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Topic Title: garden lighting
Topic Summary: wiring method
Created On: 16 October 2012 01:11 PM
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 16 October 2012 01:11 PM
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leckie

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Hi all

Have a customer that wants some garden spike lights fitting. They have got the fittings, which are class 1 GU10 fittings with 2m of hard flex fitted.

The problem is there is no way to bury an swa as the planting etc does not allow for this. The garden has a hedge dividing it from the adjoining property. Could I lay an swa directly on to of the soil along the property boundry? I would have to go into an IP adaptable box, filled with magic gel, at each point that a spot light was required in order to connect the flex from the fitting.

My concerns are
1) Would the method be allowed due to a possibility of the cable being moved which could cause strain to the cable gland - not likely as it would be out of the way, but possible.
2) the flex from the fitting is pre-wired and sealed, a flex sitting on top of the soil could be subject to mechanical damage. If I over-sleeve with flexible conduit it would look unsightly.

Any thoughts appreciated before i commit to carrying out the works

i am concer
 16 October 2012 01:28 PM
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daveparry1

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I have often laid the swa on the surface along the edge of the garden much as you're suggesting, the adaptable boxes I usualy mount on low posts and cleat the swa to them to help avoid strain on the glands. I have shown jobs such as this on my annual niceic inspections and have never been criticised for it. I also usually put a few bands of hi-vis tape along the length of the cable.
The flex from lamps I always find more of an issue, I usualy get the client to agree to have the lamp positioned as close to the adaptable box as possible and then feed the flex through a length of black flexible conduit just to give a bit more protection, if this is just laying on soil it doesn't look too unsightly, they can always put plants etc. next to it to take the eye away from the cable,

Dave.
 16 October 2012 02:03 PM
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leckie

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thanks for that Dave, good idea with the posts, I'll follow that advice.
 26 November 2012 09:03 AM
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Aalia123

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thanks

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<a name="Link removed/">junction boxes electrical</a>
 26 November 2012 09:48 AM
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zeeper

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Its not PME supply then , what with those class one fittings.
 26 November 2012 11:47 AM
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leckie

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The earthing system was not mentioned - what do you mean exactly?
 26 November 2012 12:27 PM
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Parsley

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If the earthing is TNC-S PME you need to consider if you should export it into the garden where true earth will be present. You may get a tingle in normal use between the class 1 fittings and damp true earth and something nastier if the PEN supply neutral is ever lost.

Regards
 26 November 2012 12:40 PM
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leckie

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I knew that was what the reasoning was, it always amazes me though.

There are thousands of class 1 fittings on TN-C-S all over the country including light columns, bollards, etc. Are they all converted to TT? Not a chance.

I asked the NICEIC tech line and the ECA tech services some time ago, and both said it was not normally an issue.

Ive never heard of anyone getting a belt off a bollard, etc.

If you change a lamp on on external wall mounted light whilst standing in a flower bed are you likely to get a shock? Should we ban class 1 lanterns?
 26 November 2012 12:56 PM
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zeeper

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Most people like to play it safe, do the owners have children or pets. Surely class 2 fittings woujld be a better solution.
 26 November 2012 01:07 PM
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leckie

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Not if the client wants the stainless steel spike fittings that they have already bought. This is an older thread and the job is done, as it happens it actually was a TT system but if it wasn't I would not have been too concerned for the reasons I gave. I think a spike in the ground or a column or bollard in the ground would do a pretty good job of reducing any PD's but I'm sure others would think otherwise.

Has anyone ever heard of anyone getting a shock from this situation? I haven't but then I am very young
 26 November 2012 01:07 PM
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daveparry1

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It's only worth worrying about this if there's something like a buried metal water pipe or other etraneous conductive part nearby, the conductivity of surface earth even if damp isn't very good so no need to worry I think,

Dave.
 26 November 2012 01:19 PM
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Parsley

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Leckie

I never said it was against the regs, all I said was you need to consider what could happen. Thats why the DNO's leave a nice sticker own their cut out reminding you it's your responsibility to determine whether the use of their PME earth is suitable for the installation. It's also why UKPN earthing manual recommends TT for external vehicle charging points and insulating inserts are fitted to outside water taps.

As you mention generally there won't be any problems; but if you're the designer you might want to cover your *****.

Regards
 26 November 2012 01:26 PM
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leckie

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I here what you are saying Parsley its just that in 40 years Ive never heard of an incident occuring - but Im sure someone has.

I have read Oms say about earth staking columns at the end of a run and at every 3rd column.
 26 November 2012 11:20 PM
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Legh

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The problem is there is no way to bury an swa as the planting etc does not allow for this. The garden has a hedge dividing it from the adjoining property. Could I lay an swa directly on to of the soil along the property boundry? I would have to go into an IP adaptable box, filled with magic gel, at each point that a spot light was required in order to connect the flex from the fitting.


IMO I would run the SWA out of the way of any garden cutting implements. Don't bury it unless you can get the cable down to two spade depth.
Use something like IP68 wiska boxes mounted on low stakes....and don't fill them with magic gel because you will not be able to maintain and check them periodically and believe me you will at some point need to maintain the joints which is more or less impossible once the gel is in place.

However, If you use Gwiss type boxes filled with gel and full SWA glands then you've got about 5 years, the moisture gets in, the glands rust, moisture somehow migrates into the connections where they fail. That is low IR and intermittent MCB/RCD tripping.

I hope that is some use....

Legh

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 27 November 2012 04:13 AM
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leckie

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Why would you not be able to maintain it? Magic gel doesn't set hard so you could pull it out and replace it. The new gel they make is also reusable. And I don't think brass cw glands will rust. I did it with wiska boxes, used the wiska earth bar, and filled up with gel. All mounted on a short oak post. I think it will out last me.
 27 November 2012 09:26 AM
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AJJewsbury

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It's only worth worrying about this if there's something like a buried metal water pipe or other etraneous conductive part nearby, the conductivity of surface earth even if damp isn't very good so no need to worry I think,

I my mis-spent youth, I've certainly had a belt while standing on a fairly dry solid concrete floor - I doubt that damp soil would offer a significantly higher resistance. Presumably those that wrote the PME regs for caravans didn't seem to think that grass would offer a non-conducting location either.
- Andy.
 27 November 2012 09:30 AM
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daveparry1

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Did you have bare feet at the time Andy?

Dave.
 27 November 2012 09:51 AM
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AJJewsbury

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Did you have bare feet at the time Andy?

I did - as kids often do in gardens in summer.
- Andy.
 27 November 2012 11:35 AM
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leckie

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Andy, are you saying you got a shock from touching a conductive part of external equipment that was correctly connected to a pme system?
 27 November 2012 12:20 PM
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AJJewsbury

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Andy, are you saying you got a shock from touching a conductive part of external equipment that was correctly connected to a pme system?

No - it was actually a little experiment with a 9v battery and a triac trying to switch a mains light using an open frame switch (scavenged from and old electric fire) and a bit of string stretched across a doorway. I figured the dodgy switch arrangement would be safe as it was only 9V - I hadn't reckoned on the mains voltage leaking across the triac... (I was about 14 at the time).

The point being that PME earth, under open CNE fault conditions, can be around 230V above local earth - outdoors on damp soil it feels no less risky than my experience.

- Andy.
IET » Wiring and the regulations » garden lighting

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