Generator size for 5000 BTU A/C and 11.6 AMP refrigerator?

I am trying to size the smallest emergency generator for hurricane
season(s) here in Florida.
Smaller size means less fuel, less weight, less noise.
I will start the A/C and keep it running and then flip the breaker for
the refrigerator.
I believe that 6.5 hp 3500-4000 watts would do it.
Do you have any experience with a small emergency generator?
Reply to
stu
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I have a 4kw generator that easily supports a gas furnace, refrigerator and lighting. I'm certain it would not carry my central air conditioning.
I don't know what size you need to start your window a/c. Compressors start hard.
Better mpg, smaller size, less noise are claims made by the newer inverter based units that can slow down under light load.
Reply to
Roby
Small generators (
Reply to
SQLit
I have a generator slightly larger than the one you are looking at. The only thing I have used it for is for job-site tools (compressor, drill, saw), so I have not taxed the capacity.
I do have a 5000 BTU A/C unit -- it draws about 10 Amps steady-state, but I don't know what the startup current is.
Between your refrigerator, and small A/C unit, that's about 20-25 Amps. The 33 Amps capacity of the generator-in-question should be sufficient. If you can't start the A/C with another load, then I would do as you suggest and start the A/C by itself, before applying more load.
Here's to hoping you never have to use it. Tom
Reply to
tlbs
The problem is the refrigerator. Last years I tried to run one in my truck with self made inverter. The thing worked perfectly for all tests but on the road it failed again and again.
The reason therefore is, that startup current of refrigerators depend strongly from temperature outside. The higher the temperature, the more important is the refrigerator and the higher the pressure of the cooling substance. Higher hydraulic pressure needs high motor torque resulting in extremly high startup current.
From the same reason, service technicians are not happy about hot summers. Most refrigerators and mainly air conditions are dimensioned for temperatures up to 35 degree celcius. In my truck I easily had 50 degree and more. This makes the startup current so high, that the motor protection breaker blows out and the cooling in critical situation fails.
Assume all, the generator should be able to supply 6-8 times more capacity without dropping the voltage for secure startup of cooling devices. If the voltage drops 10% at startup, the theoretically available torque of async motors drops much more (up to 50%). A solution could be refrigerators working with frequency inverter what can start with a F/U ramp but I did no tests with those expensive devices. I tackeled to buildt one myself but this is difficult since the compressor motors are hermetically closed due to noise reasons.
Reply to
Juergen Veith
5000 BTU air conditioner (running on 120VAC) will draw about 30~35 amps starting current for about 0.2 to 0.4 seconds, then draw 6~8 amps running current.
Refrigerator start up current is about 600% of running current for 0.2 to 0.4 seconds. Therefore, if your refrigerator really draws 11.6 amps of running current, then start-up current will be about 70 amps.
Worst case will be when both A/C and refrigerator starts at same time, total start up current will be about 100 amps and cause the 4000 watt generator's output voltage sag and either A/C or refrigerator (or both) not to start.
Since a typical 4000 watt generator has split phase output (120/240V), only 2000 watt is available for 120V, it would be safe to move upto something like a 7000 watt generator (then each 120V output will be rated at about 30 amps or 3500 watts, and one 120V phase could power the A/C and the other 120V phase could power the refrigerator).
Reply to
Nam Paik
5000 BTU air conditioner (running on 120VAC) will draw about 30~35 amps starting current for about 0.2 to 0.4 seconds, then draw 6~8 amps running current.
Refrigerator start up current is about 600% of running current for 0.2 to 0.4 seconds. Therefore, if your refrigerator really draws 11.6 amps of running current, then start-up current will be about 70 amps.
Worst case will be when both A/C and refrigerator starts at same time, total start up current will be about 100 amps and cause the 4000 watt generator's output voltage sag and either A/C or refrigerator (or both) not to start.
Since a typical 4000 watt generator has split phase output (120/240V), only 2000 watt is available for 120V, it would be safe to move upto something like a 7000 watt generator (then each 120V output will be rated at about 30 amps or 3500 watts, and one 120V phase could power the A/C and the other 120V phase could power the refrigerator).
Reply to
Nam Paik

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