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So I want to install an irrigation system in my garden. I am starting with one controller but there may be more. I was told, rather than install an in-use outlet, where bugs and spiders etc will hang out, the better plan is to cut the plug off of the power cord and run the cord into the non-metallic J-boxes through a sealing cable gland, and wire the hot/neutral/ground to the line from the load center (which is outdoor-rated), which would be a dedicated line (12/2 + ground) on a GFCI breaker. If I needed to add more controllers, just join them in with the others, as long as the circuit was dedicated just to those sprinkler controllers. The load center, controllers, j-boxes and cables would all be under a little three sided hooch out of the rain.

Is this a reasonable plan?

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    If possible, I'd go big on the controller and mount inside if possible. Then run the low voltage cables to the valves. If you use multiple controllers, it's a total PITA to keep them sync'd so they both don't run zones at the same time. UNLESS YOU HAVE GREAT WATER FLOW or your zones are small enough, multiple controllers are a bad idea. So IMHO just get a big enough controller that could fill your anticipated needs, mount it inside if possible and just wire up the zone valves, plug it in, program the controller, turn it on and off you go. May 2 at 20:53
  • IIRC (I ended up buying a solar one and bypassing this part) most of the irrigation controllers use a low voltage input for the power, so really you can just put the line to low voltage converter inside somewhere nice and dry and then run the low voltage where you need it. But keeping the controller inside seems reasonable as well.
    – Ecnerwal
    May 2 at 22:10

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Basic concept is good. I am a big fan of hardwired equipment when practical and code-compliant. Two issues:

cut the plug off of the power cord and run the cord into

While it is tempting to do so, technically speaking cordage is not designed for permanent fixed use. Similarly, cables designed for permanent use are generally not rated for use as cordage. While they perform the same function (get power from junction box to a device), cordage and permanent cables are designed a bit differently and you need to use the right stuff to satisfy code. But you also have to be careful about cable types as many are not designed for wet areas, and any outdoor area is considered wet.

Depending on the distances involved, a better solution might be conduit with individual wires. The wires need to be rated for wet areas, but that is pretty standard.

the non-metallic J-boxes

Why non-metallic? In fact, metal boxes are often better for outdoor use than non-metallic boxes because they conduct electricity. If there is a fault inside a non-metallic box then it may go undetected for a long time. If there is a fault inside a metal box it is likely to short against the grounded metal box and trip the GFCI.

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  • With respect to metal boxes - what about corrosion and the related risk of water ingress? Its not quite the same thing - but analogous - All the pressure controllers for the water pumps I've seen are plastic boxes?
    – davidgo
    May 3 at 5:29
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    Cutting the plug off the cord likely voids any NRTL (e.g. UL) listing, since it was certified as a plug-in device. Unless the manufacturers instructions allow such an alteration.
    – Jon Custer
    May 3 at 15:50
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I am not a sparky, and live in a different jurisdiction, so YMMV. On the flip side I had the interesting experience of running a commercial hothouse, and the current tenant still ropes me in to help him with anything with power flowing through it.

My advice would be the opposite of @manassehkatz-Moving2Codidact.

I'd prefer plastic over metal as it does not corrode and is much more likely to be weatherproof. Also, you mentioned that your system has a neutral wire - I would argue that especially when you have a neutral wired up you don't need a metal enclosure. (Our solenoid controllers are housed in plastic our nutrient control systems - which are ancient are housed in a metal box, but all the replacements are in plastic boxes - and as these things cost 2 arms and 2 legs I don't think its for price reasons)

I would suggest against hardwiring the circuit into the mains (but do make sure their is a GFCI on the mains, or if getting an electrician to do that - at least have it built into the plug point) - At least in my jurisdiction as soon as you hard wire something in to the mains you have either breached code - with the insurance problems that follow - or you need to get an electrician in - in which case you should let him do the wiring and advise authoratively - and get him to sign off on it.

You may want to check the voltage of your controller and systems. Most of the stuff I've seen runs on 24 volts DC, with a wall adaptor. Even in a commercial setup we plug things in to power strips. Of-course, although its still a wet area [ie moreso then a bathroom], its not exposed directly to the rain/weather. You might want to check your setup as I would not not want to be running 120/240 volts to solenoids.

On the other hand we do get plug-points for direct use outside (ie as a newish home - this is not growing related - and we live in a country where the rain falls sideways - ie vey high winds). Our outdoor power connections tend to be downward sloping where the plug fits in so as to reduce exposure to water ingress. [ All circuits in a residential house here need to be protected br RCD's, so the outdoor circuits are RCD protected ]

In the 10+ years I've had an outside plug I've never had a problem with spiders or the like getting in to my sockets Hell, if that could be an issue get some plastic socket covers from a baby store (or just make sure they are single plugs with the plug always in!).

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