S/phase submersible pump starting problem.

Griffey · Dec 30, 2018

Hi,
I have a s/phase submersible pump, remote float sw control, (capacitor run 20uF, capacitor start 100uF,) app 20years of age, 2in bore drawing around 6A when running on load. It has developed a problem on start up which i believe i have diagnosed and indicates that the capacitor start up relay (only 3 connections), is the culprit.

It will start after the 2nd of 3rd attempt and then run fine continuously (the capacitors test out O.K. with a capacitor meter). I am having great difficulty in sourcing a replacement relay, having tried Remco capacitors, RS, Farnell, and a pump spares company, if anyone could help with any information i should be most grateful.
thank you Griffey.

telectrix · Dec 30, 2018

what's the chance of a pic of the relay?

Pete999 · Dec 30, 2018

Have you checked the centrifugal switch is operating at the right time / speed?

buzzlightyear · Dec 30, 2018

why don't you buy a new pump , considering you had that one for 20 years ,Looks like you had your moneys worth from tha

Silly Sausage · Dec 30, 2018

buzzlightyear said:
why don't you buy a new pump , considering you had that one for 20 years ,Looks like you had your moneys worth from tha

For the price of a new relay and half an hours work?
Fix the bugger.
Typical 'throwaway' attitude!

Griffey · Dec 30, 2018

telectrix said:
what's the chance of a pic of the relay?

i can take a photo but it will be several days before i 'll have access to the site. thank you.

Griffey · Dec 30, 2018

Pete999 said:
Have you checked the centrifugal switch is operating at the right time / speed?

there is no centrifugal switch. the relay drops out at app 75% motor speed (back EMF). thank you.

Pete999 · Dec 30, 2018

Griffey said:
there is no centrifugal switch. the relay drops out at app 75% motor speed (back EMF). thank you.

You sure ?

Griffey · Dec 30, 2018

buzzlightyear said:
why don't you buy a new pump , considering you had that one for 20 years ,Looks like you had your moneys worth from tha

Hi, it's own by a museum/charity, i was just trying to help them out. thank you.

Griffey · Dec 30, 2018

Pete999 said:
You sure ?

I am as sure as i can be, there is only a 3c0re cable from from the pump to the control box for the windings. thank you.

westward10 · Dec 30, 2018

Pete999 said:
You sure ?

That is what the relay is for.

Lucien Nunes · Dec 30, 2018

Pete I think it's like a fridge compressor start relay. The relay coil is in series with the run winding and the contacts are in series with the start winding. At standstill the heavy current through the run winding operates the relay energising the start winding. Once the motor is up to speed the current drops and the relay opens the start circuit. They are used where it's difficult to fit a centrifugal switch on motors driving fairly predictable loads.

OP beware the capacitor meter as a test device. Failing electrolytic caps can sometimes measure OK for capacitance, but break down under mains voltage. However, these relays are not massively reliable and are considered a replaceable part, so your diagnosis may well be correct. I would not be surprised if the relay on your pump also has a refrigeration application so you might try that avenue.

Pete999 · Dec 31, 2018

Lucien Nunes said:
Pete I think it's like a fridge compressor start relay. The relay coil is in series with the run winding and the contacts are in series with the start winding. At standstill the heavy current through the run winding operates the relay energising the start winding. Once the motor is up to speed the current drops and the relay opens the start circuit. They are used where it's difficult to fit a centrifugal switch on motors driving fairly predictable loads.

OP beware the capacitor meter as a test device. Failing electrolytic caps can sometimes measure OK for capacitance, but break down under mains voltage. However, these relays are not massively reliable and are considered a replaceable part, so your diagnosis may well be correct. I would not be surprised if the relay on your pump also has a refrigeration application so you might try that avenue.

Thanks Lucien

ChipFanDave · Jan 1, 2019

Can you use a timer relay to open the start capacitor side after certain time ?

Griffey · Jan 5, 2019

Lucien Nunes said:
Pete I think it's like a fridge compressor start relay. The relay coil is in series with the run winding and the contacts are in series with the start winding. At standstill the heavy current through the run winding operates the relay energising the start winding. Once the motor is up to speed the current drops and the relay opens the start circuit. They are used where it's difficult to fit a centrifugal switch on motors driving fairly predictable loads.

OP beware the capacitor meter as a test device. Failing electrolytic caps can sometimes measure OK for capacitance, but break down under mains voltage. However, these relays are not massively reliable and are considered a replaceable part, so your diagnosis may well be correct. I would not be surprised if the relay on your pump also has a refrigeration application so you might try that avenue.

Hi thank you for your comments and the information, i think i shall fit a timer and power relay to switch the start capacitor. Thank you.