Extending ring to outhouse?

[MickSmith5824]

Hi all back again needing more advice.

I've included some photos. Basically customer has asked me to supply and wire outhouse. Unfortunately as consumer unit is at front of house there's no real possibility of supplying on own circuit. The outhouse will have about 3 x double sockets and couple of lights. The thing that concerns me over the adequacy of supply is that customer would like a heater in here and also a socket for a heater in the garden....a 13 amp spur is not going to suffice in my mind. As can see from photos the only possible route can see is come from one or the two ring sockets in kitchen. To make things more awkward these sockets back onto an outside toilet ? see photo. The outhouse is about 7 metres from here. Any neat feasible point in right direction be appreciated. Have heard others suggesting a ring lollipop.....So could potentially extend ring into a large junction box opposite socket and in toilet and then could run some 6mm 3 core around the toilet, punch outside into another junction box ? then take 6mm armoured either to outhouse or preferably to garden socket first (is this feasible?) Then on to junction box in outhouse and from here wire a ring for sockets and a spur for lights. Am I missing something really stupid? Does this seem compliant to you? Or is there easier ways?

Thanks

 

[mattg4321]

I think the only two methods I'd ever use are on its own circuit directly from consumer unit or via a 13A SFCU.

 

[MickSmith5824]

I think the only two methods I'd ever use are on its own circuit directly from consumer unit or via a 13A SFCU.

Thanks Matt. Do you mind clarifying why? What would you do in situation like this where no option of new circuit and 13amp spur very likely to get overloaded?

 

[littlespark]

There would be nothing to stop them from plugging these two heaters into the existing rfc, and not overloading.... so let us look at other options here.

1. keep it simple. If you’re going to extend the ring, then extend it. 2x 2.5’s out to the outhouse.
2. Spur it out, but rather than a 13A FCU, make it a 20 or 25A mcb, in a suitable enclosure, giving the option to isolate inside the house and add an RCD if there isn’t one on the circuit already.
3. Is there an unused cooker circuit perhaps you could repurpose?

Are you certain there’s no access to get to CU? Even with limited space under boards, you could push rods from back to front.
Or is it concrete floor?


I would really like to find out from customer the actual load they expect to be using.
Many a time I have been asked for an outside socket “just for the lawnmower”.... then I get to the job, and there’s a lazyspa sitting in its box waiting.

“a couple of heaters” could be 2 at 3kW apiece.

 

[MickSmith5824]

There would be nothing to stop them from plugging these two heaters into the existing rfc, and not overloading.... so let us look at other options here.

1. keep it simple. If you’re going to extend the ring, then extend it. 2x 2.5’s out to the outhouse.
2. Spur it out, but rather than a 13A FCU, make it a 20 or 25A mcb, in a suitable enclosure, giving the option to isolate inside the house and add an RCD if there isn’t one on the circuit already.
3. Is there an unused cooker circuit perhaps you could repurpose?

Are you certain there’s no access to get to CU? Even with limited space under boards, you could push rods from back to front.
Or is it concrete floor?


I would really like to find out from customer the actual load they expect to be using.
Many a time I have been asked for an outside socket “just for the lawnmower”.... then I get to the job, and there’s a lazyspa sitting in its box waiting.

“a couple of heaters” could be 2 at 3kW apiece.

Thanks Little spark that's really helpful. Unfortunately yes solid floors and loads of obstacles to get past for new circuit. I'm considering the option 2 you mentioned. So could potentially use something similar to 2 way CU? Take both my 2.5 ring conductors into top of 25amp MCB. Then use 4mm twin to outside enclosure and take 4mm SWA to outside socket then onto the outhouse. The use of 4mm should ensure not volt drop issues. Thoughts...this seem like a plan
: )?

 

[UNG]

The trunking in the first photo (toilet?) suggests that something is already spurred from the the ring

 

[MickSmith5824]

The trunking in the first photo (toilet?) suggests that something is already spurred from the the ring

Good spot that UNG. But have two sockets there in kitchen so should be able to come from one of them.

 

[mattg4321]

Thanks Matt. Do you mind clarifying why? What would you do in situation like this where no option of new circuit and 13amp spur very likely to get overloaded?

In all honesty I’d probably walk from the job unless I could run a new circuit back to the consumer unit.

Putting a 20/25A MCB protecting a spur off the ring seems like a fairly poor design to me. Quite a large load on a single point on the ring potentially. I personally wouldn’t do it, although I’m sure an argument could be made for doing it.

 

[loz2754]

It would no longer be classed as a conventional final circuit. Not to say that means it would be unsafe, but subsequent inspectors may be flummoxed. (I just wanted to use the word flummoxed!)

 

[Spoon]

I mentioned this idea in a thread.

Extend RFC to a detached building/garage/shed?

You brainy guys may be able to help with this thought I was having. There has been a thread recently about 4mm radial from ring main. This got me thinking..... (No funny comments) So my question is: If you had a building/garage/shed, say about 5 meters away from a house, is it acceptable to...

www.electriciansforums.net

Have a read.

 

[MickSmith5824]

I mentioned this idea in a thread.

Extend RFC to a detached building/garage/shed?

You brainy guys may be able to help with this thought I was having. There has been a thread recently about 4mm radial from ring main. This got me thinking..... (No funny comments) So my question is: If you had a building/garage/shed, say about 5 meters away from a house, is it acceptable to...

www.electriciansforums.net

Have a read.

Hi mate

Thanks for that had a good read of it. At this stage I think I'm more inclined to go with a 20/25 amp MCB in an enclosure and take a 4mm to outside socket then down to outhouse

 

[littlespark]

When you think about it, a small enclosure with mcb or rcbo is designed to take anything up to 100A, so whatever the load, it would cope fine.... (OCPD at 32A?)
Cope better than a 13A FCU, even pushing it to full 13A

 

[mattg4321]

I’d be less worried about the mcb and enclosure than the potential of 25amps at single point on the ring.

 

[MickSmith5824]

When you think about it, a small enclosure with mcb or rcbo is designed to take anything up to 100A, so whatever the load, it would cope fine.... (OCPD at 32A?)
Cope better than a 13A FCU, even pushing it to full 13A

I get what your saying but going with 32amp MCB in enclosure just pretty much negates the need as have 32 back at board. I am also concerned as others have pointed out if load all on short leg could be overloading this leg of ring. Think I'm more inclined to go with 20/25 atleast then if they really start to overload it would offer some protection

 

[MickSmith5824]

I’d be less worried about the mcb and enclosure than the potential of 25amps at single point on the ring.

Can you explain to me what the likely problems are other than not great design? If 2.5mm rated at 27 amps and supply a 25amp mcb from this how can the cable potentially be overloaded? If draw 25 from outhouse the mcb for outhouse kicks in and if draw 32 in total the one at CU kicks in

 

[mattg4321]

Each ‘leg’ of the ring only has to be able to take 20 amps. 2.5mm2 cable is often run in insulation etc (ref method 100) meaning the current carrying capacity is only slightly over 20 amps.

If your spur to the outbuilding was towards one end of the ring, then this side of the ring could potentially become overloaded. It might even have a kettle plugged in next to the spur off to the outbuilding. This ‘side’ of the ring could then see loads well in excess of the roughly 21 amps it may be able to take.

Yes, a lot of ifs and buts, and the situation could possibly arise with a standard ring arrangement - but the set up suggested makes it more likely imo. Thus imo poor design.

That’s without getting into it being potentially a headache for the next person that comes to work on the circuit.

 

[MickSmith5824]

Each ‘leg’ of the ring only has to be able to take 20 amps. 2.5mm2 cable is often run in insulation etc (ref method 100) meaning the current carrying capacity is only slightly over 20 amps.

If your spur to the outbuilding was towards one end of the ring, then this side of the ring could potentially become overloaded. It might even have a kettle plugged in next to the spur off to the outbuilding. This ‘side’ of the ring could then see loads well in excess of the roughly 21 amps it may be able to take.

Yes, a lot of ifs and buts, and the situation could possibly arise with a standard ring arrangement - but the set up suggested makes it more likely imo. Thus imo poor design.

That’s without getting into it being potentially a headache for the next person that comes to work on the circuit.

Thanks Matt. I hear you that this maybe isn't great design, not decided fully yet on how will go about things. So to clarify then, every ring that is installed and isn't taking into account the potential loading on the legs does have a potential if heavy loads on short leg to actually overload conductors and burn out cable OCP device kicks in. Seems the logical answer is yes?

 

[mattg4321]

In reality it doesn’t happen.

That doesn’t mean I don’t like to absolutely minimise the risk of it happening though.

If I came across a set up as you are thinking of doing, then I probably wouldn’t be too worried about it, just think it an odd way of doing things.

I’d rather make the extra effort to get back to the consumer unit.

 

[MickSmith5824]

In reality it doesn’t happen.

That doesn’t mean I don’t like to absolutely minimise the risk of it happening though.

If I came across a set up as you are thinking of doing, then I probably wouldn’t be too worried about it, just think it an odd way of doing things.

I’d rather make the extra effort to get back to the consumer unit.

Ok thanks again

 

[Vortigern]

The ring final circuit in the kitchen is prone (potentially) to overload. Say they have spurred an integrated oven and have a washing machine and tumble dryer. Put the dinner in and the washing on while drying the clothes and pop outside and pop the heater on then could be overload quite easily as all of this will be on 32a RCBO or is it MCB. You will have to provide RCD protection and how will selectivity be achieved in that case? I repeat the question asked earlier, are you sure you can not use a spare way from the CU? I guess it's a terraced house and you can't run an SWA along the side of the house? Personally If there was no way I could run the circuit from the CU then I would not install it. Is it PME? Have you thought about exporting the PME?

 

[stevethesparks]

Basically a sub main from a final ring circuit is a NO.
There must be a way of running a supply back to the main CU

 

[7029 dave]

Is the supply in external meter box, if so split tails and run a sub main.

 

[MickSmith5824]

It's tns. Consumer unit is right next to front door. Ground floor property. Hard floors, stairs in way and even if could get access through stairs then in kitchen full of fixed appliances on wall would need to run circuit. To much hag for me I think I'll give it a miss. Thanks for replies all

 

[Dave OCD]

If you can get through the stairs could you run through the kitchen under the base units ?

 

[MickSmith5824]

If you can get through the stairs could you run through the kitchen under the base units ?

No to much hag think guy wants on cheap anyway will prob leave alone

 

[DPG]

No to much hag think guy wants on cheap anyway will prob leave alone

Is 'hag' another word for hassle, or has it auto-corrected both in both posts?

 

[Dave OCD]

That's been annoying me too, or is it a drastically shortened version of 'hard graft' ....

 

[MickSmith5824]

Is 'hag' another word for hassle, or has it auto-corrected both in both posts?

It is mate. Hassle is definitely what it is ?