Pond Pump tripping new consumer unit RCD

[GriffMG]

I have a fairly recently installed consumer unit with an RCD, between it and the garden there is another, much older (25yrs?) RCB (big Wylex thing)
from which a couple of power points are provided on the wall of my fish ponds. Before the consumer unit was fitted I could run the pond pump
from the power point (double socket) without any problem. Now when I plug in the pump it runs for a few moments and then trips the
consumer unit RCD, not the old Wylex thing.

I've checked the cabling to the remote sockets and they are good, made sure the inside of the housing is dry (it is) and I can run other things
on that line (another pump) with no problem.

Is there a safe way to run this pump without tripping the RCD or should I get that replaced?

 

[James]

Sounds like a faulty pump, the old wylex thing should trip but it may have been faulty for some time too.
best thing to do may be to call the electrician back that did the board change.

 

[GriffMG]

Sounds like a faulty pump, the old wylex thing should trip but it may have been faulty for some time too.
best thing to do may be to call the electrician back that did the board change.

Thank you, I think the pump is borderline faulty, it will be total PITB to replace that, it's built in and buried in the pool somewhere.
I would call the original electrician back, but I'll need Doris Stokes to contact him... (very old reference to a clairvoyant).

Can you get more/less sensitive RCDs? or is there something I can use to isolate the pump from the earth leakage? Like a 1:1 transformer or something?

 

[timhoward]

Can you get more/less sensitive RCDs? or is there something I can use to isolate the pump from the earth leakage? Like a 1:1 transformer or something?

No, you can't use a less sensitive RCD, 30ma is required for this kind of thing.
An isolating transformer isn't the right solution, and anyway it would exceed the cost of most new submersible pond pumps by quite a margin.
Follow/Find the flex, find the pump and go from there. I'd guess that either a seal has given up the ghost and is letting water in, or the housing is cracked. Either way it's a terminal issue and spending money on avoiding fixing it is just delaying the inevitable really.

 

[brianmoooore]

Don't shoot the messenger! If your pump is tripping a 30mA RCD it is not "borderline faulty", it is very faulty, by a factor of at least x100, and needs to be replaced

 

[GriffMG]

I thought perhaps there was some tolerance among RCDs with some a bit over sensitive and some less so - rather than being exactly as rated - I have seen advice to try swapping out the RCD for another one to see what the result is...

Thank you all for your advice though.

 

[brianmoooore]

There is tolerance in RCDs, -50% +0%. Most 30mA RCDs will trip at 20 something mA, but if your pump is leaking 1/100 of that it is faulty. If it's causing the tripping, it is dangerous.

 

[GriffMG]

I think I'll decommission it.
I don't look forward to trying to remove it from the pond, or the stress to the fish of paddling around in there.

 

[brianmoooore]

If the leak is into the water, it's probably already stressing the fish.

 

[Dave OCD]

I've seen a number of very expensive fish killed by a faulty pump - the owner kept resetting the RCD.......

 

[DPG]

Pumps are devices that will fail from time to time. They should be accessible for maintenance. Not much help in thus case I know, but bear it in mind when you replace it.

 

[brianmoooore]

If these are expensive fish, I'd consider fitting a 10mA RCD in the supply to any submersible pump.