Consumer Unit Change

[Nickj]

Hi All,

I am tomorrow going to be changing a consumer unit ahead of my Elecsa assessment next week.

Just wanted to check that I'm not missing anything with regards to amendment 3.

I'm going to be using a BG consumer unit supplied with RCBOs.

It has a cut out at back for cable entry and so I am going to pass all cables through that using a grommet strip around the metal edges. Do I need to seal the entry hole? I believe not however I have heard arguments that it needs to be sealed. Passing all cables through the rear entry may require de-rating cables due to grouping however the cables enter the current board (3036's) through the rear. Can i therefore assume ratings are fine?

I am going to attach the consumer unit to the wall using dewalt wall dogs which require no anchor in wall meaning I don't have to worry about plastic wall plugs falling out in the event of a fire.


If the cables are too short (I sincerely hope they won't be) I'll use an adaptable box above the board to mount a din rail to extend wiring. Does this adaptable box need to be non-combustible too? (associated switch gear covers this possibly?)

Thanks in advance

Nick

 

[Pat H]

I believe thats true. I just prefer to do some rough calcs. Normally possible to get a rough idea of runs and lengths. Zs of cables will give an indication as well.
If that looks ok then fine. I wouldn't sweat too much on the short local group into the CCU

 

[westward10]

Have you previously tested the installation.

 

[HandySparks]

... and then terminal blocks for the cooker cable? (wago don't go high enough unless I use their din mounting stuff).

Wago 773-173 Push Wire Connector 2.5mm - 6.0mm 3 Pole - https://www.tlc-direct.co.uk/Products/WA173.html

De-rating aside (I assume I'm fine not to consider de-rating as entry is same as current board?)

With de-rating due to grouping on domestic, I wouldn't disregard completely. However, generally the typical loading on circuits will be well within the capacity of the cable. Heavy loading, eg showers, will only be of short duration. Two exceptions might be if the place is lit entirely by dozens of 50W GU10s or for storage heaters and immersion heaters, which are pulling full load for an extended period of time.

Another indication is whether the cables show signs of overheating at the grouped location.

It's better to show that you've considered the situation and deem it acceptable, rather than ignored the issue completely.

 

[Pat H]

I'd agree. Do the maths do the visual inspection. Be happy you can show you've considered those elements.

 

[westward10]

Westward how do you go about crimping solid core? I love crimping but have stopped crimping solid core due to it not being as strong a connection as I once thought :S

I use crimps and Wagos, stick with what you are happy with. if you use Wagos tuck them behind the breakers to keep it tidy.

 

[Nickj]

I have previously tested it and all appears fine ~(so hoping for a straight forward swap - fingers crossed!) no signs of overheating currently and they are grouped together. I have not inspected attic as its cram packed full of items and I've been asked to avoid going up there if possible.

I'm a little wary of doing the maths in case it doesn't comply, the likelihood of there being insulation in the attic is high and once that and grouping de-rating are taken into consideration one may find it doesn't comply...what would you guys do then?

I'll tuck the wagos behind the breakers and make it as tidy as possible.

thanks to all so far, It's greatto be able to bounce ideas around, you're saving me from going crazy

 

[Pat H]

They won't inspect the attic. Say you checked what you could access and cables are clipped to joists so you are ok.
They probably are anyway.

 

[Nickj]

To pick up on what wilko was saying earlier regarding tails in a gland and internal clamp (if provided). Its fine if they are coming in with rest of cables to not use a gland? I'll secure cables with a clamp if it's provided (yet to pick it up so not sure whats in the box)

 

[westward10]

Don't worry about grouping or clamping, it is all rear entry. Undertake a neat job and you are halfway there. They will not ask you difficult questions as I said before they are not going there to catch you out.

 

[Nickj]

thank you very much! I'm generally neat and tidy with the installs and the testing should be spot on, hopefully i'll get through it

 

[HandySparks]

To pick up on what wilko was saying earlier regarding tails in a gland and internal clamp (if provided). Its fine if they are coming in with rest of cables to not use a gland? I'll secure cables with a clamp if it's provided (yet to pick it up so not sure whats in the box)

The question is: are the cables, and therefore the terminations liable to be disturbed? If not, no need for clamping.

 

[NDG Elecs]

Plastic wall plugs into believe are fine as the brickwork will act as a heatsink, well that is what I heard.

The link below makes interesting reading (if you have a spare 10 mins). There is a download at the bottom of the link.

Fire performance of cable supports - IET Electrical - http://electrical.------.org/wiring-matters/58/bre-report/index.cfm

 

[westward10]

thank you very much! I'm generally neat and tidy with the installs and the testing should be spot on, hopefully i'll get through it

Well good luck keep us posted.

 

[westward10]

The link below makes interesting reading (if you have a spare 10 mins). There is a download at the bottom of the link.

Fire performance of cable supports - IET Electrical - http://electrical.------.org/wiring-matters/58/bre-report/index.cfm

Interesting.

 

[Wilko]

The link below makes interesting reading (if you have a spare 10 mins). There is a download at the bottom of the link.

Fire performance of cable supports - IET Electrical - http://electrical.------.org/wiring-matters/58/bre-report/index.cfm

Thanks for this ref, and thanks also @Nickj - Wall-dogs it is !