Low voltage under water wiring

[keenamateur123]

Hello, I've been an avid reader of this forum for many years but this is the first time I have an issue not covered elsewhere!

Essentially my garden is divided by a section of road, however a stream which runs through my garden passes under the road through a steel tunnel.

I want to put low voltage lights (one set 36v, one set 24v @ 100w) on the far side of the road. My current plan is to use armoured cable through the tunnel under the road (which will be probe to being submerged during storms etc) to carry the low voltage supply. My thinking is that this should be inherently safe as the cable is armoured and only carrying low voltage, but I'd be very keen to hear if there are other options I could consider (digging up the road is sadly not an option due to neighbours access rights)

Very keen to hear any thoughts or suggestions?

 

[ericmark]

There is no real problem with an extra low voltage supply if adequately protected. But to inspect or test would be a problem.

Liikely OK year one, but how will you know still OK In year ten.

So a cable in a pressured pipe with a guage would show if outer has failed, but other wise looking are regular removal for inspection.

I am sure you can see my point.

 

[securespark]

My biggest worry is whether you have a right of access under the road. Do you own it, is it public?

 

[bernardgreen]

As securespark has said the first hurdle would be to ensure you are allowed to pass a conduit with cable through the culvert. Who maintains the culvert ?

The other thing I would be concerned about is the source of the ELV ( Extra Low Voltage ) supply. My choice would be to use a supply that has a dual or spit bobbin transformer to ensure is adequate and resilient isolation between mains and ELV.

Someone standing in water on wet / flooded land could receive a significant shock from a 24 volt supply, unlikely to be fatal but very disconcerting to a drainage engineer working in the stream / culvert and unaware of the cable.

 

[keenamateur123]

We maintain the culvert, the stream on the house side and we also maintain the outflow on the other side of the road.

Naturally I want to do this as safely as possible. I'm not sure how I would manage a pressurised pipe? I had thought that the armoured cable (designed to be underground) would have been enough protection?

With regards the dual bobbin how would I choose one with suitable protection?

Edit: I was obviously naive to think I could buy a class 3 outdoor lighting kit and run an extension from the power supply to the controller unit, again, very grateful for any suggestions

 

[flameport]

I'm not sure how I would manage a pressurised pipe?

You won't.
That sort of thing was used for underground telecom circuits decades ago. Not relevant to your situation.

With regards the dual bobbin how would I choose one with suitable protection?

Specifications of the power supply - which will be an older type with a proper large and heavy transformer in it.
Not some modern switchmode piece which will weigh next to nothing and have a thin layer of Kapton tape between the primary and secondary sides.

 

[JohnW2]

There is no real problem with an extra low voltage supply if adequately protected. But to inspect or test would be a problem. .... Liikely OK year one, but how will you know still OK In year ten.

Since this cable will be carrying ELV and only supplying lights, so long as the lights continue to work I'm not sure that anyone would want to test the cable, would they?

Kind Regards, John

 

[JohnW2]

The other thing I would be concerned about is the source of the ELV ( Extra Low to ) supply. My choice would be to use a supply that has a dual or spit bobbin transformer to ensure is adequate and resilient isolation between mains and ELV.

Is that specifically relevant to the OP's situation? Although we may well have raised other issues, I don't think we would have been concerned about SWA under the road which was always (by intent) carrying mains voltage, would we? - so why would we be concerned if the SWA could, very rarely, be carrying mains voltage as the result of a PSU fault ?

Kind Regards, John

 

[SUNRAY]

Is that specifically relevant to the OP's situation? Although we may well have raised other issues, I don't think we would have been concerned about SWA under the road which was always (by intent) carrying mains voltage, would we? - so why would we be concerned if the SWA could, very rarely, be carrying mains voltage as the result of a PSU fault ?

Kind Regards, John

I'm dropping into Bernards side of the fence with this one. A faulty buried cable leaking into the earth is one thing but very unlikely to be harmful to animal life. However the same faulty live cable in open water (I assume each end there is some sort of pond) where animals could easily drink from or humans could be cleaning out is a different matter entirely.

 

[SUNRAY]

You won't.
That sort of thing was used for underground telecom circuits decades ago. Not relevant to your situation.

And currently still used for some buried cables >11KV.

 

[keenamateur123]

I'm dropping into Bernards side of the fence with this one. A faulty buried cable leaking into the earth is one thing but very unlikely to be harmful to animal life. However the same faulty live cable in open water (I assume each end there is some sort of pond) where animals could easily drink from or humans could be cleaning out is a different matter entirely.

There is a fast flowing stream, not a pond as such. Would this situation not trip the consumer unit? I.e if mains was leaking into the water?

And currently still used for some buried cables >11KV.

I doubt I'd be able to create this for my situation

 

[jj4091]

Might become a pond further downstream. Better to avoid issues from the start.

 

[mattylad]

If water can flow through this pipe then so can rats, and they like to nibble.

 

[ebee]

I might be think not just who maintains these things but who actually owns them and what conditions and bye laws etc are in place.
You might also be hindered by wildlife getting shocks sort of legislation including not just animals but insects and microorganisms too.
Also danger from people getting shocks, even just a pinprick type shock that makes you flinch can be a danger near a road etc.
To what extent would the SWA hinder the tunnel? probably near zero but might have to be considered though as an obstruction causing eventual build up if nothing else.
If it`s effectively joint ownership by a few people then you might need to get unanimous agreement too, in perpetuity.
making it SELV yes I agree and could you consider 12v instead of 24v? or even 6v instead?

 

[keenamateur123]

I might be think not just who maintains these things but who actually owns them and what conditions and bye laws etc are in place.
You might also be hindered by wildlife getting shocks sort of legislation including not just animals but insects and microorganisms too.
Also danger from people getting shocks, even just a pinprick type shock that makes you flinch can be a danger near a road etc.
To what extent would the SWA hinder the tunnel? probably near zero but might have to be considered though as an obstruction causing eventual build up if nothing else.
If it`s effectively joint ownership by a few people then you might need to get unanimous agreement too, in perpetuity.
making it SELV yes I agree and could you consider 12v instead of 24v? or even 6v instead?

I certainly coult use 12v instead, although the kits I had looked at had been 24v. Is there a clear advantage of 12v?