UK SWA feed to garage for brewing equipment

[ChrisPDuck]

Short Version

• Is it permissible to have 2 feeds to 2 separate consumer units in a detached garage?
• Is it permissible to run SWA underground through a duct/conduit or must it be direct in ground?
• What diameter SWA would I require for a 10m run, buried and clipped to wall, feeding 3 x 16a sockets (max draw 10kW) – I believe 10mm?
• What diameter SWA would I require for a 10m run, buried and clipped to wall, feeding 3 x 16a sockets and 8 normal 13a double sockets?

The longer version

I have a detached garage ~ 2m from my house which has an existing SWA feed (installed before I purchased the house).

I brew my own beer and the kit can draw quite a chunk, 3 x 16A draws at max power (this is software adjustable so at the moment I have this set to 3 x 13A and one of these I plug into the house to split the load across different breakers (these circuits are completely separate electrically so this is fine)

It’s been on my to do list for a while to get a more suitable feed installed to the garage so I can use the full power of the gear and avoid having to trail one of the plugs to the house. Bad planning on my part means I’m having a tile patio installed late this week so sorting this after that point will be much harder / costly / possibly always be visible.

No chance of me getting a sparky in time so I want to do what I can, the easiest is obviously for me to just install ducting/conduit between the buildings so the sparky can do what they want, how they want at a latter date.

However I haven’t seen SWA in ducting before and I suspect there may be a reason for this? (I’m a telecoms engineer by trade, we put everything in ducting, it makes any upgrade/maintenance/repair work so much easier in the future). If this isn’t permissible my preference would be to get the SWA buried while the foundations for the patio are being sorted.

This is where things get interesting.

The garage is fed from a 32A breaker (with 30ma RCD) in the house and then has a 63A main switch in the secondary consumer unit in the garage, this also houses a 32A breaker for the mains sockets and 6A breaker for the lighting. What seems utterly inappropriate / unsafe is upon investigation this is fed from a 1.5mm SWA between the buildings?!? A 1.5mm feed protected with a 32A breaker? Surely that isn’t right (this looks like it was done when the property was built by the way, it doesn’t look retro fitted).

So I guess I have 2 choices, the easiest would be to leave that as is and put a second SWA feed to the garage to feed a second consumer unit with 3x16A sockets (something like this Hook Up Unit 3 x 16A Socket & RCBO - https://www.toolstation.com/hook-up-unit/p34313 ) I have the space in the main consumer unit for the breaker to do this. As there would be no wiring outside the consumer unit there would be no risk of someone in the future assuming the power was off to a cable having turned off the wrong breaker, so it passes the common sense test to me but I’m unsure what the regs allow? I assume a 10mm SWA cable would be ok here (max draw 10kW, 10m run)

The alternative would be to replace the lot, so rip out everything there and put a new SWA feed in to a new consumer unit which supplies 3x16A sockets, 8x normal 13A double socket and the lighting. But I assume this will cost much, much more as I believe I will need 16mm SWA, a larger consumer unit and separate 16A sockets etc.



I’d appreciate your thoughts.

 

[James]

3 inch ducting will make it future proof.
no problem running swa in ducting, the current it can carry will be reduced but not by much Compared to direct in ground.

 

[Midwest]

Pull in a draw string if the cable is not going in the ducting now.

 

[ChrisPDuck]

Thanks both
Any requirements re colour or material for the ducting?

 

[Taylortwocities]

Thanks both
Any requirements re colour or material for the ducting?

No specific colour requirements.
This is the best stuff Twin Walled Cable Duct - https://www.tlc-direct.co.uk/Main_Index/Conduit_Pvc_Index/Cable_Ducting/index.html

 

[telectrix]

Thanks both
Any requirements re colour or material for the ducting?

none whatsoever. when's the next beer brew ready?

 

[loz2754]

It's difficult to work out the maximum current demand with the given information.
Calculating this would be the first step.
Then, armed with this information, a circuit may be designed to accommodate the demand.
It would probably be best to install a complete new cable and consumer unit.
But as I said - difficult to assess from my armchair!

 

[ChrisPDuck]

It's difficult to work out the maximum current demand with the given information.
Calculating this would be the first step.
Then, armed with this information, a circuit may be designed to accommodate the demand.
It would probably be best to install a complete new cable and consumer unit.
But as I said - difficult to assess from my armchair!

What info would be needed out of interest?
The Homebrew kit has is quoted at 3 x 16A
Or 9.5kW of resistive heating quoted at 230v plus a pump and display (minimal)
The exisiting circuits feed a small freezer, a larder fridge and some LED lighting.
The occasional power tool but not at the same time as brewing.
I don't see the second part matters too much as what's there at the moment is only relevant today obviously

 

[Strima]

I would keep it as one consumer unit.

We would need to know your incoming supply arrangements such as earthing type, suppliers fuse size etc. Existing layout, whether a circuit could be run from the existing consumer unit or split the tails after the meter and fit a KMF suitably fused.

I would be looking around 50 amps maximum demand and base my designs on that. This would give you ample supply for the meantime and scope for expansion in the future if required.

Would you also be considering electric vehicle charging in the future in the garage?

 

[pc1966]

As above, put in decent size duct with a draw string (or 6mm rope if you can) and you can worry about the details later. You might even want to pull through some network cable if wifi from house flaky, want PoE CCTV, etc, etc.

There is no specific requirement for depth other than it should be very unlikely to be damaged. So usually something like 40-50cm down is fine if not a roadway or agricultural land that might get ploughed.

 

[ChrisPDuck]

Suppliers fuse is 100A
Main isolation switch is 100A
There is a space for an extra breaker
Very easy to feed from either the consumer unit or to split the tails after the meter.
I would prefer from the consumer unit so all circuits can be shut off from one place but I know that's only personal preferance.
I don't know the earthing type, how would that affect the size of cable or termination points?

No desire to get an electric car in the foreseeable future.

I already have an ethernet cable to the garage but I wouldn't put that in the same ducting as power even if it is allowed.

 

[Spoon]

I would prefer from the consumer unit so all circuits can be shut off from one place but I know that's only personal preferance.

If you are tapping off the tails you might as well get the electrician to fit an isolator before the split, then you get your one pint of isolation.

I don't know the earthing type, how would that affect the size of cable or termination points?

Take a pic of the incomming supply to the house and meter area. post it up here.

I already have an ethernet cable to the garage but I wouldn't put that in the same ducting as power even if it is allowed.

If you are fitting one ducting then you could always fit another small one for the ethernet & alarm cable (If needed).

 

[Dave OCD]

No specific colour requirements.
This is the best stuff Twin Walled Cable Duct - https://www.tlc-direct.co.uk/Main_Index/Conduit_Pvc_Index/Cable_Ducting/index.html

Just make sure you don't use blue or yellow ducting - reasons self explanatory.... ?

 

[pc1966]

There is a space for an extra breaker
Very easy to feed from either the consumer unit or to split the tails after the meter.

A new circuit is notifiable work under Part P of the building regulations in England and Wales, so your best plan is to find a local sparky who is registered on one of the "competent person" schemes such as NICEIC to do the work as they can self-certify and submit the paper work that way.

Someone on here might be local to you.

I would prefer from the consumer unit so all circuits can be shut off from one place but I know that's only personal preferance.

That is a sensible choice. However, you won't get good selectivity by that means though, as a significant fault in the garage (i.e. above the "instant trip" current of the upstream MCB) on any circuit will also trip the MCB in the CU.

That might not matter to you, but if a concern then you might want to consider emergency lights to avoid sudden darkness (for any reason, even power cut), or having a fused-switch fitted on split tails so you get reasonable selectivity levels.

I already have an ethernet cable to the garage but I wouldn't put that in the same ducting as power even if it is allowed.

No worries.

However, it is fine to put Ethernet alongside SWA (or cables like Flexishield) as the earthed armour serves both for safety and to screen the majority of noise.

If you do put Ethernet cable in duct it might get wet so you might want to consider the outdoor style of cable such as this:

External Cat6 UTP LDPE Solid Cable (Reel) | Cat6 Cable

Category 6 unshielded twisted pair cable is designed for use in next generation data communications networks, and will comfortably support all present

www.cablemonkey.co.uk

 

[ChrisPDuck]

There's already an isolation switch by the meter ?
I had assumed you'd also need something else or the only protection the 12m length of SWA has is the 100A supplier fuse?

Pic of incoming supply attached.
The tap off the joint to the existing SWA was like that when I moved in, shocking isn't it (boom, boom)

 

[ChrisPDuck]

Just make sure you don't use blue or yellow ducting - reasons self explanatory.... ?

As a former telecoms engineer id also prefer people didn't use grey!!! ?