Running Power supply from new house to detached garage

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DIY Monty
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Running Power supply from new house to detached garage

Post by DIY Monty » Tue Nov 06, 2018 1:38 am

My son has purchased a new house with a detached garage. I want to run a power line from the house into the garage to feed twin socket, a fluorescent light and a PIR floodlight outside. The main box in the house is RCD with 16 amps feeds for the garage. There is a junction on the outside wall of the house with wires capped. Also, there is a 30mm black plastic tube conduit running for about 2 meters from under the junction box to the outside of the garage wall. I am planning to do all the labour work and call an electrician to connect and test. So was going to run a 2.5 T&E armor cable from house junction box with brass coupling through the plastic conduit, through the garage wall and into a 3-way consumer metal box inside the garage with brass coupling. Then run with 1.5 T&E cables the fluorescent light and switch from the consumer box. Also, run from the consumer box with 1.5 T&E cables to PIR flood light with a 5-amp fused switch to control the floodlight. Also, run from the consumer box another 2.5 T&E cables to a double socket (not metal).
I would be pleased if anyone can advise:
What type of connection to use in the outside house junction box to connect feed from house to armour cable?
Do I need a conduit pipe into the garage wall to thread the armored wire and also what type of fitting do I use for outside and inside the garage wall to protect the bend of the armour cable?
What is the best way to cap the black conduit pipe from house to garage to prevent water ingress?
Do I need to protect the armour cable inside the garage from the bottom level to top level to consumer box? I was going to run the cable upto the consumer box in the corner of garage foundation concrete support for added protection.
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Re: Running Power supply from new house to detached garage

Post by someone-else » Tue Nov 06, 2018 5:18 am

As we are not there, and you are going to get an electrician to check and test for you (good idea) best ask him to come and look at the job first and see what he says.

You don't need conduit if you are using armoured cable.
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Re: Running Power supply from new house to detached garage

Post by kellys_eye » Tue Nov 06, 2018 9:40 am

Armoured cable doesn't need the conduit but needs to be properly glanded/terminated into the feed and distribution units.

Given the feed to the garage is only 16A and already on an RCD circuit you could feed the cable straight into a metal twin 13A socket box and use a switched fused spur for the lighting circuit straight off it. No 'consumer unit' involved.

Any other lighting (inspection lights etc) could be simply plugged into the 13A sockets.

Personally I'd up-rate the supply feed (to 32A), fit a proper consumer unit and wire more sockets around the garage and a separate lighting run from it. As with most 'intentions' you'll find you're short of outlets and/or lighting in the fullness of time and wish you'd put in a more comprehensive system.
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Re: Running Power supply from new house to detached garage

Post by DIY Monty » Tue Nov 06, 2018 3:59 pm

someone-else wrote:As we are not there, and you are going to get an electrician to check and test for you (good idea) best ask him to come and look at the job first and see what he says.

You don't need conduit if you are using armoured cable.
Thanks for the information and fully understand that a qualified electrician should carry out all connection and test. Yes, I do have an electric meter and socket tester. I have been quoted around £500 for the whole job material, labour and test cert (£60). Which is expensive. I have no issue paying an electrician for testing and qualification.
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Re: Running Power supply from new house to detached garage

Post by DIY Monty » Tue Nov 06, 2018 4:21 pm

kellys_eye wrote:Armoured cable doesn't need the conduit but needs to be properly glanded/terminated into the feed and distribution units.

Given the feed to the garage is only 16A and already on an RCD circuit you could feed the cable straight into a metal twin 13A socket box and use a switched fused spur for the lighting circuit straight off it. No 'consumer unit' involved.

Any other lighting (inspection lights etc) could be simply plugged into the 13A sockets.

Personally I'd up-rate the supply feed (to 32A), fit a proper consumer unit and wire more sockets around the garage and a separate lighting run from it. As with most 'intentions' you'll find you're short of outlets and/or lighting in the fullness of time and wish you'd put in a more comprehensive system.
Thanks, kellys_eye for very useful information. I did think of your first option as my son is not a DIY person and only needs a light, twin socket and connection for PIR floodlight outside. The socket will only be used for lawn mover and probably by me to use a hand drill or inspection lamp. I was going to an armored cable from the house's outside junction box to the metal socket using a brass coupling kit. also, use a 5 amp spur from the socket to inside light, but not sure if I can take another feed from the socket to power the PIR floodlight outside. I could take another 5 amp fused from a socket. This will be a cheaper option.
What elbow product is good at the garage inside and outside wall to protect the armored cable?
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Re: Running Power supply from new house to detached garage

Post by someone-else » Tue Nov 06, 2018 5:44 pm

DIY Monty wrote:What elbow product is good at the garage inside and outside wall to protect the armoured cable?
There isn't one. (Which is why you can't find one) As kellys_eye said, it has to be properly terminated (Glands)
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Re: Running Power supply from new house to detached garage

Post by kellys_eye » Tue Nov 06, 2018 9:17 pm

Although you can just drill the wall to pass the cable through, fitting a junction box and drilling through the back of it, glanding a length of pipe into it (if you wanted to) would work. Fit another conduit box on the inside wall if you're that anal :lol: but into the back of the consumer unit would be better.

Any type of box will do, metal or plastic, bearing in mind the need to carry the armour earthing through but getting a decent seal between wall and box requires a good sealer.
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Re: Running Power supply from new house to detached garage

Post by DIY Monty » Wed Nov 07, 2018 10:23 pm

kellys_eye wrote:Although you can just drill the wall to pass the cable through, fitting a junction box and drilling through the back of it, glanding a length of pipe into it (if you wanted to) would work. Fit another conduit box on the inside wall if you're that anal :lol: but into the back of the consumer unit would be better.

Any type of box will do, metal or plastic, bearing in mind the need to carry the armour earthing through but getting a decent seal between wall and box requires a good sealer.
Thanks for the advice. As my son is not planning to use a lot of power source in the garage, therefore, I am planning to opt for running an armored cable to the twin metal socket inside the garage with brass coupling for the armored cable and plastic coupling for 2.5m T&E cable to 5 amp fused spur to a light. The armored cable running from the house outside junction box will run about 12 inches down to the plastic conduit buried underground and then it will run about 12 inches up the outside garage wall before entering into the garage wall and up along the inside wall to a metal twin socket fitted with brass coupling. I will protect the exposed armored cable outside the house and garage walls with steel channel or a plastic pipe. I will use the plastic inspection elbow from Screwfix on the outside and inside the garage wall.
Can I run two 5 amp spur from the twin metal socket to operate a light inside the garage and a PIR floodlight outside the garage? Also, what are the best outside connection to use inside the outside house junction box to connect the armored cable?
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Re: Running Power supply from new house to detached garage

Post by someone-else » Wed Nov 07, 2018 11:48 pm

DIY Monty wrote: I will protect the exposed armored cable outside the house and garage walls with steel channel or a plastic pipe.
I get the impression you have never physically seen SWA, is that right? it's just that it needs no mechanical protection (That's what the A stands for, Armoured) and anything plastic will give less protection than the cable already has, so would be a waste of time and money. (But then it is not my money you would be wasting)
DIY Monty wrote:I will use the plastic inspection elbow from Screwfix on the outside and inside the garage wall.
Why? SWA wont bend easily enough to go through, and they are not needed.
DIY Monty wrote:Also, what are the best outside connection to use inside the outside house junction box to connect the armored cable?
SWA cable glands for the size of cable you are using.......with shrouds. (Remember to put the shrouds on first)
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Re: Running Power supply from new house to detached garage

Post by DIY Monty » Thu Nov 08, 2018 12:12 am

someone-else wrote:
DIY Monty wrote: I will protect the exposed armored cable outside the house and garage walls with steel channel or a plastic pipe.
I get the impression you have never physically seen SWA, is that right? it's just that it needs no mechanical protection (That's what the A stands for, Armoured) and anything plastic will give less protection than the cable already has, so would be a waste of time and money. (But then it is not my money you would be wasting)
DIY Monty wrote:I will use the plastic inspection elbow from Screwfix on the outside and inside the garage wall.
Why? SWA wont bend easily enough to go through, and they are not needed.
DIY Monty wrote:Also, what are the best outside connection to use inside the outside house junction box to connect the armored cable?
SWA cable glands for the size of cable you are using.......with shrouds. (Remember to put the shrouds on first)
Thanks. I am aware the SWA has steel wires wound around to protect the main terminals inside the SWA. Also, they are difficult to bend, so I was going the drill hole at an angle into the garage wall to help with the bend. I am only planning to add extra protection to SWA cable that is exposed outside. It is very close to where the lawn mover will pass during cutting grass. Use of bigger elbow was suggested by an electrician.
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Re: Running Power supply from new house to detached garage

Post by someone-else » Thu Nov 08, 2018 5:47 pm

If you can hit a swa with a lawn mower, it will be time to get a new lawn mower.
Fret not, a forum is a collection of opinions. Above, are mine.

Which is correct? Metre or Meter? Click the link to find out more.

Working on anything electrical? have you got a multi meter? why not? Would you hit a nail with a shoe?

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Re: Running Power supply from new house to detached garage

Post by SquirrelHammer » Sat Nov 10, 2018 5:25 pm

kellys_eye wrote:Armoured cable doesn't need the conduit but needs to be properly glanded/terminated into the feed and distribution units.

Given the feed to the garage is only 16A and already on an RCD circuit you could feed the cable straight into a metal twin 13A socket box and use a switched fused spur for the lighting circuit straight off it. No 'consumer unit' involved.

Any other lighting (inspection lights etc) could be simply plugged into the 13A sockets.

Personally I'd up-rate the supply feed (to 32A), fit a proper consumer unit and wire more sockets around the garage and a separate lighting run from it. As with most 'intentions' you'll find you're short of outlets and/or lighting in the fullness of time and wish you'd put in a more comprehensive system.
Great advice kellys and was about to post something when i read the first post.

I was too stuck with two options, consumer unit or spur

Due to the technicalities of getting a feed from the consumer unit to the garage i ended up doing my homework wrong and dug a trench 30inches down, 16meters long by about 4inches wide. Purchased 6mm SWA cable and MDPE black piping, placed the SWA in the MDPE black piping and took a spur with fcu from a socket on the wall. Had a sparky terminate the ends in the JB and said i must have got carried away digging and 6mm plus mdpe was overkill. that cost me £75 which i think was well worth it terminating SWA cable into a JB can destroy hands and fingers.

Then as you say, took a spur from it, fcu for lights etc.

Thinking back what i should have done is fitted water at that depth, filled some in and then done elec rather than just elec and internet.

SWA is a tank and going for a larger cable offers options in the future.
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Re: Running Power supply from new house to detached garage

Post by DIY Monty » Sun Nov 11, 2018 12:37 pm

someone-else wrote:If you can hit a swa with a lawn mower, it will be time to get a new lawnmower.
I get the point that SWA is designed from getting damaged, but was an electrician who recommended the protection, probably for a cosmetic reason or to conform with the new build (Bloomers home).
I much appreciate the professional advice and attached is the rough sketch of my plan and produce the material list. My only concern is if I can take another spur from the twin socket for the floodlight but protected with 5 amp fuse or what will be recommended by the floodlight supplier.
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Re: Running Power supply from new house to detached garage

Post by someone-else » Sun Nov 11, 2018 3:23 pm

You can only take one spur from a socket. (Otherwise, you could have more spurs than sockets)
However, there is nothing that says you can't spur from the socket, fit an FCU and have as many whatever you likes (sockets, lights etc) connected after the FCU
Fret not, a forum is a collection of opinions. Above, are mine.

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Re: Running Power supply from new house to detached garage

Post by DIY Monty » Sun Nov 11, 2018 4:53 pm

someone-else wrote:You can only take one spur from a socket. (Otherwise, you could have more spurs than sockets)
However, there is nothing that says you can't spur from the socket, fit an FCU and have as many whatever you like (sockets, lights etc) connected after the FCU
Thanks someone-else for sound advice. I did not want to install FCU in the garage as my son will not need more power supply then to twin socket, internal light and floodlight only. So there is no way to install a third supply to the floodlight from 16 amps RCD house supply?
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