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Portable Generator for 2 Sump Pumps

I want to purchase a portable generator to run the 2 sump pumps in my house in the event of a power outage. One is in the front of my house and one is in the back. (I do not have a french drain, so they aren't pulling from the same water source.) I do not plan to run anything else.

I'm not sure if the sump pumps are 1/3 or 1/2 HP, but I used an inline amp meter and I know that one pump pulls a continuous draw of 12 amps, while the other pulls a continuous 10 amps.

I'm looking to size out a generator, but I'm having trouble doing so due to the starting amp draw. (I don't know what the draw is, as I didn't install these pumps and I can't find any model numbers on them.)

22 amps yields somewhere around 2600 watts when both are running at the same time. A small, 3000 watt generator would be able to handle that continuous wattage. The startup wattage draw is more confusing to me, because what happens if the two pumps start at the same time? I do not know the odds of that happening and I don't know if the startup draw would pull for 1 second or 1 millisecond. (The shorter the startup time, the less likely that the 2 would overlap.)

During a storm, my pumps will usually run for about 10-15 seconds and then turn off for a few minutes.

A. Spruce
Re: Portable Generator for 2 Sump Pumps

If your inline amp meter won't register the starting amps, then I would suggest erring to the side of caution and figure the motors are 3/4hp or 1hp and call a few motor shops and ask them what the typical starting draw is for such a thing.

When you size the generator to the load, make sure that it's running amps rating is well above your required draw by 25% - 30% and that it's peak amps is also well above the combined starting requirements of the motors because you never know if the motors will start in unison, and an overloaded generator will pop it's circuit breaker or worse, fail at the least opportune time.

Don't forget that you have to maintain a backup generator like any other piece of power equipment. It needs to be started and used on a regular basis, at least monthly, to insure that it will be operational when the emergency strikes.

Re: Portable Generator for 2 Sump Pumps

Very good answer from Spruce.

We don't like to endorse products here, but when you talk about generators for emergency - you got to think HONDA only. Best money you can ever spend.

Re: Portable Generator for 2 Sump Pumps

Edge you either have pumps larger than 1/2 HP (373W) or your extension cord is too small and the motor is overloaded.

Starting current is 1.5 times the running current but only last for a fraction of a sec.

You might try a larger size cord and see if the current drops down.

If it stays at 12A per pump you will need a larger generator. Why not get a 6KW and have enough power (4560W) to keep the basement dry, food refrigerated/frozen, a few lights on, enough for the microwave and maybe watch some TV?

Re: Portable Generator for 2 Sump Pumps

Good answers.
When you choose a generator, go with Honda.

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