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I am installing a home EVSE charging station. From the circuit breaker box, there are unused conduits that lead to a lamp fixture location near the end of the driveway. I have located the panel end of this conduit, and would like to tap off the conduit halfway to the direction of the EVSE.

  1. How to properly splice two conduits under a garden-tile walkway?
  2. How to locate the conduit under a garden tile walkway?

The walkway is about 3 meters wide, each tile in the photograph is about 30 cm square and the photo shows half the walkway. As can be seen, I have dug up part of the walkway looking for the conduit. However, I do not know how deep it is. Under the garden tiles I found ~10 cm of soft brown filler material, then below that seems to be some type of gravel-concrete mixture. After digging away at that for an hour I've only penetrated maybe 5 cm or so.

Is there an easier way to locate the unused (empty) conduit?

I tried having my son make noise at the conduit's end, then using a stethoscope against the ground. Alas, I have only a children's stethoscope and no access to medical equipment, and this did not work.

Walkway partially dug up

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  • 1
    450mm would be a typical "minimum depth to top of conduit" - not sure what your local regs require.
    – Ecnerwal
    Mar 31, 2022 at 13:08
  • @Ecnerwal Thank you, I will check the regs.
    – dotancohen
    Mar 31, 2022 at 13:35
  • 1
    An EVSE charger requires some quite beefy cables. If you want to re-use a lamp fixture conduit I'd check first if the existing conduit is large enough. For an EVSE I'd use at least 5x6mm² wires (three phases, one neutral and one ground). That's too much for a, say, 16mm conduit.
    – Martin
    Apr 1, 2022 at 14:11

3 Answers 3

9

A couple of options:

  1. Keep digging. You should eventually find it if it's there. The most labor intensive but people do this every day.

  2. Rent a cable locator or hire someone who provides this service. An underground cable locator is a device that can actually detect and locate a buried cable to within a few inches in any direction. The conduit will either need to have a wire in it that can be connected to or the end accessible so that a conductor or sonde (a small RF transmitter) can be threaded into the conduit and then located.

Once you have the location from the locator you can dig there and get to the conduit.

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  • Off to digging, then... Thank you!
    – dotancohen
    Mar 31, 2022 at 12:56
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    If it's metal conduit and there's no rebar in the concrete, you might even get by with a regular metal detector. Less precise, but feasible if it's not too deep and it's the only metal to be found.
    – bta
    Mar 31, 2022 at 19:35
  • Plastic conduit. By listening to the end of the conduit while my daughter was banging the trench, we were able to figure out where to bang to get the loudest sound out of the end of the conduit. I'm digging there now... I've jackhammered through 65 cm of concrete so far, an electrician tells me that the spec is 80 cm.
    – dotancohen
    Apr 2, 2022 at 18:01
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In addition to @jwh20 fine answer, once you find the conduit, if there are wires in it, you'll need to remove the existing wires and cut the conduit and route it into a hand hole along with the other end of the conduit and the new conduit to the EVSE station. Then pull and splice wires. The hand hole will need to be accessible. See picture from Granger below:

enter image description here

If you find an empty conduit like you assume that's in good shape, you can connect it to the new run of conduit and just pull wire from panel to EVSE station. If it will be a long run with bends, you'll probably need the hand hole.

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  • Terrific, thank you. Yes, the conduit is empty, I know where both ends are.
    – dotancohen
    Mar 31, 2022 at 12:55
  • 3
    When coming up into the handhole (the bottom is open) the "protip" is to use 45 degree sweeps rather than 90 degree sweeps - and coil a little extra wire there in the handhole rather than going directly from one to the other - very useful to have an extra meter or so there if there's damage in the future.
    – Ecnerwal
    Mar 31, 2022 at 13:48
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I'm not sure where in the world you are located, but in the US in order to "splice two conduits":

  1. The splice must be in a junction box of the appropriate type.
  2. The junction box must remain accessible without tools (beyond a screwdriver to remove the JB's water tight cover). AIUI, this means that if you bury the box under the walkway, you have to be able to get to it by simply lifting one of those pavers with your hands - no pry bars allowed, no digging through bedding material, etc.

Instead of destroying the rest of the walkway to get to the conduit & put the splice below there, move away from the walkway and put the splice box in the yard. It may not be quite as pretty, but the box needs to remain exposed, and it'll be a lot easier digging up dirt than it will be digging through the bedding for your walkway then trying to recompact it to keep the walkway stable.

I would imagine that your locale (if not US) would have similar code requirements. Even if it doesn't, not burying the junction box in a very difficult to access location simply makes sense.

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  • Thank you. So far as I know the entire length of the conduit is under the pavers, I've tried searching for it in lots of exposed dirt. I'll keep in mind the US code as I'm sure it is a safety and durability measure, even though I'm not in the US.
    – dotancohen
    Mar 31, 2022 at 12:58
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    If the whole thing is buried, @dotancohen, you might consider another conduit penetration from the house, or simply branching off of the light base which should already A) be accessible, and B) function as your outdoor rated junction box. It'll take more wiring to run there and back, but think of the time & effort you'll save by avoiding all that walkway destruction & repair.
    – FreeMan
    Mar 31, 2022 at 13:01
  • In the UK it's quite common to bury an armoured cable without conduit. IIRC the only requirement for armoured cable is a minimum depth, and a plastic electricity warning tape at a shallower depth in the same trench. Regulations vary A LOT between countries!
    – nigel222
    Apr 6, 2022 at 9:46

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