UK Adding RCD spur doesn't set but consumer RCD is fine

[Stevie186]

Hi all,

I have ran added a fused RCD spur off a socket to feed some electric gates. I figured as it was going outside I would put an RCD on the spur on it as I had one kicking around I believe it's probably unnecessary but when I connect it to the supply it will never set and constantly trips? The RCD in the consumer unit is fine though and I have tested and it trips out as it should? I can't understand no matter where I try and put this RCD spur it never sets, I tried wiring into a few different sockets and still the same. Any ideas? I have tried 2 different units and still the same They are the safetysure metal clad RCDs spurs if that makes any difference.

Thanks

Steve

 

[westward10]

If you have additional rcd protection at the board why fit an rcd spur.

 

[Pete999]

If you have additional rcd protection at the board why fit an rcd spur.

What Westward said

 

[Stevie186]

I thought I read somewhere it was best practice for cables that went external, also I was planning to maybe add an exterior socket also which again I thought was best practice. Still it makes me think there is something wrong with the main rcd. I didn't mention this is from the garage where the power comes in it has an old looking RCD I just did the same test inside the house which has its own modern consumer unit with RCD and it set and when tripped, tripped the house one too.....which is what I would expect to happen. The garage one does take 2 presses to actually activate.

 

[Pete999]

I thought I read somewhere it was best practice for cables that went external, also I was planning to maybe add an exterior socket also which again I thought was best practice. Still it makes me think there is something wrong with the main rcd. I didn't mention this is from the garage where the power comes in it has an old looking RCD I just did the same test inside the house which has its own modern consumer unit with RCD and it set and when tripped, tripped the house one too.....which is what I would expect to happen. The garage one does take 2 presses to actually activate.

Garage RCD needs testing properly, do you have the correct test equipment to carry out RCD testing Stevie 186?

 

[westward10]

So the garage board is the main board which supplies the one in the house also with rcd/s. Where is the new gate connected from.

 

[Pete999]

I thought I read somewhere it was best practice for cables that went external, also I was planning to maybe add an exterior socket also which again I thought was best practice. Still it makes me think there is something wrong with the main rcd. I didn't mention this is from the garage where the power comes in it has an old looking RCD I just did the same test inside the house which has its own modern consumer unit with RCD and it set and when tripped, tripped the house one too.....which is what I would expect to happen. The garage one does take 2 presses to actually activate.

Is the feed for the Garage fed from the RCD side of the House Consumers Unit?? two RCDs in the same cable run is not advisable.

 

[Wilko]

Hi - an RCD that constantly trips likely means some of the circuit conductors’ current is leaking to E or another circuit’s N perhaps. As others have said, you only need one RCD in a circuit, but it needs to be a worker .

 

[Strima]

Have you connected a load to the RCD spur? It may require a load to be connected before it can be set.

But as you already have a couple of RCDs in series it's pretty pointless adding another.

 

[Stevie186]

Thanks for all the input guys the garage is where the electricity comes in the meter(s) are there. I have attached a picture, the house has its own separate consumer units. The gate is attached as a spur off the garage sockets. No matter where I put the RCD in the garage it doesn't set, i think the main garage RCD is faulty it takes a couple of seconds of holding down the test button before it actually trips. Having said all that the last time I tested the garage RCD the house went out which doesn't usually happen but the consumer unit in the house was fine and everything the garage was still on mcbs wise. I whipped all the fuses out and tested continuity on all the fuses flipped everything off then on again went back in the house and the main rcd had tripped flipped it back and everything was back on ok. Weird.

 

[westward10]

Have you tested the garage rcd aside from pressing the button. Those Wylex rcds are normally reliable and being in a place like a garage the test facility button can get a bit sticky.

 

[Stevie186]

I thought I had I have deffo tested them in the house, I have one of those cheap RCD socket tester things that tell you if your feeds are reversed and let you test the RCD etc but I can't find it...typical. I will make sure I dig it out and test again.

 

[westward10]

Are you not providing a Certificate for the new circuit. For this you need suitable test equipment.

 

[Andy78]

Are you not providing a Certificate for the new circuit. For this you need suitable test equipment.

Agreed. The gate installation company will probably want an installation certificate to prove it has been installed correctly and in accordance with the wiring regulations.

 

[Strima]

As I understand it using an RCD FCU is not currently compliant with the regs and would be a departure.

 

[DPG]

As I understand it using an RCD FCU is not currently compliant with the regs and would be a departure.

This is to be corrected in a future edition I believe.

 

[Risteard]

This is to be corrected in a future edition I believe.

Debatable. It appears to have been a deliberate omission due to the wording of BS 7288:2016.

 

[Strima]

Debatable. It appears to have been a deliberate omission due to the wording of BS 7288:2016.

This is what I'm hearing, it's down to the manufacturers to state their devices comply for use as additional protection. It wasn't an omission but someone finally noticed they didn't comply.

Not many electricians are aware of this but then take into account other trades, such as plumbers, trying to do the right thing and are unaware of this change. this needs to be widely advertised.