• Welcome to the new forum. We're now hosted on ElectriciansForums.net rather than ElectriciansForums.co.uk - Chat about the forum upgrade by CLICKING HERE

Welcome to our Electrical Forum - We started out providing electrical advice just for the UK - But now we have specific advice for the USA too! - Register for free and share American Electrical Advice.

Discuss Radial Circuits in the Electrical Forum area at ElectriciansForums.net

Not open for further replies.

LED Lighting

Regular EF Member
Hi All, quick question before bed.
Just come back from an emergency callout

  1. No Earth in property
  2. 6 double sockets on a 15A Radial (over 2 floors)
  3. 3036 CU with big hole out of R/H side
  4. Bonding to mains Water - 16ohms through this means
  5. No Bonding to Gas
  6. Pre RCD covering 4 x 3036 CUs
  7. Pe-RCD not holding on circuit 6 (point 2) - all appliances are class 2
  8. All IRs are >150Mohms

Full installation isolated - customer re-energized when I walked out of the door due to medical conditions

Thoughts please with particular attention to point 2! - will pick this up in the morning


Electrician's Arms
start isolating each board...till you find the offender...

then narrow it down to the final on that board...
there...identified the circuit/s causing it....and that without any test gear...

it could of course also be a case of accumilated leakage....

LED Lighting

Regular EF Member
Like i said found the issue in circuit 6, well customer did before I got there.
all irs are good on everything.

the RCD only trips after about 1 min of circuit 6 being turned on, all appliances plugged in are class 2.
no tripping when nothing plugged in

this is the same circuit that had 6 double sockets on a radial

i have put it in for remedial work so just a wait and see now - out of my hands

LED Lighting

Regular EF Member
Not sure as all IRs are good and with everything connected but circuit 6 isolated at MCB the RCD held for over 30mins

could lack of earth cause this? Or the high load on circuit 6???


Electrician's Arms
get a leakage clamp on this...

if you dont have one then ramp the RCD off load...then ramp it again with everything on...the difference is leakage...


Forum Mentor
Electrician's Arms
Trainee Access
... but circuit 6 isolated at MCB the RCD held for over 30mins

could lack of earth cause this? Or the high load on circuit 6???
No and no.

And there's nothing unsafe about 6 double sockets on a 15A radial, provided that the current rating of the cable is suitable. The worst that's going to happen is the fuse blowing on overload and having to be rewired.

LED Lighting

Regular EF Member
Thanks all

I work for British gas home assist, and this was one of the call outs last night

i have put the work forward now to be done, and will await their response.

circuit 6 has 2.5mm T&E off a 15A radial. I know its safe as fuse is less than CCC of cable, but was not sure if circuit is being overloaded.

thanks for the advise on leakage, I am trying to get myself a clamp, any recommendations?

LED Lighting

Regular EF Member
Im still lost with regards to how this circuit can leak current when IR is >150Mohm with items plugged in and not (N/E).
Also all items plugged into this circuit are class 2 so there cant be any leakage there????????
If it holds with nothing plugged in and pops when something is plugged in and switched on, accessory fault. If it pops when just plugged in, accessory fault and polarity issue at socket (has customer been fiddling before you arrived). Is there an immersion heater or something similar on this circuit.

LED Lighting

Regular EF Member
no Immersion Heater or anything like this
From my memory:
  • 2 house phone chargers (class 2)
  • oxygen machine (class 2)
  • 3 bedside lamps (class 2)
  • 2 floor lamps (class 2)

IH on its own circuit - IRs over 500Mohm with on and off

What got me was it would hold for 1 min but then trip, but first time I turned it back on after main IR Testing, it held for around 30mins then tripped - everything plugged in at this stage and turned on

only thing I can think of is slightly warming the cables and POP
ramp the RCD off load...then ramp it again with everything on...the difference is leakage...
You're never to old to live'n'learn on this forum! Ive always used a clamp meter and hadn't even thought about using the RCD on ramp, thats one up my sleeve for the time my clamp runs out of battery power .....


Electrician's Arms
Is it me but if its a 3036 board where are the RCD's? am I being dim?
Not open for further replies.

Electrician Talk

Electrical Forum

Welcome to the Electrical Forum at ElectriciansForums.net. The friendliest electrical forum online. General electrical questions and answers can be found in the electrical forum.
Electrical 2 Go - Electrical Supplier and Electrical Wholesalers
Electrical Insurance
ElectriciansForums.net (formerly known as ElectriciansForums.co.uk) was setup in April 2006 to provide free electrical advice to both professional and DIY electricians. Whether seeking advice for auto electrics, trying to find electrical installation condition reports (EICR) form downloads, or whether you're here just to talk to other electricians; we've been a first-choice website for tens of thousands of sparkies for well over a decade.