Power to Outside

[gimli]

Hi All

I would like to run a power line up the garden for the lawn mower and possibly some low power lighting ran off transformers. Before I get an electrician in and waste his time, I would like to check if its feasible to run armored cable outside to a socket location and then bring it back into the house and connect to an existing ring main in the kitchen. This will then be spurred off from a socket and will include an RCD to protect the circuit.

As it is now, access to the MCB is difficult due to new ceilings and laminate floors etc

Oh, and any idea what type of armor cable would be best. I will go for labour only so an idea of cable size etc would help me get a price idea.

Thanks again in advance

Gim

 

[sparkticus]

What you propose is within wiring regulations but not good practice. If the fixed external wiring or appliance faults then you lose your kitchen circuit.


As for SWA cable size. You really must speak to your electrician first.

Understandably many people think there is "shower cable" , "lighting cable" "cooker cable" etc, etc. It is not that simple.

In general, 1.5mm or 2.5mm 3 core SWA might be fine but you need to allow your electrician to judge that.

 

[Chri5]

I take it the existing board / CU doesn't have any RCD protection ?

Simple format would be to provide a fused spur unit with in built rcd and run the external cable from that. If a fault occurs on the cable and add ons (sockets and lighting) it will be restricted to the rcd and fuse within the spur.

Unfortunately the work will require a cert, and that could mean adding in work such as gas / water bonding in 10mm earths (if they don't exist or are undersize), 16mm main earth from terminal to fuse board.

Although the main CU can be pre 17th edition, new work must comply and the bonding will have to.

 

[gimli]

Thanks and I understand what your saying. If I ask the sparks to install the RCD on the spur, will this not trip if there is a fault protecting the ring main?

Just running it by you to see if I go tthis in my head straight

Thanks again

Gim

What you propose is within wiring regulations but not good practice. If the fixed external wiring or appliance faults then you lose your kitchen circuit.


As for SWA cable size. You really must speak to your electrician first.

Understandably many people think there is "shower cable" , "lighting cable" "cooker cable" etc, etc. It is not that simple.

In general, 1.5mm or 2.5mm 3 core SWA might be fine but you need to allow your electrician to judge that.

 

[sparkticus]

Thanks and I understand what your saying. If I ask the sparks to install the RCD on the spur, will this not trip if there is a fault protecting the ring main?

Just running it by you to see if I go tthis in my head straight

Thanks again

Gim

It depends. Do you have an RCD of some type on your main consumer unit?
(either protecting just the ring circuit or several circuits including the ring or the entire consumer unit)

If YES then what is the trip current? 30mA or 100mA?

You see a fault will most likely trip two RCDs that are in series unless the first RCD(at the CU) is a delayed type or of a significantly higher trip current. Though for reliability a delayed type.

 

[gimli]

Yes CU has RCD is installed but your right, the bonding could possibly do with an upgrade. luckily the CU is over front door with the earth leading down right outside, conveniently hidden behind a PVC door makeup so easy enough access to that.

Now I know this can be done I can get a sparky in. Just out of interest, what I proposed, would this be acceptable to extend the cable run to add a few sockets into a future shed at the top of the garden?

Cheers again, much appreciated all

Gim

I take it the existing board / CU doesn't have any RCD protection ?

Simple format would be to provide a fused spur unit with in built rcd and run the external cable from that. If a fault occurs on the cable and add ons (sockets and lighting) it will be restricted to the rcd and fuse within the spur.

Unfortunately the work will require a cert, and that could mean adding in work such as gas / water bonding in 10mm earths (if they don't exist or are undersize), 16mm main earth from terminal to fuse board.

Although the main CU can be pre 17th edition, new work must comply and the bonding will have to.

 

[gimli]

Trip is 30mA

Thanks and I understand what your saying. If I ask the sparks to install the RCD on the spur, will this not trip if there is a fault protecting the ring main?

Just running it by you to see if I go tthis in my head straight

Thanks again

Gim

It depends. Do you have an RCD of some type on your main consumer unit?
(either protecting just the ring circuit or several circuits including the ring or the entire consumer unit)

If YES then what is the trip current? 30mA or 100mA?

You see a fault will most likely trip two RCDs that are in series unless the first RCD(at the CU) is a delayed type or of a significantly higher trip current. Though for reliability a delayed type.

 

[sparkticus]

Trip is 30mA

In this case a second RCD is of no real use. Any fault on the end of the SWA cable (including the SWA cable) will trip the RCD at your consumer unit.

There are options such as fitting a delayed (S-TYPE) RCD at your consumer unit then fitting a standard RCD on the SWA cable spur. But that requires careful thought about other circuits protected by a the new delayed RCD at your consumer unit.

I know you do not want to hear this but the best practice in this case is to run a new circuit from your consumer unit. Is there no alternative rout that avoids the floors?

 

[seasickstevie]

Although not ideal, surely the lack of discrimination and inconvenience of the house sockets etc tripping in the event of a fault is just that... an inconvenience.

Although the freezer going off could be a bit more dramatic.

 

[Chri5]

As mentioned an rcd spur has no use since you have an rcd protected circuit already.

If the new external service is a fuse spur feed it would be limited to 13 amp, would that be enough?

You would also need to do cals for cable size which may change depending on distance of the total run.

Best would be a totally new circuit, but with the CU at the front this could be a right PITA.

Is the house a semi or detached, which allows for a surface clip from front to back ?

Another possibility would be to run from the 1st floor if the 1st floor ring is seperate, logic being that a 13 amp load on a busy g/f ring might overload- 1st floor tends to be bedrooms and as such the circuit load is very light.

 

[sparkticus]

Although not ideal, surely the lack of discrimination and inconvenience of the house sockets etc tripping in the event of a fault is just that... an inconvenience.

Although the freezer going off could be a bit more dramatic.

Its not a disaster by any means but I know that I would not want/like it in my house. I have external power to a garage and I went to huge effort to put a dedicated RCBO protected circuit in to feed it. If it were another circuit (not the kitchen or another quite essential circuit) then not a problem.

 

[gimli]

Thanks you all for the help on this one, sorry about the delay but i have been away and just got back. All of the advice is top notch and really appreciated.

I have decided to go ahead with the installation but will limit it to low voltage applications in the main, the highest thing being run will be a flymo I guess.

One other thing if I may, is it possible to use NYY-J cable as accidental damage will be virtually impossible after installation or should I use standard armoured cable

Thanks again. This forum does exactly what it says on the tin and stops you sounding like a complete idiot when you finally talk to the professionals

Cheers again

 

[riveralt]

I have decided to go ahead with the installation but will limit it to low voltage applications in the main, the highest thing being run will be a flymo I guess.

Low voltage is the norm.

One other thing if I may, is it possible to use NYY-J cable as accidental damage will be virtually impossible after installation or should I use standard armoured cable

That would be for your electrician to determine - as would the size of the cable after various factors are taken into account, not least the potential voltage drop likely to be experienced.

 

[gimli]

Thanks again for the help all.

Much appreciated

 

[seasickstevie]

... will limit it to low voltage applications in the main, the highest thing being run will be a flymo

I have a suspicion you may mean low wattage