New cable crossing existing gas pipe - pg18 of on site guide unhelpful

[JohnW2]

My original question wasn't about bonding, it was about clearance.

It was - I'm getting confused with two current 'gas pipe' threads here - my apologies!

I'll be using PVC conduit, otherwise if it was Galvanised conduit then perhaps it would be prudent to bond to the gas pipe.

I'm not sure that using metal conduit would actually address the 'separation of cables/gas pipes' issue, anyway - even the OSG only talks about insulating barriers.

Kind Regards, John

 

[mrstitt]

Well now were on amendment 3, our CU's all need to be non-combustible, which can only be achieved through the use of metal.

If we were to see the term non-combustible with regards to such barriers then galvanised would probably be the only way to go. Wait and see for further amendments. Perhaps they will just ban electricity - that would reduce electrical fires (and save me about £600 a year on my utility bills)

 

[JohnD]

non-combustible, which can only be achieved through the use of metal.

eh?

 

[mrstitt]

Since 1st January all newly installed Consumer Units must be metal. Even counter intuitively on a TT supply.

Problems with fires in the plastic ones.

 

[Taylortwocities]

Since 1st January all newly installed Consumer Units must be metal.

Not true.
The Amendment sayas that compliant CUs must be constructed of a non-combustible material. It adds that Ferrous metal e.g. steel is deemed to be an example this.

It does not say that all CUs must be metal.

We await, with bated breath, for there to be a definition of what actually is meant by non-combustible.

 

[JohnD]

I think ceramics are more incombustible than steel, and are also insulating.

 

[JohnW2]

Well now were on amendment 3, our CU's all need to be non-combustible, which can only be achieved through the use of metal.

No metal is "non-combustible". The wording of the regulation is ridiculous, and I hope will not survive the next Amendment!

Kind Regards, John

 

[mrstitt]

I agree John and I think that the wording is poor. Plastics can be manufactured with flame retardants, but obviously any plastic will combust eventually.

Die-cast aluminium is obviously also out of the question, aluminium burns well.

But as John rightly points out, even Steel is combustible. But your not going to be getting 1,500 degree electrical fires.

This should really have been addressed through product standards, not the wiring standards. Unless electricians are expected to undertake lab tests on any products they use, they should be expected to use products which were manufactured in accordance with an appropriate standard. Let the manufacturers decide how to comply. But then they couldn't apply it to product standards because this is a UK only regulation (this requirement isn't in the parent standard IEC 60364). Product safety standards are subject to European harmonisation. Hence manufacturers are free to sell plastic consumer units in the UK, its just that electricians can't install them.

The EN standards need to be tightened up - consumer units shouldn't be combustable anyway. This is all a bit back to front.

According the London Fire Brigade, consumer unit fires have increased an order of magnitude in the past decade. London is a growing and viberant city, but there aren't 10 times as many consumer units in london now as there were a decade ago. I suspect that the new one's have been cheep Chinese rubbish without the appropriate fire retardant additives in the plastic.

For TT installs, which is basically anywhere in rural Britain, these new metal boxes pose more of a hazard. Why not require IP66 rated enclosures? fire's don't last very long without an oxidising agent, an IP66 consumer unit without any drain holes.

 

[JohnW2]

But as John rightly points out, even Steel is combustible. But your not going to be getting 1,500 degree electrical fires.

Maybe not, but that doesn't excuse BS7671 for requiring a 'non-combustible' enclosure without providing any definition (ideally by reference to other Standards) as to what they mean by that. As has often be said here, ultimately absolutely nothing is 'non-combustible'!

According the London Fire Brigade, consumer unit fires have increased an order of magnitude in the past decade. London is a growing and viberant city, but there aren't 10 times as many consumer units in london now as there were a decade ago. I suspect that the new one's have been cheep Chinese rubbish without the appropriate fire retardant additives in the plastic.

That may be at least partially the explanation, but I'm not convinced that there has necessarily been a real increase of anything like the suggested magnitude, rather than just an increase in the number of fires attributed to this cause - the more they go looking for it, the more they will find (and 'report') it. Whatever, the proper solution to the problem (if it is a significant problem) would surely be to address the reasons why the fires are starting - not to attempt to contain them once they have started?

For TT installs, which is basically anywhere in rural Britain, these new metal boxes pose more of a hazard.

Indeed, but not only with TT. As I've said many times, I am concerned about the possible consequences of introducing all this earthed metal around a CU in which people (particularly DIYers) may be 'meddling' injudiciously. The LFB are interested only in fires - deaths by electrocution are "not their problem".

Why not require IP66 rated enclosures? fire's don't last very long without an oxidising agent, an IP66 consumer unit without any drain holes.

That's one possibility. Heat/smoke detectors within them (with alarm and/or auto-disconnection) would be another. However, as above, these are all "after the event" approaches - efforts surely should be directed towards preventing the fires starting in the first place?

Kind Regards, John

 

[stillp]

Hence manufacturers are free to sell plastic consumer units in the UK, its just that electricians can't install them.

Yes they can, if they install them in a non-combustible enclosure.

 

[mrstitt]

Indeed, but not only with TT. As I've said many times, I am concerned about the possible consequences of introducing all this earthed metal around a CU in which people (particularly DIYers) may be 'meddling' injudiciously. The LFB are interested only in fires - deaths by electrocution are "not their problem".

Interesting point. All new CU's are fitted with RCD protection so a a DIYer meddling is most likely going to trip the RCD. However if the DIYer does something really stupid like disconnect the earthing connection to the Mains Earthing Block, all CPC's are now going to be bonded directly to the CU metal frame.

An internal loose wire in the CU now would mean that every fancy metallic light switch or class 1 appliance becomes a death trap.

Heat/smoke detectors within them (with alarm and/or auto-disconnection)

A simple solution would be a CO detector sticker inside the front cover. A fire in absence of oxygen would quickly fill the CU with carbon monoxide. If the sticker changed colour then you know that something has died in there. A fire in the CU is likely to be married with lots of tripping, the overload trip function on each MCB operates thermally (only the fault trip operates electromagnetically)

 

[mrstitt]

Hence manufacturers are free to sell plastic consumer units in the UK, its just that electricians can't install them.

Yes they can, if they install them in a non-combustible enclosure.

Would slightly defeat the object. My house is made out of bricks, which makes it a non-combustable enclosure.

 

[JohnW2]

Interesting point. All new CU's are fitted with RCD protection so a a DIYer meddling is most likely going to trip the RCD.

Not if the 'meddling' is upstream of the RCD(s) - main switch or (if main switch is not opened) the L busbar and everything connected to it.

A fire in the CU is likely to be married with lots of tripping, the overload trip function on each MCB operates thermally (only the fault trip operates electromagnetically)

That's one of the reasons why I don't fully understand this notion that fires originating in CUs often go undetected until the entire house in on fire!

Kind Regards, John

 

[JohnW2]

Yes they can, if they install them in a non-combustible enclosure.

... My house is made out of bricks, which makes it a non-combustable enclosure.

A good point! Another thing that Mr BS7671 has not defined adequately!

Kind Regards, John

 

[stillp]

Hence manufacturers are free to sell plastic consumer units in the UK, its just that electricians can't install them.

Yes they can, if they install them in a non-combustible enclosure.

Would slightly defeat the object. My house is made out of bricks, which makes it a non-combustable enclosure.

Not really. See the definition of enclosure.