New Summer house wiring installation - dedicated Circuit or break into existing ring main?

[striceo]

Hi all,

Planning on wiring my neighbour's summer house which will be 15 metres away from the end of the house (20-25 metres total distance from the supply CU under the stairs).

Need some advice on which option would be the most SAFE not just the quickest, cheapest method etc. If it costs more to be done properly then that’s how it will be done.

The electrical needs for the shed are:-

LED lighting

Power for a treadmill 1000w and heater 2000w

The situation is this - the house has been underpinned and has no access under it for running cables. The CU being where it is means it would be a tricky albeit not an impossible SWA run along the outside of the house, that's before you get to the drop down to the garden trench for the final stretch to the shed. The alternative to running it that way is going out to the wall behind the CU first then down under the driveway to the garden, although this would mean raising a fair few flags. I know this may sound lazy but I don't want to be lifting 5 metres of driveway flags to run the cable under that way, but if that is the best way so be it. Ideally I would prefer not to use a full run of 25 metres of SWA but again, if needs must.

There is a ring main socket situated on the downstairs back room wall adjacent to the rear garden that has a T+E 2.5mm2 coming out to a junction box on the exterior wall directly opposite. This JB is supplying flood lights (which don't work!).

Here's my first thought...

Could I replace the JB on the ext wall for a 13A FCU spur inside a waterproof casing (Doing away with the existing flood light cables) Run a 2.5mm SWA from this, bury it a foot deep along the side of the garden to one metal-clad double socket inside the shed avoiding the need for a sub-CU. Then feed off from this to an additional FCU switch 3A for the lighting circuit?

Here’s where I need guidance?

Will spurring off the downstairs 32a MCB ring main be ok for the distance and load etc?

If so, will SWA 2.5mm be enough or upgrade to 4mm, or 6mm?

Will the supply RCD be enough protection?

Do I need to ‘notify’ if done this way? If it is just an extension of the ring main I wasn’t sure if this was absolutely necessary or not. Obviously it is poor practice. Minor works?

Other considerations:-

Earthing system in house is TN-S

There will be no gas / water or extraneous metal in the shed.

I imagine in the upcoming winter months he will be having a heater on and the treadmill at the same time. 3000w / 230v = 13.04A, that is before taking into account voltage drop etc, but I can’t see him using both appliances to the max at same time. Giving that the fused spur is limiting him to only 13A I imagine this could be pushing it.

Any suggestions for better way would be great! Feel free to tear my plan apart, I’d rather set him straight with the task that’s required.

Thanks

 

[Taylortwocities]

Oh dear. Too many basic questions that lead me to suspect you arent the person who should be doing this. Did you tell your neighbour that you knew all about electrical stuff?

With respect, I will provide a straight answer to your first question

Need some advice on which option would be the most SAFE not just the quickest, cheapest method etc.

The option is for your neighbour to find a competent, registered electrician to do this job.
You could volunteer to help out, you may pick up some tips on the way.

 

[striceo]

Oh dear. Too many basic questions that lead me to suspect you arent the person who should be doing this. Did you tell your neighbour that you knew all about electrical stuff?

With respect, I will provide a straight answer to your first question

The option is for your neighbour to find a competent, registered electrician to do this job.
You could volunteer to help out, you may pick up some tips on the way.

Fair enough. I've been a sparks mate on commercial sites for a few years where I haven't had the need to look in the regs since I passed 17th.

Basically no experience on domestics but in principle I know more than the average DIYer.

So yeh I know my post come across that way and you're definitely right I should leave it to someone who knows EXACTLY what they're doing.

Just out of curiosity how would you approach that project.?
Do you think the spur off the ring main is a definite no-no..?

 

[Strima]

Dedicated circuit for the summer house, any future issues you can isolate it without affecting the main property.

Spurring off the RFC is a ---- poor design IMHO.

This would be notifiable under Part P as it's a new circuit.

 

[striceo]

Dedicated circuit for the summer house, any future issues you can isolate it without affecting the main property.

Spurring off the RFC is a ---- poor design IMHO.

This would be notifiable under Part P as it's a new circuit.

Good, thanks. At least I'm aware so I know what to say to him.

Sorry to pick your brain again. Would spurring off be a minor works gig only? I'm not going ahead with it, it's just for my own curiosity - technically it's an extension of an existing circuit but it seems like a loop hole / grey area exploitation when doing it like that. What do you think?

 

[Taylortwocities]

Agreed, you already identified that the known load is north of 13A. That should be a hint!

And there’s distance involved too (Volt drop). No point having a heater in there if it doesn’t get very hot and the treadmill slows down when you have them both running in January.

 

[buzzlightyear]

Basically no experience on domestics but in principle I know more than the average DIYer

With out blowing your own trumpet.
I would be best to get another spark in to guide you and part p the work, asking to many question could be dangerous.

 

[Pete999]

Fair enough. I've been a sparks mate on commercial sites for a few years where I haven't had the need to look in the regs since I passed 17th.

Basically no experience on domestics but in principle I know more than the average DIYer.

So yeh I know my post come across that way and you're definitely right I should leave it to someone who knows EXACTLY what they're doing.

Just out of curiosity how would you approach that project.?
Do you think the spur off the ring main is a definite no-no..?

Dedicated circuit Mate

 

[Strima]

Sorry to pick your brain again. Would spurring off be a minor works gig only? I'm not going ahead with it, it's just for my own curiosity - technically it's an extension of an existing circuit but it seems like a loop hole / grey area exploitation when doing it like that. What do you think?

Not really a grey area, could be done on a MWC and would not need to be notified.

But that's a lot of load to spur off an RFC with, it could be argued you could extend the RFC to the summerhouse but again poor design.

No point having a heater in there if it doesn’t get very hot and the treadmill slows down when you have them both running in January.

Run quicker, get warmer!!!

 

[striceo]

With out blowing your own trumpet.
I would be best to get another spark in to guide you and part p the work, asking to many question could be dangerous.

Yeh I've already decided I'm not going to do it. Don't think I was blowing my own trumpet tbh, thought I'd come on a respected site and get as much feedback as possible.

I'm not one of those that gets disheartened when people say ''get a proper spark to do a proper job'' every 5 minutes. It's hard enough to get experience in a trade these days when starting out, especially when certs and training continuously add up just to get your tools on a job.

 

[Pete999]

Yeh I've already decided I'm not going to do it. Don't think I was blowing my own trumpet tbh, thought I'd come on a respected site and get as much feedback as possible.

I'm not one of those that gets disheartened when people say ''get a proper spark to do a proper job'' every 5 minutes. It's hard enough to get experience in a trade these days when starting out, especially when certs and training continuously add up just to get your tools on a job.

I aint said get a proper Sparks in for yonks now, not PC

 

[telectrix]

at least striceo has had the balls to post on here, saying he's not sure. IMO, both options are viable but, as OP knows, coming off the RFC will limit the load. an option would be to come off the RFC into a small din rail enclosure, fit a 16A D/P MCB, but inform customer of the limitation re. loading.

 

[Dustydazzler]

at least striceo has had the balls to post on here, saying he's not sure. IMO, both options are viable but, as OP knows, coming off the RFC will limit the load. an option would be to come off the RFC into a small din rail enclosure, fit a 16A D/P MCB, but inform customer of the limitation re. loading.

funny you mention this as I did this quite often for garage & sheds supply back in the day, often hiding the little consumer unit behind the TV... but it seems rather unfashionable now with the preferred method a dedicated cable back to the consumer unit, which depending on the location can be awkward.

 

[Pete999]

Awkward or not a dedicated supply is the right option in this case, "informing the customer to keep an eye on the loading is a get out of jail card"

 

[telectrix]

Awkward or not a dedicated supply is the right option in this case, "informing the customer to keep an eye on the loading is a get out of jail card"

al depends on the custonmer's budget. do you turn down a job worth a couple of hundred when it can be done complant?

 

[Pete999]

al depends on the custonmer's budget. do you turn down a job worth a couple of hundred when it can be done complant?

Don't turn down jobs, cus I don't do any, a dedicated circuit for me.

 

[Rockingit]

One thing that's not been mentioned is where the main incomer and meter box are - possibly a third option might exist by taking a Henley split, KMF, small board in the summer house. Maybe.

 

[ipf]

Run quicker, get warmer!!!

And there’s distance involved too (Volt drop). No point having a heater in there if it doesn’t get very hot and the treadmill slows down when you have them both running in January.

I thought it was a summer house??

 

[ChrisElectrical88]

I looked at a summer house back in February before lockdown. Options were come off a ring main or a 65m 16mm SWA to the mains at the opposite corner of the house ? or a FCU 5m away.
They Wanted 2 twin sockets, indoor light and outdoor light. Got a call last week saying someone else did the work and the fuse has popped twice and could I have a look. Plugged 2 heaters in and it blew the fuse twice when the kettle was going.
They have asked me to do it properly with a sub main, told them to get someone else to do it now, can’t be arsed with it.

 

[Dustydazzler]

I looked at a summer house back in February before lockdown. Options were come off a ring main or a 65m 16mm SWA to the mains at the opposite corner of the house ? or a FCU 5m away.
They Wanted 2 twin sockets, indoor light and outdoor light. Got a call last week saying someone else did the work and the fuse has popped twice and could I have a look. Plugged 2 heaters in and it blew the fuse twice when the kettle was going.
They have asked me to do it properly with a sub main, told them to get someone else to do it now, can’t be arsed with it.

price it really high & sub it out to someone else as a cash job ...?

 

[Pete999]

I looked at a summer house back in February before lockdown. Options were come off a ring main or a 65m 16mm SWA to the mains at the opposite corner of the house ? or a FCU 5m away.
They Wanted 2 twin sockets, indoor light and outdoor light. Got a call last week saying someone else did the work and the fuse has popped twice and could I have a look. Plugged 2 heaters in and it blew the fuse twice when the kettle was going.
They have asked me to do it properly with a sub main, told them to get someone else to do it now, can’t be arsed with it.

Is this the fuse in the FCU that's blowing?
[automerge]1601307012[/automerge]

I looked at a summer house back in February before lockdown. Options were come off a ring main or a 65m 16mm SWA to the mains at the opposite corner of the house ? or a FCU 5m away.
They Wanted 2 twin sockets, indoor light and outdoor light. Got a call last week saying someone else did the work and the fuse has popped twice and could I have a look. Plugged 2 heaters in and it blew the fuse twice when the kettle was going.
They have asked me to do it properly with a sub main, told them to get someone else to do it now, can’t be arsed with it.

Having seen the job already, only you have prior knowledge of what's involved to run a dedicated supply, hard to comment.

 

[ChrisElectrical88]

@Pete999 It was the fuse in the spur, they said cause it was cold last week they had 2 x 2kW heaters plugged in and when they set the kettle off it blew the fuse.
@Dustydazzler I’ve just gave them a mates number and told them to use him, I’m to busy now to get involved.

 

[Pete999]

@Pete999 It was the fuse in the spur, they said cause it was cold last week they had 2 x 2kW heaters plugged in and when they set the kettle off it blew the fuse.
@Dustydazzler I’ve just gave them a mates number and told them to use him, I’m to busy now to get involved.

Thanks Mate so 4 KW and a possible 3KW kettle, so 7KW on a 13 Amp fuse = approx 30 Amps not really nuclear physics is it?

 

[Dustydazzler]

Thanks Mate so 4 KW and a possible 3KW kettle, so 7KW on a 13 Amp fuse = approx 30 Amps not really nuclear physics is it?

just surprised some bright spark didn’t take out the blown fuse and replace it with A cut down bolt...

 

[Pete999]

@Pete999 It was the fuse in the spur, they said cause it was cold last week they had 2 x 2kW heaters plugged in and when they set the kettle off it blew the fuse.
@Dustydazzler I’ve just gave them a mates number and told them to use him, I’m to busy now to get involved.

Still a 13 Amp fuse Mate, cold or not job done properly should have sorted the problem properly and more importantly and SAFELY.

 

[ChrisElectrical88]

Thanks Mate so 4 KW and a possible 3KW kettle, so 7KW on a 13 Amp fuse = approx 30 Amps not really nuclear physics is it?

Not really, I think the heaters were holding alright, I’ve not looked at the regs to see the time they can handle that sort of current. Bet it was bloody warm though!

 

[James]

I looked at a summer house back in February before lockdown. Options were come off a ring main or a 65m 16mm SWA to the mains at the opposite corner of the house ? or a FCU 5m away.
They Wanted 2 twin sockets, indoor light and outdoor light. Got a call last week saying someone else did the work and the fuse has popped twice and could I have a look. Plugged 2 heaters in and it blew the fuse twice when the kettle was going.
They have asked me to do it properly with a sub main, told them to get someone else to do it now, can’t be arsed with it.

add 30% to the price and requote.

 

[The Engineer]

Dedicated circuit Mate

Im in the states where we go by ohm's law and scientific load calculations in determining these things but dont completely understand UK terminology, if the terminology is what I think. This is a not brainer. It will require a dedicated circuit with a highest than you stated amp rating, use this circuit to power a secondary small breaker pannel to branch the higher power "new dedicated circuit as the dedicated for the small box it will power. Included four of whatever your standard power rating needed to supply you lower standard power on each buss bar power connection. Of these four you should be able to install what we call a double break. That taps two of the lower power supply sources joing the two to make what we refer to as 220v incase he needs it later or if your power ratings on treadmills over there are 220 volts he can use it for that but if you were accurate on th watts which even for the uk there's no way that could be, but I'm from the states. If not need cap it for a later power need. That would reserve 2 of the single power acceses if not used. Thethirdcan be used with a common amp rated circuit, here it could be used with what we'd call AWG 12-2 wire and provide 110volts which here we can run up to 20 amp breaker switch. Which would power to our code 6 110v low watt power recepticals along with two 110v rated lights or other things like radios, t.v., lamps etcetera..so if you would need to run four 110v appliances or other things. If you have extra, it won't hurt, just put covers over the unused breaker power acceses. You will need at least what we call a heavier duty gauge "thicknesses of wire and it be insulated properly to the environment in which it will be exposed to, so four 110v access point in the new box is a total of 440 volts requiring four solid 10 gauge insulated wires into a single weather proof conduit and coded properly and coated with no exposed inside metal of the wires before placed into a conduit together to run out ti the other smaller booster box/panel.This would work because of the amp draw. It wouldn't be alot out there for what you want to use and you would be able to still add two to three lights plugs or a mix as needed. In the stated this would typically be ran from a pole fixed to the roof with the conduit running to a hollow pole on top the shed running the conduit through both hollow piles and securing them, if it's a short distance away and on private property. Then water proof hollow portion of poles and weather proof. Use outdoor moisture resistant conduit and wire just incase. If different situation, stop 440v power from main power using utility approved technicians then do the rest of the conduit and wiring the same but run it in ground with properly rated wire and conduit usually weather proof, water resistant and dig 16 to 18 inches deep, fill trench 3 to 5 inches with crushed gravel then line the entire length of the trench with under ground rated black plastic on top of the crush rock, then cover over top with with under ground rated plastic plastic the same way, except going from top of trench hole about two inches before top of trench hole cover with two inches of course grade 58 gaveland top with soil about 6+ inches deep worth, compress and refill till ground is very firm with dirt again cover thr back fill material and conduit, to save expense pull power from the original breaker box... only if it has for unused power acceses. If not use same method of wires and adjust gauge according to amp draw calculations. And adjust after calculating ohms law I/e=r to install and load to calculate breaker size is safe and efficient and proper for the size of the wire.. then if not enough empty to make 440v in original box. Run what we call in America a sub panel with access or breaker ports. If no available 440v work from the box get your electric energy provider to set and connect access to 440v power for liability to the raw power supply incoming the house then use it to run your power to the shed dub panel ... hope that helps and hope you can understand my electrical terminology. You can save alot of money with this advice as a helper for your technician..lol...jk jk.. you might bre ankle to do some of it...... if toy can translate this to Englanda terminology. Or I don't know really if you guys use the same amount if electricity to power the same devices we use in the states. If not oh well at least this is done insight from the U.S. engineering side.

 

[Rockingit]

Im in the states where we go by ohm's law and scientific load calculations in determining these things but dont completely understand UK terminology, if the terminology is what I think. This is a not brainer. It will require a dedicated circuit with a highest than you stated amp rating, use this circuit to power a secondary small breaker pannel to branch the higher power "new dedicated circuit as the dedicated for the small box it will power. Included four of whatever your standard power rating needed to supply you lower standard power on each buss bar power connection. Of these four you should be able to install what we call a double break. That taps two of the lower power supply sources joing the two to make what we refer to as 220v incase he needs it later or if your power ratings on treadmills over there are 220 volts he can use it for that but if you were accurate on th watts which even for the uk there's no way that could be, but I'm from the states. If not need cap it for a later power need. That would reserve 2 of the single power acceses if not used. Thethirdcan be used with a common amp rated circuit, here it could be used with what we'd call AWG 12-2 wire and provide 110volts which here we can run up to 20 amp breaker switch. Which would power to our code 6 110v low watt power recepticals along with two 110v rated lights or other things like radios, t.v., lamps etcetera..so if you would need to run four 110v appliances or other things. If you have extra, it won't hurt, just put covers over the unused breaker power acceses. You will need at least what we call a heavier duty gauge "thicknesses of wire and it be insulated properly to the environment in which it will be exposed to, so four 110v access point in the new box is a total of 440 volts requiring four solid 10 gauge insulated wires into a single weather proof conduit and coded properly and coated with no exposed inside metal of the wires before placed into a conduit together to run out ti the other smaller booster box/panel.This would work because of the amp draw. It wouldn't be alot out there for what you want to use and you would be able to still add two to three lights plugs or a mix as needed. In the stated this would typically be ran from a pole fixed to the roof with the conduit running to a hollow pole on top the shed running the conduit through both hollow piles and securing them, if it's a short distance away and on private property. Then water proof hollow portion of poles and weather proof. Use outdoor moisture resistant conduit and wire just incase. If different situation, stop 440v power from main power using utility approved technicians then do the rest of the conduit and wiring the same but run it in ground with properly rated wire and conduit usually weather proof, water resistant and dig 16 to 18 inches deep, fill trench 3 to 5 inches with crushed gravel then line the entire length of the trench with under ground rated black plastic on top of the crush rock, then cover over top with with under ground rated plastic plastic the same way, except going from top of trench hole about two inches before top of trench hole cover with two inches of course grade 58 gaveland top with soil about 6+ inches deep worth, compress and refill till ground is very firm with dirt again cover thr back fill material and conduit, to save expense pull power from the original breaker box... only if it has for unused power acceses. If not use same method of wires and adjust gauge according to amp draw calculations. And adjust after calculating ohms law I/e=r to install and load to calculate breaker size is safe and efficient and proper for the size of the wire.. then if not enough empty to make 440v in original box. Run what we call in America a sub panel with access or breaker ports. If no available 440v work from the box get your electric energy provider to set and connect access to 440v power for liability to the raw power supply incoming the house then use it to run your power to the shed dub panel ... hope that helps and hope you can understand my electrical terminology. You can save alot of money with this advice as a helper for your technician..lol...jk jk.. you might bre ankle to do some of it...... if toy can translate this to Englanda terminology. Or I don't know really if you guys use the same amount if electricity to power the same devices we use in the states. If not oh well at least this is done insight from the U.S. engineering side.

That was quite some first post.

 

[Strima]

That was quite some first post.

And completely irrelevant as we use 230 single phase... ?