Nasty little mess again !

[Soulsurfer]

So a regular client has just had me finish doing up their flat and bought a house, been and while quoting for LED downlight etc.. they asked to have all the accessories changed out new and a few bits looked at, while there on site they showed me a cert hand written from a contractor to move boiler feed in garage and connect for E20+ off peak heating etc..

Boiler wasn't operating so found a cut out gone and HW valve defective so replaced it. All good.

Now they want a full EICR due to feeling uneasy about the place electrics as the CU for the general supply and off peak supply is a mess and a half ! Started testing this morning, Ze seemed a bit low but was o.k. tried PSSC and got 10kA !

seemed very over the top for domestic 3 bed house ! so went to try at 4 pole switch isolator and upon testing there got an arc flash when testing ? Never seen that before !

Next issue doing all usual dead tests and alright except from one ring final was low on r2,
r1 fine 0.57
rn 0.56 but
r2 was only very slightly different 0.54 but was looking for more especially on Twin cable ! maybe 0.95 or so.
Could there be a parallel path somewhere ?

1st floor ring
r1 0.29, rn 0.30, r2 0.50 so much more what I was looking for.

Problems again surfaced when attempting IR ! at main terminals on switch at CU and out to CPC's all >500MegOhms
but individually only cooker circuit and Immersion were the same !
The rings x 2 and lights x 2 plus a boiler feed all wouldn't test past the 50V touch voltage limit I think on mft.
No matter whether disconnected from mcb and Neut bars etc.. and even L+N together to earth bar nothing would let the voltage ramp up to test at 100, 250 or 500V, checked over and over for spurs, extra hidden sockets, things plugged in etc.. and found nothing from what I can gather apart from an RCD incorporated socket last thing as leaving site but thought probably wouldn't be a problem as same issue happened when trying to IR test other circuits too !

Anyone shed any light on this as I've also found live ends taped up in 2 x socket back boxes and not in a socket face and more with spurred cables disappearing into stud wall with no idea where they are going to ! I'm thinking someone has been having a right old play around and no certificates anywhere.

CU is old MK 59 series horrible thing I'll put pics on if possible it's a right mess. On main switch is 5560, each mcb is say 5930 for a 30A etc.. had to get from obsolete breaker dealer last time I had to work on one of these boards.

 

[davesparks]

A low Ze would lead to a high PSCC, just do the calculation to check that it is reasonable for the recorded Ze.

When you say arc flash do you mean a small spark when making contact with the probes or something more serious?

Most mfts will not IR test a circuit if a voltage is detected above a certain limit, which may display an error with a >50 type of symbol. If you have tested global IR and the reading was at the top end of the scale then the cables will act as a capacitor and charge up to full test voltage, this can prevent the meter from testing again until this energy is discharged.

 

[Soulsurfer]

Hi

A low Ze would lead to a high PSCC, just do the calculation to check that it is reasonable for the recorded Ze.

When you say arc flash do you mean a small spark when making contact with the probes or something more serious?

Most mfts will not IR test a circuit if a voltage is detected above a certain limit, which may display an error with a >50 type of symbol. If you have tested global IR and the reading was at the top end of the scale then the cables will act as a capacitor and charge up to full test voltage, this can prevent the meter from testing again until this energy is discharged.

It was weird Dave the flash was quite a bright blue flash after test button pressed to initiate a Zs high current L-N at the 4 pole switch for off peak & general supply board. It was quite a while after global IR that I tried the other IR tests but just seemed really worrying that none would ramp up and the cu main switch was open and the 4 pole supply switch in meter box was opened also to ensure all dead everywhere.

Haven't done a calculation at all yet, but Ze at general cu was 0.07 ohms with a 3.5kA PEFC.

 

[Soulsurfer]

I make it around 3.3kA for Ipf but if way lower say Ze of 0.02 that would give the region of 10/11kA I had registering on the MFT. Totally confused now or is meter low on batteries / really bad install ?

 

[westward10]

Bad install should not reflect upon the Ze, 0.07 isn't low.

 

[Soulsurfer]

Bad install should not reflect upon the Ze, 0.07 isn't low.

Ah the only few times I've tested myself since going on my own I've had higher Ze test results like around the 0.20 etc.. so going to 0.07 I thought was low. My lack of knowledge unfortunately. But seems a very high PSSC, and the pics show how horrible the wiring is.

 

[telectrix]

if you'r e close to sub station, 0.07 is not abnormal, and bear in mind the ground is wet atm.

 

[Soulsurfer]

if you'r e close to sub station, 0.07 is not abnormal, and bear in mind the ground is wet atm.

It's in an estate of cul de sacs so I think there is a substation within 20 mtrs of the property

 

[westward10]

The PSSC is high for 0.07, does your meter measure it separately or calculate it from Ze.

 

[Soulsurfer]

The PSSC is high for 0.07, does your meter measure it separately or calculate it from Ze.

It was on the Fluke 1653B I just sold, I would think it measures it direct as have to manually select across to L & N on screen not as is default on L & E for Ze which then gives the Ohm result then I think calculates the PEFC below in window at same time,
LN selected manually on screen then gives PSSC below when probes are making contact.

 

[Ian1981]

The PSSC is high for 0.07, does your meter measure it separately or calculate it from Ze.

Perhaps it's because the measured voltage was more like 245v rather than using the 230v calculation

 

[Soulsurfer]

Perhaps it's because the measured voltage was more like 245v rather than using the 230v calculation

Sorry mate yes most likely, anything up to 250 plus over here generally !

 

[Soulsurfer]

I don't get why it could be such a tw#t just getting results on a basic test !