Reduce well pump starting current

[yabert]

Hi

I used a 2400w 240V (10A) inverter to power my well pump. It work well since a week now, but today the inverter was in overload.
I restart the inverter (supposed to supply 20A for 5s) and the well pump work... for a moment.
I measured 19-20A peak load when the pump start so I guess it's always to the limit and sometime the inverter limit is exceed.

As the current after one second drop to 6A, how is it possible to reduce the peak current to a more reasonable 10-15A?
There is a capacitor (59-71Uf) inside the pump control box, but it's not enough. Add another capacitor in parallel?
Please let me know.
Thanks

 

[BentleyJ]

Sounds like the pump is a standard single phase induction motor. You can add a Soft Starter that will reduce inrush by up to 70%. I'm using one on a 4 ton AC condenser, works quite well.
SS1B08-16SN (230V, 60/50Hz, 08-16 FLA)

Soft Start Single-Phase | Eltwin

www.hypereng.com

 

[yabert]

Thanks Bentley. It seem like a solid solution.
But it's so expensive . It cost almost the same price than my 2400W inverter.
To me, it could be smarter to sell my 2.4kW inverter and buy a 3.2kW.

Is there less costly solution? If no, swap my inverter could be the best way to solve my problem.

 

[BentleyJ]

Is there less costly solution? If no, swap my inverter could be the best way to solve my problem.

The high inrush current still puts stress on your inverter. There are other brands available and sometimes you can find them on ebay for less.

 

[TorC]

If you have use for the larger inverter otherwise, that might work, but the soft start is probably easier on your whole system. OTOH, you do have a backup for most of your stuff if you buy a larger inverter. If you go that route, however, I'd make sure you've got at least 1s surge for the startup inrush plus all running loads you might potentially have going.

 

[yabert]

The high inrush current still puts stress on your inverter.

And what about inrush current limiter? Those devices cost few bucks only.

At the moment, I manage to reduce the current a bit.
As my inverter have adjustable output voltage (220-230-240V) I had the idea to test it at 220V instead of 240V. Peak current is now 16-17A.

I measured 19-20A peak load when the pump start so I guess it's always to the limit and sometime the inverter limit is exceed.

 

[rhino]

This doesn't help you now but I would like to re-iterate anyone reading this if you are going to potentially power it with an inverter in the future to make sure you purchase/install a well pump that does not have a startup surge. This issue is a very common problem posted here since most well installers at least in the US just install some generic 240V inefficient pump. Using a pump made by Grundfos for instance is more efficient and has no startup surge which saves you from dealing with this issue.

 

[BentleyJ]

This issue is a very common problem posted here since most well installers at least in the US just install some generic 240V inefficient pump. Using a pump made by Grundfos for instance is more efficient and has no startup surge which saves you from dealing with this issue.

For sure, better to eliminate the problem in the beginning than add additional components that will eventually fail also.

 

[Nobodybusiness]

Sounds like the pump is a standard single phase induction motor. You can add a Soft Starter that will reduce inrush by up to 70%. I'm using one on a 4 ton AC condenser, works quite well.
SS1B08-16SN (230V, 60/50Hz, 08-16 FLA)

Soft Start Single-Phase | Eltwin

www.hypereng.com

They make good stuff. Used them before.

 

[yabert]

... if you are going to potentially power it with an inverter in the future to make sure you purchase/install a well pump that does not have a startup surge. This issue is a very common problem...

Yeah, I could not imagine that a 1/2hp rated pump was in fact a 2hp continuous and 6hp peak pump. Hope my bad experience will serve others.

 

[yabert]

By chance I had an inrush current limiter in stock inside one of my EV charger. So I tried to connect a Ametherm MS35 1R040 inline on the well pump circuit.
It work. The peak amps at 240V passed from 19-20A to 11-10A with the limiter.
This limiter is way to big at 40A continuous. Those device cost 5-10$ so it wort it.
The biggest challenge is the integration of those as they can run at 65-215°C (149-419°F). I have to work on something fire proof and super reliable.

 

[Hedges]

I cooked a 2HP Dayton compressor motor due to brownout (240 from two 120V breakers not ganged, and shared with other loads.)
My motor had a thermal cutout, which activates after motor overheats, so insulation gets baked.

Thermal/magnetic breakers take a long time, sometimes 10 minutes, to trip with overload up to 5x rated current.

Your NTC thermistor inrush limiter will keep the motor from getting the current it was trying to draw to start fast, so there is a chance it fails to start. If inverter shuts off the motor is protected, but larger inverter might remain on.

I suggest putting in a magnetic-hydraulic breaker, such as Midnight/CBI.
What that will do is allow surge current for just seconds, then trip if the motor remains stalled.

 

[Risky Rob]

Why not replace the start capacitor with another that has a slightly higher value?

 

[yabert]

Why not replace the start capacitor with another that has a slightly higher value?

Simply because I don't know if this will help.
I don't want to spend money for nothing and waste component I don't need.

 

[Risky Rob]

Simply because I don't know if this will help.
I don't want to spend money for nothing and waste component I don't need.

Another starting cap might cost $10, and should plug right into the control box. Don't use one too many uF's higher. It's the simplest and cheapest option possible. I don't think you ever want to add more caps in parallel, as the uF value declines.

 

[BentleyJ]

Another starting cap might cost $10, and should plug right into the control box. Don't use one too many uF's higher. It's the simplest and cheapest option possible.

????

I don't think you ever want to add more caps in parallel, as the uF value declines.

Capacitors connected in parallel are ADDITIVE. Capacitors in SERIES will support higher voltage but the total uF value decreases. 1/Ctotal = 1/C1 + 1/C2 + 1/C3 + 1/Cn

 

[Risky Rob]

????

Capacitors connected in parallel are ADDITIVE. Capacitors in SERIES will support higher voltage but the total uF value decreases. 1/Ctotal = 1/C1 + 1/C2 + 1/C3 + 1/Cn

.

 

[BentleyJ]

Isn't that what I wrote?

No, you wrote "I don't think you ever want to add more caps in parallel, as the uF value declines."

 

[halfagascan]

how about this?

 

[Quattrohead]

Bit hacky to say the least but it will work.