Incoming mains question

[RogerS]

From our surveyors' report...

The incoming main appears not to contain an earth back to the grid; it is recommended that the incoming cable is altered to include an earth, so the electrical system can be earth-bonded and fitted with modern circuit-breakers for safety.

The incoming main passes an old main distribution box, with pull-fuses. It is recommended that the fuse boxes are upgraded to RCD boards. Ring mains and local wiring are in modern plastic-sheathed cabling

The incoming mains is underground. The property itself is out in the sticks. So is it a simple question of an electrician connecting an earth spike to the incoming neutral? That's what we currently have on our current house - fed from a transformer up a pole.

 

[Dee J]

Two choices... Get your dno (network operator) to upgrade the incoming to tnc-s ( combined neutral/earth) if they can... or get your electrician to set up an independent tt earth rod (and appropriate rcd protection).

 

[Woody2Shoes]

In my limited experience of these things, surveyors don't usually pass comment on technical matters like electrics/gas/plumbing - for the very good reason that they're not sufficiently well qualified! They usually include caveats in their reports saying things like "you may wish to pay someone qualified to look at the electrics..." or something similar. That said, what your surveyor says indicates that the electrics are old and not up to modern safety standards.

Often, houses away from others have their own earth (as already said type "TT" https://en.wikipedia.org/wiki/Earthing_system ) - which may or may not be in a safe working state in this case. I think that you should interpret the report simply as saying you should budget for a proper electrical inspection and probably some significant remedial work (a re-wire would be much easier before you move in, I think).

Cheers, W2S

 

[HappyHacker]

Get an electrician in to have a look and give a quote for any work required. If there is no earth the DNO will not usually provide one or may charge a large amount but it is always worth asking as it sometimes been omitted during a meter or supply change. It is not just a case of making a connection as it depends on how their supply has been installed and it may not be safe to do so without work on the supply.

If there is no earth and no RCD or earth leakage breaker then it is potentialy dangerous but the earth is not always obvious hence the need for an electrician.

There is usually nothing wrong with the old fuse boards but lots of people condemn them out of hand. "They are made out of wood and are going to burst into flames at any moment", sorry I hear lots of rubbish sprouted about them there are still millions installed and working OK.

You need RCD protection if you are going to have your own earth rod and that can be an upfront RCD fitted in the tails to your existing board, not recommended as you have one point of failure and may get nuisance tripping, or you can get a modern board with two RCDs and or RCBOs which incorporate the over current protection and the RCD in one unit.

Since January 2016 a consumer unit replacement in domestic premises have to be metal which introduces problems on TT (earth rod) installations which are not properly addressed in the wiring regulations.

Any competent electrician will be able to give you good advice on the options and costs. If the wiring is on PVC cable then it is unlikely to require a rewire but you may want to put in more sockets and circuits as the older installations, and some of the newer ones, were usually a bit sparse on sockets and lights.

Good luck.

 

[RogerS]

.....
Since January 2016 a consumer unit replacement in domestic premises have to be metal which introduces problems on TT (earth rod) installations which are not properly addressed in the wiring regulations.
......

Classic !! Don't you just love those Regs

Many thanks for your help.

 

[Woody2Shoes]

.....
Since January 2016 a consumer unit replacement in domestic premises have to be metal which introduces problems on TT (earth rod) installations which are not properly addressed in the wiring regulations.
......

Classic !! Don't you just love those Regs

Many thanks for your help.

A very good description of TT earthing and the metal consumer unit enclosure is given here if you're feeling the need to delve further! Cheers, W2S

https://www.youtube.com/watch?v=9JLSTjV4imA

 

[RogerS]

.....
Since January 2016 a consumer unit replacement in domestic premises have to be metal which introduces problems on TT (earth rod) installations which are not properly addressed in the wiring regulations.
......

Classic !! Don't you just love those Regs

Many thanks for your help.

A very good description of TT earthing and the metal consumer unit enclosure is given here if you're feeling the need to delve further! Cheers, W2S

https://www.youtube.com/watch?v=9JLSTjV4imA

I enjoyed that video thanks. He's a good presenter and I see he does a lot more.

I'm guessing that the trade went into hoots of laughter when the knee-jerk numpties came up with metal consumer units. I'm also guessing that they are the same numpties that came up with the knee-jerk response that triggered Part P.

 

[HappyHacker]

The video is a very good description of the issues. Of course if there is a short to earth prior to the RCD with 25 Amps flowing that is also approx 6kW of heat being generated somewhere. While this is very unlikely it is not impossible especially if the tails supplying the CU are long.

Unfortunately it is different groups of people doing the building regulations Part Pee and BS7671 Wiring Regulations so no joined up thinking. Part Pee scope was reduced in England this year but not in Wales so working in both places I have to use two different sets of rules. Scotland have a different system.

It is interesting that by reading the wiring regulations and the definitions contained therein very carefully it is possible to say that a front end RCD in a plastic box is not covered by the requirement to use metal boxes. This is what I do.

Part of the problem of fires in consumer units is rumoured to have been caused by the large manufacturers reducing/removing the amount of fire retardant in the plastic used so they became flammable and therefore not compliant with the BS standard to which they are certified by the manufacturers. So to fix the problem they made metal consumer units mandatory. There are a whole lot of other issues which are contributory factors including "value engineering" by the manufacturers and possible incorrectly tightened terminations when fitting new meters. But as there has been no proper investigation into all the causes metal consumer units are deemed the answer.

The metal consumer units do not have to be sealed nor do the cables leaving the CU need to have fireproof sealing, the metal CU is only to delay the potential fire to give people time to exit if the fire alarm has worked.

Worthy of a Monty Python sketch.

 

[RogerS]

Mmmm..incorrectly tightened terminations. That reminds me of when I worked on Outside Broadcasts and we had a mini-fire behind the mains control panel in one of the vehicles. That was down to a terminal coming loose/inadequately tightened and possibly exacerbated by all the miles that the vehicles travelled. Tightening up became routine maintenance.

Interesting that Part P has been de-scoped a little in the UK. I need to bone up on that.

Another true story and pre-Part P. I was replacing the consumer unit in a flat I was refurbishing. The flat wiring was circa 50's-60's and single core inside metal conduit. I'd physically removed the main fuse from the box on the landing and padlocked up the box. I double checked the incoming tails and definitely dead. All the wiring had been undone from the old consumer unit and I was in the process of reconnecting to the new consumer unit when my knuckle brushed against one of the unconnected neutrals and I got a belt. Turned out that when they'd done some of the wiring they'd mixed up the neutrals between some of the flats and this neutral was still being powered via whatever equipment was switched on in the other flat.

 

[bussy]

Turned out that when they'd done some of the wiring they'd mixed up the neutrals between some of the flats and this neutral was still being powered via whatever equipment was switched on in the other flat.[/quote]
Thats why when changing meters in communal meter locations where you can't trace the tails over there entire length we drop the supply neutral out of the meter meter and test between that and the neutral tail on the customers side.

Marty

 

[RobinBHM]

The video is a very good description of the issues. Of course if there is a short to earth prior to the RCD with 25 Amps flowing that is also approx 6kW of heat being generated somewhere. While this is very unlikely it is not impossible especially if the tails supplying the CU are long.

Unfortunately it is different groups of people doing the building regulations Part Pee and BS7671 Wiring Regulations so no joined up thinking. Part Pee scope was reduced in England this year but not in Wales so working in both places I have to use two different sets of rules. Scotland have a different system.

It is interesting that by reading the wiring regulations and the definitions contained therein very carefully it is possible to say that a front end RCD in a plastic box is not covered by the requirement to use metal boxes. This is what I do.

Part of the problem of fires in consumer units is rumoured to have been caused by the large manufacturers reducing/removing the amount of fire retardant in the plastic used so they became flammable and therefore not compliant with the BS standard to which they are certified by the manufacturers. So to fix the problem they made metal consumer units mandatory. There are a whole lot of other issues which are contributory factors including "value engineering" by the manufacturers and possible incorrectly tightened terminations when fitting new meters. But as there has been no proper investigation into all the causes metal consumer units are deemed the answer.

The metal consumer units do not have to be sealed nor do the cables leaving the CU need to have fireproof sealing, the metal CU is only to delay the potential fire to give people time to exit if the fire alarm has worked.

Worthy of a Monty Python sketch.

Thats interesting, I had wondered why after many years of plastic consumers units, suddenly it has become a fire risk.

This week our electrician has done the first fix on a conservatory for us. The work needed to go back to the board and because it isnt a metal unit, the electrician has fitted the mcbs into a separate metal box sitting right next to the consumer unit, which is a quite modern board with rcd and mcbs. I thought it was over the top, but apparently necessary to comply.....

Apologies for going ot, Ive heard of tnc-s but thats it!

 

[n0legs]

From our surveyors' report...

The incoming main appears not to contain an earth back to the grid; it is recommended that the incoming cable is altered to include an earth, so the electrical system can be earth-bonded and fitted with modern circuit-breakers for safety.

The incoming main passes an old main distribution box, with pull-fuses. It is recommended that the fuse boxes are upgraded to RCD boards. Ring mains and local wiring are in modern plastic-sheathed cabling

The incoming mains is underground. The property itself is out in the sticks. So is it a simple question of an electrician connecting an earth spike to the incoming neutral? That's what we currently have on our current house - fed from a transformer up a pole.

What is the service cable?

 

[Woody2Shoes]

......why after many years of plastic consumers units, suddenly it has become a fire risk.........

Interestingly, when I changed our consumer unit a couple of years ago (under suitably qualified supervision, I quickly add!), the old (plastic) one had some very distinct charring around the main 80A switch - the connections were not tight. Similarly, the other end of one of the tails was not tight in the (bakelite) main fuse connection and there was no visible charring. I think that the modern plastic was supposed to be fire-retardant, but at the expense of nasty chemicals/fumes. Our house used to have economy seven heating, which probably exercised the current-carrying capacity of the old setup pretty rigorously. I felt, on inspecting the charred plastic, that to some degree I and my family had dodged a bullet. I suspect that over time, screw connections do work loose - with thermal cycling etc. - and part of a periodic inspection should be to check and tighten these - starting with the "fattest" ones! Cheers, W2S

 

[RogerS]

From our surveyors' report...

The incoming main appears not to contain an earth back to the grid; it is recommended that the incoming cable is altered to include an earth, so the electrical system can be earth-bonded and fitted with modern circuit-breakers for safety.

The incoming main passes an old main distribution box, with pull-fuses. It is recommended that the fuse boxes are upgraded to RCD boards. Ring mains and local wiring are in modern plastic-sheathed cabling

The incoming mains is underground. The property itself is out in the sticks. So is it a simple question of an electrician connecting an earth spike to the incoming neutral? That's what we currently have on our current house - fed from a transformer up a pole.

What is the service cable?

 

[n0legs]

That`s a submain from somewhere. Where's the meter and cutout?
Seems that some earth provision has been attempted.

 

[RogerS]

That`s a submain from somewhere. Where's the meter and cutout?
Seems that some earth provision has been attempted.

That's a very good question! The photo came off the survey report. I'll have a dig round and see if I can see a meter in any of the other photos.

At least the consumer unit is metal

 

[RogerS]

That`s a submain from somewhere. Where's the meter and cutout?
Seems that some earth provision has been attempted.

I can now answer that question.

The meter is in a neighbouring property 0.26 miles away (no typo, a quarter of a mile away). I have not seen it but am reliably informed that that is where it is located. Presumably the cutout will also be there. Sounds very iffy to me.

 

[Woody2Shoes]

Sounds very iffy to me.

Sounds very expensive to me :?

 

[RogerS]

Talking to the electric company, I think I will leave it where it is!