Submersible Pump...

[sponge23]

Hi guys, I may sound like a bit of a thicko but I am puzzled by something at the mo. I am installing a 7.5kW 3P balanced submersible pump in a concrete collection chamber. The sealed leads that came with the pump were not long enough to reach the control box so I was given a resin joint kit to join the existing leads with some armoured - the joint will be submersed in water most of the time. There is no earthing point on the pump, no mention of it in the manual.

So my question is: if there is a fault, either on the metal casing of the pump or the resin joint fails, what happens to the fault current? I am a bit concerned because it is very muddy and wet around the chamber and control box so anyone near by may be affected.

Thanks
Adam

 

[benji]

how many cores in the cable from the motor

 

[sponge23]

only the three for l1, l2 & l3

 

[ian.settle1]

Think you will find even though there is metal parts on the pump it is a double insulated pump/motor and that is why there is only 3 cores .

Normally pumps like this come with a lead some 20 metres long if you have not already purchased it you could contact the manufacturer of the pump they may supply you with one with a cable as long as you want

 

[sponge23]

Well the problem was that the leads that came with it were nowhere near long enough! Only about 3m...

 

[benji]

can you purchase a longer cable of the same type /size and remove short piece and replace with longer cable then you have no joint to worry about

 

[sponge23]

well have already done the joint! you cannot open up the pump and replace the cable because it is sealed.

 

[Marvo]

Many pumps have the cable on a small low profile IP68 plug and socket.

 

[TNS]

well have already done the joint! you cannot open up the pump and replace the cable because it is sealed.

You should be fine with the joint (not the smoking kind), I’ve used them deep well pumps with no problem.

 

[sponge23]

ok thanks guys. any ideas on the earthing problem?

 

[ian.settle1]

ok thanks guys. any ideas on the earthing problem?

Are you sure the pump is not double insulated?

 

[Engineer54]

ok thanks guys. any ideas on the earthing problem?

You don't have an earthing problem if it's double insulated (Class11)!! If there is no connection means within the sealed motor cable, and no means of earthing on the motor housing then you can be pretty dammed sure it IS a Class 11 submersible pump!!!

 

[sponge23]

silly me. looked today and there is an earthing nut. seems a bit stupid to me that theres nothing in the manual about it. you would think that the pump would have some sort of multicore cable with the 3 phases + an earth. I suppose i'd better put a new earth rod in at the control box because its about 400M away from the dis board!

 

[netblindpaul]

^pardon?

 

[Engineer54]

silly me. looked today and there is an earthing nut. seems a bit stupid to me that theres nothing in the manual about it. you would think that the pump would have some sort of multicore cable with the 3 phases + an earth. I suppose i'd better put a new earth rod in at the control box because its about 400M away from the dis board!

Don't be silly!! The chances are this submersible IS Class 11 and has no need for an earth connection. As for the 400 metre run, i hope you've calculated for the volt drop on this motors starting current?? How is this supply cable to the pump being run and in what type of cable??

 

[sponge23]

16mm SWA is feeding it so that should be enough. the thing is im not strictly an electrician, i work on a farm but i have been training over the past 2-3 years as a sparks. I do what my employers ask and sometimes make suggestions but they dont pay me enough to do proper calculations!

 

[silva.foxx]

... the thing is im not strictly an electrician... but they dont pay me enough to do proper calculations!

:38::speechless::fuk2:

 

[netblindpaul]

This is scary!

Are you seriously saying that you just install with no calcs or checks.

What about testing & inspection?

I am wondering how you will manage with the earth rod connected to the pump when the earthing system for the supply is of a different nature.

If this is in a business situation you do realise what you are doing could get you, personally, a criminal record don't you?

 

[silva.foxx]

I'm not paid to be a design engineer, but for my own peace of mind and self-respect for my chosen profession, I do my calcs!

But if you just want to play at it... carry on. This game doesn't end with 'taking your ball home' but fatality!

Do it right first time.

 

[Marvo]

I'm feeling sorry for the pump