Distribution circuits in Section 705 location, RCD needed?

[timhoward]

Thanks @loz2754.

Out of academic interest, you are right about the reason. Having just read the 16th edition equivalent section it's basically the result of simplifying many very complicated regs about EEBADS, protection from indirect contact to exposed conductive parts, and requiring reduced disconnection times. (Interestingly distribution circuits were in fact excepted back then).
Requiring absolutely everything to be RCD protected in this context makes a little more sense.
--

The thing now occupying my brain is "what if D was fenced off".
The supply circuit and circuits to house and camp site become out of scope.
But the distribution circuits going into the field serving points in the field still need 300ma RCD protection.

In some ways sticking a 300ma RCD at source of it all would put this issue to bed, but would also mess up loop testing for evermore for lots of things! I'm there again tomorrow and will have a think.

 

[7029 dave]

@timhoward Give your CPS assessor a call and run it past him, would be interesting to see what his opinion/ thoughts are.

 

[mainline]

Yes.
Quick sketch:
View attachment 117323
Distro cabinet D has no outlets, it's a metal distribution panel within an IP rated box mounted within a timber 'bus shelter' style structure.
Enduring question is whether D being inside the field mean outgoing distribution circuits need 300ma RCD protection.

Other concerns exist about Sockets A being low and accessible to animals. They are at least all RCD protected and TT'd.
Rotary Isolators are also accessible to animals which is specifically mentioned in another reg.
So there are definite issues there.

Sockets B are much higher up, well out of reach of sheep, but are 2 x 32A sockets and 1 x 63 amp, and they are all 300ma integral RCDs, so that is another problem.

I believe the panel within an IP rated cabinet is sufficient protection.

The pragmatic side of me says that if the cable is deep enough, the only difference between it being there and not being there are the short sections between ground and panel, and if they were adequately mechanically protected then I can't see any benefit to RCD protecting it. As I've said before, I think fire protection inside a building is the intent of the reg.

Is the Tncs taken to the cabinet and divorced from there or is the Tncs taken to the other dbs and TT from there.

 

[timhoward]

Is the Tncs taken to the cabinet and divorced from there or is the Tncs taken to the other dbs and TT from there.

SWA is TNCS, isolated at point of entry to other cabinets, then TT.
So no requirement for RCD for fault protection of cable if that is what you were getting at!

 

[loz2754]

SWA is TNCS, isolated at point of entry to other cabinets, then TT.
So no requirement for RCD for fault protection of cable if that is what you were getting at!

And in any case, 705.411.1 requires RCDs for all circuits "whatever the type of earthing system".

 

[mainline]

And in any case, 705.411.1 requires RCDs for all circuits "whatever the type of earthing system".

I don’t believe 705 would apply to a distribution cabinet that has no extraneous, no outlets and is inaccessible to animals

 

[timhoward]

I don’t believe 705 would apply to a distribution cabinet that has no extraneous, no outlets and is inaccessible to animals

I'll take some photo's tomorrow or maybe tonight as I've been dragged there for other reasons.

If we decide the cabinet is 'inaccessible' to animals, and the cables underground are, well, underground, it remains the case that there are distribution circuits supplying points in the field that are not RCD protected.

 

[timhoward]

Ok photos.
The distro box D


The more concerning hook up point (the mobile units go before the sheep arrive)

 

[loz2754]

1. The requirements for protection against electric shock apply to agricultural or horticultural premises, indoor or outdoor, irrespective of the presence or otherwise of livestock.

2. A distribution cabinet/enclosure is itself included in the definition of electrical equipment, and if it is accessible to livestock, further measures need to be introduced to prevent the livestock interfering with the equipment. (Build a fence around it for example).

 

[mainline]

1. The requirements for protection against electric shock apply to agricultural or horticultural premises, indoor or outdoor, irrespective of the presence or otherwise of livestock.

In locations intended for livestock,

If there is no intention of having livestock, then I'm pretty sure the risk is quite low.

 

[mainline]

Ok photos.
The distro box D
View attachment 117330

The more concerning hook up point (the mobile units go before the sheep arrive)

View attachment 117329

Solar panels that are in fields that have livestock are fenced.

If horses are going to be there, then adding an electric fence could be an option.

 

[timhoward]

Let's not get into a debate about whether 705 applies, for me that is without question as for at least 4 months of a year there are sheep in that there field!

Here is where I am at:

That locked cabinet is the outer cabinet. Inside is a further metal distribution panel with a locked door. It could easily have a fence around it. A fence around it could take it completely out of the special location.

If a lockable front and back panel was made for the hookup points, we then have a distribution box outside the special location, a reasonably sheep-proof box, and every outlet 30ma RCD protected.

Given the history of the reg and taking into consideration the use of the field and the livestock concerned, I'm not considering that it's a C2 that the inaccessible underground cable between the two doesn't have RCD protection. I've asked how deep it was laid and been told 1.2m.
I'll sleep on it but at the moment it's going to be a C3.

If anyone thinks I'm underplaying any risks then let's talk about it; I do very much value the collective wisdom of you lot!

 

[7029 dave]

If it were me would fit a 300ma RCD at source. Then at the end of the day you have met the requirements of 705.

 

[timhoward]

If it were me would fit a 300ma RCD at source. Then at the end of the day you have met the requirements of 705.

So far every C3 I've issued has been actioned, so it could well still happen.
I'm intending to C2 the livestock access to distribution panel /cables and access to hookups as I consider them more potentially dangerous.
But before deciding on the remedy I need to declare how dangerous a cable 1.2m underneath some sheep without RCD protection is. I'm open to my opinion being swayed by reasoning.
To provoke thinking - if it turned out (as I have no idea) that the supply to the house ran under the same field, would that be potentially dangerous?

 

[brianmoooore]

Regulations notwithstanding, the only thing in those pics that is likely to be affected by sheep is the trailing flexibles on the ground from the hook up points.
In another life, I have shorn sheep, played midwife to sheep, de-tailed (and other things) sheep, performed chiropodist services on sheep, fed sheep and housed sheep. Hundreds of them. I know how sheep behave, and the only thing they'd do to those cables on the ground is to trample them.