Strange Readings

[matt.leung]

strange one today..

was called to someones house after stray voltage was measured at the boiler during a service between earth and neutral of 47volts. the engineer believed that this was the fault of why the timer was not working correctly. 

At the cu today i took some polarity readings and the results are as follows:

L - N = 230

L - E = 230

E - N = 47v

my Ze was 2.99K ohms and PFC of 1A

previous paperwork records record a Ze of 0.13 ohms and 1.77kA.

when taking the polarity readings the voltage between E & N started to increase when i turned on the boiler and kitchen circuits with all other mcb's off... why would this be????

i have enformed the clients to inform the DNO about the earth readings as it is a TNS installation.

any comments would be useful...

 

[SLIPSHOD & SLAPDASH]

Has to be a bad neutral connection   and the return path is via earth. But then  that means a earth fault also ???  My head hurts.....   I recon its a PME service with a N-E fault external

1A PFC ?

Second thought, Faults on the kitchen/boiler  circuit, any RCD's present ? 

 

[matt.leung]

RCD protection in place. no RCD tripping at all..

 

[SLIPSHOD & SLAPDASH]

I have had a few bottles of Magners, so i am sticking with a external PME, N-E fault. Hope someone else looks here soon.

 

[NozSpark]

Matt,

Your PFC,,, was that PEFC or PSSC??

 

[matt.leung]

PSSC

 

[NozSpark]

PSSC

Sounds like you have an external high resistance N joint and it's also TNCS at that joint,,, maybe

 

[matt.leung]

sorry pefc...

 

[NozSpark]

sorry pefc...

So what was your PSSC?

 

[matt.leung]

i always use the three lead method as pefc....

 

[ProDave]

This MUST just be a loss of your earth connection. As it's a DNO provided earth, they should fix it.

Though I have heard cases where the "solution" is they tell you to TT it.

If it were a faulty neutral, then you would have been called long ago because if Rn was 2.99K then nothing at all in the property would be working.

Go back and measure PSSC using a 2 lead method between L and N and I'll bet all is well with that.

 

[SLIPSHOD & SLAPDASH]

I think Dave is correct, i knew i wasnt quite right earlier. There must also be a fault on the kitchen or boiler circuit though .

 

[matt.leung]

I IR both circuits the results came out perfectly.....

 

[SLIPSHOD & SLAPDASH]

Leakage from an appliance, that only 'leaks' when energised. Could be the boiler or valves ?

 

[matt.leung]

if i had an appliance that leaks the current the rcd would be tripping....

 

[Riggy]

If you've no earth path it has nowhere to leak to so the rcd wouldn't trip, it would however raise the 'earth' potential relative to neutral.

I'd be contacting DNO and in the meantime seperating cpcs to see what is leaking.

 

[matt.leung]

the clients will be contacting the DNO this week and i will also be following this up. what is the best department to talk to?

 

[m4tty]

the clients will be contacting the DNO this week and i will also be following this up. what is the best department to talk to?

You are having a :slap mate trying to get anything out of them round out way is a joke. Try quoting esqcr reg 28 saying if they provide an earth connection they are duty bound to maintain it. They will say they have no records of any earth connection at this property and to TT it. I'd just get on with it. TT earth is not relying on their breaking down network earth and I've done quite a few as its cheaper than their rip off price to PME it if its available

 

[Steve3948]

Have you checked the connection at the head and tested there, just to make sure its not your side.

 

[matt.leung]

as the CU has been exported from the fuse head, i was able to turn off the cu completely and test the Ze, PFC etc at the fuse head where the MET is located along with a Henny block... i still found voltage in the neutral to earth here as well.....