Pssc Test

[Soulsurfer]

Hey all, just looking at a house for a friend who has purchased after someone suggested by his surveyor looked at the wiring from CU in garage etc.. and said it's grey so it's new colours and all fine !

Just popped by as he's had 2 belts so far and tripping breakers and it's full to the brim of green goo, wiring looks to be original which would be 46 yrs old from house build, no records of install or any testing.
No main bond to water or heating pipes and he's asking about a possible rewire, so I checked a few bits while had an hour or so free this afternoon and he only has a main earth from TN-S MET to CU which is a MEM I've never seen before and PSSC gave a weird result of >2000 Ohms ?? Never seen that before.

IR on entire board is sub 0.46 MegOhms and individual circuits quickly looked at such as ground flr lighting and ring were around the 0.36 Meg Ohm level after a held press like it was slowly drying out the cables. He has had pokes from wall lights he took down due to him thinking they were dead if lighting MCB's off ! but found they had been fed through a hidden fused spur in a lounge fitted cupboard from a lounge socket up to a 3 gang light switch ! Ze was fine but as I say PSC / PSCC not reading right. Any advice ? Looking like a rewire to sort it as I think wiring is very old and not worth patching over with odd bits of new stuff. Thanks all.

 

[westward10]

The green goo is caused by plastisiser migration and you can date the installation between 1965 and 1971. Cables between these dates were made from chemicals which over a period of time created a reaction between the copper and the PVC known as migration. The green goo is a product of this migration and is called di-isoctyl phthalate. It is slightly toxic but is not conductive and should not give low IR readings, it does mean the insulating properties of the cables are breaking down and should be rewired. The same phenomena can be seen with later PVC cables when in contact with polystyrene, also some nail in cable clips give the appearance they are melting, this is also migration.
Ohms for a PSSC reading ??

 

[Pete999]

PSSC in Ohms summat amiss there

 

[Soulsurfer]

PSSC in Ohms summat amiss there

Fair comment Pete the MFT measures the resistance as in when it does its PEFC test and displays the current underneath for the PSSC but this time at main switch tails in L-N I got >2000 Ohms and no displayed current value at all which is what confused things. I was expecting e.g. 1.2kA or 961 Amps etc..

 

[Soulsurfer]

The green goo is caused by plastisiser migration and you can date the installation between 1965 and 1971. Cables between these dates were made from chemicals which over a period of time created a reaction between the copper and the PVC known as migration. The green goo is a product of this migration and is called di-isoctyl phthalate. It is slightly toxic but is not conductive and should not give low IR readings, it does mean the insulating properties of the cables are breaking down and should be rewired. The same phenomena can be seen with later PVC cables when in contact with polystyrene, also some nail in cable clips give the appearance they are melting, this is also migration.
Ohms for a PSSC reading ??

Yep that's cool as I knew all about the goo itself, and agreed it's not strictly an issue so far as until as is happening the switches are getting stuck up when trying to operate them and it's oozing out the socket pin holes too. But the IR is showing very low readings so I'm thinking just get it ripped out and renewed inc sorting all this bonding as and when required.

 

[Soulsurfer]

I'm looking at a calculated 1.2kA PSSC which seems about right.

 

[sparkzalot]

We're you testing the PFC or PSC??
Im assuming PFC from those readings. If I'm right it would suggest no earth.
If you were doing PSC it would suggest the neutral isn't connected to earth at the supply transformer. Which I very much doubt

 

[sparkzalot]

Sorry I didn't read half the posts....