Vigilant24
New Member
- Joined
- Aug 23, 2022
- Messages
- 119
I have a "regular" 1/2 HP, 120VAC submerged well pump I'd like to be able to run on an inverter (as a backup). It's a 2 wire unit (so, the start capacitor is at the pump, not in a box above ground). It's about 120 feet down the well, water level is typically 60 feet down. I measured the running current as about 7A, I can't measure the starting amps with my meter but the stated locked rotor amps (LRA) is 50 amps.
My solar/FLA/inverter setup is for emergency backup only. 99.9% of the time we'll be on grid power. So, turning off other loads, etc is no big inconvenience while we pump water once per day for a few minutes.
I've seen some high frequency inverters that have a claimed "soft start" feature that ramps up the voltage on big loads to reduce starting current of inductive loads. The instructions from the inverter company say to use the soft start feature users should:
1) Turn off the inverter
2) Hook up the device/appliance that has the big startup load
3) Turn on the inverter. The voltage will ramp up over a short time.
This big pump motor starting current is the >only< load I've got that exceeds 1000W. It would be great to be able to use a 2000W (soft start) inverter to cover this load and everything else. I'd prefer to avoid the expense of a dedicated soft start box for this "maybe never use it" case, or the expense (and high idle wattage) of a big LF inverter. Well, that is, if the inverter soft-start function will accomplish a similar thing.
My questions
1) Is this soft-start inverter likely to do the trick? Is there a way of knowing short of just trying it?
2) Will this likely damage my pump?
2a) Potential electrical damage to windings/etc from the nonstandard voltage/current profile?
2b) Potential mechanical damage to impeller/bearings? I'm under the impression that these depend on a thin film of water to keep the bits apart, and worried that a longer period of grinding away at low RPMs on startup will wear things out sooner.
When I eventually need a new pump, a Grundfoss model might be a prudent investment.
Thanks for any assistance.
Mark
My solar/FLA/inverter setup is for emergency backup only. 99.9% of the time we'll be on grid power. So, turning off other loads, etc is no big inconvenience while we pump water once per day for a few minutes.
I've seen some high frequency inverters that have a claimed "soft start" feature that ramps up the voltage on big loads to reduce starting current of inductive loads. The instructions from the inverter company say to use the soft start feature users should:
1) Turn off the inverter
2) Hook up the device/appliance that has the big startup load
3) Turn on the inverter. The voltage will ramp up over a short time.
This big pump motor starting current is the >only< load I've got that exceeds 1000W. It would be great to be able to use a 2000W (soft start) inverter to cover this load and everything else. I'd prefer to avoid the expense of a dedicated soft start box for this "maybe never use it" case, or the expense (and high idle wattage) of a big LF inverter. Well, that is, if the inverter soft-start function will accomplish a similar thing.
My questions
1) Is this soft-start inverter likely to do the trick? Is there a way of knowing short of just trying it?
2) Will this likely damage my pump?
2a) Potential electrical damage to windings/etc from the nonstandard voltage/current profile?
2b) Potential mechanical damage to impeller/bearings? I'm under the impression that these depend on a thin film of water to keep the bits apart, and worried that a longer period of grinding away at low RPMs on startup will wear things out sooner.
When I eventually need a new pump, a Grundfoss model might be a prudent investment.
Thanks for any assistance.
Mark
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