Fire sealant for back of distribution board?

[LewisM]

Anybody recommend a good intumescent sealant that can be applied directly to PVC cables?

 

[Pete999]

Anybody recommend a good intumescent sealant that can be applied directly to PVC cables?

Any good intumescent sealer will be OK speak to your Scheme or Wholesaler they should be able to advise

 

[ipf]

If you're talking about rear cable entry sealing, there is nothing worse than a board sealed with that stuff for installation of future circuits.
Why is it needed?

 

[Dustydazzler]

If you're talking about rear cable entry sealing, there is nothing worse than a board sealed with that stuff for installation of future circuits.
Why is it needed?

agreed

i just don’t understand why people back fill the entry hole with 2 gallons of horrible mastic making it virtually impossible for the next guy to feed any new cables in...

 

[davesparks]

Anybody recommend a good intumescent sealant that can be applied directly to PVC cables?

If you make the holes in the CU a suitable size you won't need to waste your time filling the hole with sealant.

Plus why would you use intumescent sealant?

 

[Paul L]

I haven't carried out any installation work for a few years now so i am a bit out of the loop but i just want to understand what the actual requirements are for this. Say you had a consumer unit mounted on a stud partition wall with the cables coming down in the stud wall and through a nice big knockout in the back of the consumer unit.
Surely this hole would need to be sealed up somehow to prevent a potential fire going up the cavity?
I'm sure there are ways and means of getting around this but as i said i am out of the loop a bit so other than gumming it up with something i wouldn't know what would be the best solution to comply with the various requirements.

 

[davesparks]

I haven't carried out any installation work for a few years now so i am a bit out of the loop but i just want to understand what the actual requirements are for this. Say you had a consumer unit mounted on a stud partition wall with the cables coming down in the stud wall and through a nice big knockout in the back of the consumer unit.
Surely this hole would need to be sealed up somehow to prevent a potential fire going up the cavity?
I'm sure there are ways and means of getting around this but as i said i am out of the loop a bit so other than gumming it up with something i wouldn't know what would be the best solution to comply with the various requirements.

Don't make the hole in the CU so big, and don't make the hole in the wall so big.

There is no requirement to seal the entries of a CU, it is not a fire rated enclosure.

A CU is required to be manufactured from non combustible material, this means the material it is made from must not readily catch fire. It does not say anything about contain a fire or resisting the passage of fire.

 

[Paul L]

Intent of the new regulation
The intent of Regulation 421.1.201 is considered to be, as far as is reasonably practicable, to contain any fire within the enclosure or cabinet and to minimise the escape of flames.

I am genuinely playing devils advocate here but i found this statement above (hope i am allowed to use it, got it off the IET information page).
Surely a fire that happens in a consumer unit has got be contained within it if possible. I understand that the plastic ones would not be able to do that but obviously big holes wouldn't contain it either.
As davesparks said, maybe the solution is to make the holes as tight as possible but i know from past experience and cables coming in from all angles on old installations that this is not always easy.

 

[Ian1981]

I think the idea is that there’s nothing to catch fire , obviously the old plastic ones will catch fire and fuel it, steel will not but yea it would contain any fire better than plastic.

 

[Mike Johnson]

If you think the holes in a DB need sealing, you can get intumescent tape, I suspect that foam is used because its quicker and easier to use, personally any penetration into a void needs sealing of some kind, if the surface being penetrated is in a fire barrier to another room or area then it has to be an fire resistant material.

 

[davesparks]

Intent of the new regulation
The intent of Regulation 421.1.201 is considered to be, as far as is reasonably practicable, to contain any fire within the enclosure or cabinet and to minimise the escape of flames.

I am genuinely playing devils advocate here but i found this statement above (hope i am allowed to use it, got it off the IET information page).
Surely a fire that happens in a consumer unit has got be contained within it if possible. I understand that the plastic ones would not be able to do that but obviously big holes wouldn't contain it either.
As davesparks said, maybe the solution is to make the holes as tight as possible but i know from past experience and cables coming in from all angles on old installations that this is not always easy.

If that is the intent then why didn't they write that into the regulations?

If the regulations are intended to require that a CU be a fireproof enclosure then they should have written that in the regulations.

Of course then every electrician in the domestic sector would need training in the requirements for maintaining a fireproof enclosure, along with a significant cost increase as the normal CU would have to be redesigned significantly I think.

 

[Mike Johnson]

It's in the building regulations that any fire proof area has to be maintained and that includes any penetrations that could provide the spread of fire, but it all accords where the penetrations are and if they are part of a fire proof enclosure/wall or floor, but it is a moot point if a DB constitutes a fire proof enclosure.

 

[davesparks]

but it is a moot point if a DB constitutes a fire proof enclosure.

Which it doesn't, a thin steel sheet enclosure with a lid that doesn't seal onto it, and a big hole in it with just a hinged flap is not a fireproof enclosure.

 

[Midwest]

We’ve had this numerous times and there have been numerous different opinions and guidance from various organisations and schemes.

I do recall someone posting some fairly recent guidance from the IET, which indeed suggesting sealing CU’s to prevent escape of fire etc. Not something I think is relevant to 421.1.201, but who are we to say.

The building regs do suggest somewhere, that holes cut in a properties should have the level of protection it previously had.

 

[Andy78]

I'll chuck 527.2.1 into the mix.
Where a wiring system penetrates any building element that has a prescribed fire rating it should be sealed back to that rating.

Not to do with sealing a CU, but maybe the wall behind it if it needs to be. Rear entry penetrations I'm on about.

 

[DPG]

Did you have a straight face when you typed that last line Andy?

 

[Pretty Mouth]

Here's a couple of articles that are relevant to this thread, both from the IET wiring matters back in 2015. It will come as no surprise to learn that they give conflicting advice.

This one appears to say you need to (Sealing on wiring entries):

https://electrical.------.org/wirin...ble-enclosure-requirement-for-consumer-units/

...while this one appears to say you don't (last FAQ):

https://electrical.------.org/wirin...-winter-2015/consumer-units-a-brief-overview/

 

[Mike Johnson]

I think we are all singing from the same hymn book, I would agree that if it's only the DB that has been opened at the back then it should not need any additional fire protection, but if the wall behind the DB has been penetrated then it may need fire stopping if that wall was a fire barrier to the next room or to the ceiling or roof above, well that's my take on it.

 

[westward10]

Cavity walls should have internal cavity barriers in place to prevent the spread of smoke and fire. You should consider cavities as individual cells and at no point should a cavity barrier be breached without fire stopping. The only time a cavity wall needs sealing is where both sides are breached which would allow spread from one compartment to another. Using one side as a cable route will not necessarily breach its protection due to the internal cavity barriers and on this basis no additional fire sealing is required.

 

[Mike Johnson]

If I remember correctly the regulations say horizontally at floors and vertically at party walls, the interpretation of that leaves a lot to be desired, you only officially get party walls on terraced house's, so unless the cavity is fire stopped in a detached house you could get a spread of fire or smoke from room too room if the internal skin had been penetrated and not fire stopped, just a thought.