Shallow well pump soft start.

[Jack Rabbit Off Grid]

I have searched the forum and the net but don’t understand what I need.

I have a Magnum MS4448PAE with 600ah of LifePO4 batteries. I’m powering a small 1 bedroom manufactured home that they handle no problem. But I have a Red lion 1/2hp 230v shallow well pump hooked to a 500 gallon cistern tank. Every time it cycles on the whole house flickers and the tv turns off. I know I need a soft start of some sort but don’t know which one? Everything I find says they are for A/C units not well pumps. The pump specs are 11.8 amps at 120v or 5.9 amps at 230v. I currently have it wired 230v.

Thank you in advance for any suggestions.

 

[pollenface]

I'd like to make my own soft start but have never been able to find a suitable vendor for ntc thermistors

 

[12VoltInstalls]

I have a Red lion 1/2hp 230v shallow well pump hooked to a 500 gallon cistern tank.

Feeding the tank from a well? Or supplying from cistern to house?

Sounds like cistern to the house…
I’d just change it out for a lower-volume lower-wattage pump. 1/2HP seems like it exceeds the need by a lot- a much smaller pump and a bladder tank to mask it’s initial low-flow would seem like a good solution.

I don’t know what’s available but look up VFD pumps. Might be less $$ than an added device.

 

[Hedges]

I'd like to make my own soft start but have never been able to find a suitable vendor for ntc thermistors

Thermistors can be soft-start for the rectifier/capacitor front end of a switching power supply.
They would be terrible for an induction motor.

I think "Soft Start" for induction motors acts more like a dimmer ramping up, smaller pulses to begin with to give motor a push but not present a dead short circuit to load.

For OP, smaller pump, not induction motor, seems ideal. As a shallow-well pump, any suction pump can turn on and lift water. There are also cheapie in-the-well pumps, which don't need to self-prime or worry about a foot valve leaking. Something like a 230V ShurFlow pump on the surface, either AC motor or DC motor fed by rectifier, could do it.

Alternate possible solution - check wiring. Skimpy wiring stalls motor, takes longer to start while drawing excessive current.
Wiring from inverter through house then to pump means house sees voltage drop across wiring. Separate run from inverter direct to pump, sufficiently large gauge.

5.9A running, expect 30A surge. 30A x 240V = 7.2kW; surge should last less than a quarter of a second.

4400W 48VDC Pure Sine Inverter Charger MS-PAE | Magnum Dimensions

www.magnum-dimensions.com

Output Power	4,400W
Peak Watts	8,500W

That ought to do it. Try dedicated wire run.

file:///C:/Users/the_f/AppData/Local/Temp/MS-PAE-series_datasheet_64-0275_RevE_web_0.pdf

"100 msec surge current (amps AC) Line-Neutral: 75, Line-Line: 40"

100 msec is marginal. 40A is sufficient, unless other loads are powered.

Spinning an impeller in water is going to be more difficult. Self-priming is very slow, may only work with a pocket of water on impeller to help it take gulps of air. Maybe something that drained back so motor started in air would successfully re-prime after letting motor start easier, maybe not.

Possibly backpressure from discharge pipe makes starting more difficult. A mechanism to drain discharge pipe could help in that case. If pump was higher than tank, and vacuum breaker and gravity drained, that would relieve pressure. But most likely, your pump is at ground's surface just above well, and it pushes water higher to fill tank. Making that do a pressure relief would be a bit more complicated.


Does pump have a capacitor? How old? weak capacitor could make starting harder.

 

[Jack Rabbit Off Grid]

Alternate possible solution - check wiring. Skimpy wiring stalls motor, takes longer to start while drawing excessive current.
Wiring from inverter through house then to pump means house sees voltage drop across wiring. Separate run from inverter direct to pump, sufficiently large gauge.

5.9A running, expect 30A surge. 30A x 240V = 7.2kW; surge should last less than a quarter of a second.

4400W 48VDC Pure Sine Inverter Charger MS-PAE | Magnum Dimensions

www.magnum-dimensions.com

Output Power	4,400W
Peak Watts	8,500W

That ought to do it. Try dedicated wire run.


Does pump have a capacitor? How old? weak capacitor could make starting harder.

I have it wired from the Magnum feeding a sub panel with 8 ga THHN less then a two foot run. In the sub panel a double pole 40 amp breaker going to the house main panel also with 8 ga. also from the sub panel I have the pump wired though a double pole 15 amp breaker to a 240v receptacle with 12 ga solid core About 6 to 8 inches of wire. That’s where the pump plugs in.

I am going to double check the cord that‘s connected to the pump. It did seam kinda small to me but I didn’t think much about it when wiring.

Also the pump is brand new. it is bolted to the floor right by the 500 gallon tank. It never has to draw water up.

 

[MichaelK]

I would not be as concerned about the wiring to the pump as I would be about the wiring from the batteries to the inverter. The Magnum manual recommends at least 00 copper wire for your battery connections. It might be that too thin wire leading into the inverter is not allowing the required amps to get in fast enough.

Your 600Ah battery bank should be more than enough to support this inverter. If it turns out the the wire gauge is sufficient, and your Magnum can't handle it's surge, a more elegent solution might be to get a second Magnum inverter and run them in parallel.

It's important that they are exactly the same model with the same firmware version. Once linked together, they match phases, and double your output.

I would think that your battery bank is still large enough to handle the supply for both inverters.

 

[RCinFLA]

I would say that inverter should be able to start up that pump. I used a 4kW LF inverter to start a similar 5/8 hp centrifugal pump with no problem.

You should use 2/0 battery cables to inverter to handle the high current surge.

You may want to check the starter cap on the pump. If its electrolyte has dried out its capacitance decreases resulting in less starting torque on motor.

For water pumps, soft starters don't usually help much because of the initial mechanical load on pump. You just end up a with a lower starting amperage that last longer. Usually results in inverter exceeding its surge current maximum time length.

It may be worse if you have your turn on water pressure set higher. I used 20 psi turn on and 40 psi turn off to an air bladder tank. Not sure if your 500 gallon cistern tank is just gravity feed or an actual pressure tank. 20 psi head pressure would be a tank at about 45 feet above pump if gravity feed. You can try to start it without pump output connected to cistern tank to see if it is too much head pressure to start up against.

 

[rcrracer]

Ever thought about a DC pump?

 

[Jack Rabbit Off Grid]

Ever thought about a DC pump?

No.

Two reasons why.
1. I have owned many RV’s and have seamed to replaced a lot of them in my life.
2. I purchased two off grid property’s just before the KungFluse/Black plague. one where I live and in the middle of setting up from new and one already done for my daughter to live. The one already set up had a DC pump. It quit working within the first month of owning it. We also found in one of the rooms a spare and 5 old broken pumps.

Im thinking my wire AWG is on the light side.

 

[Jack Rabbit Off Grid]

I used 1AWG wire from the batteries to the inverter. I had it on hand that day and didn’t think it would be that big of deal for less the 24” but evidently it does. So today I went to town and picked up proper 0/0AWG wire and copper ring terminals. It’s to late also getting cold today but will get this changed out tomorrow and see what happens.

 

[izmail]

Just in case - take a look at this soft start unit from reputable Schneider Electric
https://www.amazon.com/Soft-Start-110-460VAC-12A-3Phase/dp/B007ID28MU

 

[HarryN]

The soft start feature is there to deal with the "locked rotor amps" number, which can be quite high on an induction motor.

I don't understand why it would be different for an air conditioning compressor motor vs a pump motor, but I am not certain.

A somewhat more sophisticated approach is to use what is called a variable speed drive or variable frequency drive. They start the motor up on a slow ramp up to the final speed needed. This is done by essentially turning the incoming AC - into a noisy DC internally - then back to the output AC at the desired frequency.

This method is widely used industrially to manage power in chemical plants and is credited with major power savings by the department of energy. AFAIK, pretty much all new, industrial motors are installed with VFDs now.

Quite a number of firms build VSDs (variable speed drives), mostly for 3 phase, but some do for single phase as well.

I don't know anything about this particular company, but since it starts with an "A", it came up early in an internet search.

Single Phase VFD, control speed for single phase motors | ATO.com

www.ato.com

Like most things, it probably makes sense to purchase a 1 hp version for a 1/2 hp pump so that it isn't running anywhere near the max.

 

[Hedges]

From wiring diagram, this appears to connect to both starting and running windings. I think that could actually work, much like the soft-starts.
Provide a good phase shift to the starting winding, and use PWM to limit total current.

https://www.ato.com/Content/doc/GK3000-single-phase-vfd-user-manual.pdf

Compared to using 3-phase motor and VFD, keeping original split-phase motor leaves you the fallback of powering with your existing inverter or a generator (assuming it is the no-name electronics not the motor that dies.)
Spare pump seems like a good idea to have on hand.

 

[Jack Rabbit Off Grid]

Th

Just in case - take a look at this soft start unit from reputable Schneider Electric
https://www.amazon.com/Soft-Start-110-460VAC-12A-3Phase/dp/B007ID28MU

Thank you I will have to do some research into this If upgraded cable does not fix the problem.

 

[Jack Rabbit Off Grid]

I did not know there were

The soft start feature is there to deal with the "locked rotor amps" number, which can be quite high on an induction motor.

I don't understand why it would be different for an air conditioning compressor motor vs a pump motor, but I am not certain.

A somewhat more sophisticated approach is to use what is called a variable speed drive or variable frequency drive. They start the motor up on a slow ramp up to the final speed needed. This is done by essentially turning the incoming AC - into a noisy DC internally - then back to the output AC at the desired frequency.

This method is widely used industrially to manage power in chemical plants and is credited with major power savings by the department of energy. AFAIK, pretty much all new, industrial motors are installed with VFDs now.

Quite a number of firms build VSDs (variable speed drives), mostly for 3 phase, but some do for single phase as well.

I don't know anything about this particular company, but since it starts with an "A", it came up early in an internet search.

Single Phase VFD, control speed for single phase motors | ATO.com

www.ato.com

Like most things, it probably makes sense to purchase a 1 hp version for a 1/2 hp pump so that it isn't running anywhere near the max.

I did not know they made single phase to single phase VFD’s. I was under the impression there were 3 phase or single to 3 phase. My late father owned a machine shop that he used them to run 3 phase lathe and milling equipment at our family home small garage/shop.

Thank you for the link. I will do more research into this alternative if upgraded cable does not work.

 

[Hedges]

I did not know they made single phase to single phase VFD’s. I was under the impression there were 3 phase or single to 3 phase.

Starter winding.
It says not to run below 80% of full speed for an extended time.

 

[12VoltInstalls]

have owned many RV’s and have seamed to replaced a lot of them in my life

I read this often. I have gotten YEARS out of 12VDC pumps. Filters probably make a big difference , so does not buying just the thing available or the best price you can find. Shurflo and the other brand I can’t think atm of have lasted very well for me.

 

[RCinFLA]

I did not know they made single phase to single phase VFD’s.

You are essentially correct.

A variable frequency drive needs a motor that produces a self rotating field with windings capable of continuous run current. A three phase motor does this.

Theoretically a single phase motor with auxiliary winding could be run as a two phase motor with VFD but most auxiliary (starter) windings are made with smaller gauge wire not intended to be run with full continuous run current. Running it on a VFD would likely burn up the auxiliary winding. Most all variable frequency drives include soft starting voltage ramp so you could use that function on a single phase induction motor, just don't use the variable speed function as it will likely burn up motor.

A soft starter alone is just a 'light dimmer' triac device. It effectively ramps up the applied voltage to reduce the initial surge current but this will lengthen the motor's startup time by two to five times. The amount of initial current reduction is usually not reduced enough and the lengthened starup time trips the inverter surge time limit. Soft starters have two adjustments, initial minimum voltage and ramp time.

There are soft starters with momentary start capacitor boost which do provide a significant benefit for reducing startup surge current on air conditioner compressors. Air conditioner compressors typically do not include an optimum starter capacitor, instead relying on the smaller value run capacitor to provide initial rotating field and improve run power factor.

Problem with water pumps is they have a higher initial external mechanical load during startup so there is more than just the getting the motor's rotor inertial mass rotating.

 

[Jack Rabbit Off Grid]

So today I upgraded the cables to 2/0 and It still does it. So I called Magnum’s tech support. After about 30 min of troubleshooting he had determined the Chinese 1/2hp motor is to blame. Which I do agree with him Because my other house runs a MS-4024-PAE and it starts a 1hp shallow well pump no problem.

he recommended for me to wire this inline with the pump. And it should take care of the problem. Or buy a better pump.

https://www.grainger.com/product/DAYTON-Motor-Run-Capacitor-2GU21

 

[Zwy]

The soft start feature is there to deal with the "locked rotor amps" number, which can be quite high on an induction motor.

I don't understand why it would be different for an air conditioning compressor motor vs a pump motor, but I am not certain.

A somewhat more sophisticated approach is to use what is called a variable speed drive or variable frequency drive. They start the motor up on a slow ramp up to the final speed needed. This is done by essentially turning the incoming AC - into a noisy DC internally - then back to the output AC at the desired frequency.

This method is widely used industrially to manage power in chemical plants and is credited with major power savings by the department of energy. AFAIK, pretty much all new, industrial motors are installed with VFDs now.

Quite a number of firms build VSDs (variable speed drives), mostly for 3 phase, but some do for single phase as well.

I don't know anything about this particular company, but since it starts with an "A", it came up early in an internet search.

Single Phase VFD, control speed for single phase motors | ATO.com

www.ato.com

Like most things, it probably makes sense to purchase a 1 hp version for a 1/2 hp pump so that it isn't running anywhere near the max.

The only issue I've seen in the forum here with starting a well pump slow that isn't designed for it, is there needs to be a thin film of water that quickly covers the seal for the bearings. Whether that really is true, I can't say but one member here had stated as such. Hedges mentioned it here: https://diysolarforum.com/threads/well-pump-never-ending-discussion.33967/post-421061

A cistern pump would possibly be different dependent on the design used.