Posted: 9/17/2010 4:07:58 PM EDT
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I'm looking at purchasing a portable inverter generator for my house as a back up power supply. I'm mainly interested in something to run the central heating system (natural gas forced hot air). The fan blower is rated at 9 amps and it is on a 15 amp circuit breaker. The generator websites suggest 2 to 3 times higher than the rated amps to account for start up loads. I find it tough to believe that a 9 amp fan blower is drawing 18-27 amps without tripping the 15 amp circuit breaker.
I realize I shoud just get an amp meter and measure the startup load, but I'm trying to determine if I need a 2000 or 2400watt genny before my trek to Cabelas tomorrow. I'd like to go smaller to save money since this won't be used much. What say the hive? Thanks. |
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I have a Honda EU2000, which is a great generator.. Very quiet and sips gas when not pushed to the limit..
I know that when I hooked my generator up to the deep freezer it really grunted when the compressor cut in, but it never tripped the generators breaker.. I dont know how the deep freeze compares to furnace fan though.. IF you go with a +/-2k generator you wont leave room for much else.. the Honda/yamaha 2k generators may be outside of your budget, but the clean electricity and how quiet they are are a HUGE plus.. Based on what you have said, I would go with at least a 3k generator since that will give you some room to spare.. OR you could buy 2 EU 2k's and connect them together to give you 4k of electricity.. You may want to shop online for the generator though. I got my EU shipped for about ~$150 less than I could buy locally Brian |
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Quoted:
…… I find it tough to believe that a 9 amp fan blower is drawing 18-27 amps without tripping the 15 amp circuit breaker…... Tripping is a function of both current and time. A 15A breaker can remain closed for a substantial length of time while passing 16A, maybe 10 minutes or more depending on the time-current curve. |
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Quoted:
I'm looking at purchasing a portable inverter generator for my house as a back up power supply. I'm mainly interested in something to run the central heating system (natural gas forced hot air). The fan blower is rated at 9 amps and it is on a 15 amp circuit breaker. The generator websites suggest 2 to 3 times higher than the rated amps to account for start up loads. I find it tough to believe that a 9 amp fan blower is drawing 18-27 amps without tripping the 15 amp circuit breaker. Actually, motors often draw 6X (sometimes more) their rated FLC at startup. The circuit breakers in your house are what is referred to as thermal magnetic. The thermal part is an actually heating element that if it warms up enough the breaker trips. Thats why a breaker that is loaded is warm to the touch. The warming introduces a lot of time delay into the system so that at startup, the motor can pull more current for a short period of time. The magnetic part of the breaker is sometimes called instantaneous, but it really is a time delay too, just over a much shorter time (like milliseconds). All breakers like this have a trip curve that will give you an idea how fast it might trip, although there is a lot of variability. There is no guarantee that a 15 A breaker will ever trip at say 18 amps. It may well stay on because it is cool where the breaker box is and the thermal part of the breaker never gets warm enough to trip. Here is a fairly typical trip curve. In the gray area, it may or may not trip. http://static.schneider-electric.us/docs/Circuit%20Protection/Miniature%20Circuit%20Breakers/QO-QOB%20Circuit%20Breakers/730-01.pdf |