Fuse board change with rear entry mounted on wood

[Michaelwgroves]

If you use rear entry you will compromise integrity of CU, you must therefore seal the openings. Two options I use is Rockwool rammed in tight, or Fire rated foam, just don't get carried away with foam............

 

[Octopus]

If you use rear entry you will compromise integrity of CU, you must therefore seal the openings. Two options I use is Rockwool rammed in tight, or Fire rated foam, just don't get carried away with foam............

Disagree.

There are no guidelines for ip ratings on the rear face

 

[Michaelwgroves]

It’s not for ip rating, it’s for protection against fire

 

[Octopus]

It’s not for ip rating, it’s for protection against fire

none of those either

 

[sparksfly]

The metal CU's in domestic is to contain a possible fire, not to be fire proof. Just use common sense, I also mount on wood ( so to speak!) and use a mini grinder to cut large holes in the back to accommodate a bunch of cables from all angles. So long as there are no unsheathed wires touching wood or metal...no problem. You only have to look at the old Wylex wood backed boards to see there was no issue with fire if installed properly. The only issue they had....a lack of space. I am not a fan of foam with any cables, lack of future maintenance.

 

[Spoon]

The metal CU's in domestic is to contain a possible fire, not to be fire proof. Just use common sense, I also mount on wood ( so to speak!) and use a mini grinder to cut large holes in the back to accommodate a bunch of cables from all angles. So long as there are no unsheathed wires touching wood or metal...no problem. You only have to look at the old Wylex wood backed boards to see there was no issue with fire if installed properly. The only issue they had....a lack of space. I am not a fan of foam with any cables, lack of future maintenance.

If this was always true then there would have been no need for the current reg on 'fire resistant' CU's

 

[Spoon]

There are no guidelines for ip ratings on the rear face

416.2.1. Live parts shall be inside enclosures or behind barriers providing at least the degree of protection IPXXB or IP2X

Doesn't this IP2X also apply to the back of CU's?

Might be me just being thick but what's the point of having a 'fireproof' CU due to fire risk and then cutting a bit hole in the back for the cables, which also lets the fire spread.

 

[Octopus]

Doesn't this IP2X also apply to the back of CU's?

Sides and bottom.

 

[Spoon]

Sides and bottom.

But 416.2.1. implies all sides.

what's the point of having a 'fireproof' CU due to fire risk and then cutting a bit hole in the back for the cables, which also lets the fire spread.

You understand what I'm getting at with my comment above.... It just makes no sense to have no IP rating for the back of the CU.

 

[Octopus]

You understand what I'm getting at with my comment above.... It just makes no sense to have no IP rating for the back of the CU.

I do.

But if you mount the CU on 19 mm supports, its hard enough to get a length of cable into the CU, let alone get your hand and fingers down.

However if you were to mount the CU on 300 mm supports then yo may have a point

 

[davesparks]

what's the point of having a 'fireproof' CU due to fire risk

We don’t have fireproof CUs, we have CU’s which are manufactured from a non-combustible material.
This means that the material which the CU is made of must not be combustible, it does not put any requirement on it being fire-proof.

 

[davesparks]

If you use rear entry you will compromise integrity of CU, you must therefore seal the openings. Two options I use is Rockwool rammed in tight, or Fire rated foam, just don't get carried away with foam............

Why must you seal the openings? There’s a big one in the front where the MCBs go which is not sealed.

Do you de-rate the cables suitably for the increased thermal insulation you install round them?

 

[Spoon]

We don’t have fireproof CUs, we have CU’s which are manufactured from a non-combustible material.
This means that the material which the CU is made of must not be combustible, it does not put any requirement on it being fire-proof.

Non-combustible material.... That's the wonderful phrase I was looking to use.
You all know what I meant anyhow..

 

[ipf]

Non-combustible material.... That's the wonderful phrase I was looking to use.
You all know what I meant anyhow..

Sunk in?........and I don't mean the CU....

 

[Michaelwgroves]

BS7671 421.1.201 is not clear, the IET Guidance Note 4 "Protection Against Fire" seeks to clarify the intention of the regulation.
3.8.1 Consumer Units and similar assemblies in domestic premises pg. 29 states
>"The non-combustible enclosure or cabinet must provide a complete envelope (e.g. base, cover, door and any components such as hinges, screws and catches) as necessary to maintain fire containment. All blanks, circuit-breakers and other devices must be contained within the non-combustible enclosure or cabinet"
>"The installer must seal all openings into the non-combustible enclosure or cabinet for cables, conduits, trunking or ducting that remain after the installation of cables. Good workmanship and proper materials must be used and account must be taken of the manufacturer's relevant instructions, if any."

Hopefully this clarifies the situation.

 

[Octopus]

^^ What you need to consider is that most people don't buy the guidance notes .............

If, and I say if the IET had this in mind, then it needs to be spelt out in BS 7671 18th Edition.

I would add that I've shown a number of CU's to my assessors over the years and they have never commented about the use of rear entry panels.

 

[Michaelwgroves]

I agree it should either be in BS7671, or the guidance notes should be a compulsory addition. Personally I now have the vast majority of guidance notes as they add clarify to BS7671.

Stroma are hot on this.

 

[Octopus]

I agree it should either be in BS7671, or the guidance notes should be a compulsory addition. Personally I now have the vast majority of guidance notes as they add clarify to BS7671.

Stroma are NOT hot on this.

Edited for you based on my personal experience

Guidance notes should be given away free for everybody paying for the 18th Edition.

Allowing the IET to produce additional documents that they can sell, is not exactly encouraging them to improve BS 7671

 

[davesparks]

BS7671 421.1.201 is not clear, the IET Guidance Note 4 "Protection Against Fire" seeks to clarify the intention of the regulation.
3.8.1 Consumer Units and similar assemblies in domestic premises pg. 29 states
>"The non-combustible enclosure or cabinet must provide a complete envelope (e.g. base, cover, door and any components such as hinges, screws and catches) as necessary to maintain fire containment. All blanks, circuit-breakers and other devices must be contained within the non-combustible enclosure or cabinet"
>"The installer must seal all openings into the non-combustible enclosure or cabinet for cables, conduits, trunking or ducting that remain after the installation of cables. Good workmanship and proper materials must be used and account must be taken of the manufacturer's relevant instructions, if any."

Hopefully this clarifies the situation.

No it doesn’t clarify it because the thin steel which the CUs are manufactured from will not provide fire containment, fire will get through it.
Unless they specify fire containment properly then it’s impossible to meet the requirements. For a start fire containment needs to have a length of time associated with it, just look at the standard practices and regulations regarding fire barriers and compartments within buildings.

Plus the guidance notes are not part of the regulations, they are additional information. A lot of time and consideration is put in to the wording of the regulations and they are very specific, as far as I know the guidance notes are not written and approved by the full regulations committee so cannot guarantee to carry the full ‘intentions’ of the regulations.
The term ‘non-combustible’ will have been selected over ‘fire-proof’ for good reason.

What is the point in having a set of regulations where we are expected to comply with the ‘intention’ or ‘spirit’ of the regulations rather than what is clearly written?

 

[Michaelwgroves]

Edited for you based on my personal experience

Guidance notes should be given away free for everybody paying for the 18th Edition.

Allowing the IET to produce additional documents that they can sell, is not exactly encouraging them to improve BS 7671

I think since Grenfel everyone is tightening thier belts.