Upgrading my garage supply.

[Mr_Freeze]

Hi Everyone,
I moved into a new build house 1 year ago.
I’ve got round to investigating the supply to my separated garage.
At the house the builders have fitted a fused spur (non switched) internally onto a ring circuit fused at 13amp.
From this is a short length of 2.5 T&E going externally to a plastic Ip66 mounted external JB.
From this a 1.5 SWA is run underground to the garage and terminated into a metal clad switched fused spur inside the garage.
A double socket is connected to the spur on the incoming side.
The lighting circuit is connected to the load side and the fuse is 5amp. The switched spur therefore acts as the light switch.

The SWA has an earth conductor but the armourings are not earthed separately in the plastic JB. No banjo is fitted at the metal clad spur but the back box is bonded to the earth core.

Questions on existing instal.
Should the internal spur have a switch providing DP isolation before it leaves the house?
Should the armourings be earthed by bonded banjos to the earth core at both ends?

Planned changes.
I would like to replace the metal clad switched spur with a new garage CU with a main isolator with RCD and 2 x MCB’s fitted. 6amp for lighting and 10amp for sockets.
I then plan to wire multiple sockets around the garage in plastic conduit with LNE singles.

Would there be any issues in doing this as in my mind I’m providing DP isolation in the garage with RCD protection and separate rated MCB’s for lights and sockets?

Appreciate any comments?

 

[kenny7askew]

not much point in putting additional RCD in garage because if new build should already be in the house(check),could maybe change spur to double pole so as to be able to isolate in the event of fault in garage,sockets in garage already on 13 amp fuse so not much point in changing to mcb/garage unit,maybe easiest to just extend socket circuit in garage from socket already there,SWA should be earthed.

 

[buzzlightyear]

the non switch feed from you existing circuits should be 2.5mm SWA to the garage not 1.5mmSWA considering you have a light and socket feed from s/fs in the garage
. not bright sparks who put that in, and you want to alter the circuit in that garage .

 

[HandySparks]

Typical cheap option used by builders. OK for a light and the odd small power tool or electric lawnmower.

No point in doing what you're proposing unless you're going to put in a separate non-RCD circuit specifically for the garage.

 

[HandySparks]

the non switch feed from you existing circuits should be 2.5mm SWA to the garage not 1.5mmSWA...

As it's fused at 13A, why would you need a bigger SWA, unless for voltage drop reasons?

 

[buzzlightyear]

its like the film jaws (need a bigger boat) in order for you up grade in the garage a new cross sectional of SWA and separate feed for your garage from the c/u if possible.

 

[Cadgey123]

You are not going to have more ‘power’ in your garage with these changes. You will still be regulated by the 13amp fuse from the house.

 

[Spoon]

Why do you require "multiple sockets"?

 

[Mr_Freeze]

not much point in putting additional RCD in garage because if new build should already be in the house(check),could maybe change spur to double pole so as to be able to isolate in the event of fault in garage,sockets in garage already on 13 amp fuse so not much point in changing to mcb/garage unit,maybe easiest to just extend socket circuit in garage from socket already there,SWA should be earthed.

Hi Kenny, thanks for the first sensible answer.
When you say should be earthed, I thought the same but does it have to be earthed as if it does I can have the builder on that?
I know about the 13a supply but again do they have to provide DP isolation on the spur or is this a nice to have?
The Garage CU I was looking at has a 30ma RCD incuded in the DP isolator, so was just going to use it as its there.
The 6 & 10a are there for further discrimination and I want to wire additional lights in 1.5 and additional sockets in 2.5 singles.

 

[Mr_Freeze]

You are not going to have more ‘power’ in your garage with these changes. You will still be regulated by the 13amp fuse from the house.

Please don't state the obvious, not helpful.

 

[Mr_Freeze]

Why do you require "multiple sockets"?

Why not, its my garage?

 

[Octopus]

Mr Freeze... With the greatest respect unless you plan a new dedicated feed from your fuse box, you are wasting time and money....

 

[kenny7askew]

Hi Kenny, thanks for the first sensible answer.
When you say should be earthed, I thought the same but does it have to be earthed as if it does I can have the builder on that?
I know about the 13a supply but again do they have to provide DP isolation on the spur or is this a nice to have?
The Garage CU I was looking at has a 30ma RCD incuded in the DP isolator, so was just going to use it as its there.
The 6 & 10a are there for further discrimination and I want to wire additional lights in 1.5 and additional sockets in 2.5 singles.

Hi,with double pole spur you will be able to isolate garage in the event of a neutral earth fault in garage to stop house RCD tripping,with more than one RCD on the circuit it will be pot luck wich one trips first if not both,changing to mcbs wont make much difference to discrimination,swa should be earthed

 

[Cadgey123]

If it is easy enough to get a cable from your consumer unit to the garage, install a 4 or 6mm2 SWA and feed it with a MCB to a RCD protected garage Consumer unit.

That will give you plenty juice for garage items, lights, sockets, tools, electric door etc.

 

[telectrix]

Hi Kenny, thanks for the first sensible answer.
When you say should be earthed, I thought the same but does it have to be earthed as if it does I can have the builder on that?
I know about the 13a supply but again do they have to provide DP isolation on the spur or is this a nice to have?
The Garage CU I was looking at has a 30ma RCD incuded in the DP isolator, so was just going to use it as its there.
The 6 & 10a are there for further discrimination and I want to wire additional lights in 1.5 and additional sockets in 2.5 singles.

answer to the above, in red. the steel wire armouring of the SWA MUST be earthed, even if not used as a protective conductor for the cable, the supply end must be earthed, generally by use of a SWA gland and banjo or earth nut. you can pull the builder upon that.

 

[kenny7askew]

answer to the above, in red. the steel wire armouring of the SWA MUST be earthed, even if not used as a protective conductor for the cable, the supply end must be earthed, generally by use of a SWA gland and banjo or earth nut. you can pull the builder upon that.

Thank you you are quite right i should have said MUST not SHOULD

 

[Mr_Freeze]

answer to the above, in red. the steel wire armouring of the SWA MUST be earthed, even if not used as a protective conductor for the cable, the supply end must be earthed, generally by use of a SWA gland and banjo or earth nut. you can pull the builder upon that.

Thanks Tele.
So what about DP isolation at the spur, I know its a nice to have to totally isolate outside, but is it a must that they should've supplied this or not?

 

[Mr_Freeze]

Hi,with double pole spur you will be able to isolate garage in the event of a neutral earth fault in garage to stop house RCD tripping,with more than one RCD on the circuit it will be pot luck wich one trips first if not both,changing to mcbs wont make much difference to discrimination,swa should be earthed

Why not, surely a lighting fault will trip a 6a MCB before a 13amp fuse?

 

[Wilko]

Why not, surely a lighting fault will trip a 6a MCB before a 13amp fuse?

Hi - descrimination between protective devices is an interesting topic. For a short circuit fault where you will have say 500A current, it would be a bit of a race but quite likely the 6A MCB will trip and the 13A fuse will also melt. For an overload fault where lighting was drawing say 18A then the 6A MCB should trip only.

 

[Spoon]

Existing installation has a 5A fuse for the lights and a 13A fuse for the sockets... I don't see the problem.
I have also asked the OP why we are discussing this in private messages and also on the post...

 

[Mr_Freeze]

My apologies I don't use this forum very often and I think ive hit "quote in conversation" rather than reply.
My mistake sorry.
I just wanted to tidy up the install and provide separate circuits to wire from in the garage rather than the all on the 13amp spur in the house.
It would just seem wrong to me to be wiring the sockets from the incoming side and lights from the load side of the fused spur in the garage.
Forget costs and time, I have these at my disposal.
Other than having 2 x RCD's in series (I understand both or either could trip) am I not improving the install by providing MCB protection in the garage.
I am electrically trained a long time ago on industrial kit and have never done domestic regs, so I was searching to find out if:-
a. The builder should've earthed the armoured at one or both ends?
b. Should he have provided DP isolation on the outgoing external supply?

The install doesn't easily allow for replacement of the armoured with 2.5 or to take straight to the house CU.
I'm trying to make the best of a poor job.

 

[Toneyz]

Why not, its my garage?

Mr Freeze... With the greatest respect unless you plan a new dedicated feed from your fuse box, you are wasting time and money....

Apart from the usual circuit design constraints, I can't see why not it is all from a fused spur limiting to 13A can have as many sockets as he likes for convenience.

 

[Toneyz]

Mr Freeze, what do you intend to use the garage for and the load requirements?

 

[Pete999]

Mr Freeze, what do you intend to use the garage for and the load requirements?

Couple of big FREEZERS maybe?

 

[Toneyz]

Couple of big FREEZERS maybe?

Then we are going outside the realms of standard use of a family garage is used for, Oh I get it now

 

[Octopus]

Please don't state the obvious, not helpful.

Actually his input was constructive if you ask me, and as yet you've ignored my earlier response.

As for new builds, they are typically built with many issues .... Trying to get a builder to resolve is almost impossible.

 

[Pete999]

Then we are going outside the realms of standard use of a family garage is used for, Oh I get it now

Doh wake up Ant

 

[Spoon]

Mr Freeze, what do you intend to use the garage for and the load requirements?

I tried asking this... and got this back.

 

[Pete999]

I tried asking this... and got this back.
View attachment 39821

Makes me wonder what I'm going to get back with my comical post? #24

 

[Toneyz]

Makes me wonder what I'm going to get back with my comical post? #24

You are making me think he is an ice cream seller Mr Wippy

 

[Pete999]

Apart from the usual circuit design constraints, I can't see why not it is all from a fused spur limiting to 13A can have as many sockets as he likes for convenience.

Not working today Ant?

 

[Spoon]

I just wanted to tidy up the install and provide separate circuits to wire from in the garage rather than the all on the 13amp spur in the house.

But what you suggest will still be wired to the 13A spur in the house.... or have I missed something.

 

[Toneyz]

Not working today Ant?

Having the day off to do Christmas shopping !!!!!!!! well, I better got off from here and do some then wish me luck.

 

[Pete999]

You are making me think he is an ice cream seller Mr Wippy

Having the day off to do Christmas shopping !!!!!!!! well, I better got off from here and do some then wish me luck.

Good luck Mate

 

[Spoon]

Having the day off to do Christmas shopping !!!!!!!! well, I better got off from here and do some then wish me luck.

Don't forget to get me a 3TB external hard drive... best pal, buddy of mine...

 

[Mr_Freeze]

Your focusing on the wrong things.
I want sockets where they suit my requirements, as in a couple above a bench, one double at each corner of the garage for convenience etc.
I'm not growing weed in my garage and wont be running effing big grow lamps!
I'm aware I have 13amps to use.
Its not easy to upgrade the supply so I have to live with what I've got.
I just want to make sure what the builder put in is right or if not confirm its wrong and I will pursue them (you have 2 years to do this).
Also what I plan to do has no issues to current regs.
That is all.

 

[Mr_Freeze]

Actually his input was constructive if you ask me, and as yet you've ignored my earlier response.

As for new builds, they are typically built with many issues .... Trying to get a builder to resolve is almost impossible.

Murdoch, with the greatest of respect you have failed to answer my original question, other than raising pointless questions that have no bearing.
Don't worry about whether I can manage to get the builders to sort it, that's my problem and I've not failed yet.
Just confirm or deny whether they have done anything against regs, that's all I asked originally.
After that, comment on if I'm doing anything wrong in the garage other than spending my money and time on what theoretically I don't need to do?

 

[Midwest]

Your focusing on the wrong things.
I want sockets where they suit my requirements, as in a couple above a bench, one double at each corner of the garage for convenience etc.
I'm not growing weed in my garage and wont be running effing big grow lamps!
I'm aware I have 13amps to use.
Its not easy to upgrade the supply so I have to live with what I've got.
I just want to make sure what the builder put in is right or if not confirm its wrong and I will pursue them (you have 2 years to do this).
Also what I plan to do has no issues to current regs.
That is all.

With your 13amp supply, you can have as many sockets lights etc as you want. Think that's already been said? The FCU, is probably good idea to have a DP switch, but I don't think there's a requirement for it within BS7671. Your fused spur can easily be replaced with a switched fused connection unit

 

[Spoon]

Your focusing on the wrong things

But you are contradicting yourself. Initially you are asking if the FCU in the house should be switched and the next you are stating "I just wanted to tidy up the install and provide separate circuits to wire from in the garage rather than the all on the 13amp spur in the house."

The SWA has been answered.
The house FCU has now been answered.
The 2 RCD's in series is really bad design.... It sounds like you are happy to have a bad design, as long as it works.
How about getting a garage CU without an RCD fitted.........

 

[davesparks]

It would just seem wrong to me to be wiring the sockets from the incoming side and lights from the load side of the fused spur in the garage.

Other than having 2 x RCD's in series (I understand both or either could trip) am I not improving the install by providing MCB protection in the garage.

a. The builder should've earthed the armoured at one or both ends?
b. Should he have provided DP isolation on the outgoing external supply?

.

There is nothing wrong with this as the feed in to the garage is fused at 13A already.

2 RCDs in series makes it very hard for you to test the RCD tripping times when you carry out the essential tests before putting your new work in to use.

The additional MCBs won’t make any improvement as the current protection is correct, however they will have no practical negative effect on the installation.

Yes the armour should be earthed at least at one end, preferably the supply end.
No DP isolation is not normally required.

 

[telectrix]

succinctly put by ^^^^^ dave. no further comments required, unless they are funny.

 

[Mr_Freeze]

There is nothing wrong with this as the feed in to the garage is fused at 13A already.

2 RCDs in series makes it very hard for you to test the RCD tripping times when you carry out the essential tests before putting your new work in to use.

The additional MCBs won’t make any improvement as the current protection is correct, however they will have no practical negative effect on the installation.

Yes the armour should be earthed at least at one end, preferably the supply end.
No DP isolation is not normally required.

Thanks Dave,
It took a lot of work to get there so thanks for your clear definitive answer.
If others would have done this rather than go off on tangents as to why I wanted more sockets etc we would've been done a lot sooner and I wouldn't have needed to sound like a bolshy git, which I'm not unless people get up my nose.
Again thanks Dave.

 

[Spoon]

Thanks Dave,
It took a lot of work to get there so thanks for your clear definitive answer.
If others would have done this rather than go off on tangents as to why I wanted more sockets etc we would've been done a lot sooner and I wouldn't have needed to sound like a bolshy git, which I'm not unless people get up my nose.
Again thanks Dave.

Glad you are now sorted mate.
On the flip side of the coin, if you would have just given the info at the beginning then "we would've been done a lot sooner"

 

[Mr_Freeze]

Glad you are now sorted mate.
On the flip side of the coin, if you would have just given the info at the beginning then "we would've been done a lot sooner"

Spoon, thanks.
To be fair if you read the original post again, the info is there and the questions are there.
Will have to agree to disagree.

 

[Midwest]

succinctly put by ^^^^^ dave. no further comments required, unless they are funny.

View attachment 39825

I dunno, thought my reply was spot on and Spoons weren't bad. Funny enough?

Edit; and davesparks came in on the last knockings, just larging it up!

 

[westward10]

Unusual thread that, don't get many garage supply queries.

 

[telectrix]

Spoon, thanks.
To be fair if you read the original post again, the info is there and the questions are there.
Will have to agree to disagree.

asking a lot for some forum electricians to read an OP properly before replying. esp. if it's more than 2 lines.

 

[Spoon]

Spoon, thanks.
To be fair if you read the original post again, the info is there and the questions are there.
Will have to agree to disagree.

That is ok mate... I don't expect everyone to agree with me..

 

[Spoon]

Deleted... Double post..

MODS: Any reason why there isn't a Delete Post option, like the Edit option?

 

[Spoon]

asking a lot for some forum electricians to read an OP properly before replying. esp. if it's more than 2 lines.

and I'm illiterate......