What size generator to handle water pressure booster pump surge current? FAQ

Why such a big booster pump?

Thanks for that real-world input as I don't have the experience of others.

Your setup is interesting. You have lots of water. You must. If you don't need to fill up tanks, I'm assuming you have lots of water to tap into.

We have in the Santa Cruz mountains only water pockets here & there. So we drill much deeper and the well pump runs only for a minute or so.

The point being it takes a few days to fill up a water tank for us. You seem to getting the volume on demand. So that knocks out one pump.

Am I correct in assuming you have only 1 pump which does all 3 jobs?

1. The pump pulls water out of the well "on demand"
2. The 30-feet of 70'-100' cylinder "is" your water "tank" (so to speak)
3. The same pump pressurizes the bladder tank for the whole system

It's interesting your pump is half the size of mine (in terms of HP), yet it does all 3 jobs at the same time (storage + pressure + volume).

I wonder which takes the most pump energy (pressure or volume)? But even so, your Honda has surge current capacity my DuroMax doesn't have.

Honda EU7000iS a. Honda EU7000iS has 7000 surge watts (DuroMaqx XP5500EH is 6900 on gas) b. Honda EU7000iS has 5500 rated watts (DuroMax XP5500EH is 5500) c. Honda EU7000iS has an inverter (DuroMax XP5500EH is not an inverter) d. Honda EU7000iS has ~35¡V40 A surge (DuroMax XP5500EH is 30A max)

Notice they're seemingly close, but the Honda is way (way!) better. The Honda has sustained surge capability & excellent voltage regulation.

My Duromax XP5500EH generator noticeably slows down (whoooom...) and within a second (or so) speeds up when it trips from the booster turning on.

My neighbor told me that since my booster pump already starts but the breaker trips within seconds as it kicks on, I'm not torque-limited. a. The generator can supply the initial inrush, b. But it cannot sustain the surge long enough to reach full speed.

He says an electronic soft-starter reduces the peak inrush current in half. He said he has a Variable Frequency Drive but that's more expensive.

PS: I just learned NEMA code L means a high locked-rotor kVA per hp a. Locked-rotor kVA per HP is about 10 b. So at 240VAC, that's ~40 amps inrush current

Looking this up, it seems a. The generator almost gets the motor through startup b. But the problem is duration, not peak c. So a soft-starter may reduce the duration & severity of the inrush d. Which lets the motor reach speed before the breaker gives up

Given: General Electric AC Motor Thermally Protected Jet Pump Motor Mod: 5KC39QN1157AX HP: 1 HZ: 60 V: 115/230 PH: 1 RPM: 3450 CODE: L Note for some strange reason, motors use 230 V but generators use 240 V.

Apparently that 1 hp, code-L motor is pulling ~38-44 A at startup on 230V.

The big fat inductor is acting like a short circuit on startup. LRA = (1000 x 9.5) / 230V = ~41 amps

The Honda EU7000iS spec *looks* like it can't handle that current. a. 7000 W starting, 5500 W running, 120/240 V inverter b. Running 5500/240 = 22.9  A c. Peak 7000/240 = 29.2 A But the vastly better inverter rides through brief spikes, apparently.

Apparently a single-phase soft-starter can cut startup current by ~50-60%. It might bring inrush current low enough for the DuroMax XP5500EH. Or not.

What size? Hell if I know.

Dunno what the spec is, as I never dealt with electronic soft starters. Looking it up... it goes in series with both hot legs between the pressure switch (which is mounted on the motor) and the motor.

I think I'd need *more* than these minimum soft-start specifications: a. For a 1 hp, 230 V, single-phase pump motor b. Locked Rotor Amps (at least ~40-45 starting amps at 230 V) c. Full Load Amps (at least ~7-10 running amps at 230 V)

Thanks for that real-world interesting information, as each of us has a different setup for our region's water supply. If you have a 6-inch casing, and water from 40 to 100 feet, that's about 88 gallons static.

Just to make the 60 psi (at 2.31 psi/foot) that's 138 feet of dynamic head.

That puts you around 200 to 230 feet of total dynamic head, which Google tells me is about 5 to 7 gpm for a 1/2 HP submersible pump.

Is that about right?

My DuroMax XP5500EH has 4,500 running watts with 5,500 surge which, at 240V is only 19 running Amps and 23 surge amps, which doesn't cut the mustard.

Your EU7000iS has a larger engine, better voltage regulation, and a much more conservative rating philosophy. From what I've read, Honda inverters handle starting surges cleanly and recover voltage almost instantly.

But your Honda costs 10 times what my DuroMax cost, so I would have needed, I think, something in between that is less expensive but could handle the surge current for my booster pump.

The $2000 HF Predator 9500 Inverter Generator has a 40 Amp surge and 32 amp running current (rated 9500W peak and 7600 running) so maybe a soft start is cheaper since I only have the problem when PG&E's grid drops on me.

At this point, unless I replace the generator with one like yours, I'm thinking I'd need a soft start with at least these minimum specifications: a. For a 1 hp, 230 V, single-phase pump motor b. Locked Rotor Amps (at least ~40-45 starting amps at 230 V) c. Full Load Amps (at least ~7-10 running amps at 230 V)

Eltwin Hyper SureStart Single Phase Soft Starter $290 230V (16-32 FLA) - SS1B16-32SN

But both are a guess since I'll never know until I plug it in. :( That's why I was asking for real-world use models, like yours.

Thanks for your insight. It was very helpful.