Question regarding SWA Cable

[AVI_8]

That’s another question I’ll have for the spark tomorrow
I don’t want the garage supply to come from the house CU
The house used to be 3 phase, when we bought it we got the whole house re wired, it’s now single phase, but, the old garage its going to be converted next spring for my wife’s business and that will come from the house CU, there’s already a cable from the CU to supply that, it’s currently unconnected.
I’m presuming that I can get a spur from the switch which is downstream from the meter to be split to get an independent supply to my workshop, that I’ll know tomorrow. That way there won’t be 3 buildings supplies from a single CU, and hopefully won’t mean I have flickering lights in the house or the other building whenever I weld or a compressor starts up.
Maybe I should have kept the 3 phase with hindsight haha!
A hundred amp fuse from the meter will be more than enough for all 3 buildings though
And I presume that the 10mm swa will need a fuse or CB to protect it after the tail/spur from the main fuse though I’m not sure what ratings these come in, this is above my knowledge just now.

 

[GRW]

That’s another question I’ll have for the spark tomorrow
I don’t want the garage supply to come from the house CU
The house used to be 3 phase, when we bought it we got the whole house re wired, it’s now single phase, but, the old garage its going to be converted next spring for my wife’s business and that will come from the house CU, there’s already a cable from the CU to supply that, it’s currently unconnected.
I’m presuming that I can get a spur from the switch which is downstream from the meter to be split to get an independent supply to my workshop, that I’ll know tomorrow. That way there won’t be 3 buildings supplies from a single CU, and hopefully won’t mean I have flickering lights in the house or the other building whenever I weld or a compressor starts up.
Maybe I should have kept the 3 phase with hindsight haha!
A hundred amp fuse from the meter will be more than enough for all 3 buildings though
And I presume that the 10mm swa will need a fuse or CB to protect it after the tail/spur from the main fuse though I’m not sure what ratings these come in, this is above my knowledge just now.

You're in for more costs if you want to break in to the supply between your Utility Feed and your House CU.
I doubt you'll have an Isolator, so you'll also have to get the Utility Co to cut the seals and pull the fuses to make dead to do the mods.

Even then, as you're still pulling off the same 1ph supply I'm not at all sure you're going to really alter anything (ref potential flickering etc) than by simply having a dedicated 40A breaker for the workshop fitted in your existing house CU (assuming you have the spare spaces in your CU to add extra breakers that is).

If you get any issues or are worried about say the wife's internet modem, WiFi, phone or PC from varying voltage, then you could get a small full online plug in UPS to run those things off sited in her office. A full online ups would ensure no break in supply and would filter the supply to those office items.

 

[GRW]

not at full power the supply to the house is 100 amps so I think the most we could take off for the shed was 80 amps or something.....

I went to a Care Home in rural Pembs a few years back to survey the place for a backup generator.
Place turned out to be pretty big, and old, and had been extended quite a bit over the years since its change of use.
Supply had been upped from 1ph to 2ph (as no 3ph available)..... and I went to clamp the 1st phase and found the cable tail was VERY warm.
Clamp revealed that the site was (while I was there mid-morning when the kitchens and Laundry etc are flat-out, plus residents are active) - was consistently up over 160 Amps - off a 100A Utility Fuse (which was also pretty warm but not blowing).

Basically (as long as all the other properties on the LAN aren't using their allowable capacity when you do it) .... if you occasionally exceed your 100A limit demand off Mains - then you'll get it (but are of course technically overloading your system, & Utility Co won't be thrilled if they knew ).
It's quite surprising the abuse household circuits will tolerate (if they are in good nick)!
I've been to quite a few business premises, farms and local authority places over the years where the load is consistently up/over the stated Incomer Fuse Rating.

 

[123hotchef]

Maybe I should have kept the 3 phase with hindsight haha!

can you not get 3 phase put back in?

 

[brightspark]

can you not get 3 phase put back in?

it will still be there on the supply cable and cutout. just a matter of getting a 3 phase meter put in

 

[Onoff]

My first house, an 1860 terrace, had a 3 phase head in but single phase meter.

 

[AVI_8]

There’s a big old cable still there under the floor, would love to just connect that up to my garage and be done with it …. Free electric!
But I’d probably fry myself trying to, so that’s a no go.

With regards to 3 phase, you would not believe the world of problems I had dealing with the utility company when we went back to single phase, it took more than 1 year to get them to understand.

There was 6 electric meters, the spark removed 5 of them, brightspark you mentioned a 3 phase meter, I seemed to inherit 6 single phase meters when I bought the place, by the way I live in an old house and it’s not a mansion, not the Shard!

 

[AVI_8]

You're in for more costs if you want to break in to the supply between your Utility Feed and your House CU.
I doubt you'll have an Isolator, so you'll also have to get the Utility Co to cut the seals and pull the fuses to make dead to do the mods.

Even then, as you're still pulling off the same 1ph supply I'm not at all sure you're going to really alter anything (ref potential flickering etc) than by simply having a dedicated 40A breaker for the workshop fitted in your existing house CU (assuming you have the spare spaces in your CU to add extra breakers that is).

If you get any issues or are worried about say the wife's internet modem, WiFi, phone or PC from varying voltage, then you could get a small full online plug in UPS to run those things off sited in her office. A full online ups would ensure no break in supply and would filter the supply to those office items.

There’s a small box which has a switch after the meter, not sure if that’s an isolator.

 

[MetalMonkey]

There’s a small box which has a switch after the meter, not sure if that’s an isolator.

Can you take a picture?

 

[Onoff]

There’s a small box which has a switch after the meter, not sure if that’s an isolator.

One of these? Colloquially known as an "REC2" this is a Wylex one and tbh the best imho. REC standing for "Regional Electricity Company". Wylex have incorporated the ref in their part number. Just a double pole switch to isolate your side from theirs safely. You can lock it off too.

 

[awemawson]

I feel your pain running cables through an existing slab. I had to get 35 mm csa 4 core SWA from my 110 kva generator to the Induction furnace. This involved coring a 60 mm hole at 45 degrees through the slab and wrestling a python down through it. The runs in the foundry had to go at high level so that was a joy, and it involved pouring a 'resin joint' - something I hadn't done before.

 

[brightspark]

I feel your pain running cables through an existing slab. I had to get 35 mm csa 4 core SWA from my 110 kva generator to the Induction furnace. This involved coring a 60 mm hole at 45 degrees through the slab and wrestling a python down through it. The runs in the foundry had to go at high level so that was a joy, and it involved pouring a 'resin joint' - something I hadn't done before.

View attachment 327713

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good job it didnt have red tape on the end there

 

[AVI_8]

One of these? Colloquially known as an "REC2" this is a Wylex one and tbh the best imho. REC standing for "Regional Electricity Company". Wylex have incorporated the ref in their part number. Just a double pole switch to isolate your side from theirs safely. You can lock it off too.

View attachment 327712

 

[AVI_8]

I’m mistaken, it does just go from the meter to the CU

 

[brightspark]

its pointless having them you allready have a mains isolation switch on the twin rcd board

 

[Onoff]

its pointless having them you allready have a mains isolation switch on the twin rcd board

Except for when you want to bin it and go all RCBO to fully comply with 7671...

 

[brightspark]

Except for when you want to bin it and go all RCBO to fully comply with 7671...

that still have the double pole main isolator switch built in

 

[Onoff]

that still have the double pole main isolator switch built in

I was jokingly getting at you don't have to cut the seals to change the cu.

 

[AVI_8]

Just to update, the electrician came round today, cracking down to earth guy, he had a look at the house side of the supply and then had a look at the workshop, asked me a few questions to gather info in what I was requiring and had a look at the install I’ve done already, I’ve 9 led strip lights all wired up through conduit and temporarily connected to a plug run off an extension cable so I can see what I’m doing.
Theres a connection box at each light with joining terminations using Wago connectors, his only criticism was that I should have used glands where each light cable goes through the 20 MM cutout at the junction boxes, that’s an easy fix.
He‘s going to add a tail from the house supply which will go into a mini CU and suggested that a 40 Amp RCD should go there that way it protects the cable and I won’t need one at the garage CU then at the garage end I can have a CU with everything I asked for as he understood that it’s just me myself and I and said that as long as I use common sense there should be no problems with tripped CB’s
So I can have a 32 amp socket , he suggested a C breaker for the welder
A 16 Amp C breaker for the car lift
32 amp ring main and 6 amp lights
He was happy with my lights wiring so he’s fine with me wiring all the sockets, told me not to connect all the faces so he can check them, he told me I can get the house and garage CU’s, glands etc and he’ll fit them, he recommended Hager CU, but as long as its metal with a 40 amp RCD.
So on looking at CU’s I see a small one which has a 100 amp switch with space for an RCBO for the house end, I’m presuming that an RCBO can be used instead of an RCD as it does the same thing but with overload protection?
I‘ll also get a good metal CU for the workshop with no CB’s and just get the cb’s separately with the C rating needed where required.

 

[Dave-sparks]

He‘s going to add a tail from the house supply which will go into a mini CU and suggested that a 40 Amp RCD should go there that way it protects the cable and I won’t need one at the garage CU

SWA doesn't normally need RCD protection, it has an earthed steel armour to give all the protection it needs.

I would advise having the RCD at the garage CU and not at the house, if the RCD trips while you are working in the garage you don't want to be having to go in to the house to reset it. Especially if there is a fault and you end up resetting it a couple of times whilst narrowing down the cause of the fault.

I would also suggest having RCBO's for each circuit at the garage end rather than a single RCD. So again if a power tool you are using develops a fault, or you accidentally damage the cable, you won't be plunged into darkness at the same time due to the single RCD tripping.