I’m sorry, External power to a utility room question

[shedssssssss]

Long time lurker finally registered as I’ve got to ask. And before someone mentions the search feature, I’ve searched and searched on this topic on here (else where to) and the more I read (several times infact) the bemused by the whole thing I get, so I apologise in advance to the regulars who help mortals like me out.

I currently have an old Wyrex consumer unit (wired fuses) with one spare fuse point because I removed the monster oven cable a long time ago as I had no use for it. My immediate problem is I want to change how my external utility room is powered as currently it’s really scary (predates me). What I’m considering doing is using a 30amp wired fuse on the MCU, connecting 6mm TE to run about 12m under a suspended floor to the external brick wall, bury the cable in conduit for about 5m into the utility room and then up to a Volex RCD Garage Unit (Screwfix unit 40a 30mA RCD, 1x6a & 1x16a). From there I want to power a 5ft strip light and a 70w & 500w security lights (using either 1mm or 1.5mm TE) from the 6a feed. From the 16a (2.5mm TE) I would like to run a single double socket inside the utility room however I also want to run an additional 15 / 20m of 2.5mm TE down into the garden inside conduit mounted to a wall to power an IP56 double socket and an IP56 Switch / Fused spur to a low voltage lighting transformer.

The maximum wattage I will be using at any one time is around 3400, I calculated this based on what I could image running at any one time and then adding another 1/3 to that figure.

My obvious consideration is the ratings of the cable / fuses, and more importantly the 6mm of TE going underground. I have considered SWA however I already have the 6mm and the 5m underground run will be underneath concrete flags with no danger of human interference, I know this wouldn’t be an RCD protected cable because the MCU lacks anything like that but do I absolutely have to use SWA? And is there anything else I should consider as i've seem mentioned in a few of the posts on here about having an Earthing Spike as well?

Many thanks

 

[plugwash]

i guess by wyrex you mean wylex

well the alternative to swa is continuously welded gavanised conduit or micc (pyro) and i really don't think you want to fit either of theese

so realistically for a diyer swa it has to be

i would strongly advise useing a mcb rather than the wire fuse (yes wylex do make mcbs for the old wylex standard boards any decent supplier including tlc and screwfix and even some sheds should have them)

volt drop to the end point may be a bit on the high side though so i would probablly use 10mm rather than 6mm swa for the run to the garage

finally i would use a CU with a few more ways (probablly a 4 way metalclad) and run the wiring out into the harden from a seperate 16A mcb

finally note that it is a bad idea putting 2 high drain appliances in a double socket

 

[shedssssssss]

i guess by wyrex you mean wylex

well the alternative to swa is continuously welded gavanised conduit or micc (pyro) and i really don't think you want to fit either of theese

so realistically for a diyer swa it has to be

i would strongly advise useing a mcb rather than the wire fuse (yes wylex do make mcbs for the old wylex standard boards any decent supplier including tlc and screwfix and even some sheds should have them)

volt drop to the end point may be a bit on the high side though so i would probablly use 10mm rather than 6mm swa for the run to the garage

finally i would use a CU with a few more ways (probablly a 4 way metalclad) and run the wiring out into the harden from a seperate 16A mcb

finally note that it is a bad idea putting 2 high drain appliances in a double socket

Thanks for the rapid reply

Yeah i got the name wrong, knew it as i posted and thought u muppet I should have also put i'd considered fitting an MCB, i've "retro fitted" these to the current downstairs and upstairs circuits already .

As for the SWA do I have to use it (can you sense that I don’t want to), is there a legal requirement for me to use it as a DIYer. And if you have any links to a larger 3 or 4way CU I’d be very grateful, I confess I didn’t look around a lot of sites but 2way seemed to be the standard.

Thanks

 

[plugwash]

you don't *have* to use swa but you will hate the alternatives even more

burring T&E is asking for trouble on numerous counts im not sure if its actually illegal on your own property but it is an extremely bad idea especially for a non-rcd run

any decent electrical supplier will have CUs in a huge numer of sizes from 2 way up to about 20 way

note if you use 10mm you may have to buy a 25mm holesaw as not much stuff somes with 25mm knockouts and i think 20mm glands are too small for 10mm swa

 

[shedssssssss]

Could i take 6 or 10mm of TE from the CU to a juntion box (inside of my property), take 6 or 10mm of SWA to a junction box inside the utility room and again from that junction box 6 or 10mm of TE to the CU? The reason i want to work as much with the TE is i have some and can get various cable size very cheaply, i also imagine it is a lot easier to work with than the SWA 6 or 10mm?

If i could use TE - SWA - TE what type of juntion boxes would you suggest, would standard plastic heavy duty 30A boxes do, or do i need metal instead? Also i've never worked with SWA so would i need to earth the outer metal sheath?

Again thanks for the advice

ps. I've also decided to replace the MCU with a new model with RCD protection etc. I'll let a spark do that tho.

 

[plugwash]

yes the armour has to be earthed and this is done with the gland and the bajo that comes with it from which you should lead off an earth wire

metal adaptable boxes with terminal block or crips inside are the normal way if you just wan't to join swa to T&E

 

[shedssssssss]

yes the armour has to be earthed and this is done with the gland and the bajo that comes with it from which you should lead off an earth wire

metal adaptable boxes with terminal block or crips inside are the normal way if you just wan't to join swa to T&E

Can the armour earth be earthed to the earth in the core, ie. in each junction box (house / utility room) connect it to the mains earth terminal point?

cheers

also looking for a decent spark in the Tameside area of Manchester to swap my consumer unit over with an installation certficate.
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