School me on motor starting solutions

[jrcampbe]

Hey guys,

Had a recent extended power outage and was feeling pretty damned cocky about my military surplus generator. If you haven't looked in to these, it's right up the alley of most on this board. Mine is an MEP-002a, which is a 5KW steady state, 10KW peak at 10,000 feet above sea level. Diesel powered, with military 24V starting system, which also runs glow plugs and intake air preheaters, so it is designed to start and operate down to -25F with appropriate fuel. Mine fired up at 10 below (it lives outside) after a 45 second preheat cycle. It will also make 3-phase power to run your machine tools. Check them out!

ANYHOW...

It works great but will not start my well pump. It never got off the starter windings or made full pressure. I deliberately got the 5KW model because it uses half the fuel as the 10KW, which is the same design except for the engine size.

The alternator is rated for 26A at 240V split phase.

When the motor tries to start, the load meter on the generator goes to about 50% load, which should be 13 amps or so. It doesn't pull more current than that.

What's going on here? I understand there are motor start assists which are basically big capacitors you wire in. Can someone explain whether this could help?

Why does the load only go to 50%?

Thanks guys!

Jim

 

[Stuart in MN]

What size is your well pump motor? horsepower, voltage, amps.

 

[lametec]

Not an answer to the question, but probably a solution: If the well pump is not already wired for 240V, make it so (if possible).

I have a 3/4HP Jet pump myself, running on 120V. It starts just fine off my 5kW genset.

 

[chrispyny]

I also have an MEP-002a.

Inductive loads such as electric motors are very very tough for generators. They much prefer resistive loads. I suggest investing in a three phase well pump if possible. I bet the MEP-002a will get a three phase pump going but even that will probably be close to the max.

Or invest in a Mep-003a. The problem is that super affordable MEP's under a few hundred dollars were gone several years ago. I hopped on the MEP band wagon very late. I got mine 2 years ago and paid $1,150 for a trailered MEP-002a. I sold the trailer for $450 but still wish i hopped on the wagon years ago when you could bring home 4-5 of these on a trailer for less than a grand.

 

[gungatim]

I may be way off base here, but it may be a ground issue...seems like when they wired my deep well pump they only run the two hots, no ground, maybe the generator isn't grounded or earthed the same?

i'm probably way out of my league here so someone knowledgeble please chime in!

 

[chrispyny]

When the motor tries to start, the load meter on the generator goes to about 50% load, which should be 13 amps or so. It doesn't pull more current than that.



Jim

Does the generator compensate for the load and jump back up to 60 hz after the initial surge ? Or does it stay bogged down ?

 

[jrcampbe]

Does the generator compensate for the load and jump back up to 60 hz after the initial surge ? Or does it stay bogged down ?

It bogs down to about 58Hz.

 

[jrcampbe]

It's a 240V motor. I will look at how large.

I was hoping to figure out a solution other than a bigger generator. I'll keep my eye out for an 003. I got my 002 for $600.

 

[larry_g]

I have a constant pressure pump also known as a variable speed pump. Part of the system is a soft start and a slow run if the system is only calling for little water. It is a 2hp pump and will start with a 2 amp draw, no inrush like a standard pump. I have run it off or a 4k generator powered by a brigs motor.

lg
no neat sig line

 

[wyliesdiesels]

Hey guys,

Had a recent extended power outage and was feeling pretty damned cocky about my military surplus generator. If you haven't looked in to these, it's right up the alley of most on this board. Mine is an MEP-002a, which is a 5KW steady state, 10KW peak at 10,000 feet above sea level. Diesel powered, with military 24V starting system, which also runs glow plugs and intake air preheaters, so it is designed to start and operate down to -25F with appropriate fuel. Mine fired up at 10 below (it lives outside) after a 45 second preheat cycle. It will also make 3-phase power to run your machine tools. Check them out!

ANYHOW...

It works great but will not start my well pump. It never got off the starter windings or made full pressure. I deliberately got the 5KW model because it uses half the fuel as the 10KW, which is the same design except for the engine size.

The alternator is rated for 26A at 240V split phase.

When the motor tries to start, the load meter on the generator goes to about 50% load, which should be 13 amps or so. It doesn't pull more current than that.

What's going on here? I understand there are motor start assists which are basically big capacitors you wire in. Can someone explain whether this could help?

Why does the load only go to 50%?

Thanks guys!

Jim

U are aware that inductive loads such as motors have in-rush currents....get a clamp meter that measures in-rush current(typically during 100ms-300ms in the beggining). In-rush current can be anywhere between 4x-8x FLC. Youre generator probably cant handle the in-rush current, drops the cycles(and the voltage) and the pump motor cant get upto speed. Snow ball effect.

How many HP is the pump? How deep is the well?

I may be way off base here, but it may be a ground issue...seems like when they wired my deep well pump they only run the two hots, no ground, maybe the generator isn't grounded or earthed the same?

i'm probably way out of my league here so someone knowledgeble please chime in!

Grounding would have NOTHING to do with it.

EGCs provide a low resistance path for fault current. This rnables the breaker to trip.

Is the stack pipe metal or plastic? And what about the conduit feeding the wire?

 

[Charles (in GA)]

I cannot imagine a well pump for a single residence being big enough HP to cause any issues. I have operated one of our community well pumps, 5 hp, and a 28 amp steady draw (measured with a clamp amp meter) using my 6500 watt (continuous) Northern generator with a 10 hp Yanmar diesel. Its max load for the generator and it starts and carries it without a grunt of the Yanmar.

Charles

 

[wyliesdiesels]

I cannot imagine a well pump for a single residence being big enough HP to cause any issues. I have operated one of our community well pumps, 5 hp, and a 28 amp steady draw (measured with a clamp amp meter) using my 6500 watt (continuous) Northern generator with a 10 hp Yanmar diesel. Its max load for the generator and it starts and carries it without a grunt of the Yanmar.

Charles

Unless he has a huge pump(I doubt it) then the generator shouldnt have an issue due to pump motor size.

Unless the well is really deep, his pump wouldnt be more than 1-2hp. Many small houses have 1/2hp-3/4hp submersable pumps...

 

[Aceman]

If the well pump runs fine on utility power, but won't start on generator power, then that tells you your gen is too small.

One of the other electricians in our shop had a service call a few weeks ago for the same thing. Someone had bought a generator, I believe it was a 5-5.5kw Generac and according to the ratings they thought it would run the well. But, inrush current is a killer and it wouldn't start.

They ended up buying a slightly bigger generator and this time the well pump ran.

If you want an idea of how much inrush some motors can have over their ratings, I started up a new pump today:

125HP 480v 3 phase 146 amps on the nameplate

Inrush was 992 amps. I tripped the breaker a couple times before I had the instantaneous setting adjusted right. And this was a DRY pump, no water was in the system yet.

Now imagine how much inrush your little submersible well pump will have sitting below the water line, not starting up dry like mine was.

 

[Charles (in GA)]

We need to hear a whole lot more about how the generator is connected to the well. Directly with a selector switch? feeding the house panel with an interlock? Some other odd combination of devices or equipment?

What else is being powered at the same time that you don't see or realize?

You need a clamp amp meter and volt meter to see what is happening when the pump starts.

Charles

 

[chrispyny]

It bogs down to about 58Hz.

If the 002a bogs down and doesnt pick back up, you may need things done to generator. Have you had the injectors adjusted? You may also need your injector pump rebuilt or governor linkage adjusted.

Tell me this. Have you run your generator at full load with other things? Is it just the well pump causing the gen to droop or any load after so many amps drawn?

 

[jrcampbe]

Thanks for this great discussion, guys.

I'm home this evening and will post details about the motor. I can put a clamp probe on it and measure inrush current while on municipal power.

The generator is connected to the hose panel through an interlock. Same symptoms when I turn off all circuits except well pump.

To clarify on the load on the generator, I lose a little speed at high load, but I actually think this is a mechanical governor accuracy issue. With it loaded down, I can turn up the governor a little and get it back to 60Hz. When it goes back to no load, it will jump up to 62Hz or something. It's not like it's losing a huge amount of RPM, just a couple percent. If it should be more stable then this, I will take a look at the governor linkage. Good idea.

I suspect this is an inrush current issue. It "sounds" like a pretty big *** motor. I'll post more tonight.

Is there a way to address inrush current without a bigger generator? This variable speed pump comment is interesting.

I'll make measurements and report back.

Thank you again!

Jim

 

[larry4406]

On large AC units, HVAC techs sometimes install a "hard start kit " (capacitor) to deal with inrush current issues on starting (dimming house lights, etc). I have no idea if this would help with the well pump but its a thought.

 

[chrispyny]

Jrcampbe,

In the technical manual for the 002a, you are to bring the rpms up to reach 62 hz at no load. Once a 100% load is applied, the generator should droop down to no less than 59 hz on a healthy 002a with a properly adjusted governor, mechanically healthy injector pump, an engine with good compression, clean fresh diesel and properly adjusted fuel injectors.
Injectors pop off at something like 1800 psi. If yours are off buy more tham 100 psi, they need adjusting. I got mine done by a member named storeman on steelsoldiers.com. I think he charged $35 for both and.that included return shipping if i recall.

Just an fyi, my 002a needs adjusting somewhere also. It droops at less than half load. So i.m experienced in this matter. I suggest incrementally adding a 100% load to the generator with everything you have in the house OTHER than the well pump, and see what the generator does. Take it from there.

I have to troubleshoot my issue come spring.

Keep us posted.

 

[wyliesdiesels]

On large AC units, HVAC techs sometimes install a "hard start kit " (capacitor) to deal with inrush current issues on starting (dimming house lights, etc). I have no idea if this would help with the well pump but its a thought.

Typically, well pumps have a starter that has one or more capacitors for this exact reason.

 

[bjcouche]

More motor data on your pump would be helpful, however sometimes this is not easy to get. My well pump was the deciding factor when I bought my generator. As an electrical engineer, I had some idea what I was up against, but I didn't have pump motor data to work with. I did know that my pump was set at 325' and had a 6" casing. I would consider this fairly deep, so it likely has a good size pump to get the water up that high. I used a scopemeter to measure the peak starting currents, as well as steady state current when operating on utility power. The rule of thumb for 3 phase motors is about 6-10X rated current is drawn on startup. Now our well pumps are single phase, and usually draw less than that on startup, but also have less stall torque. Anyway, I can't find my scope measurements, but it drew a LOT of current for about 2 seconds before coming up to speed and dropping to steady current draw. On generator power, the current was significantly less (still more than 2X rated though) and the generator bogged down, sped up, overshooting a little bit. It did this 2 or 3 times before settling down to a constant load. I scoped the voltage and current during starting. The inrush current is lower on generator power for a couple reasons. First, the generator has a much higher impedance than the utility. Second, when the generator initially boggs down, the voltage and frequency reduce in proportion, thus as long as the V/Hz ratio is maintained, full motor torque is available. The lower voltage and frequency causes less inrush current. Then as the generator speeds up, the pump speeds up with it, like a soft start.
Your military generator should be rated like 125-150% current for more then a few seconds, plus it's military so it's got a LOT of extra copper, reducing the impedance. Plus a huge engine for it's KW rating providing a lot of rotational inertia for surge, motor starting loads. I'd look into if your generator is putting out 100% power. Then look to see if you have a large voltage drop, like running 300' of 14awg wire between your generator and house... Remember, there's already a LOT of cable between your house and the well pump, causing some voltage drop already.
In my case I'm running my pump with a Generac 8,000W (12,000W starting) gas generator I got from a big box store. I'm fairly confident that a 5KW model of the same product line wouldn't have been big enough.
From your description, it sounds like your pump is stalling and not getting up to speed. I would check: genset capable of making 100% load, voltage drop at pump, or at least at house breaker panel. (you can't measure it at the submersible pump) Also as others have said, use a clamp amp meter to measure the peak inrush current when started on utility power. You shouldn't need quite that much current on generator power, but if your generator was rated for it, it would help...

Brian

 

[Charles (in GA)]

Our big wells owned by the HOA have starter/overload boxes, but they are 5 hp pumps that pull close to 30 amps.

Friend of mine had a well installed for her old house since she did not want city water (house had not been lived in in 40+ years) and the pump does not have any sort of starter box. Kinda surprised me. Deep well, about 200 ft, 8 in casing, with a 20 amp 240v circuit, 12/2 w/grd UF supplying the pressure switch, which goes straight to the well head. Pump works good and flows all the water a garden hose can flow, which is all she needs.

Charles

 

[wyliesdiesels]

Our big wells owned by the HOA have starter/overload boxes, but they are 5 hp pumps that pull close to 30 amps.

Friend of mine had a well installed for her old house since she did not want city water (house had not been lived in in 40+ years) and the pump does not have any sort of starter box. Kinda surprised me. Deep well, about 200 ft, 8 in casing, with a 20 amp 240v circuit, 12/2 w/grd UF supplying the pressure switch, which goes straight to the well head. Pump works good and flows all the water a garden hose can flow, which is all she needs.

Charles

Interesting.

Never seen a submersable without a pump controller!

 

[TractorJeff]

Mine at 90 feet is wired like Charles states his friends is plus my brothers house the well pump was at 200 plus feet and wired the same way.