Untraceable/unknown circuits

[Brightspark2]

Fair point but why would unknown/untraceable circuits only be a c3 on a PIR test???

Used to be recommended as a code 3 on PIRs as required further investigation...but thats a different situation from yours...

But PIRs are redundant now, there EICRs with different codes...but I assume you know this...

 

[FAA Greenie]

I did a kitchen rewire last year and found an FCU feeding a 1.5mm T&E into a wall which disappeared to nowhere!! After I disconnected it I tried allsorts; outside lights, looked for spurs, under cupboard lights, extractor. All still worked.

Owner said it had just always been switched on and they never turned it off.

I left it disconnected and told the owner if they noticed anything not working I would go and test/reconnect it. I've still not heard anything to this day.

 

[Spoon]

I thought that all circuits on a CU have to be marked for the purpose they serve. e.g. Kitchen.. How can you quote to replace a CU and add the circuits back in without knowing what they do? What did you put on the new CU? What was on the original CU? What fuse rating was the original circuits wired to?
You can understand how the general public get the wrong image about electricians when they get someone to do a job and they expect the job to be done only to be told that they have to spend more money cause the job was not done fully in the first place..

 

[ajl_02]

The old board was a 3036 board with no labels at all. I've replaced it with a dual rcd board. Traced all circuits and labelled new board but there's 2 circuits which I couldn't trace. I've just been and disconnected the 2 circuits and have now just left them as spare ways in the board. I left them in because the electrics haven't been touched since the house was built until I changed the board. All sorted now.

 

[yellowvanman]

Best way is to not connect, but leave them accessible so they could be if the customer realises something doesn't work.

 

[Octopus]

If you can't 'trace' them then you shouldn't be doing an EICR.. or changing a CU for that matter. It's not a codeable thing. If you don't know where a circuit goes or what it is for, how is this a C3? How does it not comply with the current regs??

What rubbish, I couldn't disagree with you more - C3 requires investigation.

There are tens of thousands of houses around with untracable circuits in them. On an EICR its a C3, on a board change you can either leave the cable "safely" within the board or connect it to e MCB with the same rating as the old board and the MCB switched off.

Did one myself about 6 months back, EIC stated unknown as circuit description and as the owner was a retired engineer we discussed the options - we agreed to connect the cable to the MCB and leave it switched off. 2 months later got an email saying he had found what the circuit did and I duely went round and tested said circuit.

Maybe I've got the wrong end of the stick, BUT a RCD board with 1 unknown circuit in it is far, far safer than a BS3036 board with no RCD's

 

[ajl_02]

Exactly!!! The old board with no rcd protection had been used with no problem for about 30 years. The board now has rcd protection on all circuits so its gota be a lot safer than it was!!

 

[plugsandsparks]

What rubbish, I couldn't disagree with you more - C3 requires investigation.

There are tens of thousands of houses around with untracable circuits in them. On an EICR its a C3, on a board change you can either leave the cable "safely" within the board or connect it to e MCB with the same rating as the old board and the MCB switched off.

Did one myself about 6 months back, EIC stated unknown as circuit description and as the owner was a retired engineer we discussed the options - we agreed to connect the cable to the MCB and leave it switched off. 2 months later got an email saying he had found what the circuit did and I duely went round and tested said circuit.

Maybe I've got the wrong end of the stick, BUT a RCD board with 1 unknown circuit in it is far, far safer than a BS3036 board with no RCD's

Agree, when you are doing Comm and industrial i have had many issues tracing ccts, even with the help of the site based electricians, they dont know either. Its the nature of the beast.
As for the OP, nearly all old houses had an immersion heater cct but often these are redundant with combis, that may be one of them ....

 

[infinity]

^^^ Agree with Murdoch, in older installs especially comm industrial you will usually always have at least one circuit you spend over 30mins looking for until you have to move on. I'd be very surprised if you have been carrying out EICR's and always found every single circuit on older installs?

C3 - further investigation

 

[Steve_P]

These aren't a cooker and heating circuit with a 100mA time delay RCD main switch are they?

 

[kingeri]

All I meant was not knowing what a cable does isn't in itself a C3. What reg no. would you quote?

 

[High Tower]

Murdoch, thank you!!!,

Gentlemen it's not a ideal world, never will be!, there will always be unknown circuits!

I do the same as Murdoch says, I change the board and put cables in place but do not connect.

And I second that a rcd and a mcb will always be a drastic improvement on 3036's.

 

[HandySparks]

All I meant was not knowing what a cable does isn't in itself a C3. What reg no. would you quote?

At the least, 514.1.1 and 514.1.2 regarding labelling of switchgear and wiring will apply. 514.1.2 says: "So far as is reasonably practicable, wiring shall be so arranged or marked that it can be identified for inspection, testing, repair or alteration of the installation."

If you can't work out what it does, it's clearly missing labels, diagrams or schedules.

 

[Jerry H]

Upon testing an installation after a fuse board change there are 2 x circuits which ate untraceable. I have left them connected but was just wondering if these circuits would be noted down in the departures from bs7671 box on the install cert??

Have just finished a CU change on a 1960's house. There were several 'unidentifiable' circuits but we made an effort to trace them. One was an old electric clock point plastered into the wall by the fire place, another was an old electric bathroom heater and a third was some sort of weird gizmo in the loft that was supposed to stop the water pipes firing up. If you can't find them, don't connect them. They'll soon let you know when things don't work

 

[richy3333]

If you can't 'trace' them then you shouldn't be doing an EICR.. or changing a CU for that matter. It's not a codeable thing. If you don't know where a circuit goes or what it is for, how is this a C3? How does it not comply with the current regs??

Labelling?