Need a lot of help with a subpump please...

Hi. I hope someone here can help me. My father gave me an old submersible pump. A Gorman Rupp subpump. It's probably over 50 years old and it doesn't work anymore. I want to test and repair it if possible.

It's a pump with no dry kill switch attached right next to the pump like we are seeing on the newer model ( no flowtation on/off swicht. It also a pump with a big disconnect box, in witch there are old electronic/electric parts: there is a electrical breaker , a relay , and a capacitor.

This pump runs on 115vlt, 1 ph. It's a 2 hp pump and 28 amp

I don't have much knowledge in electricity or electronic , but I would really like to see if this pump can work again. I know if was working fine when I was a kid. My father stored the pump and the switch box in an underground pit for many years and now it's all corroded and it's not working

Ok here is a picture of the pump:

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Now below is the picture of the switch box : Now in this switch box, the electricity comes in from the left side of the box , it goes into a relay and a capacitor , and comes out to the pump from the right side of the box. One thing that may trick you is regarding the electricity coming in, I know that usually one use the black and white wire for this but What they did here is used the black as live and the red as neutral. The white wire seen bended down is actually spare and not connected in any way.

Also I'm no electrician and I'm not used to see a double breaker connected to a neutral.. ( remember what you are seeing is 115 vlt, not 220 vlt.) why is that?

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And here is the picture of the electrical diagram: this I'm sure will explain all the mistary of this pump, but unfortunately I can't understand or read this..

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now for the questions..

How can I test the pump to know if it's fixable? I will tell you what I checked already: I check the breakers with my tester and they do not work anymore. So what I did was bypassing the breaker to see if the rest of the electronics work, and they don't. ( it's either the relay or the capacitor , or both that don't work imo.)

So what I did after this is connecting the 115vlt right on the pump's black and white wire ( I believe the red wire has to do with the capacitor, that's why I didn't check??? ) my 115 vlt was coming from a 15 amp braker . I saw a big spark when the live wire touched the black pump's wire , so I terminated the test right away as I thought It would trigger my home breaker ( remember my pump pulls 28 amps..)

Would it make sense to hooked the pump into my oven plug ( 40amps). By hooking I mean bypassing all the electronics and connecting to the white and black wire of the pump itseft? Or no sense because if the relay and capacitor are not working, he pump won't start anyway?

In order to buy new parts for the switch box, can someone with a brain give me some specs for a relay, a capacitor, and the discharge resistor ( connected to the capacitor, see diagram )

Also do one know if this pump is equipped with a kill switch if it ever runs dry? Can you guess it has or not form the diagram?

Thanks for our time

Thanks for you help

you can reach me at


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Reply to
John Fields

Be very careful in doing anything while trying to understand--you just might kill yourself!

The red wire goes to the motor's starter winding. This is energized with the start capacitor to get the motor started. The start relay then disconnects the start winding and the motor runs on a single winding.

Here's where you can *really* kill yourself! The oven plug is 240V!!!

If you've got this far and are still breathing--STOP while you're ahead!!!

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My opinion, If life is sweet and you want to be around much longer, take it to a electric motor rebuilder or someone acquainted with such equipment. Better safe than in oblivion...

All you need is one bad gasket or seal to allow water into the motor guts. Once that happens, insulation resistance goes to hell and you get rampant corrosion. My gut feeling is that it is more likely worth more in scrap value for its copper and bronze content than anything else.

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The electrical components are badly corroded, the motor winding is in unknown condition, and you know nothing about electricity. Please do not play with this, as it can kill you! The first step would be to megger the motor winding to determine the insulation condition. If you don't know what that means, throw the pump out and do NOT connect it to electrical power!


Ben Miller

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Ben Miller

ok .... guys you are a bit hard on me.... ok I already knew sn oven runs on 230 volt , I forgot to point I would only take one faze of it... I might take your word for it and sent it to a specialist, or I might give it a shoot myself. I'm know I won't electrocute myself with this project. (43yom here...)I know a capacitor is a thing to treat with respect... if you guys would answer some of my questions, and some of you already did, I would greatly appreciate. this pump has a special value to me... thanks again stef.

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The predicted outcome might be kinder!

Reply to
ian field

Ditto. Submersible pumps in water are just to much of a danger for clueless tinkerers to handle. The most basic problem is how are you going to be sure to seal the pump even if you are able repair it?


-- Ferme le Bush

Reply to
Salmon Egg

treat the project as if you were restoring a classic car or any other antique.

first disassemble the entire unit, taking photos at each step (so you can refer to them upon re-assembly.

clean and refurb each piece. replace or machine new parts for one that seen to degraded to function. (yes i know you wont be able to just order replacement parts for this but that part of the challenge)

mark or label each piece and store in a tackle box like container or parts bin with drawers. an electric etching tool will help.

the motor rebuild i would not even attempt myself no matter how much sentimental value it held. i would send it out to a motor rebuild. almost certainly the rebuilder might urge you to replace it because it is so old or be hesitant about offering any warranty.

for the pump you probably will end up relying on the "make a gasket" gels and goos. you might, with patience, cut your own gaskets out of a solid sheet of material.

as part of the cleaning process i find an ordinary dishwasher with Cascade detergent come in handy. also brass brushes, dremmel tool with wire brush, steel wool and emmery paper all come in handy. add a little oven cleaner powder (Zud) and whatever other cleaners are handy (simple green, orange blast engine cleaner).

whenever you finally decide to test the rebuilt unit please incorporate the use of a GFI circuit breaker. if it trips you have a problem in the unit. fix the problem. do not bypass the GFI. if you ever place it in service power it through a GFI.

the guys are "a bit hard" on you because they, like me, get asked questions similar to this in person time to time. when replying face to face, or even on the phone i is easier to convey earnest conviction. many probably have worked "under the gun" trying to restore aging equipment still in use in industry. please believe me when i advise that "it aint gonna be easy, fast, or cheap"

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28 amps is what you would expect a 240 volt pump to use. Look at your circuit breakers in your house, they are all 15 maps or less. Except for the dryer and A/C which run off 240 and have 30 amp breakers.
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Chiming in with all the others, don't bother. I suppose it's a bit of nostalgia but by the description of it the best you can do is fixing up the appearance and use as a decorative piece.

To get it back to working condition you'll have to consult a pro and probably spend much more than it's really worth, certainly more than a new pump would cost you.

- YD.

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after ensuring the body is intact get the insulation and windings tested if that checks out replace all rubbing parts, bearings, glands etc and any other perishable parts, (seals etc)

dissasemble the pump, (and check what it looks like inside, half-full of water is not a good look..)

take it into a motor repair place and get them to check the windings and insulation, they can probably source the other bits you'll need to replace too. (this is a 5 minute job with the motor dissasembled)

when reassembling it use new bolts if the old ones show any signs of age, old bolts just aren't worth the hassle.

test that capacitor and the contactors

it probably needs the capacitor to start.

the details of the correct replacements are probably on a "boilerplate" attached to the pump or the contactor box.

it possibly relied on a float switch in the sump to start/stop it,

It sounds like a split-phase induction motor and they are generally low maintenance machines, but as it's been sitting for a while a full overhaul of the mechanical part is indicated. if the shaft-seal starts leaking two weeks after you get it running it'll have all been for nothing.

Bye. Jasen

Reply to
Jasen Betts

Sorry if I was unnecessarily hard on you. Something of this power level, submersible yet, is not recommended for a first project. Perhaps, get your feet wet on something else (and use a Ground Fault Interrupter).

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ok thanks guys. I appreciate your help. I can deal with simple things in electricity, like last year , I changed the electrical panel in my house for a bigger one, and I built a few PC... but as far a making calculations for knowing what size capacitor , etc etc, that I'm in the dark... I will keep in mind SAFETY if I ever play the technician...I understood it won't be fast, cheap and easy.... Regards


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