Can I use a PSX-240 Autotransformer to step up to run a well pump?

Discussion about adding energy storage to grid-dependent inverters using OutBack Power technology
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mlammens
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Can I use a PSX-240 Autotransformer to step up to run a well pump?

Post by mlammens »

Hi,

First time poster and a newbie here. I have a SunRun installed PV system with a backup storage battery (LG Chem RESU 10H SEG). During a power outage, the PV and battery run four 110V circuits in my house. My problem is that my well pump requires 220V. It seems like I could use the PSX-240 Autotransformer to step-up the voltage from one of the four 110V circuits and run the well pump from that, but after reading the manual for the autotransformer, I'm not confident that my intuition is correct on this. Any thoughts or suggestions would be appreciated.

Thanks - Matt
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Re: Can I use a PSX-240 Autotransformer to step up to run a well pump?

Post by raysun »

mlammens wrote: Thu Aug 06, 2020 7:15 pm Hi,

First time poster and a newbie here. I have a SunRun installed PV system with a backup storage battery (LG Chem RESU 10H SEG). During a power outage, the PV and battery run four 110V circuits in my house. My problem is that my well pump requires 220V. It seems like I could use the PSX-240 Autotransformer to step-up the voltage from one of the four 110V circuits and run the well pump from that, but after reading the manual for the autotransformer, I'm not confident that my intuition is correct on this. Any thoughts or suggestions would be appreciated.

Thanks - Matt
The autotransformer is likely not the best choice. A standard 110 to 220V step up transformer with proper wiring should do the job.
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Re: Can I use a PSX-240 Autotransformer to step up to run a well pump?

Post by fcwlp »

Before considering a transformer of any type, you need to do some design analysis.
1) How much does your well pump draw when running?
2) What is the starting amps for the well pump?
3) What is the VA capability of your present inverter for both steady state and surge?
4) Can the LG Chem RESU 10H SEG supply the required surge current?

The inverters that SunRun installs do not use transformers and therefore typically have almost no surge capability over their nameplate capacity. Typically a well pump or other motors will have a surge current requirement of ~3X the running amps. The running amps are most easily determined using a clamp-on ammeter. If you do not have the current, it can be estimated from the HP of the well pump.
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Re: Can I use a PSX-240 Autotransformer to step up to run a well pump?

Post by ralphday224 »

Before I put in a Grundfos soft starting submersible pump I had a 220vac pump run with an autotransformer (Xantrex flavour). When the pressure switch turned on the transformer would get power, saturate and start the pump at the same time. If you were watching tv the colour would dissapear and the picture reduce by 1/4 at least (from the sides of the screen).

One time I watched the meter on the Xantrex 4048 and it flashed up to 45 amps, only because that's as high as it would read I think. The tv didn't last too long doing that, it was an old crt picture tube set, not lcd. It couldn't have been too good for the inverter either. I replaced the pump and that problem went away. Locked Rotor Amps starting ac motors is a limiting factor for inverter sizing in house system design.
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Re: Can I use a PSX-240 Autotransformer to step up to run a well pump?

Post by sparksalot »

fcwlp wrote: Fri Aug 07, 2020 1:07 pm Before considering a transformer of any type, you need to do some design analysis.
1) How much does your well pump draw when running?
2) What is the starting amps for the well pump?
3) What is the VA capability of your present inverter for both steady state and surge?
4) Can the LG Chem RESU 10H SEG supply the required surge current?

The inverters that SunRun installs do not use transformers and therefore typically have almost no surge capability over their nameplate capacity. Typically a well pump or other motors will have a surge current requirement of ~3X the running amps. The running amps are most easily determined using a clamp-on ammeter. If you do not have the current, it can be estimated from the HP of the well pump.
Oh the PSX_240. @6kVa in and of it's self can be quite capable to start and run a 1/2 - 3/4 horsepower pump motor...
Your pump situation is the unknown to us...Must use all 4 above...anything less will disappoint...
THEN...transformer MIGHT work for YOUR situation...any chain is only as strong as the weakest link...
mlammens
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Re: Can I use a PSX-240 Autotransformer to step up to run a well pump?

Post by mlammens »

Thanks all. These were super helpful comments. I found more specs on my backup system here (https://www.solar-electric.com/lib/wind ... eet_na.pdf) and from what I can tell, during backup power situations I should be able to get 5000 VA, with a max of 7600 VA for 10 seconds. The battery (LG Chem RESU 10H SEG) specs are 5 kW max output, 3.3 kW continuous output, and a 10 sec surge of 7 kW. As for the well pump, that's a been a bit harder to get info on, but looking around, I see a typical 3/4 HP pump is 1500 kW for running and up to 3000 kW to start. My control box says running current is 8.6 amps and max current is 9.8. All your input leads me to think that I should be able to run the pump with something like this step up (https://www.110220volts.com/220v-20a.html), since I do have two outlets on two different backed-up circuits I can pull from.

Again, thanks!
Matt
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Re: Can I use a PSX-240 Autotransformer to step up to run a well pump?

Post by raysun »

mlammens wrote: Sat Aug 08, 2020 6:07 pm Thanks all. These were super helpful comments. I found more specs on my backup system here (https://www.solar-electric.com/lib/wind ... eet_na.pdf) and from what I can tell, during backup power situations I should be able to get 5000 VA, with a max of 7600 VA for 10 seconds. The battery (LG Chem RESU 10H SEG) specs are 5 kW max output, 3.3 kW continuous output, and a 10 sec surge of 7 kW. As for the well pump, that's a been a bit harder to get info on, but looking around, I see a typical 3/4 HP pump is 1500 kW for running and up to 3000 kW to start. My control box says running current is 8.6 amps and max current is 9.8. All your input leads me to think that I should be able to run the pump with something like this step up (https://www.110220volts.com/220v-20a.html), since I do have two outlets on two different backed-up circuits I can pull from.

Again, thanks!
Matt
Hmmm.... might want to double check the input requirements for that unit and make sure your system can deliver that.
mlammens
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Re: Can I use a PSX-240 Autotransformer to step up to run a well pump?

Post by mlammens »

@raysun Maybe a problem with the requirement that the two circuits be out of phase? On second thought, I could see that as a problem, since I assume the 4 circuits backed up from the battery aren't necessarily out of phase.
raysun
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Re: Can I use a PSX-240 Autotransformer to step up to run a well pump?

Post by raysun »

mlammens wrote: Sun Aug 09, 2020 9:45 am @raysun Maybe a problem with the requirement that the two circuits be out of phase? On second thought, I could see that as a problem, since I assume the 4 circuits backed up from the battery aren't necessarily out of phase.
Yes, I don't know anything about the Inverter, but it looks like the device is meant to convert 240 split phase (two 120V circuits with a common neutral and 180° out of phase) into 240V single phase (to power foreign 240V gear). I may be wrong about this, but it doesn't hurt to double-check.

It seems a standard 120V to 240V center tapped transformer of proper rating would power the pump.
fcwlp
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I install and maintain grid-tied and off-grid systems in my area and consult on solar system design/operation.
Location: 80 miles NE of Phoenix at 5500'

Re: Can I use a PSX-240 Autotransformer to step up to run a well pump?

Post by fcwlp »

mlammens wrote: Sat Aug 08, 2020 6:07 pm Thanks all. These were super helpful comments. I found more specs on my backup system here (https://www.solar-electric.com/lib/wind ... eet_na.pdf) and from what I can tell, during backup power situations I should be able to get 5000 VA, with a max of 7600 VA for 10 seconds. The battery (LG Chem RESU 10H SEG) specs are 5 kW max output, 3.3 kW continuous output, and a 10 sec surge of 7 kW. As for the well pump, that's a been a bit harder to get info on, but looking around, I see a typical 3/4 HP pump is 1500 kW for running and up to 3000 kW to start. My control box says running current is 8.6 amps and max current is 9.8. All your input leads me to think that I should be able to run the pump with something like this step up (https://www.110220volts.com/220v-20a.html), since I do have two outlets on two different backed-up circuits I can pull from.
Matt, I would recommend using the SolarEdge autotransformer that is designed for this system and specified in the first pdf above.

I have one client who was quoted the same system. His "absolute requirement" was that he could pump water from his 600' deep well with a 3HP pump that drew ~20 amps while running. I went thru the facts with him that the quoted system would not work. Also after reviewing the design schematic they had managed to forget to even hookup the well. :eek:
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