Burying Galvanised Steel Conduit

[Darkwood]

BS7671 stopped using the term equipotential zone when the 17th Edition came out.

My bad, just going back on how I was taught but it essentially is the same answer just referred to differently, the PME stops at the cutout and is no longer classed as PME on the consumer side so you are not exporting it as commonly expressed by many.

Lets call it zone of protection ... seems even the term equipotential zone was ambiguous to some hence it was dropped to which I forgot

 

[Pat Tester]

I prefer mercury-filled sausage casings, but SWA would do.

3

 

[Deleted member 26818]

Having a combined neutral and earth does not necessarily equate to PME.
PME is Protective Multiple Earthing and can apply to TN-S.

 

[Darkwood]

Never implied it did @spinlondon but the term exporting PME was used to which I commented on, unless you were just making a general point regarding combined N/E and not reflecting on my post then I absolutely agree ☺

 

[bailes1992]

The O.P posts on LOTS of other forums, usually car related.
He's,,, unusual in his approach to things sometimes

Agreed! However, this isn't particularly straight forward.

I should have probably put more detail into my initial post.

I'm currently in the middle of purchasing a new house. It's a 3 year old 4bed detached with a separate garage. Earthing system is PME/TNC-S and there's no bonding required in the outbuilding(s) concerned.

Ideally I'd have bought something older and gutted it myself and made it how I want it but my Wife is pregnant so I don't have that luxury.

I'm also maxing myself out on the mortgage of this out on the basis that it's only going to get easier.

I plan on making the current garage into a small workshop and the current 20A supply isn't going to work for me. Therefore I need to do what I can with what I have. And what I have is quite a lot of galvanised conduit & trunking along with 6491B.

My plan is to have a 6A circuit for lighting, a 16A circuit for heating and a 32A circuit for power all fed from individual RCBO's in the house consumer unit.

I also need to get data out there. Ideally a fibre or at least a shielded Cat5e/6.

I don't intend on doing anything dangerous. There is absolutely nothing wrong with using well constructed metal containment as a CPC. I personally find the installation of CPC conductors in a metal containment system where they are not required totally wasteful and makes for sloppy containment installation.

The issue here is ensuring the conduit underground will last. I have an old Land Rover Defender so I have all sorts of primers, paint and underseal about. Weirdly I also have a 100m roll of 32mm 2:1 heat shrink which would be ideal to cover a 25mm conduit.

This isn't going in for at least another 6 months. Maybe it's worth prepping a small off cut of conduit and burying it underground and seeing how it holds up?

I'll also be putting up a shed in the back garden for the lawn mower, bikes, strimmer etc and will be planning on putting a light and a socket out there using the same method.

 

[Octopus]

Covering steel conduit isn't going to stop it rusting. 6 months is not long enough to test it..........

You can lead a horse to water ..................

 

[bailes1992]

Covering steel conduit isn't going to stop it rusting. 6 months is not long enough to test it..........

You can lead a horse to water ..................

I'm not sure I can believe that it cannot be stopped rusting?

Surley if all threads are protected, the full length of the conduit is painted thoroughly and covered in PVC then it's going to last a long time? After all an SWA is just galvanised steel wires covered by a PVC sheath! Or even covered in denso tape which pipe fitters use to stop their non galvanised steel pipes from rusting!

 

[snowhead]

Or even covered in denso tape which pipe fitters use to stop their non galvanised steel pipes from rusting!

I'm not going to bother after this as I've seen how other posts go, but Steel pipe used for Heating / Gas has a much thicker wall than conduit.

 

[Octopus]

I'm not sure I can believe that it cannot be stopped rusting?

Surley if all threads are protected, the full length of the conduit is painted thoroughly and covered in PVC then it's going to last a long time? After all an SWA is just galvanised steel wires covered by a PVC sheath! Or even covered in denso tape which pipe fitters use to stop their non galvanised steel pipes from rusting!

So how do you plan to completely "seal" your conduit .....

In fact why are you just making this so complicated ....... it can't be about costs as SWA is much quicker to install, and when done properly will last for decades

unlike steel conduit

A couple of years ago I was swapping a panel heater in an out building - I did a Zs - which showed there was no earth .... a galv box, installed above ground was almost completely disintegrated ...

 

[westward10]

How will you prevent internal corrosion from condensation.

 

[Pete999]

I'm not sure I can believe that it cannot be stopped rusting?

Surley if all threads are protected, the full length of the conduit is painted thoroughly and covered in PVC then it's going to last a long time? After all an SWA is just galvanised steel wires covered by a PVC sheath! Or even covered in denso tape which pipe fitters use to stop their non galvanised steel pipes from rusting!

Sorry Mate how on earth are you going to cover lengths of conduit in PVC, it's just not a practical option, OK in the world of theory, but totally impracticable.

 

[bailes1992]

So how do you plan to completely "seal" your conduit .....

In fact why are you just making this so complicated ....... it can't be about costs as SWA is much quicker to install, and when done properly will last for decades

unlike steel conduit

A couple of years ago I was swapping a panel heater in an out building - I did a Zs - which showed there was no earth .... a galv box, installed above ground was almost completely disintegrated ...

Installation time isn't an issue as I will be installing myself.

There's also the other issue of getting data out to the garage. I could run a seperate PVC tube underground for the data, but I would still run galv up the side of the house as PVC never looks as good as galv conduit in my opinion.

 

[Pete999]

Installation time isn't an issue as I will be installing myself.

There's also the other issue of getting data out to the garage. I could run a seperate PVC tube underground for the data, but I would still run galv up the side of the house as PVC never looks as good as galv conduit in my opinion.

I'm out

 

[Toneyz]

Well the O.P. has asked what the forum thinks and has a consensus answer that this is a bad idea.

 

[willy fixit]

I'm glad the PME/Equipotential zone issue has been clarified.

 

[snowhead]

Well the O.P. has asked what the forum thinks and has a consensus answer that this is a bad idea.

That won't stop him.

 

[Toneyz]

The run cannot be that long SWA can't cost that much.

 

[Pete999]

That won't stop him.

Good quals in building services, makes you wonder if all that studying was worth it.

 

[bailes1992]

The run cannot be that long SWA can't cost that much.

The run is approx 30 meters.
I will have to purchase either 30m of 10mm² 3c SWA and a consumer unit for the garage.
Or, 30m of 1.5mm² 3 Core for lighting, 30m 2.5mm² for heating and another 30m 4mm² for power.

Not a huge issue I admit, but if there was a way I could use the materials I have then I'd probably keep the few hundred quid in my pocket.

Shame I don't have any stainless conduit.

 

[bailes1992]

Good quals in building services, makes you wonder if all that studying was worth it.

Difference between having an idea and seeing if anyone else has experience in it than going right ahead and just doing it!

After all someone may have said they've buried a galv conduit wrapped in denso tape and it was fine 10 years later. In which case I'd probably give it a go myself.