Mains power from house to pier

[souls33k3r]

Hi All, 

From my other thread I gathered that I really should have a mains power from inside my house to the pier (about 15m).

The purpose of this would be firstly to power the kit at the pier and secondly to power some sort of moisture control gizmo.

Currently what i do is, I reel out my 10m cable (RCD connected inside the house) and then daisy chain another extension to give me necessary power sockets and length. I would like to eliminate this altogether for the reasons I mentioned above and also with something that will last forever. 

The idea is to have long enough cable, RCD at one end which will be in the house, weatherproof power cable and at the pier end will be a weatherproof socket powering my astro gear. 

My knowledge around electronics and anything electrical is next to nothing so any advice on the cables and type would be appreciated. What I saw on wickes were these and I'm not sure if any of these will be fit for purpose

https://www.screwfix.com/p/nexans-pond-flex-3183p-3-core-0-75mm-25m-black/169fk

https://www.screwfix.com/p/nexans-3183yag-arctic-flex-3-core-25m-ylw/773gp

Thanks in advance.

[wxsatuser]

Is your pier metal and part of earth?

[souls33k3r]

2 minutes ago, wxsatuser said:

Is your pier metal and part of earth?

Yes it's metal but it's not part of the early. It is bolted on 4 x M16 bolts

[wxsatuser]

That may be classed as an extraneous conductive part.
If so you will need to bond it and depending on your supply you will at least need a 6mm and may be a 10mm bonding.
So the wandering leads earth wire will not be big enough.

Edited February 9, 2020 by wxsatuser

[Saganite]

Following on from you original thread which I contributed to, I finished the area by screening the pier with trellis to ' camouflage' the area and make it acceptable to my wife, and ran an armoured cable along the top of the garden, around the edges until I reached the stone slabs, at which point I passed it underneath through a steel tube, to a weatherproof 2 socket box. From memory I think it was 6mm armoured cable. It was not expensive. My EQ6  mount simply plugs in when I run it.

[wxsatuser]

Needs bonding 6mm minimum on a TN-S or 10mm on a TN-C-S system, preferably 10mm anyway.

[Saganite]

20 minutes ago, Saganite said:

Following on from you original thread which I contributed to, I finished the area by screening the pier with trellis to ' camouflage' the area and make it acceptable to my wife, and ran an armoured cable along the top of the garden, around the edges until I reached the stone slabs, at which point I passed it underneath through a steel tube, to a weatherproof 2 socket box. From memory I think it was 6mm armoured cable. It was not expensive. My EQ6  mount simply plugs in when I run it.

I should make it clear that whilst I did all the ground work and laid the cable chosen by an electrician, it was he who did all the connecting.  Like you souls33k3r I would not dabble with things II know nothing about.

It was definitely worth making the permanent connection to mains though.

[souls33k3r]

1 hour ago, wxsatuser said:

Needs bonding 6mm minimum on a TN-S or 10mm on a TN-C-S system, preferably 10mm anyway.

You absolutely lost me there mate. I have no idea what those terminologies actual mean

1 hour ago, Saganite said:

I should make it clear that whilst I did all the ground work and laid the cable chosen by an electrician, it was he who did all the connecting.  Like you souls33k3r I would not dabble with things II know nothing about.

It was definitely worth making the permanent connection to mains though.

Appreciate you chipping in mate. Do you remember what cable and where did you buy it from? 

[daz]

I think wxsatuser means you need to run a separate green/yellow earthing wire from the main earthing block (in the distribution board in your house) to the pier itself. This is separate and different to the earthing cable in the armoured cable that you'll install. And again, I think this is because you are using a metal pier and have attached your sockets to the pier.

This separate cable should be 10mm in diameter.

 

Of course, you should check with a qualified electrician to confirm!

[souls33k3r]

Ah ok, makes sense. Time to get in the sparky then. Cheers guys. 

[Paul M]

How complicated would you like it to be?

As wxsatuser says above, you can just put a cable in using an appropriate installation method (more woe!) bond it and in all reality that'll be fine! (that's what I'd do at home). But..

Many or most network operators don't allow you to export their PME (TNCs) earth and if that is your earth arrangement, it's possible for the main earth terminal (MET) to have a potential relative to true earth under normal but high loads or fault conditions. That potential can be sufficient to cause shock or electrocution. A metal post bolted to buried concrete should be considered to be at true earth potential and the risk is that metalwork on your circuit is at different potential to the pier. The recommended method is to export a TT supply ( effectively earth free though if an armored cable is used that should be earthed at the origin but left insulated at the extremity) and bang an earth rod in at the extremity of the circuit.

If your supply is already TT (quite common in rural area down south, rare as parrots teeth here) then you need to bang an earth rod in at the pier end and put in a 10mm main bond.

If it's a TNS supply your MET should already be at true earth potential. But I'd still put a chunky main bond in there.

In all cases an RCD is required. Not just built into the external sockets but at the origin to protect against damage to the cable.

[souls33k3r]

This all sounds super complicated tbh. I appreciate all the input and suggestions but I thought this was going to be a simple job and by the sounds of it, this clearly isn't 🤦‍♂️ 

[JamesF]

Basically, you need an earth at the pier.  The easiest way to do that is probably to take one out there that's connected to the house earth.  To work properly it needs to be of sufficiently low resistance, which isn't really the case with a normal cable reel.  The figures wxsatuser gave are the minimum cross sections for the conductors to give a suitable resistance.  So, what you'd probably be looking at is a 3-core (live/neutral/earth) SWA (steel wire armoured) cable with a minimum conductor size of 6sqmm.  You can bury that in the ground and forget about it, but it's probably not going to be a bundle of fun to work with.  I'd guess 25m is going to cost you in the region of £100, weighs around 15kg and has a mind of its own when you try to uncoil it.  For 10sqmm it's probably half as much again, both cost and weight.

If you got a sparky in to do it I'd not be surprised if their preference was to take a separate feed from the consumer unit for it, which might not be very convenient depending on how the cable might need to be routed and can be a pain if you don't have enough space left in the consumer unit.  Probably the only way to find out is to get someone out to give you a quote.

You may well decide that it's a world less pain to invest in a single decent, long extension lead to be honest.

James

[JamesF]

1 minute ago, souls33k3r said:

This all sounds super complicated tbh. I appreciate all the input and suggestions but I thought this was going to be a simple job and by the sounds of it, this clearly isn't 🤦‍♂️ 

It's kind of a simple job, but the regulations significantly limit the ways it can be done legally.

James

[souls33k3r]

2 minutes ago, JamesF said:

Basically, you need an earth at the pier.  The easiest way to do that is probably to take one out there that's connected to the house earth.  To work properly it needs to be of sufficiently low resistance, which isn't really the case with a normal cable reel.  The figures wxsatuser gave are the minimum cross sections for the conductors to give a suitable resistance.  So, what you'd probably be looking at is a 3-core (live/neutral/earth) SWA (steel wire armoured) cable with a minimum conductor size of 6sqmm.  You can bury that in the ground and forget about it, but it's probably not going to be a bundle of fun to work with.  I'd guess 25m is going to cost you in the region of £100, weighs around 15kg and has a mind of its own when you try to uncoil it.  For 10sqmm it's probably half as much again, both cost and weight.

If you got a sparky in to do it I'd not be surprised if their preference was to take a separate feed from the consumer unit for it, which might not be very convenient depending on how the cable might need to be routed and can be a pain if you don't have enough space left in the consumer unit.  Probably the only way to find out is to get someone out to give you a quote.

You may well decide that it's a world less pain to invest in a single decent, long extension lead to be honest.

James

I supposed buying a long extension cable sounds far more easier but how would they react to being outside throughout the year? I thought it would've been a simple case of buying a cable, attach a 3 pin plug at one end which will go in to an RCD plugged inside the house, wire up a weatherproof socket and I'll be all done. 

Most of the stuff that is being talked about has gone way over my head

[JamesF]

7 minutes ago, Paul M said:

If your supply is already TT (quite common in rural area down south, rare as parrots teeth here) then you need to bang an earth rod in at the pier end and put in a 10mm main bond.

These days I think you have to not only bang in an earth rod, but ensure that the impedance to earth is sufficiently low, which means you need to be able to measure it properly and potentially bang in several earth rods joined together to get that far.

James

[Paul M]

2 minutes ago, JamesF said:

These days I think you have to not only bang in an earth rod, but ensure that the impedance to earth is sufficiently low, which means you need to be able to measure it properly and potentially bang in several earth rods joined together to get that far.

James

It used to be 21 ohms I think but once RCD's were promoted from "supplementary" protection to primary protection it allowed touch voltages up to 50v thereby, through the back door a rod impedance of 1666 ohms !!   -  50v (max touch voltage on exposed conductive part) / 30mA (operating current of the RCD) = 1666.000 ohms!

Might have changed again in the 18th though but they kinda gave up on 21 ohms because it was almost impossible to (a) achieve and (b) guarantee to stay like that!

[david_taurus83]

Why not just run a 12v supply outside? I have a Nevada 12v supply indoors and I run out a 15m cable, the yellow ones used on building sites with the 110v plugs (stays flexible even when cold). I cut the plugs off and I use 2 of the cores. Banana plugs on the supply side and a multi cigar socket on the outside? Simple, safe and doesnt need the skills of an electrician.

[JamesF]

2 minutes ago, souls33k3r said:

I supposed buying a long extension cable sounds far more easier but how would they react to being outside throughout the year? I thought it would've been a simple case of buying a cable, attach a 3 pin plug at one end which will go in to an RCD plugged inside the house, wire up a weatherproof socket and I'll be all done.

Well, yes, you could probably do something like that, but you'd almost certainly have to do it yourself and it's unlikely to be as safe as doing it properly in the event of an electrical fault (always more of a possibility when stuff is exposed to the elements).

If you get an electrician in to do it they'll obviously have to comply with the relevant regulations.  If you do it yourself you can play fast and loose with what's acceptable, but you can create something that may be dangerous in the event of a fault.  If it's not a permanent connection then you probably have a bit more freedom as to what's acceptable, but you still don't really want to go wiring up something that could become live in the event of a fault (ie your pier).  If electrics isn't your bag, then DIY isn't really a good game to play.

James

[souls33k3r]

15 minutes ago, david_taurus83 said:

Why not just run a 12v supply outside? I have a Nevada 12v supply indoors and I run out a 15m cable, the yellow ones used on building sites with the 110v plugs (stays flexible even when cold). I cut the plugs off and I use 2 of the cores. Banana plugs on the supply side and a multi cigar socket on the outside? Simple, safe and doesnt need the skills of an electrician.

I do have a linear PSU that runs all my gear outside (apart from the laptop). What I want to achieve with this topic was to have a permanent power cable to the pier (rather than having to reel out the extension and then bring it back indoors every time). A double socket at the pier end from which I will constantly use one of the sockets to power a pet bed to keep the moisture out when the mount is under covers and when I'm imaging, I'll just simply plug the PSU and run my gear off of that. Mind you, the end that is coming from the house will have an RCD attached to it all the time. 

18 minutes ago, JamesF said:

Well, yes, you could probably do something like that, but you'd almost certainly have to do it yourself and it's unlikely to be as safe as doing it properly in the event of an electrical fault (always more of a possibility when stuff is exposed to the elements).

If you get an electrician in to do it they'll obviously have to comply with the relevant regulations.  If you do it yourself you can play fast and loose with what's acceptable, but you can create something that may be dangerous in the event of a fault.  If it's not a permanent connection then you probably have a bit more freedom as to what's acceptable, but you still don't really want to go wiring up something that could become live in the event of a fault (ie your pier).  If electrics isn't your bag, then DIY isn't really a good game to play.

James

I really don't get it tbh, isn't this supposed to be a simple job of just making my own  (cut to length) extension sort using a rugged power cable? 

[Paul M]

For the record, I exported PME many times professionally and have never seen a domestic TT installation locally. NICEIC never minded.

The strengths of PME far outweighed the esoteric benefits of TT in most electricians minds (without RCD's you'd never, pardon the pun, touch it).

Suppliers don't like you exporting their earth because they are quite bad at maintaining them. As the infrastructure continues to crumble it's not unusual to find an older domestic installation with no earth! I used to phone them and they'd come and dig the road up and reinstate the earth- very, very expensive for them. But there are many stories out there now of suppliers claiming they aren't required to supply an earth, it's the customers responsibility, bang an earth rod in they say!

Well, maybe they are trying it on, their own regulations ESQCR, don't require them to supply an earth connection but they are required to maintain an existing one.

 

[ian_bird]

There is a lot easier way to do all of this. It has worked for me for the past 15 years.

[souls33k3r]

16 minutes ago, ian_bird said:

There is a lot easier way to do all of this. It has worked for me for the past 15 years.

Which is what Ian? I like easy

[WanderingEye]

1 hour ago, souls33k3r said:

I supposed buying a long extension cable sounds far more easier but how would they react to being outside throughout the year? I thought it would've been a simple case of buying a cable, attach a 3 pin plug at one end which will go in to an RCD plugged inside the house, wire up a weatherproof socket and I'll be all done. 

Most of the stuff that is being talked about has gone way over my head

Yes that’s all you need to do, make sure you have waterproof outdoor rated sockets at the pier, and an RCD on the other end, unless like me all the switches on your fuse board are RCBO’s in which case then it’s already RCD protected.... dont over complicate it for yourself, Just make sure it’s safe... 👍😀

[souls33k3r]

23 minutes ago, WanderingEye said:

Yes that’s all you need to do, make sure you have waterproof outdoor rated sockets at the pier, and an RCD on the other end, unless like me all the switches on your fuse board are RCBO’s in which case then it’s already RCD protected.... dont over complicate it for yourself, Just make sure it’s safe... 👍😀

Yeah that's exactly what I thought I'd need but all these super technical stuff has got me even more confused than I started this topic 🤣

I already have an RCD and use that regularly. 

The sockets that I've been looking at are

Just wanted to be sure of the cable really. 

Like I said before, I thought all what I'll need to do is plug in the RCD in to the wall socket in my house, get this outdoor cable and extend it all the way to the pier and on the pier will have the above waterproof socket and that's it.