really confusedwith this, need help!!!

twitch1984

Got called out to a job yesterday, a water pump for a well in a domestic house kept tripping.
When I arrived I see that the swa which is coming from the fuse board has a socket attached to the end which is quiet damp, so I presume it is water interference and hit off to get a weatherproof socket. at this point the pump is plugged into an extension lead being run out from the house and is not tripping.
When I get the weatherproof socket I decide to use it as a junction box and take the plug off the pum and just connect it directly with the swa in the back of the socket box. when I have this done the rcd is now tripping once the pump kicks in. So I now believe that the problem maybe the swa coming from the house to the pump house. Check this cable and it is fine.
Here is where the mystery lies, I leave the socket connected to the swa and try the pump on a plug again still tripping, but yet I can plug anything else into the socket and it doesent trip.
Yet when the socket is plugged into the extension lead it is working fine.

Sorry if this seems confusing basically
1 Swa works fine when pump is not connected ( seem like faulty pump)
2 Pump works fine when plugged into an extension lead run from kitchen (seem like problem with swa coming out to pumphouse)
3 swa connected to 20a mcb through rcd, kitchen sockets connected to 20a mcb through rcd.

Any help is greatly appreciated, this is really puzziling me.

ps this house has been built with 3 years and this is the first problem they have had with the pump

meercat

how have you checked the swa cable

M cebee

a couple of IR tests should clear up the mystery

meercat

twitch1984 wrote: »

Got called out to a job yesterday, a water pump for a well in a domestic house kept tripping.

what tripped
how are you sure it is the pump that caused it

twitch1984

meercat wrote: »

how have you checked the swa cable

checked continuity from both ends live to live, neutral to neutral, earth to earth, all perfect no continuity between any of the 3 cores either. also the socket which I connected on the end works perfect only trips if the pump is plugged in

twitch1984

meercat wrote: »

what tripped
how are you sure it is the pump that caused it

first the mcb tripped, now its the rcd. pump is on its own mcb nothing else connected

Kildare Resident

What have you tried the SWA with? If what you've tried is not drawing the same power it my not trip, it might be the breaker that is faulty. The pump should be no bigger than 400w, I'd try a kettle on it......

twitch1984

M cebee wrote: »

a couple of IR tests should clear up the mystery

Sorry lad I must be getting rusty, whats an IR test?

meercat

twitch1984 wrote: »

checked continuity from both ends live to live, neutral to neutral, earth to earth, all perfect no continuity between any of the 3 cores either. also the socket which I connected on the end works perfect only trips if the pump is plugged in

m cebee has the right idea
it may be advisable to put the pump circuit on separate rcbo
if the rcd is tripping it may not be the pump causing the problem

twitch1984

Kildare Resident wrote: »

What have you tried the SWA with? If what you've tried is not drawing the same power it my not trip, it might be the breaker that is faulty. The pump should be no bigger than 400w, I'd try a kettle on it......

Tried it with a welder, changed the breaker already.

meercat

twitch1984 wrote: »

Sorry lad I must be getting rusty, whats an IR test?

insulation resistance
megger test

twitch1984

meercat wrote: »

m cebee has the right idea
it may be advisable to put the pump circuit on separate rcbo
if the rcd is tripping it may not be the pump causing the problem

Rcd is fine until I switch on the pump.

twitch1984

meercat wrote: »

insulation resistance
megger test

Ah yeah megger test, ( actually forgot the proper name was an insulation resistance test)

meercat

"2 Pump works fine when plugged into an extension lead run from kitchen (seem like problem with swa coming out to pumphouse)"

you check this extension lead for an earth?

twitch1984

meercat wrote: »

"2 Pump works fine when plugged into an extension lead run from kitchen (seem like problem with swa coming out to pumphouse)"

you check this extension lead for an earth?

Actually didnt think of that, wont get back there until the morning but will deffinetly check that and will do a megger test

meercat

bring a 20 amp rcbo with you
it may help fault finding and would be no harm anyway
let us know how you get on

twitch1984

meercat wrote: »

bring a 20 amp rcbo with you
it may help fault finding and would be no harm anyway
let us know how you get on

will do thanks for the help, really had me flummoxed, and needed some fresh perspectives

meercat

hope you find the problem
stick the plug back on the pump
its advisable for isolation and it saves you returning to reconnect the pump if it has to be replaced(plumber should be able to fit plugtop)

Bruthal

Extension lead earth continuity might we worth checking anyway. Try plugging the pump directly into a socket.