Integral garage wiring

[gingerprince69]

Hi

So recently moved into new house (early 1990's build). I'm wanting to fit an extra socket to my garage (integrated). Having looked at the wiring in the garage, it's fed off a spur from the ring main in the lounge through the wall.

So the spur goes to a single unfused socket. That then feeds a light switch via a 13A JB to feed 3 independent lights, including security light.

It also feeds the backup immersion heater (which we never use - only if the boiler breaks) unfused, and then feeds the boiler and controls via another 13A JB. A schematic is as below: -

So a couple of questions: -

• My understanding was that to feed more than one socket or appliance off a ring main spur, it must be connected via a 13A JB to protect the initial spur wire. In the above configuration, the single socket and the immersion heater are unfused - is this therefore currently against code?
• I have read conflicting information about whether an immersion heater should be on a separate circuit or fed from a ring. My understanding is that it's probably OK (notwithstanding the above), but dedicated feed is preferred for isolation purposes?
• I assume there's nothing wrong with the lighting side of things?

Assuming I'm correct that it should all be protected by a 13A JB and that the immersion heater is "OK" here, then would this configuration be OK: -

Basically: -

• Swap the single switch and fused JB to protect the spur (would actually replace fused JB with a switched, fused JB)
• Fit a single socket via a JB on the feed to the immersion heater/boiler.

Is there anything wrong with this proposed setup?

Obviously I only have 13A in total to play with, so if the boiler's broken and the immersion heater is on, I won't be able to use anything high powered from the sockets without blowing the fuse.

 

[terryplumb]

Fused connection unit on the spur first ,and everything fed from its load terminals. You are correct that the total load would then be limited to 13amps ,by the fuse in the FCU ,and the immersion heater would draw close to that.
Your reference to 13 amp JB' s I assume you mean Fused connection units !!
Is the circuit RCD protected as it needs to be ?
Seperate fcu with smaller 3amp fuse for lighting .

 

[chivers67]

Where's this Immersion Heater exactly, does the Spur go to the garage and then back inside.


I'd certainly think about running a 6mm for future proof Car charging or similar with a small DB to the Garage.

 

[JohnW2]

So the spur goes to a single unfused socket. That then feeds a light switch via a 13A JB to feed 3 independent lights, including security light. ... It also feeds the backup immersion heater (which we never use - only if the boiler breaks) unfused, and then feeds the boiler and controls via another 13A JB. A schematic is as below: - ...

• My understanding was that to feed more than one socket or appliance off a ring main spur, it must be connected via a 13A JB to protect the initial spur wire. In the above configuration, the single socket and the immersion heater are unfused - is this therefore currently against code?

• Indeed it is, and would almost certainly also have been non-compliant with regulations when installed.

I have read conflicting information about whether an immersion heater should be on a separate circuit or fed from a ring. My understanding is that it's probably OK (notwithstanding the above), but dedicated feed is preferred for isolation purposes?

It's not just "for isolation purposes". Immersions are nearly always fed from a 'dedicated' circuit (rather than a ring sockets circuit), not the least because an immersion represents one of the greatest semi-continuous loads on an electrical installation. Feeding it from a ring circuit is certainly 'recommended against', but is not actually 'forbidden' by regulations. However, one needs to take into account the fact that it will be used very arrely.

I assume there's nothing wrong with the lighting side of things?

The Fused Connection Unit (FCU) (what you call a "13A JB") should really contain a 3A fuse for the feed to the lights.

Assuming I'm correct that it should all be protected by a 13A JB and that the immersion heater is "OK" here, then would this configuration be OK: - ..... Basically: -

• Swap the single switch and fused JB to protect the spur (would actually replace fused JB with a switched, fused JB)
• Fit a single socket via a JB on the feed to the immersion heater/boiler.

Is there anything wrong with this proposed setup?

Assuming that both feeds out of the FCU come from it's 'load' (i.e. fused/output) side of the FCU, then that's a good start. With everything connected to the output of that FCU, if you change it to a switched FCU (as you propose) that obviously means that its switch would 'switch everything' (i.e. lights as well as everything else). ... and, as you say, you'll then only have a total of 13A to play with - so almost nothing 'spare' if/when the immersion is on.

As above, you theoretically should have a second FCU, with a 3A fuse, in the feed to the lights (after the socket), but I wouldn't personally regard that as crucial.

As has been indicated, it all needs to be RCD protected (hopefully your ring circuit already is).

Kind Regards, John

 

[gingerprince69]

Thanks all.

Is the circuit RCD protected as it needs to be ?

The ring is on modern CU so has RCD protection. Is that sufficient or do I need additional for the garage, e.g. FCU (not fused JB ) with built in RCD?

Where's this Immersion Heater exactly, does the Spur go to the garage and then back inside.

It's in the garage where the boiler and cylinder are located. Not looping in and out of the garage.

Seperate fcu with smaller 3amp fuse for lighting .

Makes sense.

I'd certainly think about running a 6mm for future proof Car charging or similar with a small DB to the Garage.

I may at some point have a separate feed fitted, for electric car as you say and also I may get an urge to buy a welder and compressor. That will obviously want a dedicated feed.

Indeed it is, and would almost certainly also have been non-compliant with regulations when installed.

Thought so, but odd. It was notified in 2013 when I believe the boiler was moved to the garage. Doesn't mean someone hasn't messed with it after though I guess.

that obviously means that its switch would 'switch everything' (i.e. lights as well as everything else).

Do you think the switch here is pointless then? I figured it might be useful to isolate the garage.

All sounds reasonable though whilst I don't need any high draw appliances.

Thanks.

 

[JohnW2]

The ring is on modern CU so has RCD protection. Is that sufficient or ...

That is sufficient.

Makes sense.

As I said, I personally wouldn't regard it as particularly crucial, but an additional FCU with a 3A fuse for the lighting would be 'nice'!

Thought so, but odd. It was notified in 2013 when I believe the boiler was moved to the garage. Doesn't mean someone hasn't messed with it after though I guess.

I think the prohibition of more than one 'thing' supplied by an unfused spur from a ring circuit has existed since long before 2013, quite probably ever since ring circuits were invented (just after WWII).

Do you think the switch here is pointless then? I figured it might be useful to isolate the garage.

No, not pointless - as you say, there's something to be said for being able to isolate everything in the garage. I was just reminding you that you would lose everything (including lighting) if you switched it off.

All sounds reasonable though whilst I don't need any high draw appliances.

It sounds like it.

Kind Regards, John

 

[gingerprince69]

Perfect, thanks.

 

[SUNRAY]

How close is the socket in the lounge?
Will it be easy to run another cable to the socket?
There is nothing wrong with your design but extending the ring with a join behind the lounge socket such as this:

Or other variations:

would be a lot nicer Unless you wish to have the means to isolate the entire garage.

 

[JohnW2]

There is nothing wrong with your design but extending the ring with a join behind the lounge socket such as this: .... would be a lot nicer Unless you wish to have the means to isolate the entire garage.

I don't disagree with that but, FYI ...

Do you think the switch here is pointless then? I figured it might be useful to isolate the garage.

No, not pointless - as you say, there's something to be said for being able to isolate everything in the garage. I was just reminding you that you would lose everything (including lighting) if you switched it off.

Kind Regards, John

 

[SUNRAY]

I don't disagree with that but, FYI ...

Kind Regards, John

No, not pointless - as you say, there's something to be said for being able to isolate everything in the garage. I was just reminding you that you would lose everything (including lighting) if you switched it off.
It sounds like it.

Kind Regards, John

Yes I did see that and due to editting my reply there was not the double check/emphasis that has started out.