Garden water features tripping rdc

[ltodd2]

Hi.
After a bit of advice. I got 3 small water features all connected to a junction box and into an outside rcd socket. Been working for a long time. recently it keeps tripping so ive checked and cleaned all the pumps no joy. I then disconnected 1 pump one at a time to try and find the issue. 1 pump and it stays on. tried this with all 3 and all stay on. Tried 2 and stayed on for a while. change round the order of the 2 and same issue. That was a couple of days ago. Gone back to them today and now its single works. 2 it stays on for about 20 seconds then trips. all 3 and trips in about 1 second. does not matter what order I do them. Any idea wha this could be.

Thanks

 

[Richard-the-Ninth]

With nothing connected, but switched on does the RCD trip?
Are there any other junction boxes/joints anywhere? (Of any description)

As a rule of thumb RCD's should never trip on their own, so something must have happened, the question is what? So have you or anyone else carried out any alterations in the garden?

 

[Geoff1946]

It's not impossible that you have developed slight leakage on every pump. They can be dodgy things.
I had one that had a combined UV filter which kept getting water in the lamp housing.
I changed the seal twice, greased it with silicone grease, all to no effect, and eventually found it was getting in via the cable gland.

 

[ltodd2]

With nothing connected, but switched on does the RCD trip?
Are there any other junction boxes/joints anywhere? (Of any description)

As a rule of thumb RCD's should never trip on their own, so something must have happened, the question is what? So have you or anyone else carried out any alterations in the garden?

On its own all good.
All 3 pumps go to this single box and thats connected to the rcd socket by a plug

 

[Richard-the-Ninth]

As I said previously RCD's don't often trip of their own accord, and you have proven that yours is working as it should, therefore your easiest option is a process of elimination. (The best option would be to get all pumps and cables tested to find out what the insulation resistance is)

I presume "this box" is a junction box? Picture may help.
What type of cable connects this box to the plug?
Have you physically checked all the cables? (Looking for any damage)
Its the simple things that cause the most problems, have you opened the plug?

 

[ltodd2]

As I said previously RCD's don't often trip of their own accord, and you have proven that yours is working as it should, therefore your easiest option is a process of elimination. (The best option would be to get all pumps and cables tested to find out what the insulation resistance is)

I presume "this box" is a junction box? Picture may help.
What type of cable connects this box to the plug?
Have you physically checked all the cables? (Looking for any damage)
Its the simple things that cause the most problems, have you opened the plug?

hi Richard

thanks for the reply.
I've used one of the insulation testers before but was at last place I worked. Will the resistance setting on volt meter be any good as a simple first step.
the cable from the junction box to plug is about 40cm of 16amp flex on the Wall next to the box. Plug is all ok

what I can see of the cables I've check. Most is in a tube under ground. My suspicion is if its cables related its going to be in there cos it will be hardest part to check.
Thanks for the advice. Will try and check it tomorrow if not raining

 

[SPECIAL LOCATION]

hi Richard

thanks for the reply.
I've used one of the insulation testers before but was at last place I worked. Will the resistance setting on volt meter be any good as a simple first step.
the cable from the junction box to plug is about 40cm of 16amp flex on the Wall next to the box. Plug is all ok

what I can see of the cables I've check. Most is in a tube under ground. My suspicion is if its cables related its going to be in there cos it will be hardest part to check.
Thanks for the advice. Will try and check it tomorrow if not raining

A basic volt meter will not be able to test the insulation resistance, as it will not be able to output a sufficient voltage to measure the resistance through deteriorating insulation..

Also... it could be sensible to test that your RCD is actually still operating correctly..
i.e. a 30ma RCD must NOT trip at 15ma or less..
but MUST trip at 30ma or greater..

Occasionally an RCD can become over sensitive and trip below 15ma!!
{ an RCD tester, preferably with a ramp-test function, would be advantageous for this. }

Some appliances can have an element of natural leakage...
e.g. if you had three items all with 10ma natural leakage individually they would all be ok connected to their own RCD...
But all connected to the same RCD they would cause it to trip!

An incorrectly sealed external junction box is always a good place to check with any problems relating to outdoor wiring tripping RCD's..
insects have a cunning ability to get into very small apertures on external wiring.... and start creating bridging paths to earth!
Damp can start penetrating cables and accessories that have had exposure to UV light...

In your investigations remember that RCD's are detecting current leaking to earth..
and as your problem involves water features they are most likely "Double Insulated" devices with no exposed 'earthy' parts,
or any direct connection back to earth...

So the earth leakage path may be directly to the actual external mass of earth itself, rather than a wiring connection back to electrical earth.

Wish you well with your investigations....
Intermittent faults can be a bit of a time consuming sod to resolve!!

 

[Richard-the-Ninth]

as your problem involves water features they are most likely "Double Insulated" devices with no exposed 'earthy' parts,
or any direct connection back to earth...

Just saying. All the mains pond/fountain pumps I have come across for outdoor use have a 10m 3 core cable, so are not double insulated.

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Itodd2, Picture of this box would be nice.

If you really wanted to..................disconnect the cables from the box, tie (don't tape) string to them and pull them out, check the cables, then you can use the string to pull them back But if you are going to do that, do them all at once, to prevent the string "burning" through any one cable.

Another thought. Is there another RCD protected socket in the house? If so, run an extension lead from it, unplug the plug, plug the plug into the extension lead switch on. If the RCD trips shortly it is NOT the RCD at fault. This would only be temporarily as you did say

all 3 and trips in about 1 second.

The other thing is, what about the cable that is not in the tube? What is mechanically protecting that? (Pictures would be nice )

Oh, what make/model are the pumps. (Just very curious) or if you want to be really nice..........pictures of the water features.

 

[Mike P]

A lot of pond pumps are double insulated with no earth. I have had this with a single pump. I dismantled the impeller section cleaned it reassembled it and it was fine. I can’t see how you can do an insulation test on a double insulated pump. As Special Location said it's possibly going to the ground mass. So new pumps, but worth cleaning them first.

 

[Murdoch]

Imported lights and pumps often use poor quality "copies" of decent cable to supply these devices - the cumulative leakage could be the issue across these devices ........

 

[ltodd2]

A lot of pond pumps are double insulated with no earth. I have had this with a single pump. I dismantled the impeller section cleaned it reassembled it and it was fine. I can’t see how you can do an insulation test on a double insulated pump. As Special Location said it's possibly going to the ground mass. So new pumps, but worth cleaning them first.

The sticker on it shows its double insulated but it also has an earth cable. I've took the impeller out of all and cleaned them. Individually they pump perfectly. Think its sounding like the cables may be the issue so will pull it all out when weather allows.

 

[binky]

The sticker on it shows its double insulated but it also has an earth cable. I've took the impeller out of all and cleaned them. Individually they pump perfectly. Think its sounding like the cables may be the issue so will pull it all out when weather allows.

I would guess at damp in the tubes causing the cable to fail.

 

[ltodd2]

Thanks all for you input. After looking again today I've decided just to scrap all 3 and get new. I tried connecting it via extention cable to nowhere socked on other side of the house which is also an rcd one. This time it tripped but was not the red in the socket but the main one in the cu. Again thanks