1rcs trips when the other has use

[watson789]

hi all

very strange issue i have here...basically my consumer unit has 2 RCD's

RCD1 : downstairs lights
Outside lights
smoke alarm(currently off)
shower(currently off)

RCD2:upstairs lights
All house sockets + boiler(boiler currenly switched off)
Cooker (currently off)

my BIG problem and i cant figure it out is when i plug my 500W drill into the house socket (on RCD 2) it trips all RCD1 off but leaves RCD2 on with no problems. also alternativly if i switch the living room lights(downstairs lighting) on and off quick they trip RCD1.

i have wired the outside lights onto RCD 2 and when i do as soon as the outside lights come on it trips RCD1.

few other things to bear in mind are - i am renovating the house so no cooker/washer/dryer /fridge/shower in use, as above says 'curretly off' means at the MCB switch is in the 'off' position.

this has only happened this week when i have started to use my drill and it has been weeks since i have messed with any electrics BUT i have been using the drill regularly in all sockets.


please help!

 

[Sintra]

hi all

very strange issue i have here...basically my consumer unit has 2 RCD's

RCD1 : downstairs lights
Outside lights
smoke alarm(currently off)
shower(currently off)

RCD2:upstairs lights
All house sockets + boiler(boiler currenly switched off)
Cooker (currently off)

my BIG problem and i cant figure it out is when i plug my 500W drill into the house socket (on RCD 2) it trips all RCD1 off but leaves RCD2 on with no problems. also alternativly if i switch the living room lights(downstairs lighting) on and off quick they trip RCD1.

i have wired the outside lights onto RCD 2 and when i do as soon as the outside lights come on it trips RCD1.

few other things to bear in mind are - i am renovating the house so no cooker/washer/dryer /fridge/shower in use, as above says 'curretly off' means at the MCB switch is in the 'off' position.

this has only happened this week when i have started to use my drill and it has been weeks since i have messed with any electrics BUT i have been using the drill regularly in all sockets.


please help!

Sounds to me like you have borrowed neutrals between some of your circuits. More than likely your lighting circuits.

 

[watson789]

do you mean connected neutrals from diferent circuits?
i can check this.
how else do you mean "borrowedcircuits" ?

 

[Sintra]

do you mean connected neutrals from diferent circuits?
i can check this.
how else do you mean "borrowedcircuits" ?[/QUO


I would check your neutrals on your hall stair lights.

In a lot of cases the 2 way circuit from bottom of stairs to top of stairs has both lights on downstairs circuit but the neutral to the top light is taken from the upstairs lighting circuit.

Worth checking.

 

[legge]

spot on Sintra!
A borrowed neutral on the landing light as a classic one. Another one to look out for is wall lights switched from a wall switch but neutral taken from local socket.

check between the neutral bars on the CU they should be clear (Mohms)

 

[watson789]

'check between the neutral bars on the CU they should be clear (Mohms)' not sure what you mean by this legge?? can you expand more?

 

[Sintra]

'check between the neutral bars on the CU they should be clear (Mohms)' not sure what you mean by this legge?? can you expand more?

What legge means is that between the 2 neutral bars in your consumer unit with the main switch turned off you should have no connectivity. This can be checked by carrying out an insulation resistance test between the 2 neutral bars. If you have a connection between the 2 then proceed to dicsonnect neutrals in turn and retest untill you can find the culprit.

 

[legge]

Each rcd has a neutral bar so with a 2 rcd board, there will be 2 neutral bars so all the circuits supplied via rcd1 will have the neutrals terminated to neutral bar 1 and all circuits supplied via rcd 2 will have the neutrals terminated to neutral bar 2.
Thus there should be no connection between neutral bars 1 and 2. Insulation readings should therefore be in the range of megaohms.
If you have any borrowed neutrals ie crossed circuits for example the landing light, then as soon as that light is turned on, the energy travelling via a live on one rcd will return via the neutral to the other rcd therefore tripping the rcd/s!

 

[watson789]

i will check this tomorrow and get back to you all - thanks so far!

i have 1 more question...

i have 1 spur from the MCB (2.5m) which connects to 2 sperate outside lights 1 300w and 1 500w which are on 1.5m cable each, is this acceptable and will it cause me any problems???

 

[electricAl]

Hia there. Unsure of what you`re numbers mean - is that 2.5m? & 1.5m?

Not much to go on my friend. Better chance of help if you give more info - cable sizes & MCB rating...

Also, are you sure you`re confident, & competent to be even opening that CU, let alone doing IR testing?

No offence intended i assure you, but safety before bravery & all that

 

[watson789]

apologies there didnt explain myself clearly,yes i ment the cable sizes.

 

[electricAl]

Then if you`ve used 1.5 mm

At its simplest, I = P / V so 500w / 230 = 2.2 amps only & 1.3 amps for the 300W lamp

Clearly a fraction of the current carrying capacity of any 1.5 mm (unless you`ve routed it somewhere naughty)


As for the IR testing, have you got suitable equipment to carry this out? Not something most folk would have TBH