Outdoor Electrics

[MrT4643]

Good afternoon
I am planning an extension and outdoor electrics and I'm looking for some advice to plan ahead. Ultimately a qualified electrician will be doing the work, but as I'm not at that stage yet, I just want to plan roughly what we are doing rather than waste someones time planning and quoting.
We currently have the board upstairs, and a 10mm t+e currently supplying the outside which is on an rcbo. This currently joins to swa via a wiska box and goes out to a very old outside supply which will be being removed.
I need to supply a greenhouse, small workshop, outdoor lighting and summer house. Nothing massively high load, just heating and lighting really.

I was looking at terminating the 10mm t+e into a second consumer unit in the extension, which would then supply 3 smaller garage consumer units in the summer house, workshop and greenhouse allowing individual socket and lighting circuits in each location. There would be no water or gas in these outbuildings.

Does this sound feasible? The 3 locations are around 50m apart each way in a triangle, so I don't want to be burying miles and miles of cable hence the idea of putting a small consumer unit in each location.

I would end up with 5 consumer units, but one main one.

Does that sound like a realistic solution or am I barking up the wrong tree?

Thanks in advance

 

[telectrix]

no way could anyone advise on a forum. a site visit would be essential.

 

[pc1966]

One issue with cascading those CUs is a fault will most likely trip out all of them. If one is a workshop that could be quite dangerous so for that reason, or indeed any other loss of power situation, you might want to include an emergency light that gives you a battery backed-up light so it is not complete darkness if at night, etc.

However, the idea of cascading a sub-main from CU to CU is reasonable, but then the overall sub-main has to be rated for the supply over-current protection value and end-of-run Zs good for disconnection time, etc.

As already said, needs a proper investigation.

 

[Craighrvy]

I would say your going to have a lot of voltage drop if there is 50 meters between outbuildings x 3 on a loop, that's a long run of cable. Best and safest practice would be to have a supply to each out house from seperate mcbs from the consumer unit in the extension

 

[David Prosser]

If your consumer unit is upstairs where is your meter and service head? It may be better to have your incoming supply split after the meter to switch fuses for each out building.

As noted earlier site visit by a competent electrician is needed but a few picture of your meter, your consumer unit and currant installation would be useful.

 

[ipf]

You want a qualified electrician in to begin with...not ultimately.

 

[Electwix]

I'll do it for £150

 

[DPG]

I'll do it for £150

From the lighting circuit?

 

[MrT4643]

Thanks for the replies. For clarification, the intention was to supply each of the small CU's individually from the CU in the extension, rather than daisy chain them all off each other.

Taking them all back to switchfuses at the meter would probably be a better option, but with the meter and main CU being upstairs, I want to avoid ripping the main part of the house apart again as its all decorated and floors laid. It was all recently rewired and renovated. (yes, it's certified before someone asks). The 10mm t+e was put in to supply the garage once built but we've since changed our plans a bit.

The workshop incidentally is not as elaborate as it may sound, its literally just a large shed with a bunch of woodworking tools and a convector heater that will be used when someones in there. Just a hobby workshop really.

I fully appreciate we need a visit from an electrician to properly plan everything, but as we are still in the process of deciding what to do and may change our plans yet, I didn't want to waste someone's time. Plenty of tradesmen have found it difficult over the last few months, and the last thing I want to do is get someone out to quote a 'maybe job'. Then get them out again because we've changed our plans.

Made sense to me to get a rough idea of what was possible, wait till we have fully planned everything out, got planning permission accepted for the extension, and built the outbuildings.

Not expecting a full spec from anyone, really just a rough idea of the best way to do it. I like a rough idea in my head of every stage of building work, otherwise, it sits on my mind all the time.

I'm not at the house at the moment to take any pictures, but the supply comes in overhead, so the meter is on the landing too. I'm pretty confident though that if any of the work involved ripping up floors and making a mess in the house, then my wife would not let me do anything anyway.

Thank you for the constructive responses though.

 

[pc1966]

If you can't sensibly replace the T&E run, and it is not definitely safe for no-RCD use (i.e. not less than 50mm from any wall surfaces, etc) then you are going to have selectivity issues anyway as feeding from a switch-fuse off the tails is not on.

But if the use-case is such that is acceptable then the basic plan is OK. I would still go for emergency lighting in the workshop though as it is not too expensive and shows the issue has been considered. You can get LED baton lights with it built in to replace florescents, etc, and it looks neat and professional.

 

[Dustydazzler]

I'll do it for £150

Rate per hour...???