What sockets

[steviez]

Hi,

What sockets and fused spurs can be used in a large polytunnel (60 foot water tight green house) ? it currently has metal clad and they were installed by a professional electrician. Do they need to be weather proof?

Thanks

 

[ban-all-sheds]

 

[Steve]

Not sure on the actual rules, I'd be inclined to want weatherproof fittings. But it depends on what you do in the polytunnel - if theres water jets flying around at all, you should opt for weatherproof, but make sure its weatherproof with a plug in!

 

[steviez]

Not sure on the actual rules, I'd be inclined to want weatherproof fittings. But it depends on what you do in the polytunnel - if theres water jets flying around at all, you should opt for weatherproof, but make sure its weatherproof with a plug in!

There are no water jets about but it can get very humid!

 

[xr4x4]

I'd want waterproof, because of the damp and moisture.

I would of thought that the metal clad will rust.

 

[mfarrow]

I'd want waterproof, because of the damp and moisture.

Every time you open and close the lid you'll then trap that moisture inside it. If you plug in a cold plug from outside, water could condense on the pins which would then dip off on removal.

Go for plastic.

 

[bernardgreen]

If they are metal then the "earth" for them almost certainly has to come from a local ground rod. It cannot be supplied from the "earth" of a building "protected" by a PME supplied "earth".

IP 44 minimum plastic sockets would be preferable.

 

[securespark]

Here's a good thread on the PME argument.

//www.diynot.com/forums/viewtopic.php?p=937171#937171

 

[securespark]

Here's a good thread on the PME argument.

//www.diynot.com/forums/viewtopic.php?p=937171#937171[/QUOTE]

As far as I understand the situation, it hasn't changed. You can export PME providing there are no extraneous conductive parts. If there are, you can still export, but need to ensure either the CSA of the CPC is big enough to use as a bonding conductor or run a seperate one in.

 

[bernardgreen]

If it is exported and the equipotential zone is extended to include the polytunnel then the ground in the tunnel has to be bonded to the CPC as it could introduce an extraneous potential into the zone. The ground is far more likely to introduce a voltage than a plastic gas pipe which has to be bonded.

In reality if the neutral providing the PME earth bounces then anything "earthed" or bonded to the CPC in the polytunnel would present a shock hazard to someone standing on the ground.

 

[PrenticeBoyofDerry]

My experience of greenhouse are not only do they get humid, they can also be a lot muck and dust about.
I would take this in to consideration as well. I would also want something that was durable and had some mechanical resistance against damage.
Also it would be handy to have them switched, so you could still isolate the item of equipment that is plugged in, without having to remove the plug, reducing risk of the plug getting damaged after removal.
Something like these, would be ideal.
http://www.tlc-direct.co.uk/Products/SMTGV201.html

 

[steviez]

Thanks for all your input guys, Ive gone for some impact resistant water proof sockets.

 

[JohnW2]

As far as I understand the situation, it hasn't changed. You can export PME providing there are no extraneous conductive parts. If there are, you can still export, but need to ensure either the CSA of the CPC is big enough to use as a bonding conductor or run a seperate one in.

I'm sure people will be tiring of my views, but I really think that, if one has any interest in safety, one has to think broadly and consider wet soil as an extraneous-conductive-part. To my mind, it's ridiculous to get excited about a metal water pipe emerging from wet soil and provide that with adequate primary bonding in the belief that this will make the exported PME 'safe', whilst ignoring the hundreds of square feet of wet soil out of which that pipe is emerging!

I agree that the risks (of serious injury/death) are extremely small - but if it is nevertheless regarded (by regs) as necessary to main bond the water pipe in the interests of safety, it seems totally illogical to be allowed to ignore the soil!

If one accepts (as I presume we all do) that wet soil can conduct electricity, I then see no reason why it does nor count as an extraneous-conductive part, per the BS7671 definition.

Kind Regards, John.

 

[ban-all-sheds]

Do you ever/have you ever used metal bodied Class I portable appliances outdoors?

 

[JohnW2]

Do you ever/have you ever used metal bodied Class I portable appliances outdoors?

I'm sure I must have done in my time. I've certainly had touchable Class I outdoor metal light fittings.

But, there again, I've never had a TN-C-S supply, so the concerns I was discussing above have never really applied to me.

As I keep saying, even with TN-C-S, I think the risks of having unbonded paths to true earth in one's environment are so small that I could quite understand if the regs had decided to ignore them. However, that is definitely not what the regs have decided - and it's therefore the inconsistency of taking MPB of pipes very seriously, yet ignoring other potential paths to true earth that I find hard to understand.

Kind Regards, John