco

Yes, but your blower motor can be around 10. Bottom line, it all needs to work together, so he really needs the total fla

Reply to
RBM

Tables like this will help:

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My generator 5,500 watts, 7,350 starting watts, handles my furnace, well, refrigerator, freezer, several lights and a TV. Not hooked up are electric water heater, central AC, electric stove and clothes dryer, the big energy hogs.

Reply to
Frank

What size blower. Condition and age can make a difference if the motor is worn. Get a clamp on amp meter and test yours, mine takes about 350 running and 700 startup, that is when it was new.

Reply to
ransley

You also need to remember the ignitor and the blower fan will NOT be operating at the same time under anything resembling normal application. Also, startup current of the eductor motor and ignition will not happen simultaneously.So, what really matters is normal running current of the eductor fan motor and startup current of the blower. If the blower is a brushless DC motor it will also be soft-start and will not exhibit a large starting current spike.

Reply to
clare

I think the total load is supposed to be on the furnace manufacturer's tag. You can just use that without going through any calculations of the furnace's individual components. I was about half listening at my last code class when the subject came up.

Reply to
Dean Hoffman

From memory, I think the ignitor uses 2 amps on my furnace. The blower about 6 amps. Not sure about the inducer fan.

Reply to
Mikepier

Well, what you are describing is what I want to avoid. Typical motor for running one of those is a 10HP unit. If I can do what I need with a 2HP, my fuel will last longer. Run the furnace till the temperature is where I need it, with sweaters, switch it over to the freezer each day, then to the refrigerator and be frugal about opening it, and use candles when necessary. Yeah, I know a refrigerator has a high startup surge. But a lot of the stuff can be in the freezer for a while.

The furnace says it has a total input of 6.8 amps. But I'm needing to know if the glow ignitor has needs that would transiently exceed that. Because if it doesn't, I could run it on a single kilowatt generator. Bet I could run my freezer on a lot less.

Reply to
Michael B

Well, what you are describing is what I want to avoid. Typical motor for running one of those is a 10HP unit. If I can do what I need with a 2HP, my fuel will last longer. Run the furnace till the temperature is where I need it, with sweaters, switch it over to the freezer each day, then to the refrigerator and be frugal about opening it, and use candles when necessary. Yeah, I know a refrigerator has a high startup surge. But a lot of the stuff can be in the freezer for a while.

The furnace says it has a total input of 6.8 amps. But I'm needing to know if the glow ignitor has needs that would transiently exceed that. Because if it doesn't, I could run it on a single kilowatt generator. Bet I could run my freezer on a lot less.

Reply to
RBM

well a furnace will easily run on a fifteen amp circuit, so any old

1500 watt gen will do it if that's all you're running.
Reply to
Steve Barker

are you planning on some major outage, or just living in the sticks without service?

Reply to
Steve Barker

Neighbor across the street has generator half the size of mine and gets by but said if he had to do it over, he would have gotten larger one. Depends what your needs/wants are.

Reply to
Frank

And with the starting current of a typical 1/2 hp blower, you'll be frying your undersized generator

Reply to
RBM

May be true on traditional-designed furnaces but on new stuff, the ignitor can run with the blower. Mine does it all the frequently. It's a Goodman propane furnace, with a heat pump and a variable speed blower. When it decides to de-ice the heat pump, the blower will continue to run while firing up the propane. On these things, the best way to know the current accurately is to monitor it over time.

Reply to
Art Todesco

I have 4400 cheapo generator for emergencies. I feed the entire house with it. Runs 2 gas furnaces, a regular fridge, a bar min fridge, and assorted lights, tv, etc.

Reply to
jamesgangnc

If he has a heat pump then he needs a lot more generator.

Reply to
jamesgangnc

An old ONAN will do the job too. I don't know how many hundred hours are on my old beast - it was used as a construction site generator for over 20 years and it still runs great. A bugger to start though with just a rope pull - not even a recoil!!

Reply to
clare

I got rid of my Coleman 4KW which was quirky. Regulation was poor. When a fridge or the like would start, it would drastically change speed and thus voltage and frequency. I tried a whole bunch of stuff and nothing helped. When it was new, it was very hard to start, but after some adjustment and cleaning of the carb, it started easily. But I could never get it to regulate better. So, now for power outages, we use the Onan 4KW in the motor home, which is parked 10' from the house. It is hooked up right now to the generator panel and can by switched on at moment's notice. It is far better regulated, starts with the touch of a button and is pretty quiet. I think it's 2 cylinders because is runs sooooo smoothly. I've always heard Onans are great and this one is not not an exception. That said, I had a 7KW Onan in a mobile TV truck which was horrible. It was repaired multiple times by the installing company and by Onan and no one could make it reliable. It bounced around in speed, and thus frequency and voltage, whenever it felt like ... nothing starting, etc. It's now a anchor weight in the TV truck replaced by an Auragen belted off the V8. This works very well and as it has an inverter, it is dead on. Of course you pay to run the V8. And, if the belt breaks, as it did a few weeks ago, you have no power.

Reply to
Art Todesco

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