Commercial Fuse box covered with plywood casing

[James Jones]

At work we have a fuse box with a door that will not close due to a broken latch. The fuse box is located by a fire door in an office.
To hide the issue a plain plywood box has been used to completely cover the fuse box. I have raised a safety issue with this but there is disagreement on it's safety. Could somebody point me to any regulations that cover this?

Thanks in anticipation.

 

[davesparks]

If the lid was open and a fire started within (CB/cabling) it may spread to outside of the board, i.e. containment would be compromised and the end result may be the same as if the board were of plastic...

The same will happen with the lid closed, the steel CUs currently being sold are not in any way rated as fire barriers or fire containment, they are manufactured from a non-combustible material as per bs7671.
‘Manufactured from non-combustible material’ means that the material used to make the enclosure does not combust, it makes no mention of containing or restricting the spread of fire.

 

[Pete999]

In my opinion the onset of the decision and reports of CU fires are a bottom covering excercise by those with the clout to change things, and to eleviate the poor installation methods taught to unsuspecting people, who attend short courses with the promise of becoming a qualified Electrician at the end of the course, and allowed to charge the unsuspecting public, to let them carry out electrical work within their dwellings. Combustable CUs where a common occurrence in Domestic premises far in advance of the reports of CU fires with that the assumption for the fire was the fact that the fire was caused by the CU construction,the fires, apparently had nothing to do with poorly trained people, well thats my take any way.

 

[Deleted member 105166]

The same will happen with the lid closed, the steel CUs currently being sold are not in any way rated as fire barriers or fire containment, they are manufactured from a non-combustible material as per bs7671.
‘Manufactured from non-combustible material’ means that the material used to make the enclosure does not combust, it makes no mention of containing or restricting the spread of fire.

Are you saying a fire or by-product of a fire, such as molten metal, is not more likely to remain contained and extinguish within a metal unit, as opposed to a plastic one? That's where I'm coming from.

 

[westward10]

A metal consumer unit will not contain a fire and it is inevitable that it will spread if it is not noticed but not as rapidly as a plastic enclosure which aids fire spread.

 

[Spoon]

A metal consumer unit will not contain a fire and it is inevitable that it will spread if it is not noticed but not as rapidly as a plastic enclosure which aids fire spread.

Has there been any tests for fires within metal consumer units?
Isn't there the possibility that the metal CU will produce enough smoke in the CU to extinguish the fire? This is of course you don't put a hole in the back of the CU and put the cables through that, stating that there is no IP rating for the back of the CU in the regs....... (Unless you put suitable sealant round them)

 

[Devonchris]

If a metal cu is fitted correctly, fire proof glands, no entry from top etc. Then it's not inevitable that the fire will spread beyond it. Apart from the cable insulation, there's not much in there to burn.

 

[westward10]

Not much in there to burn!

 

[Spoon]

...there's not much in there to burn.

Please explain?
What about all the breakers/rcbo's/isolator. (Any other equipment I haven't mentioned)

 

[davesparks]

Are you saying a fire or by-product of a fire, such as molten metal, is not more likely to remain contained and extinguish within a metal unit, as opposed to a plastic one? That's where I'm coming from.

I would be very surprised if a fire inside a CU remained contained or extinguished itself. Fire requires fuel, heat and oxygen, once a fire has ignited then it can only be extinguished by removal of one or more of those elements.
Nothing about current CUs will remove the fuel or heat and they certainly don’t exclude oxygen.
If the fire is hot enough that molten metal is a product of the fire then the metal CU doesn’t stand much chance.

Some of these CU lids are held closed by magnets, which lose their magnetism when exposed to fire so they may well just open themselves anyway.

 

[davesparks]

If a metal cu is fitted correctly, fire proof glands, no entry from top etc. Then it's not inevitable that the fire will spread beyond it. Apart from the cable insulation, there's not much in there to burn.

What fire proof glands are you using? There’s a whole bunch of MCBs etc in there to burn, and once the main switch has melted or the tails then they’ll short against the steel case and blow a hole in it.

The steel is not thick enough to contain fire, the heat will very quickly be conducted through it and ignite materials outside of the unit

 

[westward10]

If a fire has started within a consumer unit you have a serious problem. For plastics to ignite a fair amount of heat is required to create a transition from solid to gas, gas which burns. Plastic like wood does not burn, it is a component of their structure which burns, components which are only released when molecules break down due to extreme heat exposure. Once the break down occurs and the flammable gas is released a source of ignition is then required and as I say once this stage is reached, you have a problem and a metal CU will only hold this problem for a short time.

 

[Devonchris]

My understanding of the requirement for Metal CUs was to contain any fire within it.

From IET
"The non-combustible enclosure or cabinet must provide a complete envelope (for example, 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.

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. "

MCBs, RCBs etc manufactured to the BS -EN 60965 sect 3 Fire hazard testing, should not propagate a fire but should go out when any flame is removed. You can see in most electrical fires that all the plastic insulation has gone but the main components, whilst badly burned, are still present.

Its not inevitable that the fire will spread.
However its integrity is down to quality of workmanship. If someone doesn't believe it then perhaps they are not going to ensure it.

The IET also said
"Whilst the main cause of fire within plastic consumer unit enclosures is without doubt poor workmanship......."

So what made them think a metal CU would change anything?

 

[davesparks]

One of the many things I do for a living is setting fire to things, and I’m pretty confident that a fire in an ‘amendment 3’ CU won’t stay inside the CU for long. Eapecially not when that 100A supply coming in to it hasn’t been disconnected.

 

[Devonchris]

What fire proof glands are you using?

I'm not using any, but there are plenty about. Even screwfix sell them.

What do you set on fire Dave fireworks and things? Sounds interesting.

 

[davesparks]

Isn't there the possibility that the metal CU will produce enough smoke in the CU to extinguish the fire?

To extinguish a fire you need to remove one of the three sides of the fire triangle. These are heat, fuel and oxygen.
Smoke won’t remove the fuel or the heat and it’s pretty unlikely to remove all of the oxygen.
The heat of a fire will cause a draught through the enclosure (hot air rises) which feeds oxygen to the fire.