A story of bonding

[SimpleSimon]

Thought I'd share this with you today.
Went to a customers house who after coming back from his holidays had a leak in the bathroom and spread to the airing cupboard.
On having this leak it's made all the water pipes in the property live. So customer disconnected immersion circuit at the fuse and I come round.
IR the circuit, get poor reading of 0.43 N-E. Looks like water damage in the wall. But why didn't the fuse blow when he got a shock? No RCD, support bonding non-existent in bathroom but present in airing cupboard.
Go downstairs to main bonding conductor under sink, do a continuity between disconnected bonding conductor at both ends of the run and find that the conductor which can be no more than a 1.5m has a reading of 1.05ohms. Hmm its seems the bonding was so old and corroded under the sink it wasn't allowing enough fault current to flow to blow the fuse. So always check the 0.05ohms reading regardless of length because you never know.
Can't go behind the walls just yet as it housing association.

 

[Octopus]

Sounds like fun, let us know what else you find and what you did next!:icon6:

 

[MarkieSparkie]

Salutary lesson for us all. Keep us posted Simon.

 

[malcolmsanford]

The bonding I saw was a 6mm then, from MET to stop cock in kitchen BS 951 clamp with the 6mm in. Just did a continuity check and got a reading of .80ohms for a piece of cable maximum 12 metres. There for an hour checking connections re testing, test with cable on ,cable off and then fit new clamp just in case, finally told the customer that IMO there is something wrong it needs changing, but was run under floor. He told me that he was renovating the kitchen in a few weeks, so I ran a surface cable temp and came back.

Lifted the floor and found the 6mm going under from MET then a piece of bell wire twisted onto it run the length in bell wire, then out to stop cock in 6mm, but that leg was in a choc block ..........

 

[sparc]

Coming back to BS 951 .... stopped off in Screwfix today to pick up some clamps to do a spot of supp bonding. On the counter they had Tenby 'Rpaid Clamp Ultra'. I don;t know if these have been around for ages, and I've just missed them - did a search on Forum just now, but didn't find any mention.

Anyway, I asked how much and I think it was something like £35 for a bag of 20 for 15mm pipes. Ha-ha-ha, yeah, no thanks, I'll take the usual please ...

So I was putting supplementary bonding on the pipework around imm tank in an airing cupboard - using the cheapo clamps. First one on no problem, then the clamp I'd attached to the other end of the bond fell apart while I was attaching it. To cut a long story a little bit shorter, I ended up messing around with this crappy things for best part of 10 minutes sweating away because of heat from tank. Stood back to admire my handywork then spotted in my frustration I'd securely attached it to the same bit of pipe as first clamp.

This new clamp had A-E on it - I'd like to take the designer to A+E.

So next time I'm in screwloose ... In case you haven't seen them ... http://www.legrand.co.uk/en/en/liblocal/pdf/Tenby Rapid Clamp Ultra DL.pdf

 

[Plonker 3]

They do look very usefull, except for there doesn't seem to be a warning label with them.

 

[sparkinlee]

They do look very usefull, except for there doesn't seem to be a warning label with them.

If I remember rightly, though I don't have one to hand now, the warning label wording is moulded into the plastic body, although you can't see it in the picture from the link above.

 

[PC Electrics]

They are very useful, especially where access is poor - you can connect the cable before putting them on the pipe.

The label is moulded into the side of the plastic cover.

I buy mine singly from Edmundsons.

 

[sparc]

Correct, the 'do not disconnect .. ' is printed into the side - not very visible, but anyone who's going to disconnect a piece of Y-G cable that is obviouslypart of the electrical installation is going to do it anyway, IMO. Having tried the sample in the shop I can confirm it takes only a couple of seconds to attach clamp to pipe. Shame you need to different sizes for 15mm and 22mm, but I guess that would be stretching the design a bit to have one clamp do both.

 

[sparc]

Thanks for that tip, PD - I'll bag myself some to try ... Screwfix would be smart if they gave one away with every order over £x...

 

[SimpleSimon]

So gents let's see if anyone can help me on this one. Same property, have yet to go back and do any work. When I left the first day I left the guy with an alternative. His two immersions where on plug top plugged into immersion circuit. I told him when I rewire the circuit these will be hard-wired in. So I put them on an extension and plugged it into the main ring so he can have hot water. Got a call couple days later saying he's tried it for 10 hours, no hot water.
Plumber got sent today to change immersions. Same thing, changes them over and starts working (can hear it in the cillender) them stops. Plumbers on the phone to me, continuity of 20 ohms on the immersions, power to it still not working with two new elements. Any idea lads? I'm sure it's got something to do with it still flowing to earth but can't figure of the pieces, any help?
Many thanks

 

[malcolmsanford]

If they started working and then just stopped surely it as got to be a thermostat/timer problem if there is power going to the elements.

With the elements in the non working mode, is there power to the thermostat ? If there is power to the thermostat then is there power on the supply side of the thermostat?

 

[SimpleSimon]

If they started working and then just stopped surely it as got to be a thermostat/timer problem if there is power going to the elements.

With the elements in the non working mode, is there power to the thermostat ? If there is power to the thermostat then is there power on the supply side of the thermostat?

Not too sure. I'm going over tonight so that will be checked.
It's also turned out they are still getting shocks off the pipe work.
My theory is- the water damage has damaged the immersion flex causing a live to earth fault as this is the only part of the new immersion that has been reused. So when I get there IR the flexes. But my reason for that theory won't work is that BOTH immersions don't work.

 

[malcolmsanford]

Si if you have power to the elements then the only way they can not work is open circuit, but you say you have 20ohms which is about 2.9kw @ 240v.

So if they started work and then stopped there must be something interrupting the supply mate.

 

[sparky3366]

like a popped fuse in the plug top mebbe?

 

[malcolmsanford]

So gents let's see if anyone can help me on this one. Same property, have yet to go back and do any work. When I left the first day I left the guy with an alternative. His two immersions where on plug top plugged into immersion circuit. I told him when I rewire the circuit these will be hard-wired in. So I put them on an extension and plugged it into the main ring so he can have hot water. Got a call couple days later saying he's tried it for 10 hours, no hot water.
Plumber got sent today to change immersions. Same thing, changes them over and starts working (can hear it in the cillender) them stops. Plumbers on the phone to me, continuity of 20 ohms on the immersions, power to it still not working with two new elements. Any idea lads? I'm sure it's got something to do with it still flowing to earth but can't figure of the pieces, any help?
Many thanks

Thank you Sparky 3366 spot on ................try the extension lead plug.

 

[Knobhead]

Si, their not on E7 are they? It’s just the fact you mentioned 2 immersion heaters that made me think.

 

[SimpleSimon]

Yes Tony E7. My other theory is that the leak has damaged the ring even though there are no socket outlets close to the ring so I'm unable to confirm if the ring is even there.
It's a strange strange one. My other theory is plug it on the downstairs ring and see what happens than.

 

[SimpleSimon]

Ok mystery over.went last night to check it out and the extension lead he was using was one he took from work that serviced a bank of computers. Naturally it had blown the 5a fuse that protects the outlet. Case closed for now.

 

[ezzzekiel]

Hmm its seems the bonding was so old and corroded under the sink it wasn't allowing enough fault current to flow to blow the fuse.

isnt the bonding there too make sure all bonded pipework rises to the same potential under fault conditions and earthing to disconnect the fault

 

[SimpleSimon]

Yep. And it wasn't