rcd tripping after smoke alarm fitted.

[DC-backfrom the past]

to the one covered by the other rcd ?

Yep

Apologies I'm missing the point to doing this... apart from thinking the rcd might be too sensitive or to check it trips the other one ?

 

[Ian1981]

How have you installed the 3 core and earth cable. Could you have possibly damaged(drilled/screwed) an existing cable located in the fabric of the property such as the wall?

 

[Pete999]

Apologies I'm missing the point to doing this... apart from thinking the rcd might be too sensitive or to check it trips the other one ?

It could be you have the L and N across 2 different RCDS I'm clutching at straws but worth proving a point, hence borrowed N

 

[Ian1981]

Is your cable supplying the smoke detectors the white 2.5 LSOH cable?

 

[Octopus]

Are you 100% sure you used the same cores in the interconnecting cable the same in each leg?

If you did IR at the board this wouldn't include the interconnecting cable so I suggest that you dis the smoke base and do IR across all 4 cores and see what comes back - and at the same time double check the colours and consistency.

 

[Pete999]

It could be you have the L and N across 2 different RCDS I'm clutching at straws but worth proving a point, hence borrowed N

I understood you supplied the new detector straight from the CU

 

[DC-backfrom the past]

Is your cable the white 2.5 LSOH cable?

That's the original cable that was connected to the first smoke alarm. I took the photograph prior to removing any cables for testing

 

[DC-backfrom the past]

Are you 100% sure you used the same cores in the interconnecting cable the same in each leg?

If you did IR at the board this wouldn't include the interconnecting cable so I suggest that you dis the smoke base and do IR across all 4 cores and see what comes back - and at the same time double check the colours and consistency.

yes Murdoch I had checked using a wander lead for each cable at the different areas.
This was before connecting to any equipment.
I also visually checked the cable and connections as well in case of loose connection,... although any faults should have been picked up in the initial IR / test.
I cant understand how even reverting it back to the original circuit it now still trips.

All the new cabling can be seen as there are no cable drops for the new circuit and the only part that is hidden is the drop to the consumer unit (this is the original cable which was operating beforehand).

 

[DC-backfrom the past]

I understood you supplied the new detector straight from the CU

I used the original cable and used that as a supply for the original smoke alarm then linked the other two via three core and earth cable.

 

[Octopus]

I am trying to help here!

So there was originally 1 smoke alarm, fed by T&E from the fuseboard.

You've added another smoke and a heat alarm to the existing smoke.

Now either 1 or the other RCD will trip.....

You've used 3 core cable for the new smoke & heat?

Or have I missed something?

 

[DC-backfrom the past]

I am trying to help here!

So there was originally 1 smoke alarm, fed by T&E from the fuseboard.

You've added another smoke and a heat alarm to the existing smoke.

Now either 1 or the other RCD will trip.....

You've used 3 core cable for the new smoke & heat?

Or have I missed something?

apologies Murdoch if I seemed ungrateful I didn't intend to come across that way.
correct the supply is t&E from board then three core thereon
the third core is used for the interlink facility. if one alarm sounds they all sound together
I have drawn a very rough diagram I have left out the earth for clarity.

 

[Octopus]

No offence taken!

Are you 100% sure you have the neutrals in the correct places in the smoke alarm bases

L
IC
N

 

[DC-backfrom the past]

No offence taken!

Are you 100% sure you have the neutrals in the correct places in the smoke alarm bases

L
IC
N

yes mate I'm sure ...I checked three times or possibly four .That's why I took it back to the original circuit (T&E) to try and ascertain if it was a faulty unit to blame.
I checked with two base units and two detectors.
I couldn't understand why the other rcd tripped on two occasions though.
there was a lot of junk in the loft and I had to move some of it
I can only presume that somewhere I have maybe damaged another circuit ...but cant think if that's the case why it only trips when this circuit is made live and connected to the alarm..

 

[Octopus]

What is the "new" cable run like? all clipped?

Still think you need to dis the new part and IR the new bit - and you must IR between ALL cores to make 100% sure.

 

[DC-backfrom the past]

What is the "new" cable run like? all clipped?

Still think you need to dis the new part and IR the new bit - and you must IR between ALL cores to make 100% sure.

Its all clipped in the loft area...
I appreciate what your saying. but I've disconnected the new part completely and the original cable, which was ok, is now the only part connected and its tripping the rcd !!!!

I disconnected it and IR tested that T&E as well

hence my headache !!!!

 

[Octopus]

Next step, which seems a bit odd, but I think you should run the smoke from a new piece of t&e direct from the board at cu level. Do this to test the bases and heads you have.

You need to do this to rule them out of the problem ....

 

[Toneyz]

Sorry if I've missed something here but what is that other cable in the MCB? if the other RCD is tripping sounds like the crossed neutral. Just a thought but have you checked the two neutral bars are doing the corresponding MCB bank.

 

[westward10]

He has yet to clarify how it is connected and which parts are new and what is existing.

 

[DC-backfrom the past]

Thanks I've resigned myself to replacing the initial cable.
Or hoping the rcd fixing fairy has visited during the night
Thanks to all for your help
Fresh eyes and clear head may help

 

[DC-backfrom the past]

Sorry if I've missed something here but what is that other cable in the MCB? if the other RCD is tripping sounds like the crossed neutral. Just a thought but have you checked the two neutral bars are doing the corresponding MCB bank.

The other cable is lighting circuit for hall.
However I have tried the smoke alarm cicuit in the adjacent mcb on it's own.
As stated by you and others I will double check the neutral bar in case there is a crossover or borrowed neutral.
Thanks