Cables to run accross concrete floor

[sidekick]

I will have to get tails from meter more than 15m to consumer unit.
Will also gave to either 12m through concrete floor or through a double skin wall to a room with suspended floor for 10m and back 5m through concrete floor. Whats the best way to do and protect this within regs etc.

 

[ringer]

Regarding the issue of 16mm or 25mm, I would be thinking along the lines of futureproofing. If you install 16mm and then in 5 or 10 years time it needs upgrading to 25mm, imagine the cost and disruption involved with ripping up that concrete floor again!

 

[Darkwood]

Sidekick.... try avoid the situe where the cart is pushing the horse, it good to go on site next time knowing all you need to, your customers demands etc are fine in an ideal world but not always practical from an electrical installation point of view, it seems to me that its been correctly established you need a fused isolator unit which is either adjacent to the meter or opposite on the inside wall, if adjacent to meter and dosnt fit in meter cupboard then you either need to fit an IP rated enclosure that surrounds the meter cupboard and enough room to fit our fused isolator or a lean-to hut needs building. This enclosure/hut will need the same access lock that the meter cupboard uses to the meter reader can get to read the meter. If you go through the wall to mount isolator internally then you need to have a conduit within the wall to span the cavity and large enough to carry the cables, this would be the prefered method re' time costing etc, a good joiner could fit a neat looking cupboard in the extension that may satisfy the customer.

 

[Guitarist]

I don't see an issue with fitting the switch-fuse in the meter cabinet, just as long as you don't interfere with the DNO equipment. The cabinet is your property (customers). Only the equipment belongs to the DNO.

 

[Spoon]

Wouldnt the size of cable installed depend on what size switch-fuse is fitted, which depends on the size of the DNO fuse?

 

[ringer]

Wouldnt the size of cable installed depend on what size switch-fuse is fitted, which depends on the size of the DNO fuse?

No - select the cable size required to supply the CU, then fuse accordingly. DNO fuse does not come in to the equation - that's the whole point of putting in a switch fuse.

 

[drew35]

Some suppliers now give you a four way csu if you ask for a switch fuse anyway, so just use a metal four way csu in the meter cabinet, and terminate SWA directly into it. The cabinet usually has printed on it that no other equipment is to be fitted, but the DNO have to allow a switchfuse because they ask for them if the csu is over 3m away. And the DNO are usually happy to install switch fuses in new installs and charge an arm and a leg for them. And I would use 16mm SWA because I'm small and weak!

 

[Spoon]

No - select the cable size required to supply the CU, then fuse accordingly. DNO fuse does not come in to the equation - that's the whole point of putting in a switch fuse.

I might be reading this wrong, but are you saying that you are allowed to fit a 100A switch-fuse even though the DNO fuse is only 80A? Dont you use discrimination when using fuses? So if the DNO fuse is 80A then the switch fuse has to be smaller?

 

[Engineer54]

Whatever method of cabling you choose to wire these tails in, you'll probably find that the concrete floor isn't concrete at all but concrete slab or whatever with at least a 4'' cement float on top. Usually more than enough depth to run a SWA or conduit/duct in after chopping it out....

Chopping concrete out is a far more odious task, than chopping a weak cement float out. the float is there to make the floor level and give the floor a smooth finishing surface...

 

[rich.250]

I might be reading this wrong, but are you saying that you are allowed to fit a 100A switch-fuse even though the DNO fuse is only 80A? Dont you use discrimination when using fuses? So if the DNO fuse is 80A then the switch fuse has to be smaller?

That was my point spoon. Discrimination.....
Although volt drop and length could still mean 25mm
Hard to say without being there

 

[sidekick]

Now on site and route for cable is straight run 12m accross new concrete floor (not yet laid) to csu up walls either end. metal switch fuse no rcd to be put in cabinet, 16 or 25.mm swa to run to existing plastic csu. if 25mm would be 2 core with seperate 16mm earth. wanting to know best method to run in or under floor.
In hardcore below, or in the 4 inch of insulation, or in screed. All should be easy if i get in first.

 

[Engineer54]

Now on site and route for cable is straight run 12m accross new concrete floor (not yet laid) to csu up walls either end. metal switch fuse no rcd to be put in cabinet, 16 or 25.mm swa to run to existing plastic csu. if 25mm would be 2 core with seperate 16mm earth. wanting to know best method to run in or under floor.
In hardcore below, or in the 4 inch of insulation, or in screed. All should be easy if i get in first.

1/ ... Do Not run in or on the slabs hard core layer if using SWA cable, ...Full Stop!! Also Definitely don't run any system in the insulation!!!

2/ ...Run either SWA or conduit/duct in the slab using any re-bar steelwork to fix too.

3/ ...If you use SWA, then 3 core SWA not 2 core with a separate earth. Apart from any other considerations, it'll be cheaper!!

4/ ...Personally, if price allows i would go for a re-wirable system (large enough duct with singles cores)

5/ ...If using SWA then go with 25mm, at least you'll cover any future upgrades...

 

[sidekick]

2/ ...Run either SWA or conduit/duct in the slab using any re-bar steelwork to fix

5/ ...If using SWA then go with 25mm, at least you'll cover any future upgrades...

Thanks for your advice.

Think i will use 25mm 3 core but not sure about terminating 25mm earth at either end to allow a 16mm length to csu or/and incomer

If swa in concrete, does it need conduit. If not on hardcore, assume will either be in conduit or will have to chase out.

 

[Strima]

I would put it in some form of conduit, easier to replace in the future if there are faults.

 

[Lee1994]

Tails will need fusing down as they enter, via a switched fused spur. Then flexible ducting can be used for beneath the concrete. Also an RCD would be ideal as they are not in steel conduit or anything similar.

 

[sidekick]

Tails will need fusing down as they enter, via a switched fused spur. Then flexible ducting can be used for beneath the concrete. Also an RCD would be ideal as they are not in steel conduit or anything similar.

I assume your talking standard pvc tails and not swa. what conduit would be best for swa.