Running DC power across a garden

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neb

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#303902 19-Mar-2023 00:51

Helping a friend set up an outdoors PTZ camera to monitor floodwater levels at the end of his garden, the basic plan was to run 12VDC in flex conduit with yellow caution tape buried above it since it's low voltage and that stuff is much cheaper than tape meant for 240V lines. The idea was to run it to some sort of outdoor junction box at a fixed location and then from there on to wherever the camera might need to go, possibly with a halfway-point junction box somewhere in case we need to power something a bit closer to the house, and also because running two 15-20m lengths will be easier than running a single 30-40m length.

This leads to some questions for people who have done this before, the main one being the problem of pulling 15-20m of cable through the corrugated conduit, I assume it's going to be more or less impossible without fish tape but even then, will that work through such a length of corrugated conduit?

Second question is what sort of outdoor junction box and connectors to go with, there's an infinite number of types and varieties. Since we're running it through conduit the idea was to get an IP66 flange-mount enclosure with the conduit carried in via 20mm single-sided grommets from underneath which provides some flexibility in terms of connecting one thing to another, rather than IP66/67-rated low-voltage connectors, but if there's better options or problems with that one I'd be interested in hearing them.

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#3051714 19-Mar-2023 01:07

Why not PoE?

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neb

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#3051715 19-Mar-2023 01:12

Tinkerisk:
Why not PoE ethernet?

Because that's several times the complexity of two wires carrying DC power. Beyond not solving any of the existing issues it's actually making things worse by adding even more wiring complexity to deal with.

Also, having a remote device subject to god-knows-what connecting directly into a network full of other IT gear isn't a good idea.

Tinkerisk

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#3051716 19-Mar-2023 01:34

There are inexpensive PoE/optical converters for this - but ok, they are more complex.

SirHumphreyAppleby

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#3051720 19-Mar-2023 07:41

Personally, I would use PoE for this and isolate the CCTV system from the rest of the network using a VLAN.

I installed 12V power to a greenhouse last year. I needed 10A, so the cable ended up being very thick and expensive, plus I still needed a capacitor to smooth out the variation caused by pumps/solenoids. If you're just running a camera, you won't need particularly thick cable.

I would suggest using direct bury cable instead of running conduit. For thin cable (or Cat6), it wouldn't be too expensive, and you only need a narrow slit in the ground to install it. If you do want to use conduit, use the solid stuff. Medium duty PVC pipe can be found for a fraction of the cost of the Marley product. If you're in Auckland, NZ Pipe sells 4m lengths of 25mm conduit for $6, or $4.5 for the 20mm stuff (I'd stick with 25mm).

k1w1k1d

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#3051723 19-Mar-2023 07:47

As you said, getting cable through flex conduit is next to impossible over that length.

Have you considered using just the ac cable that sparkies bury?

I used twin sleeved auto cable for the 12vac pump in our goldfish pond. Trade name is 151(2x1.13mm2).

Ideal Electrical etc have a range of IP67 plastic boxes and glands that would be suitable.

Where are you located?

Tinkerisk

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#3052109 19-Mar-2023 17:27

Tinkerisk:

There are inexpensive PoE/optical converters for this - but ok, they are more complex.

I installed *this* unit for network separation for the outside PoE wiring.

neb

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#3052126 19-Mar-2023 17:53

SirHumphreyAppleby:
I would suggest using direct bury cable instead of running conduit. For thin cable (or Cat6), it wouldn't be too expensive, and you only need a narrow slit in the ground to install it. If you do want to use conduit, use the solid stuff. Medium duty PVC pipe can be found for a fraction of the cost of the Marley product. If you're in Auckland, NZ Pipe sells 4m lengths of 25mm conduit for $6, or $4.5 for the 20mm stuff (I'd stick with 25mm).

Yeah, I'm leaning more and more towards solid conduit, the route will be quite a bit longer but we can clip it to the base of the boundary fence which saves burying a lot of it. The reason I want to avoid burying cable directly is because that's what previous owners of the Casa de Cowboy did, they just threw TPS cable across the ground and scraped soil over it, I don't know how much of that stuff we've pulled up as we've discovered it while planting or digging somewhere. Conduit at least lets you know there's cable there, and also means we don't have to dig so deep to put it in, since it has to go through stuff like this:

With a shallow-buried conduit we don't have to worry about digging around tree roots as thick as your arm to run it, and as another poster mentioned flex conduit will be tricky to pull that much cable through while there are plenty of Youtube videos of people pulling cable through 15-20m of rigid conduit with multiple right-angle bends, or just pull it in sections before welding the conduit lengths together.

neb

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#3052130 19-Mar-2023 18:06

k1w1k1d:
I used twin sleeved auto cable for the 12vac pump in our goldfish pond. Trade name is 151(2x1.13mm2).

Ideal Electrical etc have a range of IP67 plastic boxes and glands that would be suitable.

Where are you located?

Close to an Ideal Electrical branch, Orkland's North Shore. However don't they make it a huge pain to buy anything, you need to set up a trade account and... yeah, they still do that, ugh.

Thanks for the 151 hint, may get a roll of that and use the bury-able nature to run the final length to where it needs to go, which is currently TBD.

neb

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#3052138 19-Mar-2023 20:08

Having looked at what's available from non-trade suppliers, looks like Bunnings have all the Deta conduit and fixings we'll need which avoids the Marley tax, so just run it through rigid conduit which'll be a bit longer due to needing to go in straight lines but easier to pull cable through, particularly since we can do it in segments before we join up each lot. The fact that they have T-shaped 3-way junction boxes is also perfect, we can run the cable in one side and out the other and take a drop off the third, downward-pointing one.

The last I heard the plan was to use 25mm and run both a DC power cable and Cat6 through it and use whatever's required, since the major cost/effort will be running the physical conduit/cable, not using up some leftover Cat6 from a 100m spool.

elpenguino

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#3052153 19-Mar-2023 21:32

neb: Having looked at what's available from non-trade suppliers, looks like Bunnings have all the Deta conduit and fixings we'll need which avoids the Marley tax, so just run it through rigid conduit which'll be a bit longer due to needing to go in straight lines but easier to pull cable through, particularly since we can do it in segments before we join up each lot. The fact that they have T-shaped 3-way junction boxes is also perfect, we can run the cable in one side and out the other and take a drop off the third, downward-pointing one. The last I heard the plan was to use 25mm and run both a DC power cable and Cat6 through it and use whatever's required, since the major cost/effort will be running the physical conduit/cable, not using up some leftover Cat6 from a 100m spool.

This is where the suggestion for PoE is quite a good one - it was designed for this kind of thing after all. PoE steps the DC voltage up to reduce resistive power losses in the cable and it also saves you spending money on separate DC cable.

You expressed concerns about isolation but you didnt say whether that was electrical isolation or network security isolation. If it's electrical isolation, you need to isolate your DC feed as well as your network cable for transients.

With PoE you would only need to consider the network cable , again reducing cost and complexity.

Can point you at an Ethernet isolator if you're interested.

Most of the posters in this thread are just like chimpanzees on MDMA, full of feelings of bonhomie, joy, and optimism. Fred99 8/4/21

SomeoneSomewhere

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#3052156 19-Mar-2023 21:43

Rigid conduit doesn't need to be in very straight lines; you can bend it a fair bit; more if you apply heat and a lot of caution, or borrow a bending spring. Smaller conduit is far, far easier. Especially when you've got a trench to hold it in place, you should be able to manage at least 1.5-2m radius curves just by pushing it in.

Flexible conduit at those lengths is terrible to pull through, and provides almost no protection against a spade. Consider it cosmetic only, and not great at that.

AC-DC converters provide sufficient isolation for that to not be a problem, but I would probably be considering a 48V supply and a buck converter at the far end.

neb

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#3052157 19-Mar-2023 21:55

Good point, thanks! I've bent that stuff in the past with a heat gun and sand in the conduit to avoid kinks, but since you can get non-Marley swept bends for $1.80 instead of $15 I'll just go with those and, as you say, curve it in the trench if required. In any case not trying to go via the most direct route means it's lots of nice 90-degree runs so not much to bend unless there's a large tree root near the surface.

The camera has a DC/DC converter in it so should run off whatever's left of 12V through the circuit, and the 12V may also end up powering a PIR spotlight which will run down to 9V or so so voltage drop isn't really an issue. It's just a lot less messy going with 12V directly than having a PoE injector at one end and a splitter at the other to undo it again for 12V devices, with all of that needing to go in waterproof enclosures, so we'll run both cables and have open options later.

richms

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#3052166 19-Mar-2023 23:58

Not sure where my reply went but again,

I would not suggest running lower voltage into the internal DC to DC of the camera, the input current is whats switched and depending on the max of the chip and the heatsinking it may cook it up. Like with some of the older 12v routers that people were all "look, its fine on 5v because it has a DC to DC on it" and they didnt last.

The splitters with buck converters to 12v or USB as needed are a commodity item - 12v 1A is dirt cheap, 12v 1.5 or 2A are a little more.

Injectors are again dirt cheap - this is where you probably want to find someone with a unifi one since thats legit, vs a $8 aliexpress one that will probably blow up because its built without any regard for isolation.

Richard rich.ms

deadlyllama

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#3052453 20-Mar-2023 18:39

Today I learned

* BUNNINGS HAS CHEAP CONDUIT!!!!!! HAPPY DAYS
* My local rubbish Bunnings that doesn't actually stock anything I want, does not, of course, stock conduit. Next Bunnings is an hour away.
* Mitre 10 only have Marley at 5 times the price.

neb

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#3052464 20-Mar-2023 18:58

deadlyllama:
Today I learned

* BUNNINGS HAS CHEAP CONDUIT!!!!!! HAPPY DAYS

The only thing they don't have is swept bends which are useful if you're drawing anything more rigid than a piece of string, but you can get those from online retailers at a bit over one tenth of the Marley price.

For the perpetually-out-of-stock problem, phone them and request a given quantity, their restock day (at least the local one here) is Thursday so you might still be able to get it this week.

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