Fuse board change with rear entry mounted on wood

[Gringoking88]

Hi all,

I'm looking to change my board at home and wanted some advice on the most practical way for cable entry please.

I was thinking to do rear cable entry, through the rear knockout but wanted to know if this is acceptable as it is mounted on wood. This would seem a lot more practical and neater than having loads of glands along the top. Or doing what it is has now which is just a load of nockouts.

Let me know your thoughts please.

M

View attachment IMG_20180204_133155.jpg

 

[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.

 

[Octopus]

I think since Grenfel everyone is tightening thier belts.

Not been assessed since Genfel.

But the blame for the Grenfel disaster can mainly be laid at the door of the DCLG ........... they are the people that come up with the feeble building regs ..............

 

[Michaelwgroves]

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?

I agree it would be helpful if they requested a time as they do for doors, but we all know you dont need to follow BS7671 or the guidance notes, but if the CU caught fire and the fire took hold in the cavity having not sealed the rear entry, you would have a tough time defending yourself should the need arise.
Fortunately for everyone on here we are all in here to learn and help others, so hopefully we will never find ourselves in a difficult position.

 

[Michaelwgroves]

Not been assessed since Genfel.

But the blame for the Grenfel disaster can mainly be laid at the door of the DCLG ........... they are the people that come up with the feeble building regs ..............

Pre Grenfel my assessment was for CU with rear entry and no containment. - passed
Post Grenfel same assessor, CU with rear entry and no containment -fail. I had to add fire foam before he would pass. He referred to guidance note 4, that’s why I purchased it so I could see for myself.

 

[Octopus]

The schemes would do better to team up and get BS 7671 written properly in 1 book, and cheaper too.

 

[sparksfly]

O dear we are again left with lack of clear specific information in parts of BS7671.....gaps for interpretation. I was assessed on one board enlarged hole in back mounted on trunking to accommodate some surface wiring incl tails, not sealed but IP rated...... passed no problem.

FYI.. I did write to the LFB regarding increase in CU fires as I was worried about specific makes of CU to avoid...

"Many thanks for your request for information dated 19 February 2015.
We are hesitant to release the names of individual manufactures as their products would be compliant to the regulations. You may be interested in the following press release on our website which showcases fuse board incidents in recent years and the most recent change in electronic installation regulations. When the new regulations are in place (2016) then all consumer units will be made to a fire resistant standard.".....hey ho...could be a standards problem, bad workmanship, storing flammable materials nearby or general public messing around with CU's in spare time with nothing else to do.