Black, slime on 1970s era singles in attic...

SpaceTime

I will be calling an electrician but I was just wondering if anyone could shed light on this for me in the meantime.

I was up in the attic and noticed a couple of 1 inch or so areas of dark black shiney/slimey discolouration on one single that comes up in a bundle from the distribution panel.

There is a bundle of about 20 grey PVC singles coming up from the distribution board and this one wire has black slime where it touches the others.

The wiring is from about 1972-1975 and is generally in fairly condition and had a new board fitted about 7 years ago or so and also had earthing of luminaries added and it was converted from TT to neutralised TN-C-S neutralised earthing with all of the bonding etc retrofitted.

So it has a recent cert.

Any ideas what might be causing this?
I'm hoping it's not an indication of a need for a major rewire as its a pretty big and complicated installation with three rows of breakers.

The only unusual thing that was going on recently was a completely new roof put on. So it could be a spillage of something too.

Insulation is fibreglass so I don't think that's likely to have reacted with wiring

2011

SpaceTime wrote: »

I was up in the attic and noticed a couple of 1 inch or so areas of dark black shiney/slimey discolouration on one single that comes up in a bundle from the distribution panel.

There is a bundle of about 20 grey PVC singles coming up from the distribution board and this one wire has black slime where it touches the others.

Insulation is fibreglass so I don't think that's likely to have reacted with wiring

I don't know what the slime is, but I agree it is not likely to be related to the fibreglass.

The wiring is from about 1972-1975 and is generally in fairly condition and had a new board fitted about 7 years ago or so and also had earthing of luminaries added and it was converted from TT to neutralised TN-C-S neutralised earthing with all of the bonding etc retrofitted.

That is definitely a move in the right direction.

I'm hoping it's not an indication of a need for a major rewire as its a pretty big and complicated installation with three rows of breakers.

Whether the house needs a rewire is another story.
If the original wiring dates back to 1972-1975 and has not been rewired since the chances are a complete rewire is required. Back then thee typical home presented a far smaller electrical load and homes were wired accordingly. Even if the installation met the regulations at the time the load may now be 6 times greater than it was designed for.

Earthing and bonding did not feature much during that time either.

If this was my home I would decide this by looking at several areas including:

1) Cables got PVC insulation & copper conductors.
2) Are the cables correctly sized? Minimum sizes are:
1.5 mm sq. for lighting circuits
2.5 mm sq. for socket circuits
6 mm sq. for (electric) cooker
6 mm sq. for < or = 8.5kW instantaneous shower (short cable run).
10 mm sq. for < or = 9.5kW instantaneous shower
3) Descent earthing i.e cpc a minimum of ½ the size of the phase conductor, 10 sq. mm to earth rod , gap pipe bonded etc..
4) Tails to ESB meter minimum of 16 sq. mm T + E.
5) No circuit overloaded.
6) All sockets protected by an RCD & instantaneous shower with redacted RCD + MCB or RCBO.
7) Sufficient number of circuits for the installation.
8) Bathrooms / wet areas: No sockets in bathrooms (except shaver sockets), lights are suitable (IP rated etc...), no light switches within bathroom (other than pull cord).

dolittle

i`ve seen this before dark green/black sticky oozing from the cables
as far as i can recollect it was deemed that the cable was breaking down

tomdempsey200

2011 wrote: »

Back then thee typical home presented a far smaller electrical load and homes were wired accordingly. Even if the installation met the regulations at the time the load may now be 6 times greater than it was designed for.

maybe- but not to that extent

SpaceTime

The house actually has a huge amount of wiring for that mid 70s era. Original setup was a Hager panel with mcbs.

There are
4x10 amp lighting circuits.
10 x 20 amp socket circuits.
1 x 32 amp cooker circuit
1 x 16 amp for the central heating boiler and pumps
1x20 amp water heating.

Two RCDs

1 main fuse at 63A switch fuse.

Meter tails are to spec from 7 years ago.

All rooms have at least 2 x 2 gang mk switch sockets.

Kitchen has 7 doubles across three radials. Utility has three doubles across two radials.

I could be over estimating its age but its a fairly beefy installation by any standards.

We don't have any electric showers or electric heating other than the immersion. Water is heated by gas and solar.

tomdempsey200

it should be possible to upgrade installation if circuit wiring is in good condition imo

final circuits haven't changed all that much except for addition of lighting cpcs

SpaceTime

I'm just wondering if those cables were walked over or physically damaged during the roof installation.

SpaceTime

Here's an image of it :



It doesn't look like burn to me, but I could be wrong.

SpaceTime

tomdempsey200 wrote: »

it should be possible to upgrade installation if circuit wiring is in good condition imo

final circuits haven't changed all that much except for addition of lighting cpcs

It has earths to all the light fittings but not to the switch plates which are all plastic anyway.
The original setup was actual TT installation with an RCD across the whole system. On advice from an electrician who was doing some work on it, it was converted to TN-C-S and neutralised by the ESB.

The original installation had 3 earth rods and an higher value RCD on the entire supply and a couple of 30mA RCDs on the final circuits (except lights).

Apparently it reflected the state of the overhead lines in the area when the house was first built rather than some kind of sloppy wiring. The original wiring in this area of Cork City wasn't suitable for bonding earth to in that era and was re-done in the 80s sometime and put underground.

It has everything pretty much to spec.
There's no sockets in bathrooms/wet areas (no shaver sockets either though!), light switches outside bathrooms only etc.

Bathroom lights are also on a separate circuit and RCD'd so, I think someone went above and beyond the regulations for that era.

Bruthal

Its likely that dark green substance which comes from PVC cables probably from the 60's and 70's era, probably from an ingredient of the PVC used at the timer, reacting with the copper. It will usually be seen where the cable has been cut, such as at connections.

SpaceTime

Bruthal wrote: »

Its likely that dark green substance which comes from PVC cables probably from the 60's and 70's era, probably from an ingredient of the PVC used at the timer, reacting with the copper. It will usually be seen where the cable has been cut, such as at connections.

Can anyone make a guestimate of the age of that cabling based on the pic?

It's red/black core and the lighting is all singles from the usual old round black MK junction boxes.

The problem with us guessing the age is that the house was originally built / designed in the 70s but the project was very slow (we don't know the exact history of it) so, it could have been wired anytime from about 1972 to 1982.

The original panel was a fairly modern looking Hager board and the standard sockets used in most of it (other than where fancier ones were fitted) are MK logic with the square edges (not the current ones) which I would assume are more like late 70s to 80s?

On the surface of it, it doesn't look that old tbh.

There was no trace of DZ fuses or anything that old.

I think the old meter (was replaced for electronic night/day one) said 1978 though.

2011

tomdempsey200 wrote: »

maybe- but not to that extent

6 times might be a bit of an exaggeration alright, but significantly higher.

Since the 1970s many homes would have added the following:
Instantaneous shower (additional 9.5 kW)
Iridium hob (sometimes another 9.5 kW)

SpaceTime

2011 wrote: »

6 times might be a bit of an exaggeration alright, but significantly higher.

Since the 1970s many homes would have added the following:
Instantaneous shower (additional 9.5 kW)
Iridium hob (sometimes another 9.5 kW)

Our consumption would have actually dropped since the original installation:

Dryer - went from 3kW to 1kW (heat pump)
Dishwasher - vastly more efficient than it was then.
Hob is induction vs old hob which was >3kW
Original oven was this huge monstrosity of a built-in Creda thing which used about 50% more power than the current one.

Also, the house made a lot of use of old-style recessed spots (Full size reflectors) which are now all LED.

So, all in all I'd say our power consumption's dropped 30% or more since the house was originally put together in the 70s.

Hot water was never primarily electrically heated. Was oil / immersion now natural gas/solar.

2011

SpaceTime wrote: »

The house actually has a huge amount of wiring for that mid 70s era. Original setup was a Hager panel with mcbs.

There are
4x10 amp lighting circuits.
10 x 20 amp socket circuits.
1 x 32 amp cooker circuit
1 x 16 amp for the central heating boiler and pumps
1x20 amp water heating.

Two RCDs

1 main fuse at 63A switch fuse.

Meter tails are to spec from 7 years ago.

All rooms have at least 2 x 2 gang mk switch sockets.

Kitchen has 7 doubles across three radials. Utility has three doubles across two radials.

I could be over estimating its age but its a fairly beefy installation by any standards.

We don't have any electric showers or electric heating other than the immersion. Water is heated by gas and solar.

That sounds like your wiring is pretty good.
I would think it may take little or no work to get it to meet current regulations (or close enough to be satisfied).

SpaceTime

The original kitchen lighting system they put in in the 70s would have slow-roasted a turkey!

There were 10 X 60W full-sized recessed spots!! 600 W of lighting was a bit nuts to put it mildly from both an environmental and ESB bill point of view.

Now 10 X much lower wattage LEDs

tomdempsey200

2011 wrote: »

6 times might be a bit of an exaggeration alright, but significantly higher.

Since the 1970s many homes would have added the following:
Instantaneous shower (additional 9.5 kW)
Iridium hob (sometimes another 9.5 kW)

energy saving lightbulbs and appliances

less electric water and space heating

gas hobs

rising energy costs

trend could be other direction imo

SpaceTime

tomdempsey200 wrote: »

energy saving lightbulbs and appliances

less electric water and space heating

gas hobs

rising energy costs

trend could be other direction imo

Definitely a massive reduction in this case. We've made a very deliberate attempt to cut energy consumption big time both from a economic and environmental impact point of view.

Cooking appliances - much lower consumption.
Lighting - LEDs where possible and probably 10X lower consumption.
Tumble dryer - about 4X less consumption.
Heating - south facing roof - ideal for solar so put it in and saved a fortune.
Insulation levels improved.

If anything that system should be under much less strain than it ever was.
Also, while there are a lot of sockets around, most of the time they're only being used for a few watts for electronic stuff.

Even televisions etc have dropped power consumption massively since we've switched to LCDs and LEDs

There's no electric space heating used at all either and the immersion only goes on on very dull days if it's not cold enough for the gas.

I think you're better off putting some cash into energy-saving and picking the right appliances rather than just going for the cheapest one as you do genuinely save quite a lot of cash over the years. It all adds up (very quickly!). You just have to do it all gradually by buying the efficient item when the old item needs to go in the bin anyway.

Money-wise it's not really possible to just do it all in one go. You'd need to be pretty flush for cash, but on a bit-by-bit basis, you can make a pretty huge impact on the bills without noticing that much tbh.

tomdempsey200

i'm thinking it may have been rising since the 70's but sharp drop in recent years

energy efficiency and rising cost of electricity

tomdempsey200

SpaceTime wrote: »

Apparently it reflected the state of the overhead lines in the area when the house was first built rather than some kind of sloppy wiring. The original wiring in this area of Cork City wasn't suitable for bonding earth to in that era and was re-done in the 80s sometime and put underground.

the neutral wasn't reliable probably-that would be a hazard

it's a lot more reliable now generaly

SpaceTime

Yeah, most likely.
Combination of rising energy costs and improving appliances and lighting.
I think there's a much bigger awareness of it these days than there was.

In an Irish context, just reading the eirgrid consumption data doesn't really tell you much as there was a big growth spurt in population and housing during the building bubble/boom.

I don't think Ireland was that lacking in appliances at any stage really since the 80s anyway. A lot of homes would have had things like dryers and dishwashers here earlier than they had them in general in England in my experience of the two places. Although, perhaps I just knew people with bigger houses in Ireland and smaller ones in England. It's hard to know.

That and the weather tends to increase use of dryers here compared to most of Europe.

I'd also say that a lot of people probably cut-off storage heating systems and electric space heating in the 90s as the costs got ridiculous so that probably reduced a lot of power consumption on a per-capita basis.

tomdempsey200 wrote: »

the neutral wasn't reliable probably-that would be a hazard

it's a lot more reliable now generaly

I think around here it would have been the old 4-wire stack system as there are still a few streets with that on it even now. A lot of them seem to have been modernised and tidied up and put underground since then.

SpaceTime

Bit of digging around - found the old meter seal in a drawer with 'important stuff'.

Definitely 1978.

2011

tomdempsey200 wrote: »

energy saving lightbulbs and appliances

less electric water and space heating

gas hobs

rising energy costs

trend could be other direction imo

In general I think is is fair to say that in the 1970s people had very few electrical appliances. I have seen plenty of houses from that era that have 4 sq. tails :eek: and no issues. Back then most rooms had 1 socket and one light end of.

I have even seen some modern houses blow 63A main fuses from overload, yet many 1970 houses had a 40A main fuse or smaller with no issues.

Although energy costs have increased in recent times where I grew up in the 1970s people had very little money and certainly no dishwashers, tumble dryers or such luxuries.

A 9.5 kW shower alone would draw a larger current that the average 1970 home would ever have drawn.

SpaceTime

I was in a house in France with a 20A single phase service for the whole house!

3 sockets : 2 in the kitchen and one for the telly.
4 lights

That was it! No sockets in any of the bedrooms. If you wanted to hoover you used an extension lead or if you wanted to dry your hair or whatever, you did it in the kitchen!

You also had to carefully add things up in case you blew the main fuse.

My gran's place in Dublin had 1 socket per room and only 2 in the whole kitchen. Two of her bedrooms had no sockets. They were only in the master bedroom and the other 'main' bedroom.

I think though that kind of wiring pre-dates the late 70s. Mostly 50s or even earlier.

tomdempsey200

2011 wrote: »

In general I think is is fair to say that in the 1970s people had very few electrical appliances. I have seen plenty of houses from that era that have 4 sq. tails :eek: and no issues. Back then most rooms had 1 socket and one light end of.

I have even seen some modern houses blow 63A main fuses from overload, yet many 1970 houses had a 40A main fuse or smaller with no issues.

Although energy costs have increased in recent times where I grew up in the 1970s people had very little money and certainly no dishwashers, tumble dryers or such luxuries.

A 9.5 kW shower alone would draw a larger current that the average 1970 home would ever have drawn.

yes i think the trend may have been upwards until recently...there was a time
when appliances were all go... instantaneous showers,incandescents, immersions

it's certainly going down now the last while

SpaceTime

tomdempsey200 wrote: »

yes i think the trend may have been upwards until recently...there was a time
when appliances were all go... instantaneous showers,incandescents, immersions

it's certainly going down now the last while

Back in the olden days when we used to have money and electricity wasn't so expensive that you had to think about switching on the kettle!

But anyway, back to my rather oddly stained wires...

Does it look like overheating or just some kind of degrading of the insulation? It's probably from 1978 then given the date on the meter tags.

2011

SpaceTime wrote: »

Does it look like overheating or just some kind of degrading of the insulation?

It looks like neither to me.

If it were my house I would:
1) Clean the slime off.
2) If I was concerned that the insulation was damaged I would carry out an insulation resistance test on it.
3) Measure the load per circuit (with as much switched on was possible) with a grip on ammeter. Then check that the MCBs and cables are suitable for the load.

The above tests are quick, cheap and simple.

Then you will know that the cables are in good condition, properly sized and adequately protected.

I would guess that all is good.

Bruthal

2011 wrote: »

If I was concerned that the insulation was damaged I would carry out an insulation resistance test on it.

An insulation resistance test possibly wouldn't show much if a single core wire has damaged insulation in open space.

tomdempsey200

Bruthal wrote: »

An insulation resistance test possibly wouldn't show much if a single core wire has damaged insulation in open space.

no but worth doing..


doesn't seem to be much damage from pics anyhow

2011

Bruthal wrote: »

An insulation resistance test possibly wouldn't show much if a single core wire has damaged insulation in open space.

Correct, but carrying out an insulation resistance test is standard practice once there is a concern about the integrity of the insulation of a cable.

SpaceTime

There's a distinct possibility that the roofers splashed some kind of torch-on product on them too. Or, it could be something that dripped onto them somehow.

I'm just not taking any chances! I don't fancy a fire.

Bruthal

SpaceTime wrote: »

There's a distinct possibility that the roofers splashed some kind of torch-on product on them too. Or, it could be something that dripped onto them somehow.

I'm just not taking any chances! I don't fancy a fire.

That would be exceptionally unlikely.

Bruthal

2011 wrote: »

Correct, but carrying out an insulation resistance test is standard practice once there is a concern about the integrity of the insulation of a cable.

Its worth pointing out that passing an insulation test is an indicator, not proof, that a cable is in good condition.

2011

Bruthal wrote: »

Its worth pointing out that passing an insulation test is an indicator, not proof, that a cable is in good condition.

Agreed (again:D) but as already said:

no but worth doing..

carrying out an insulation resistance test is standard practice once there is a concern about the integrity of the insulation of a cable.

Bruthal

2011 wrote: »

Agreed (again:D) but as already said:

Yea but in the context of this thread, and the actual photos of single core cables with marks on them, and a poster concerned about a fire, it should be made clear that a good result in an insulation test would not certainly mean that the insulation at them marks is perfect. That's my point.

If it is in fact that black-greenish liquid that forms on some cables from the 60s, that would indicate copper is exposed, since it is a component in the PVC reacting with contact with copper that causes it. It doesn't look like that stuff in the photos though. Hard to tell really.

Risk of fire would be very remote anyway, assuming no other serious problems.

2011

Bruthal wrote: »

Yea but in the context of this thread, and the actual photos of single core cables with marks on them, and a poster concerned about a fire, it should be made clear that a good result in an insulation test would not certainly mean that the insulation at them marks is perfect. That's my point.

You are pushing an open door here.
It is a valid point that has been agreed with each time it was made.

It does not change the fact that an insulation resistance test would be prudent.

2011

I think this thread has run its course.
If anyone has anything new to add please PM a Mod and it will be unlocked.

Stoner

dolittle wrote: »

i`ve seen this before dark green/black sticky oozing from the cables
as far as i can recollect it was deemed that the cable was breaking down

That's what I would have thought, often got this type of gunk on my hands pulling out old cable, I put it down to the cable being past its sell by date.