Putting electical conduit under driveway

[jeremy]

Hi all,

I'm putting in a new concrete driveway and would like to future proof my electrical and communication options. It is a big driveway so I want to put some conduit under it to allow me to pull a cable television cable or power cable later. Some questions.

- What is the best size conduit to use?

- Do I need to dig a trench for it or can it go just under the concrete (100mm concrete thinkness)?

- Do I need to put a rope or something in the conduit to allow a later pull-through or is this something that can be done later? If so, what?

The length will be about 15m.

Thanks!
Jeremy

[davo2310]

if it was mine, i would dig in 2 100mm pipes, electrical possibles for 1 and 1 for any other that may pop up. you should definately dig it in, 100mm isnt anywhere near safe depth for any service. I think some electrical services in the same conduit as phones and other type services may interfere with each other, but, its not my trade.

[thatirwinfella]

if you're thinking you may need power and comms, you'll have to run two conduits. They're intended as seperate services, and the actual conduits need to be about 100mm from each other.

As it's under concrete, you can get away with having the conduit only 300mm underneath, but it needs some form of mechanical protection 75mm above it. If your concrete will be at least 75mm think above the conduit, than it counts as the mechanical protection. don't forget to put marker tape about the conduit as well, this goes just underneath the concrete.

I'd use nothing less than 32mm conduit, and would be pushing for larger if the budget stretches that far. If i was to do it, yes, i would leave a draw wire in place, taped to each end, with about two foot excess at each end. Use a single piece for the entire run if possible. I'd go for 2.5mm building wire, but rope would be sufficient if it was synthietic or not prone to rotting. Make sure the ends of the conduit are covered in tape to prevent anything foreign objects entering.

if it was a straight run, a draw wire may not be needed, as the sparky should have a snake, but it certainly would save time and effort for it to be there.

[MrFixIt]

Hi

Hi all,

I'm putting in a new concrete driveway and would like to future proof my electrical and communication options. It is a big driveway so I want to put some conduit under it to allow me to pull a cable television cable or power cable later. Some questions.

- What is the best size conduit to use?

Well that depends on your need

There are (at least) a couple of methods. Put in a small, say 50mm, conduit and (possibly with some difficulty) run all your wire through that.

Using 240v power cable in the same conduit as audio/video/network cable may not be allowed under your local regulations. There is also the possibility of inducing a 50hz "hum" into adjacent cables. It is not recommended to run cat5 network cables (or other) communications cables alongside AC power cables.

Potentially a better approach is to run a 100mm "duct" first, (maybe -if the budget allows, install two "ducts") then run future cables through their "own" conduit, through the "duct". This has benefits in that each cable can be run through its own grade of conduit and the conduit will be EASILY pushed through the duct.

This method makes it easier to run the wires through individual conduits and you may not even need to use a "snake" (fibreglass "rope").

It will of course be more expensive to do it this way, but you will appreciate the ease of cable installation. This would be my approach and I would lay the 100mm "duct" with a fall to one end so that any moisture will "drain" to one end. You could of course cap the ends until you are ready to run some cables (recommended).

- Do I need to dig a trench for it or can it go just under the concrete (100mm concrete thinkness)?

In theory, you *could* just lay it under the concrete, however you will need to comply with your local electrical regulations if you intend to run 240v power cables. Therefore I suggest you dig a suitable trench,

- Do I need to put a rope or something in the conduit to allow a later pull-through or is this something that can be done later? If so, what?

Depending on the method chosen (see above) you may need what is referred to as a "snake". There are two styles of snake, one that can be coiled up and is therefore much more flexible - goes around corners more easily.

However because of this flexibility, the coil type of snake cannot readily be pushed - although within a conduit it travels ok. When you have one or more wires in the same conduit then you may find that the (coil) snake is more awkward to push through.

In such cases you can then use the straight snake, which comes in a set of joining lengths, my set came as a set of 4x 1.2m. Each snake has their own advantage. In your case if you have to have a snake then probably the straight snake would be the better choice.

If you use the 100mm duct then each conduit will be its own snake, MUCH easier

HTH

.

[hildahoop]

Definitely leave a nylon rope draw wire in conduit, it makes life so much easier.
The conduit for the mains cable must be the orange in colour not the grey stuff

[Ivan in Oz]

Defiantly 32mm Minimum.

No mention has been made of what length the Conduit run would be under the Conduit
If only ................say up to 3 [THREE] lengths of Conduit,
Then I would not worry about a Draw wire.
The BETTER Snakes would do that easily

Mind,
where you come out from under the CONCRETE.
Then you might have to be back down at the 600/550mm Depth.
Tape and the Sand embeddedment of the Conduit has to be again included.

[AV Elec]

You might not need 100mm. I am not sure of the cost difference, but if you envisage putting in a lot of cabling later on, don't go too small.

Only use sweeping bends, not right angle joins.

• I would recommend you run 2 conduits - 1 for power and 1 for comms.
• Ensure you put in a draw wire to pull in the cables later, it will save a lot of mucking around later on. 2.5mm power cable should be fine.
• Every time you put in a service, replace the draw wire for next time.
• Seal the ends with end caps to prevent dirt/moisture entering, but ensure you don't lose the draw wire down the pipe.
• Possibly, you could consider putting an enclosure in each end to simplify breaking out the cables, but this doesn't need to be done now.

[manoftalent]

I would assume your going to be there for some time, and cabling as it is these days, sometimes needs replacing ..saying that ....if it were me and the opportunity to place the infrastructure before laying concrete, I would run one 100mm conduit for power and one for cable/tv/computer etc ......but I would place three 25mm conduits inside of each one to keep seperate all the cables ....you never know how handy this feature is untill you need to replace one without causing damage to another ....and it minimises water/rodent problems

[Smurf]

I've installed an awful lot of cables into new and existing underground conduits over the past decade or so and my observations are this:

1. Do NOT use any conduit less than 50mm.

2. If the budget allows, use 80mm.

3. Keep the run as straight as possible.

4. If you're bending more than a few degrees, put a pit in at the point of direction change.

5. Don't have any sharp bend unless there really is no choice. And expect trouble if you do.

6. The blue / yellow rope available from electrical wholesalers is by far the cheapest and best draw wire for most applications. It's ridiculously cheap too - you'll get change from $50 for 400 metres of the stuff.

7. A good snake is less trouble than messing about with draw wires. That means a snake that is typically in a 1m+ diameter coil in a frame with wheels NOT one that you carry around with one hand.

8. Don't use any type of clothesline, fencing or other wire. It will rust, get stuck or break.

9. Don't have a run longer than about 70 metres between pits.

10. Always make the connection between draw wire / snake and the cable at least twice as strong as you think it needs to be.

11. Always make sure no rocks etc get in the conduit during installation. They'll cause more trouble than you thought possible so keep them out. Always look inside before gluing.

As for your driveway, I'd be putting in 2 conduits. One orange (electrical) and one white (communications). 50mm should do but go larger if you can afford it and want to be sure. There's unlikely to be any benefit in going above 80mm however.

I'd also install an empty water pipe (nice big one) if there's any chance that you'll want to run a sprinkler system etc pipe through later. Also put in a gas pipe with both ends capped if there's a chance that you'll need it sometime.

Make sure the location of the empty conduits / pipes can be identified somehow. There's hundreds if not thousands of km of "lost" conduit under the streets and you don't want that in your driveway. Memory is useless when you're digging to find it - mark it somehow in a way that can't be erased.

Note for others reading this - bitumen (hot mix) and plastic conduits are not a good combination. Use steel if it's going to get hot during construction works as plastic will melt and make the conduit useless.

[Ivan in Oz]

No mention has been made as to what distance the run is.

ALSO,
Thake Digital photographs of EVERYTHING
Very useful when it comes time to remember What went WHERE

The problem is

" Where did I save the Photos to? "

[AV Elec]

Ensure you draw a plan to scale of the locations of everything.

[Barry_White]

No mention has been made as to what distance the run is.

Ivan

In the first post he said the run is 15 metres.

[Ivan in Oz]

15 M Whoops!
Sorry ppl

BUT,
I could push the Old Electrical Snake at work that distance EASILY!
I wouldn't bother with a Pullthrough.

[rrich]

Thinking about it and referencing American standards...

Nothing smaller than 50mm. The wire required to get 100 amps through is a snug fit in 50mm conduit. When I added a sub breaker panel in the garage, the contractor had one H*** or a time feeding the wire through about 6 feet of conduit.

The thickness of the driveway (100mm) seems to be a bit thin to me. When we did ours I had 150mm poured, using fiber concrete and over a 300mm grid of 9mm rebar. But my truck (F-250) weighs almost 3400kg and is always parked in the driveway.

I would bury the conduit at least 300mm below the bottom of the driveway concrete. Back fill the trench with sand. Cover the ends of the conduit with caps and tape them in place.

As mentioned above, a single picture is worth a thousand words.

Two conduits are best, one for electricity and one for communications. If you think that you may need sprinklers on the other side of the driveway, put a supply pipe under the driveway. For the sprinklers, you'll only need one supply pipe as you can put valves on the other side of the driveway and run the control wires through the communications conduit.

[jeremy]

Thanks all for the answers.

I bought some 'draw wire' from the electical wholesalers. It is simply 1.25mm steel wire. Is this fine? I'm guessing rusting could be an issue...

They (electrical store) said that I could use the orange conduit for either power or comms. However I noticed on the optus specs they specify the white conduit. Does this matter? If they come to install would they refuse to do it just because it was orange?

I've got the 'sweeping bends' for the 2 right angles I need to do. These should be fine shouldn't they? I don't need a pit as well??


Thanks for your help,
Jeremy