1968 Domestic Switch oozing green stuff

Calahonda52

Picture attached.
There is another much more modern, dimmer switch showing the same symptoms in a different room so just wondering what the cause is.
Thanks as always

cml387

Copper oxide from water ingress of some sort. It's what happens when copper is corroded (hence the green domes of public buildings which have copper rooves).

cml387

actually it could also come from ordinary condensation.

Delta Lima

Ectoplasm.

You need to call Ghost Busters!

Calahonda52

Seems to be a bit more earthly

This calls for a full rewire, so wonder what the folk out at the coal face every day do in this case.

Green gunge is most prevalent in cables made between 1965 and 1971. The
gunge is degraded di-isoctyl phthalate and is the result of the reaction
between the plasticisor in the insulation and the copper. Between 1965 and
1971 the temprature performance of PVC was uprated by the inclusion of an
anti-oxidant in to the PVC. An unappreciated side effect was that the
anti-oxident encouraged the production of exudate.
Evidence suggests that that high ambient temperatures accelarate the
process. The exudate is of low flammability and low toxicity. Although
unsightly it does not reduce the electrical integity of the conductor or the
insulation.

See also the draft BCA statement (April 2001) below: -

1) PVC
PVC comes in two main grades, plasticised and unplasticised PVC.
Unplasticised PVC (UPVC) is used for example in double glazing window frames
where a rigid material is required.
The PVC used for manufacture of cables is a plasticised PVC that conforms to
the relevant British Standard for the cable type in question.

2) Ageing effects
As a cable ages; (at temperatures above normal ambient), the elongation to
break decreases (also the Insulation Resistance increases). The life
expectancy of a cable is arbitrarily considered to be when the elongation to
break of the PVC is 50%.
A lower elongation to break value could be considered suitable especially
for a fixed wiring cable. Therefore, providing the cable is not subject to
movement or when moved due to inspection of socket outlet or the like, the
PVC does not crack, a much lower value of elongation to break is considered
by some as suitable.

3) Greening
Greening is the appearance of a wet green substance that is a product of an
adverse reaction between certain types of plasticiser and the copper
conductors. This greening, which is a rare occurrence, can happen either
after a long period of time for some cables, or if the cable has been
severely overheated.
The plasticiser itself is a clear oily liquid that is non conductive. The
green substance is a combination of copper oxide and plasticiser which may
become conductive under certain adverse conditions.

4) Action if Greening is found
Therefore whenever this green substance is found at socket outlets etc.
initially it should be removed and the terminations cleaned (gloves should
be used) otherwise it is possible that tracking/overheating may occur. It is
strongly recommended that rewiring should be carried out as soon as
possible.

If further information is required, the original cable manufacturer should
be contacted

colm_mcm

It's the plasticiser in the insulator reacting with the copper.

Edit^ what he said

Tuco88

Good info Cala have you got a link? Any more good info on the site?

Calahonda52

Tuco88 wrote: »

Good info Cala have you got a link? Any more good info on the site?

stick
1968 Domestic Switch oozing green stuff
into google, they all reference the article above

Risteard81

Commonly known as "green goo".

colm_mcm

Bigclivedotcom on YouTube did a video on this too

Tuco88

Make sure to play the ghost busters theme for the electrician. I'm sure that counts as a substantial discount...