exterior wiring for sprinkler control panel

Old 05-31-14, 09:20 PM
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exterior wiring for sprinkler control panel

First, thanks to everyone that helps with answers on this forum. I really appreciate all of the effort. Itís been fun reading the historical postings even when theyíre not relevant to my needs.

I need to replace a sick 18-zone irrigation controller. I have the new one ready to install. This seems like a good time to clean up some past sins in the wiring, but Iím unsure of the best way to do so. On paper, all the connections are easy and I completely understand that from a schematic point of view. What Iím looking for is more recommendations on materials.

The attached photo shows the controller box mounted to an exterior (stucco) wall. AC power comes from a junction box at the right, through what I believe to be Carflex or similar. An ancestor of that controller box used to be mounted on the brick wall to the left. When it was replaced, the power line should have been shortened, but was not, leaving way too much slack, as you can see in the photo.

The 24 VAC zone wiring runs through 2 inch PVC at the base of the brick wall, then into an elbow (90 degrees right). The wiring from there to the controller is not protected very well from the elements, including animal teeth. This seems like a good time to clean that up, but there is not much slack in that and I want to mount the new box at a more comfortable height to use it. That means adding some sort of junction box.

The zone wiring is 19 wires that are more hefty than they need to be Ė probably solid 16 AWG with very thick insulation. The controller manufacturer recommends 18 AWG wire, but I gather thatís more for underground durability than for actual current need. The zone solenoids appear to draw < 1.7A at 24 VAC. Only 1 of the 18 zones is active at any given time. Given that, even something like 22 AWG wire seems like it should be fine for the short distance from the base of the wall to the terminal strips inside the controller. I need to do that transition somewhere along that short distance.

A complication is that the AC power junction box in the picture is to the right of the controller, while the transformer it connects to is at the bottom left corner of the controller. The incoming power feed has to cross (horizontally) the (vertical) 2 inch conduit adapter for the zone wiring and the controller box isnít deep enough to do that easily with 2 inch conduit. Given the very modest current demands on the 24 VAC lines, Iím thinking it might help to reduce the diameter of that conduit adapter and use lighter zone wiring as it enters the box.

The brick wall surrounds a pool area. I donít want to add any junction boxes, etc. in places that would give unauthorized people footholds to climb that wall. Putting them on the stucco wall is fine, other than the pain of drilling into stucco.

My questions are therefore:
1) Whatís the best way to protect the zone wiring between the base of the wall and the controller? Rigid conduit or standard PVC elbows donít seem like good matches due to the short distance and need for a number of rapid changes in direction. (Minimum curve radius issues and ď%fullĒ issues, especially with the large number of wires (19) and thick insulation on them). Is there some form of flexible conduit that could be used for this short distance? It would need to contain a wire bundle of about 1-1/4 Ė 1-3/8 inch diameter, independent of any NEC constraints. Something like hollowed out Carflex but in a 1.5 or 2 inch diameter would seem sufficient but Iím open to any suggestions. Iíve tried to think how I might build this out of standard PVC conduit elbows, etc. and havenít found anything that seems practical. Metal conduit in an area that is frequently wet seems suboptimal, too. How is this normally dealt with in the real world?

2) It would seem cleaner, for lots of reasons, to drop the 16 AWG wire down to a much smaller gauge for those last few feet. Jamming 19 wire nuts into a junction box doesnít sound easy and I donít see obvious sources of junction boxes that accept 2 inch conduit yet are otherwise sanely sized. Some form of dual post terminal strip for each of the 19 wires would simplify that, allowing a much smaller conduit to connect to the controller box but Iím not sure what type of enclosure to do the transition to the smaller wires in or how to attach terminal strips within the box.

3) For the incoming AC power, the controller manufacturer hints at using a Ĺ inch conduit body for the wire nuts that connect the transformer to the incoming AC, but I see elsewhere that that may be frowned upon depending on specific ratings of the conduit body and local codes. The transformer is mounted in a way where they clearly intend the junction to be outside the controller box. Otherwise it would be simple to just use wire nuts inside the controller box. Whatís a proper way to deal with this junction outside of the controller box? Given how painful it is to drill into stucco, Iím not eager to add more boxes than necessary.

4) Looking ahead many years into the future, when the controller box is next replaced, it would be nice to set things up now to make that easier. That makes me think it would be nicer to do the transition from heavy wire to thinner stuff in a junction box, conduit body or similar rather than inside the main controller box. That way, the next time it would be a simple matter of attaching all of the zone wires to the corresponding terminal strips inside the box.

Given the above, I'd welcome any suggestions about how to deal with this, any pitfalls you see, etc.
Thanks for your help!
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Old 05-31-14, 09:35 PM
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Where's the other end of that 2" pipe? Does it go all the way to the valve manifold or is that just a 'sleeve' to get it through the brick and the rest is buried? If it goes to the manifold, just pull a pair of 12 or 13 wire 18ga sprinkler cables and do the splice in the valve box. Follow directions below for extending PVC..

If it's just a sleeve, I'd carefully cut that elbow off and drill a 2" hole in the back of a 4x4 or 6x6 deep PVC box, and just mount the box right over the cut end. Seal it with silicone if you want, but you'll be using grease caps on the splices so it doesn't have to be waterproof, the PVC is just protection from critters. Sprinkler wiring is designed to be exposed to the weather. Then drill a hole in the side for a 1" fitting, and run it along the ground under the downpipe (cut an inch or two off the downpipe if you have to), then do two right angles to bring it up.

As for the power, unless you have some compelling reason to change it, just shorten the CarlFlex and strap it down. It doesn't matter if it runs over the other conduit.

You're way overthinking this.. There are no box fill constraints, no turn radius constraints (which it would be in compliance anyway, since it's only 180 degrees), no nothing. You're going a couple feet. Just keep it simple.
Old 05-31-14, 11:11 PM
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exterior wiring for sprinkler control panel

The other end dives underground just on the other side of the wall and spreads throughout 3.5 acres or so. Because it's an 18 zone system, valves are scattered in many places throughout the property, some as far as 550 feet away, so there's no clean way to pull new wiring to it all. I wish it were that simple.

Because there are legal requirements about not having "steps" or equivalent along/near pool area walls that could make it easier for outsiders to scale the wall, and county inspectors who check for such things each year, I had hoped to find a solution that didn't compound that issue. Absent that issue, the "cut up a box" solution would be an option. I'm kind of surprised those boxes don't seem to be readily available with knockouts of that size. Maybe a small Christy box on the other side of the wall would give space for splices without further opening the can of worms with the pool.

In other postings on this forum, responders had stressed that irrigation PVC is not to be confused with electrical PVC but did not explain why that's important. I have not seen electrical PVC elbows like are commonly available for irrigation PVC. Is that because of turn radius issues? One of my initial thoughts was just to use that style of elbow, but I assumed that the pros would know of some sort of better solution.
Old 06-01-14, 06:25 AM
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I'd agree with Matt, I think you're overthinking it.

I would shorten the watertight conduit providing the 120v feed.

As for the low voltage, keep the same gauge wire, especially with such long runs. Will you have the same "step" issue with using a box on the other side of the wall? You just need a space to make your splices, then I would probably just use some PVC pipe or conduit to run to the box. Not that it's needed, but just to keep it looking neat. You could also use an LB to make the connections in. (for 120v it's typically not allowed, but for low voltage, as long as it fits, you're good.

As far as PVC conduit goes, for regular voltage, it's a code requirement to use gray electrical PVC conduit. But again, for low voltage runs, you can use whatever works for you.

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