Sizing a standby generator

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  #1  
Old 10-06-12, 07:09 AM
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Sizing a standby generator

Want to add a gasoline powered outdoor standby generator to power the furnace, water pump, some lighting circuits, the refrigerator and a TV in case of long term loss of power. ( Out for a whole week last winter). Furnace is an Armstrong Air, model EFC20LAA-1A, heat pump. Water pump is a standard 1/2 hp jet siphon, and TV is a LED 36" model. What wattage and amperage should I look for as a minimum requirement? Thanks.
 
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Old 10-06-12, 09:18 AM
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The pro's should be along with a better answer, but I'll opine you're going to need something pretty big for those requirements.
 
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Old 10-06-12, 09:44 AM
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We can only guess unless you tell us how many amps each item draws.
 
  #4  
Old 10-06-12, 10:30 AM
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I count a total of 315 amps of circuit breakers for the furnace, heat pump, hot water heater, refrigerator and water pump, plus an extra 30 amps for two of the lighting circuits.
 
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Old 10-06-12, 11:25 AM
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You do not add up the amps of the overcurrent devices, you need to look at the nameplate of each item you wish to run with the generator. You should then plan to oversize it a little for things like the heat pump and well for start up current.
 
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Old 10-06-12, 12:24 PM
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I wish I knew

I know that, but the well pump is 260 feet underground, the refrigerator is built in, and I cannot find anything on amperage on the furnace nameplate. I was hoping the furnace model might give someone a clue as to what the amperage might be. The hot water heater is listed at 4500 watts max. I am looking at an 8000 or 10,000 watt generator. Should they do the trick?
 
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Old 10-06-12, 01:11 PM
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Look on the pump control box for a label.
 
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Old 10-06-12, 04:37 PM
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Believe me, I have looked for amperage numbers on all of these items, but they are not there. I was hoping someone could give me an approx. idea based on the model of the furnace and on the size of the other equipment...50 gallon water heater, 1/2 horsepower siphon jet pump motor, 60000 BTUH cooling capacity heat pump with 1/2 hp blower. If I need to have the amperage I will need to go online and see what I can find on these 30 year old components and then get back to you. Thanks.
 
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Old 10-06-12, 04:41 PM
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The label will likely list MCA (minimum circuit amps) or FLA (full load amps) I can not find any info on that furnace/heat pump model.

10KW generator will likely work for you but you should really find out what your load is.
 
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Old 10-06-12, 05:35 PM
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Buy a cheap clamp on amp meter from somewhere like Harbor Freight and measure the amperage of these in use.
 

Last edited by ray2047; 10-06-12 at 06:43 PM.
  #11  
Old 10-06-12, 06:21 PM
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The FLA on the A/C side of the heat pump is 4.3. I assume the furnace side is less, but can't find a number. Still find no number for the pump and heater.
 
  #12  
Old 10-06-12, 07:33 PM
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Here's a good wattage calculator to help you figure your needs:

Generator Selector - Champion Power Equipment

Andy
 
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Old 10-07-12, 08:00 AM
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I don't care for the Champion generator selector, a quick look and I saw two big problems. One was that an electric water heater was listed as 4,000 watts, that's an immediate 500 watt error as most residential water heaters are 4,500 watts. The second problem I saw was the starting amps of a heat pump are lower than the running watts. I assume this selector was designed and written in China. I also doubt Champion has a standby generator in their lineup, but most likely only makes portable generators. This selector tool may be good enough, but take a look at this one from Generac as well.

Generac Power Systems - Generator Sizer


Want to add a gasoline powered outdoor standby generator
The next issue I see is that you probably won't find a standby generator that operates with gasoline. Typical residential standby generators are fueled with either natural or propane gas.

Want to add a gasoline powered outdoor standby generator to power the furnace, water pump, some lighting circuits, the refrigerator and a TV in case of long term loss of power
The third issue is that in the original post you never mentioned a water heater, but in post 4 you added it and omitted the furnace. In post 4 you just about doubled the loads you want to back up. You need to decide what you want to back up and stop making changes.

10KW generator will likely work for you but you should really find out what your load is.
I agree with TI, a 10 KW will likely handle it, but you really need to do a load calculation before buying.
 
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Old 10-07-12, 08:34 AM
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Just to mention one more time a cheap clamp on amp meter will allow you to make reasonably accurate measurements of those items you can't find a name plate for that gives the amps.
 
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Old 10-07-12, 11:37 AM
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This was a big help. Thanks. Plan to go with the 10,000 kw and limit what I attach to just the essentials.
 
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