How to seal a new CU (long)

[Robin]

In summary:

a. is it still sufficient to seal a new, metal consumer unit to meet IP ratings without using intumescent glands or the like?

b. is it worth adding something on this to the Wiki on ?Changing a consumer unit?? Cock-shy:

?Sealing

After you have tested you should check for gaps which would allow wires or fingers into the consumer unit.

The only formal requirement is to meet the IP codes [[link to

IP4X on the top surface and IP2X on other surfaces. But it is good practice to seal all gaps using conduit, foam strip, glands, or sealant.

You do not have to use intumescent or fire resistant sealant etc.?

Background

1. Reading the revised article on ?Changing a consumer unit? (as one is wont to do when in want of means of procrastination) I wondered about sealing a CU under the currents regs. Specifically, do the cable entries need to be fire resistant? And if so, what meets the standard?

1. I don?t own the 18th edition but AIUI the requirement is still an ?enclosure manufactured from non-combustible material?. Nothing there about grommets, glands etc.

2. But Wiring Matters[1] in 2015 had a piece which included:

"It is important for the installer to seal all openings into the enclosure or cabinet for cables, conduits, trunking or ducting that remain after the installation of cables - see Figure 6. The intent of the sealing is to ensure that, as far as is reasonably practicable, any fire is contained within the enclosure or cabinet and the escape of flames to the surroundings of the cabinet or enclosure or into conduits trunking or ducting is minimised, as intended by Regulation 421.1.201. Good workmanship and proper materials must be used, and account must be taken of the manufacturer?s relevant instructions, if any.?

1. That was depressing given I'm inclined to channel Jimmy "Yosser" Hughes. And wasn't brought up ?proper.

1. But I finally came across another piece from the IET in 2015[2] that has a Q&A:

?When I put cables into a new metal consumer unit, do I have to use intumescent glands to enforce the fire protection of the consumer unit?

No, the metal consumer unit is designed to encase a fire within it and restrict the likelihood that a fire may spread. Manufactures? have carried out exhaustive tests on this issue and have found that the cable entry does not have to continue the fire rating of the consumer unit, for it to be effective. The only requirement is to keep IPXXD or IP4X on the horizontal surfaces (Reg 416.2.1) and IPXXB or IP2X on all other surfaces (Reg 416.2.2). Intumescent glands and sealants may be used to ensure the IP ratings are maintained, but they are not a requirement and existing methods of ensuring IP are acceptable.?

1. But is that current - and likely to pass "good workmanship"?

[1] [2]

[sm_jamieson]

? (as one is

Nothing there

?

rief-overview/

Sorry I didn't read all that, but I have to seal top cable openings in a pl astic CU, installed to the old regs, and this looks useful

Simon.

[sm_jamieson]

?? (as one is

Nothing there

??

-brief-overview/

plastic CU, installed to the old regs, and this looks useful

Actually given the cost of that I might use this:

145

[Tricky Dicky]

Read Adams reply in the "Running cables into trunking from CU". It's the same issue.

Richard

[Robin]

Bugger, I somehow missed that thread. It suggests I ought at the very least to have drafted to steer people towards use of intumescent sealant as "good practice".

[tabbypurr]

I wonder what the purpose is of bringing a noncompliant CU to another noncompliant standard.

[Robin]

If all the CU needs is some sealant in order to comply with the standards applying when it was installed I cannot see in what way it would then still be "noncompliant".

[ARW]

I am sure the installation instructions on some metal clad CUs state that the fire rating of the CU must be preserved.

I always used to silicone up the top entry of the plastic CUs I fitted. Now I use fire mate etc.

[tabbypurr]

It is, even if you don't see it. Plastic CUs are mostly no longer compliant.

NT

[Robin]

You seem to be assuming this is a newly installed CU. I assumed it was one installed before compliance with Amndt 3 was required. Perhaps the OP will clarify.

[ARW]

I have just had a long day at work.

So help me out.

You seem to be the OP of this thread.

Cheers

[Robin]

Ahem, yes, that should indeed have been "Perhaps Simon will clarify". Sorry.

(It's tempting to pray say that's what you get from too many 14 hour days in the past but suspect the truth is just my poor choice of genes.)

[Robin]

I did have a quick look for manufacturers' instructions but all I found was a rather fluffy Wylex/Crabtree note that repeated the IET line and then went on to (as I read it) "sell" their intumescent add-ons without actually saying they needed to be used[1]. But I can well believe some go further now so it all points to pointing people to use intumescent/fire rated seals. I'll have another go later.

[1]

G from

"The cable installation entry method shall, as far as is reasonably practicable, maintain the fire containment of the enclosure. This can generally be achieved by the installer ensuring that the cable access holes they make in the enclosure do not leave gaps greater than:  1.0mm for the horizontal top surface and  2.5mm for all other surfaces

The installer could for example, select as they deem appropriate; trunking, conduit, cable gland or cable entry accessories to minimise the opening around the cables. For rear cable access, the minimum number of rear knockout(s) shall be removed to accommodate the cable(s).

However, customer questions remain as to what further steps could be taken to ensure that the necessary cable entries do not undermine the intention of this new and important fire safety requirement.

Intumescent material when exposed to heat rapidly expands and fills the surrounding area effectively smothering fire and preventing spread by extinguishing flames.

The Crabtree Solution

Working with a leading UK manufacturer of intumescents, Crabtree have introduced the CRFS range of intumescent material strips which fit inside the consumer unit (self adhesive). If this intumescent strip is exposed to heat the fire resistant ?char? flows around the cables filling the enclosure smothering the fire by reducing the oxygen supply further, so extinguishing the fire at source."

[tabbypurr]

No I'm not. But I am concluding from your comments that you don't now how it all works

NT