Main bonding, following on from other threads

[Sidewinder]

So,

What would you do?

Domestic.

No main water bond can be identified.

Water enters under sink at rear of property in the middle (ish).

Internal stop tap there.

15 m run around the exterior of the property to the CU to put a bond in.

CU under stairs toward, but not at, the front of the house to one side.

Gas boiler adjacent & I mean adjacent to CU about 18" away in a straight line as installed by BG (!) under the stairs.

CU & water about 6m away from each other as the crow flies.

All downstairs.

No easy access through the house, fitted kitchen, tiled walls all fitted carpets upstairs.

Boiler cross bonded (even though all pipes are terminated in a metallic plate, Worcester Combi) in 4mm, gas bond below CU in 4mm adjacent to meter.

TN-C-S/PME single 100mA up front RCD.

Have to make changes to upstairs socket circuit on a 15A radial need to extend the cct.

I will do this job 3rd week in June, I am posting as a constructive discussion exercise, as I am not looking for advice, I have a solution, which I will not post until the thread is exhausted, and, hopefully this will not turn into a slanging match!

I have done similar before, and as it happens my AE has inspected them and was happy with my solutions.

So, please, can we politely discuss & debate the options here as a learning exercise?

My materials list is already done and quote sent to the customer.

I am not going to post the reason for the changes, suffice to say it is an extension to the 15A radial socket circuit upstairs as it may cloud the issue.

Overload of the mcb not an issue.

The wiring in the existing cct is 2.5mm sq and the existing Zs is well in at the end of the radial and will be well in within the modification.

All modification wiring to be surface mounted in trunking.

100mA RCD up front.

Al circuits mcb protected.

 

[Sidewinder]

No mate, domestic and nothing like this required really, equipment to be used is connected via 13A plug top apart from that I install as part of the mod and this is nothing to write home about.

 

[ADS]

I can't decide what to do with my own job - and I haven't got half the problems 'Sidewinders' got. :innocent

 

[Sidewinder]

I don't have any problems mate job is as good as done!

Comments welcome though, this is not rocket science you know no 2nd order differential equations with two variables here.

 

[ADS]

OK, I'll start everyone off with the easy bit - you need to upgrade the gas bond to 10mm.

---------- Post Auto-Merged at 22:33 ---------- Previous post was made at 22:31 ----------

Just out of curiosity - why is there a 100mA RCD up front?

 

[Sidewinder]

Because that was what was already there, I did not do the original install so I don't have the insight of the original designer.

More info:

Wylex 3871 board with retrofit MCB's.

 

[ADS]

Because that was what was already there, I did not do the original install so I don't have the insight of the original designer.More info:

Wylex 3871 board with retrofit MCB's.

No, I know you didn't do it - just thought you might have info as to why...........seems strange on a TN-CS unless earthing was dodgy at some point and inserted for earth fault protection.

By the way, when you say 3rd week in June, I take it you mean July......unless you've got one of those time-machine thingies?

 

[Sidewinder]

You are correct with respect to the month mate!

No EIC's on site, home owner has no idea, you should see the pics!

I am going to recommend a CU upgrade and a full PIR, though my client is not the home owner even though the house is privately owned and the resident is the owner.

I would have to undertake further investigations to check the history out and I am not paid for that!

 

[Manator]

I already know what I would do, and it would comply. I will PM. I do not want to ruin the thread, looks like it could be a constructive exercise.

 

[Sidewinder]

OK

 

[sellers]

Install water bond if incomer isn't plastic. maybe access under the floor?

If your adition to the circuit doesn't require rcd protection then add on at your leisure, if it does require protection, install new board, seprate board, rcd module, or rcd spur.

I don't see a reasonable way of getting around putting the bond in? Could argue its all connected at the boiler but whos to say they don't change to electric heating system. Suppose you could bond onto the water incommer at the boiler and note on cert.

 

[Sidewinder]

Sellers,

Concrete floors, kitchen tiled, so that is out!

Not adding an additional circuit, just modding an existing one.

 

[ADS]

Come on then, is no-one having a go?

I would say:

The 100mA RCD has to go.

Upgrade bond to Gas to 10mm.

Install 10mm bond to water pipe feeding boiler and confirm negligible resistance between MET and rear stop tap.

Cross bonding can stay.

Install in-line 30 mA RCD to cover whole of 15 A extended circuit.

 

[Sidewinder]

Ditching the 100ma for what ADS?

 

[Manator]

Well I was half right, but mostly wrong

 

[ADS]

To comply - an earth fault on the extended circuit would cut power to the whole installation.

As the circuit that you are extending is fed via this 100 mA RCD, it should comply with current regulations.

 

[sellers]

I think how you are modifying the circuit is quite relevant, are you installing extra sockets, or 1 socket for certain equipment or a fused spur

 

[Sidewinder]

I am installing a 30mA RCD fused spur to supply 2 off 30mA RCD twin switched socket outlets and an emergency light with a test switch.

All wiring and accessories surface mounted, wiring in trunking.

 

[ADS]

Assuming the job is not in Scotland,

Approved Document P, Section 2, 2.1

Where any electrical installation work is classified as an extension, the addition & alteration work must include:

a) such works on the existing fixed electrical installation in the building as are necessary to enable.....

the addition/alteration (the extension) ;

the circuits which feed it;

the protective measures &

the relevant earthing and bonding systems..........

....to meet the requirements

AND....

B) Establishing that the mains supply equipment is suitable.

So all four items listed above have to meet the requirements of the current regs........the 100 mA up-front RCD doesn't, and neither will a RCD fused spur......what about RCD protection for the rest of the circuit?

 

[Sidewinder]

Job is not in Scotland.