A lintel for a flush mounted consumer unit?

[epsilonGreedy]

I would like to fit a consumer unit mounted within my inner block wall (100mm cavity), however I assume the fitting of the this will not happen until my house has a roof. Will the hole in the wall require a lintel?

[PeterW]

Yes as it will require a fairly big opening - 16 way CU is 500mm wide and you need clearance all round. That’s a 600mm opening minimum. 
 

How are you planning on mounting it in the opening as I’m sure they need to be mounted on a non-combustible surface now. And why recessed ..? 
 

@ProDave - thoughts ..? 18th Edition have anything to say about it ..?

[Russell griffiths]

I was wondering how you would get cables out from it, I can see how the supply in can run up the cavity, but how do you get cables out without them having to turn a Nasty corner. 

[ProDave]

You can't just miss out the inner leaf of a cavity wall.  3" block instead of 4" for that bit?

 

Are you having any form of service void?

 

I flush mounted mine, in the depth of the 50mm service void in the utility room.  Mine was fitted pre the requirement for metal consumer units, but as it happens it was a Hager board with a metal body and just the front is plastic, so the bit recessed into the wall is metal. 

 

With it recessed into the 50mm service void, all cables exit the sides of the CU direct into the service void.

 

Sorry this is the best photo I have at the moment.

 

 

 

[epsilonGreedy]

10 hours ago, PeterW said:

And why recessed ..? 

 

 

I thought recessed CUs were the height of self builder trendiness, particularly since the updated regs require the circuit breakers to be at wheelchair reach height? I would not have a problem with a conventional surface mounted CU box if it was located just below ceiling height. The natural location for the CU is in the rear entrance lobby which will be the daily entrance to the property. The cavity wall mounted meter box will be less than a meter away on the outside wall. Cable runs for the high amperage circuits from this CU location would be 10m to 12m.

 

10 hours ago, PeterW said:

Yes as it will require a fairly big opening - 16 way CU is 500mm wide and you need clearance all round.

 

 

It is a 2-story 3 bedroom house so I was expecting to get away with a smaller unit, this feels like another question about whole house circuit planning. Funny how these questions stack up as only yesterday my house rose from DPC to about 8 courses high along the utility wall where both the meter and CU will be located.

 

My electrical extras will be ASHP supply, patio infrared heaters, electric oven, DW tank heater element, garage spur plus the standard stuff.

 

10 hours ago, PeterW said:

How are you planning on mounting it in the opening as I’m sure they need to be mounted on a non-combustible surface now.

 

 

I assumed it would simply push into the block wall opening, perhaps your concern is with the back of the unit plus cables pushing up against the cavity batt insulation?

 

[epsilonGreedy]

12 hours ago, ProDave said:

You can't just miss out the inner leaf of a cavity wall.  3" block instead of 4" for that bit?

 

Are you having any form of service void?

 

 

Now you have got me thinking.

 

To bump up my wall U values (brick, 100m Drytherm-32, medium/light block) I am costing out 32mm PIR lined plasterboard. Since the rear entrance lobby can run a couple of degrees colder than the main body of the house perhaps I could form a service void within a battened wall, PIR sheet capped with regular plasterboard.

 

Ok so my latest thinking today is:

1. A small concrete lintel (100mm x 75mm ) over the box that forms an oversized the recess for the CU.
2. Brick up the back with regular coursing bricks on their side = 25mm recess.
3. Batten the internal wall with 2" x 1 1/2" wood += 62mm recess. This wall is 2.6m long.
4. Create a service void within the inner batten wall for circuit cables running up to the ceiling void plus another for the incoming supply from the meter in the cavity immediately outside.

Edited February 11, 2020 by epsilonGreedy