"live" waterpipe

[securespark]

You shouldn't need to lift boards to check the PEB's. Can't you see anything near the stopcock or meter(s)?

What is the supply type OOI?

So your 55V is between the incoming neutral and the pipe?

 

[bengasman]

Thinking outside the box - is it the water pipe raising above earth potential or is an open circuit CPC/earthing conductor causing the electrical system exposed conductive parts to all raise above true earth, escallated by no Protective Main Bonding in place?

I'll have my 50p on this

Try doing a Ze test and see what you get. Main PEBs need sorting as a priority.

Bit of a challenge doing a proper Ze as I can not disconnect the the main bonding at the pipe side, and not too keen on taking them off at the CU as I am not sure where the voltage on the pipe comes from or goes to.
Tried to do a pfc/Zs using the socket connector, but the tester (meggar 1552) does not start the test due to incorrect voltage and just keeps bleeping to tell me so.

I agree that main PEB need sorting (pronto), or at least inspecting/testing, but I have no idea where the gas comes into the flat, and the water stopcock for the flat only has the top of the spindle sticking out of a little hole in the floor.
Only way to get to it is hacking the floor open. I was hoping to get some sort of an idea what the cause of the problem is.
And don't say: "because it is a botchjob" I figured that one out by now

 

[securespark]

Leave the PEB connections as they are. Switch off all power, disconnect the main earthing conductor at the CU: check no voltage is present first!

Then connect your flying leads to the earth and live/ neutral at the main switch.

This should give you a Ze.

 

[bengasman]

You shouldn't need to lift boards to check the PEB's. Can't you see anything near the stopcock or meter(s)?

Couldn't agree more, but hey, it is done that way.
Can only see the top of the stopcock, barely half an inch above the floor, let alone anything else.
The meter is 2 floors below, and the CU is fed by what looks like 16mm2 twin and earth. No idea how it gets to the topfloor; from the meter, it disappears under the floor and comes out of the floor about a foot under the CU.

What is the supply type OOI?

OOI? Not familiar with the abreviation. I would call it your typical London TNS.

So your 55V is between the incoming neutral and the pipe?

Between Neutral bar and earth inside the CU, and between the incoming water mains for this flat, and an incoming mains for the neighbour's flat.

 

[securespark]

OOI = Out Of Interest

Is the neigbouring pipework effectively bonded?

 

[Spark123]

Tried to do a pfc/Zs using the socket connector, but the tester (meggar 1552) does not start the test due to incorrect voltage and just keeps bleeping to tell me so.

Yep - just backs up what I am suspecting. Open circuit protective conductor.
Neutral to earth of 55v is saying the same - they should be about the same potential.
Where is the meter / DNO intake for the flat?

 

[securespark]

the CU is fed by what looks like 16mm2 twin and earth.

Is the CPC in the cable the only earthing conductor, or has it been supplemented by another conductor?

What size fuse is protecting this 16 milli T&E?

 

[Spark123]

You'll probably find the other end of the CPC in the twin and earth is connected to free air!

 

[securespark]

I've seen it done...

 

[bengasman]

Leave the PEB connections as they are. Switch off all power, disconnect the main earthing conductor at the CU: check no voltage is present first!

Then connect your flying leads to the earth and live/ neutral at the main switch.

This should give you a Ze.

Will switching off at the main breaker on the CU suffice? Switching off anywhere else will be a bit of a challenge.
I will give this a go when I go back.

Couple of other things came to mind.

Could be anywhere between 10 and 20 metres of what looks like 16mm2 T&E between the meter and CU. If memory serves, the cpc is 4mm2 on these; it would provide an earth, but not exactly heavy duty, to say the least.
Can I run a separate 16mm2 from the CU back to the MET downstairs, and leave the existing T&E as it is?

How bad/legal/illegal is it to feed a CU with a long 16mm2 T&E.

The downstairs neighbour asked me to have a quick look at her installation to see what I thought.
Meggar out, plug-lead in socket, Zs.............. 18
Started doubting myself and tester.
PFC test: ............13A
Repeated test in kitchen: same result.
Didn't think I was overdoing it by telling her she should consider having some work done in near future.

If this was gas, it would be a RIDDOR case.

 

[bengasman]

OOI = Out Of Interest

No wonder I did not recognise that technical term

Is the neigbouring pipework effectively bonded?

Neighbouring pipe works as in: the other flats in the building?
If so, no idea.
Zs readings in 2 of the 4 flats about 0.4, one impossible to read, and one 18.

 

[Spark123]

16mm twin and earth is fine providing it is adequately protected and volt drop is not excessive.

16 ohms is a bit over the top too. As some of the flats are reading OK it says that the earthing is fine to them from the building MET so the DNO side of it is probably fine. Have a peep in the metering room / cupboard and all will probably be revealed.
A 16mm from building MET to flat MET should be fine, providing of course the Zs is sufficiently low.

Still - even once the main issue is fixed, don't let them get away without sorting main bonding!

Hope this helps - at least it gives you something to go and look at!

 

[bengasman]

You'll probably find the other end of the CPC in the twin and earth is connected to free air!

Trust me, the only things that surprise me in this building are those bits I come across that actually up to spec.

 

[bengasman]

I've seen it done...

So have I.

The bit that really puzzles me is how a pipe ( a big fat lead one) can be live on one floor, and perfect on the next.

 

[securespark]

Zs readings in 2 of the 4 flats about 0.4, one impossible to read, and one 18.

Just a brief flash of a thought B4 I hit the sack:

Could it just be possible that the flat with the high Ze and the one with the unmeasureable Ze have their supplies linked somehow at the service end?

You could do with taking a Ze on the incoming side of both switchfuses for these flats and a Ze on the outgoing side.