Plastic Switchgear Enclosures - Acceptable in barn?

[SparkyChick]

Hi all,

I've tried to find the answer to this question, but I've drawn a blank.

Situation... location is a barn, attached to a domestic property. This will be a sub-board supplied in T+E from the main board in the house.

The question is... is a plastic board acceptable or should it be metal?

My interpretation of the regs is no, plastic is not acceptable because it's attached to the house.

Comments and thoughts?

 

[WillWX]

Same interpretation as you.

If it was me personally, I'd go metal as it's attached to a house/dwelling.

 

[SparkyChick]

The plan is a small plastic enclosure in an IP rated box, to provide some additional mechanical protection and weatherproofing. The barn has some large openings and some daylight through the roof

But, just trying to ensure I'm complying whilst not spending too much of the clients money

 

[bcm_spark]

How about a metal ip rated enclosure with a din rail etc. No need for 2 boxes and if the worst did happen it wouldn't catch fire and destroy the barn

 

[SparkyChick]

How about a metal ip rated enclosure with a din rail etc. No need for 2 boxes and if the worst did happen it wouldn't catch fire and destroy the barn

If it was an industrial/commercial setting, I could be tempted, but it's basically a domestic setting (a small holding effectively) so I'm reluctant to go down that route due to the exposed live metalwork that would be present. If I use a small CU at least all of the live stuff can be contained.

 

[bcm_spark]

So long as it's not at risk of damage I suppose that would be ok. I know what you mean about containing live parts in the cu. If someone opens the metal box they could potentially touch anything in there that is live.

I wouldn't worry about potentially exposed live metal work, a good earth should sort out that problem.

 

[Ian1981]

You can use a plastic cu contained within a non combustible enclosure

 

[SparkyChick]

You can use a plastic cu contained within a non combustible enclosure

Thats the plan

 

[Ian1981]

Thats the plan

I wasn’t sure if by ip enclosure you meant plastic.
I should have known better tho

 

[bcm_spark]

You can but I'd still be concerned about damage. Especially from those nasty little rodents that like to chew through everything. If there is food about it's hard to keep the rats away. I've seen cables that have been chewed through by rats before

 

[WillWX]

Is the price difference between plastic/metal CU fairly substantial? I haven't looked at plastic for a while.

 

[SparkyChick]

The plastic CU is going in a steel IP68 enclosure which will be mounted at head height (roughly). The cables will all be SWA. Conduit makes it prohibitively expensive. There was evidence of one cable being chewed through by a rat, but that was at ground level. Within the barn itself, I saw no evidence of any rodent damage to any of the existing installation (now decommissioned and in a sorry state) which was wired in T+E.

Since I've no chance of getting a suitably sized bond through (the T+E that will supply is already in place and looks to be in good nick), I'll be TT'ing, with a 10mm bond running with the SWA that goes through to a separate shed. This will be buried, and protected where it runs down the walls.

The main driving force for my question is that metal weatherproof enclosures seem to stop at garage units which only have 3 circuits... this requires more. After that, if you want metal, they become prohibitively expensive... cheaper to whack a non-weatherproof board in a weatherproof box.

 

[suffolkspark]

I wouldnt be using a t/e submain in a barn that's open to the elements and our little furry friends! id stick an off the shelf metal board inside a plastic meter box

 

[SparkyChick]

If the supply cable was going to be installed, I'd agree with you, but it's not, it's already there so I'm just going to be using it.

Like the idea of the meter box though, good thought

 

[suffolkspark]

sori when I read your first post... "this will be a....." I assumed none of it was in yet

ive used a surface mount meter box before with a metal board inside, took the swa cables through compression glands in the meter box, then armoured glands into the dis board inside it... no creatures getting in there!

 

[Ian1981]

Can you install metal containment like galv trunking for the t&e supply?

 

[SparkyChick]

I'm in the process of putting final pricing together for the job and I've been giving it some thought... I'm going to cut a hole in the back of whatever enclosure I use and stick it over the cable entry into the barn... problem solved

 

[westward10]

How are you going to support the swa cables considering the entire area of the barn being an escape route.

 

[SparkyChick]

How are you going to support the swa cables considering the entire area of the barn being an escape route.

I'm planning on clipping the cables to the lights to the roof trusses (metal trusses, using clips designed for the purpose). They are the only cables that will go overhead in open space, the rest will be running along the walls, nothing going over doors. They'll be fixed to the walls with plastic cleats with some glav band on every other one.

 

[SparkyChick]

I wasn’t sure if by ip enclosure you meant plastic.
I should have known better tho

Sorry Ian, didn't really make that part clear originally. My bad

 

[bcm_spark]

Sounds to me like you're sorted

 

[SparkyChick]

sori when I read your first post... "this will be a....." I assumed none of it was in yet

ive used a surface mount meter box before with a metal board inside, took the swa cables through compression glands in the meter box, then armoured glands into the dis board inside it... no creatures getting in there!

That double glanding is what I was planning.

 

[westward10]

As the the board I would definitely choose metal and find a brickie who will knock up a small room to put it in.

 

[Richard Burns]

The main driving force for my question is that metal weatherproof enclosures seem to stop at garage units which only have 3 circuits... this requires more. After that, if you want metal, they become prohibitively expensive... cheaper to whack a non-weatherproof board in a weatherproof box.

According to GN4 the non combustible idiocy is applicable to inside domestic premises and their attached garages/outbuildings and those nearby, therefore I interpret this to mean that with an outbuilding attached or near the house non combustible containment inside the building would be required.

If the largest size consumer unit is 5 module then could you get two consumer units and stack/link them together with non combustible couplers of appropriate size and have a main switch and three circuits in one enclosure and the remaining circuits in the other enclosure whilst maintaining the CCC with link cables ?
It may be a bit of a contrivance but would be more familiar to a domestic user and possibly easier to install.

 

[SparkyChick]

According to GN4 the non combustible idiocy is applicable to inside domestic premises and their attached garages/outbuildings and those nearby, therefore I interpret this to mean that with an outbuilding attached or near the house non combustible containment inside the building would be required.

If the largest size consumer unit is 5 module then could you get two consumer units and stack/link them together with non combustible couplers of appropriate size and have a main switch and three circuits in one enclosure and the remaining circuits in the other enclosure whilst maintaining the CCC with link cables ?
It may be a bit of a contrivance but would be more familiar to a domestic user and possibly easier to install.

I did think about getting two BG garage units as they are 5 modules each. Put the main switch in one and the MCBs in another... unfortunately, but the time you add up the cost of the boards, a main switch and the hardware to join them (and the fact I'm trying to ensure all cables enter through the bottom panel of the CU) and you're costing more than sticking a metal CU inside a meter box.

Plus... as you suggest it's a bit of a contrivance and for me I think it would just look like a bodge job.

I'm pretty happy with the metal CU inside a standard surface mounted meter box. It's not a massive saving, but it cuts some of at least.

Thanks for the discussion guys, much appreciated

 

[Phil Thompson]

According to GN4 the non combustible idiocy is applicable to inside domestic premises and their attached garages/outbuildings and those nearby, therefore I interpret this to mean that with an outbuilding attached or near the house non combustible containment inside the building would be required.

If the largest size consumer unit is 5 module then could you get two consumer units and stack/link them together with non combustible couplers of appropriate size and have a main switch and three circuits in one enclosure and the remaining circuits in the other enclosure whilst maintaining the CCC with link cables ?
It may be a bit of a contrivance but would be more familiar to a domestic user and possibly easier to install.

2x BG shower boards are £80-90, you’ll have a spare BG RCD and 2 spare 50A MCB, they may switch for 8xMCB with ratings of your choosing.
Depends on wholesaler.

 

[The Ghost]

Why put it outside, just a thought you could install it in the house and take supply to outside.

 

[elsparko]

id go for metal for added protection against farmers and their equipment squashing all my nice install.