Shed submain SWA RCD protection

[TomSparkman]

Hi all,

Went to a house on friday due to sub-main to shed not energising. This was simply due to the MCB playing up. I flicked it on and off a few times and it works fine now.

However im not happy with the way the submain has been installed poorly.

The sub-main is in the form of a 3 core SWA. It isnt buried properly as i can see it in some places and the armour isnt earthed. Only the end at the shed D.B is made off using a gland and the supply end in the house is just coming through the wall in to a 4x4 box and in to the C.U on top.
The SWA is rcd protected in the house but the small 2 way D.B in the shed is not.
The shed has a few sockets and lights and i believe the customer intends to plug in a jacuzzi which will be inside the shed.

1. Does the SWA that runs outside have to be RCD protected?

2. Is it ok to have the RCD in the house, protecting both the sub-main and the circuits in the shed?

I advised the customer that the submain was potentially dangerous due to installation methods.
I also advised to fit IP sockets in the shed due to being in close proximity to the jacuzzi

 

[westward10]

If the swa has fault protection with the rcd removed then probably no. Is the armour not earthed at all.

 

[The Ghost]

That all sounds so wrong. The SWA made off at the garage end, wrong, should be the other end, assuming a TT arrangement at the garage. S type RCD for supply and RCD in the garage with TT arrangement. As for sockets anywhere close to a Jacuzzi, I don't think so. Seems like a recipe for a bad accident waiting to happen. You did not say what the supply is i.e. TNS or???

 

[davesparks]

How do you know that the mcb is fine now? How do you know that it is not damaged internally?

SWA need only be earthed at on end if not used as the cpc.

What's wrong with being able to see the SWA?

How can you say the DB in the shed is not RCD protected if the submain is RCD protected?

Without the necessary information I cannot say whether the SWA needs RCD protection or not, it may require it for fault protection is the efli is too high.

I don't think you are justified in telling the customer that this circuit is dangerous and though it appears to be through lack of knowledge it could be viewed as the bullying tactic of a cowboy.

 

[Leesparkykent]

By flicking the mcb on and off you may of blown the fault clear and potentially left it in a dangerous situation. The only time the Distribution circuit may need to be on an RCD is if the earthing arrangement is TT or if TN and can't meet disconnection times due to poor design. If the distribution circuit is on an RCD then there would be little point in putting the final circuits at the far end on another RCD as you are not going to achieve discrimination/selectivity. With regards to the earthing of the armour of the SWA it's ideal to do it at the front end but if it's earthed at the far end then it's not really an issue. With regards to the buried depth of the cable is it likely to be damaged?

 

[TomSparkman]

The supply to the house is TNCS. The SWA is fed from the C.U in the house, to the shed(no gland at this end).
It goes in to the shed after being lightly covered by soil on it journey across, and goes in to a proper gland but no banjo! So the armour braiding is not earthed.

 

[davesparks]

The supply to the house is TNCS. The SWA is fed from the C.U in the house, to the shed(no gland at this end).
It goes in to the shed after being lightly covered by soil on it journey across, and goes in to a proper gland but no banjo! So the armour braiding is not earthed.

A banjo is not the only possible means of connecting to an SWA gland.

If it has braiding then it is not regular SWA.

 

[bigspark17]

Are you an electrician? not sure how you can give paying customers this advise and then ask on here you cant be sure so why advise customer its dangerous?!
flicking an mcb on a few times is not a proper fault finding process, testing the submain first would have been a better approach.

 

[TomSparkman]

How do you know that the mcb is fine now? How do you know that it is not damaged internally?

SWA need only be earthed at on end if not used as the cpc.

What's wrong with being able to see the SWA?

How can you say the DB in the shed is not RCD protected if the submain is RCD protected?

Without the necessary information I cannot say whether the SWA needs RCD protection or not, it may require it for fault protection is the efli is too high.

I don't think you are justified in telling the customer that this circuit is dangerous and though it appears to be through lack of knowledge it could be viewed as the bullying tactic of a cowboy.

I havent "blown the fault clear". I know this as i removed the MCB before flicking it a few times.

 

[TomSparkman]

A banjo is not the only possible means of connecting to an SWA gland.

If it has braiding then it is not regular SWA.

How else would you propose to earth the armouring if at both ends the D.B/4x4 box are plastic???

I also performed insulation resistance tests on both circuits withing the shed and the SWA sub-main which came up clear. Sufficient Zs reading from all circuits also.

 

[Deleted member 9648]

I note you have given advise on the sockets 'in close proximity' to the Jacuzzi.
Are you aware of the actual requirements for the siting of sockets in such a situation? Does the siting of the sockets meet the requirements?

 

[Leesparkykent]

How else would you propose to earth the armouring if at both ends the D.B/4x4 box are plastic???

I also performed insulation resistance tests on both circuits withing the shed and the SWA sub-main which came up clear. Sufficient Zs reading from all circuits also.

piranha nut.

 

[davesparks]

How else would you propose to earth the armouring if at both ends the D.B/4x4 box are plastic???

I also performed insulation resistance tests on both circuits withing the shed and the SWA sub-main which came up clear. Sufficient Zs reading from all circuits also.

I use earthing nuts on SWA glands

 

[Deleted member 9648]

How else would you propose to earth the armouring if at both ends the D.B/4x4 box are plastic???

I also performed insulation resistance tests on both circuits withing the shed and the SWA sub-main which came up clear. Sufficient Zs reading from all circuits also.

Wiska supply a twin earthing plate for their boxes....much easier than effing about with a banjo.

 

[TomSparkman]

There is no jacuzzi yet, but he said he wants to put one in there. Its 3.5 metres from the edge of the jacuzzi as it is above ground level, also must me 30ma rcd protected

 

[davesparks]

There is no jacuzzi yet, but he said he wants to put one in there. Its 3.5 metres from the edge of the jacuzzi as it is above ground level, also must me 30ma rcd protected

From your description RCD protection is already in place, so that's not a problem.

Why 3.5m?

 

[westward10]

As it stands everything is rcd protected, have you confirmed earth continuity to the armour.

 

[ED17]

What load is the Jacuzzi he's thinking of putting in?

 

[TomSparkman]

What load is the Jacuzzi he's thinking of putting in?

Its about 8 amp. (On a plug top)
Reading the regs, would you class it as a swimming pool, an basin above ground, or a bath? As there is nothing specific to a jacuzzi

 

[telectrix]

bath