black sticky liquid??

[Dean Williams]

Hi
while testing a DB in a primary school today, i found all the conductors within the DB coated in a black sticky, tar-like goo. see attached photos. im assuming its the conductors overheating and the insulation melting. can anyone confirm this. If that is the case, i can't understand it. there are no significant heat sources nearby apart from a stage lighting DB below, which i switched on with all the spotlights on full and left it all day to see if it produced any heat, which it didnt.
any help would be greatly appreciated.
cheers guys

 

[Kiers1970]

Glad its not sticky white stuff.

 

[Guitarist]

If you were a real detective, you would taste it too, but I don't recommend that :wacko:

 

[J&M Electrical]

It was all over the old cables on a rewire we did last week, however the mainsboard was fine and it was at the sockets that this black goo occurred. Could it be something in the PVC outer sheathing that has failed over time?

 

[Dean Williams]

it doesnt smell of anything. the wiring is 20 years old

 

[Guitarist]

it doesnt smell of anything. the wiring is 20 years old

It's amazing how many decades certain smells can linger. If it's still sticky and anything oil-based (ie. insulation etc) I would expect it to have a pungent smell. Maybe at some point in the distant past, a teacher or cleaner used it as a shelf and something leaked inside.

 

[Edd]

cables dont run through a roof space and been pulled through roofing tar, and the poor sparks got covered and couldnt be bothered to clean it off befor doing the board.. been covered in sticky crap like that before and got it everywhere, just dont come off

 

[Dean Williams]

thats a good point. the school has a flat roof and most prob has had bitumen or something on it. i'll have a search tomorrow.

 

[Darkwood]

Couple of points here, doing my csi... the likely cause is leaching of plastercisers out of some of the older cables, the majority in your picks is second hand contact (transfer) probably caused by other sparkies getting it all over their hands like yourself too, for the plastecisers to leach out their has to be a chemical reaction and may have taken decades this could all come down to the original installers greases the wires to drag them in or as mentioned before the tar issue is a likely cause too, if they were dragged through tar (even set tar) they will have black streaks rubbed onto them, tar reacts with the pvc causing leaching of the plasticisers which in turn liquifies the tar to a sticky goo. The issue is that when the plastisicers leach the cable insulation can change it properties for the worse, ive seen insulation showing 230v to earth before where leaching occured.

 

[Darkwood]

Or the obvious one is the previous sparky left his bag of liquorish allsorts on top of the dist board,....... give it a lick :wink_smile:

 

[Dean Williams]

cheers Darkwood. most of the goo was tacky, but some had set a bit and when i picked it off, the insulation came off too. i originally thought that it was some sort of plasticiser migration, i saw a similar thing at a theatre i tested last year, except it was green goo...the dreaded migration of the plasticiser di-isoctyl pthlene.

 

[SPARTYKUS]

my money is on roof tar, awful stuff.

What a mess!

Just spray a can of WD40 into the CU........ !

 

[Darkwood]

Its always hard to pinpoint without knowing the full history but i do recall seeing old pvc cables run over tar in a cellar and it layed in a line of sticky wet tar where the rest was solid, its seems that both react to each other and yes its a 'bitumen' to get off your hands (see what i did there! lol).... , but im on the understanding modern cables dont suffer like the old stuff but are prone under the right conditions.

 

[Darkwood]

my money is on roof tar, awful stuff.

What a mess!

Just spray a can of WD40 into the CU........ !

Only if your trying to blow it up!!!!!!!!! I seriously hope this is sarcasm!!!!

 

[SPARTYKUS]

Darkwood


Worry ye not. Meant to be sarcastic!


Want a quick flamethrower? One match, can of WD....

 

[Darkwood]

Darkwood


Worry ye not. Meant to be sarcastic!....

A emoticon of destruction would have been nice on this one as it can come across as advice to those who dont know its conductive, flamable and eats many types of plastic even i had to check your post was siding with humour.... ive seen an apprentice turn a motor into a ball of fire before with WD40! :willy_nilly: