Low voltage/underground wiring question


I'm helping a friend install a solar pool heater for an inground pool. There will be a solar pool controller mounted on the side of the house. This controller runs the pump and valves and basicly turns the pump on and repositions a valve when pool heating is needed and it's hot enough to do so. It has a low voltage, 24V section that gets connected to the motorized valve and also to a temp sensor that goes into a line bringing water from the pool. The motorized valve and sensor are on the cement pool equipment pad that is located just a few feet from the solar controller mounting location on the house.
Here's the issue. The sensor and the valve motor have low voltage wiring that are outdoor rated, but apparently not direct burial rated. So, how to get from the solar controller on the house over to the pool pad? This area also needs to be accessible, so whateve is done needs to go underground.
My current thinking is to use multiconductor sprinkler cable which is direct burial to go from the controller over to the edge of the pool pad. At that point, mount a weatherproof PVC junction box that has only one 1/2" fitting. On that 1/2" fitting, attach a 90 PVC elbow that will extend down below grade. That will put the end of the elbow about 6" underground. The sprinkler cable will come up through the elbow into the box. Drill two small holes in the other end of the junction box for the sensor and motor cables to come in through, make the connections in the box, then seal the sensor and motor cable entry points with silicone. Complete the rest of the wire runs on the pool pad, using cable ties, etc.
Sound OK? Meet code? Is leaving the end of the elbow that is buried open OK? How does one normally transition from direct burial to above ground? Any better ideas?
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That's the way I've seen it done by the pros. It might be good to use conduit all the way for mechanical protection, though, but no big deal.
The solar systems I'm familiar with also have a temp sensor that goes beside the pipe on the roof. One in the RETURN water line tells the differential thermostat whether the pool is at the setpoint or below, while the roof mounted one (air temp) tells it whether the panels would increase the pool temp or would cool it. Both are necessary. The roof mounted sensor wiring is merely strapped to one of the pipes going to the roof.
Nonny

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Thanks for the input. Good to hear that is how the pros do it. I considered conduit all the way, but didn't want to for a couple of reasons. The main one is the other solar temp sensor that you pointed out. That requires another cable run that will come out of the single low voltage hole in the solar controller that the two cables I was talking about also use. If conduit were used, then you'd have to mount some kind of junction box below the solar controller to split off the cable to the solar sensor. Or, I guess you could drill another hole, but since it's a UL listed box as is, not too keen on making modifications.

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On Thu, 19 Aug 2010 08:26:27 -0700 (PDT), snipped-for-privacy@optonline.net wrote:

Why not just run the whole thing on PVC conduit?
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wrote:

or a combination of pvc and Carflex
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Reason for not using conduit is that the solar controller on the house only has one hole for low voltage cables. It's located on the bottom of the controller box and has one of those split rubber seals for passing the cables through. And as RES pointed out, there is another low voltage cable that gets run to measure the solar temperature. I guess the hole with the seal is probably just a 1/2" hole and I could remove the seal and connect conduit, but not sure. But if I use it for conduit, then I have to mount a second weatherproof box on the side of the house below it to split off the other cable run and it isn't going to look very good. Using the underground sprinkler wire, I can just wire tie the cable to one of the 2" pool water pipes that run down the side of the house right next to the controller, through the ditch, etc. I'll think about it though. If I did mount that second PVC box, how do I bring the other cable out? Just drill a small hole in the bottom and silicone seal it?
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wrote:

Reason for not using conduit is that the solar controller on the house only has one hole for low voltage cables. It's located on the bottom of the controller box and has one of those split rubber seals for passing the cables through. And as RES pointed out, there is another low voltage cable that gets run to measure the solar temperature. I guess the hole with the seal is probably just a 1/2" hole and I could remove the seal and connect conduit, but not sure. But if I use it for conduit, then I have to mount a second weatherproof box on the side of the house below it to split off the other cable run and it isn't going to look very good. Using the underground sprinkler wire, I can just wire tie the cable to one of the 2" pool water pipes that run down the side of the house right next to the controller, through the ditch, etc. I'll think about it though. If I did mount that second PVC box, how do I bring the other cable out? Just drill a small hole in the bottom and silicone seal it?
Trader, pardon my dyslexia, as I'm not sure I'm getting a clear picture of the situation. If the purpose for conduit of some sort, above ground is just essentially cosmetic, why not just terminate it 1/2" below the single cable entry point of the controller. That way both cables can slip into the controller, but not be unsightly. Then continue the pvc underground, as required protection for the non underground rated cable. Then when you come up out of the ground by the valve, if necessary transition to carflex, for flexibility and protection.
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It's always hard to visualize this kind of thing, but I think you have it essentially correct.

Is that OK to do? It would seem that if the conduit ends 1/2" below the controller instead of being fastened to it, then rain could get inside and fill the conduit with water. So, I thought it would be something that would look odd and an electrical inspector would flag.
The purpose for the weatherproof box and 90 deg elbow extending down into the ground from the pool eqpt pad on the other end were to be a splice point and provide protection for the low voltage cable where it exits the earth. Meaning it's at the edge of the pool pad and close to where you can walk. Someone could just snag it with no protection. On the house side, under the plan, the low voltage direct burial cable would leave the controller and be wire tied against one of the 2" pvc pipes, following it into the ground. Essentially no different than how sprinkler system wiring is done. That should be sufficient protection, no?
Also, I checked the low voltage hole on the controller. It's about 1" with a split rubber seal for passing the cables through. So per your suggestion, a 3/4" conduit fitting might have worked to actually attach conduit directly to it, BUT inside there is a plastic tunnel that meets it and is part of the controller assembly. It serves to keep the low voltage seperate from the line voltage stuff that is already there. The tunnel takes the low voltage cables past that section into the top left of the controller where the low voltage section is, ie the connection points, microprocessor, etc. With the tunnel there, you can't get to the backside of the hole in the box to put a nut on. I guess I could take the seal out, shove a conduit fitting into it and just not put a nut on the inside, but again, that would seem less Kosher to me than just runnning the direct burial cable out the hole without a conduit, like it was designed for.
If I did run conduit from 1/2" or so below the box, do you feel that is a lot better than using underground direct burial sprinkler wire? I can see it would make it easier to replace the cable someday, but since it's low voltage, not deep, only goes 3 feet, etc, didn't seem to make that much improvement to me.

On the pool pad, once the cables leave the weathertight box, there is no need for conduit or flextight as wire ties can fasten them to the pool eqpt piping and they only go a couple of feet.
As always, thanks for all the help and input.
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wrote:

It's always hard to visualize this kind of thing, but I think you have it essentially correct.

Is that OK to do? It would seem that if the conduit ends 1/2" below the controller instead of being fastened to it, then rain could get inside and fill the conduit with water. So, I thought it would be something that would look odd and an electrical inspector would flag.
The purpose for the weatherproof box and 90 deg elbow extending down into the ground from the pool eqpt pad on the other end were to be a splice point and provide protection for the low voltage cable where it exits the earth. Meaning it's at the edge of the pool pad and close to where you can walk. Someone could just snag it with no protection. On the house side, under the plan, the low voltage direct burial cable would leave the controller and be wire tied against one of the 2" pvc pipes, following it into the ground. Essentially no different than how sprinkler system wiring is done. That should be sufficient protection, no?
Also, I checked the low voltage hole on the controller. It's about 1" with a split rubber seal for passing the cables through. So per your suggestion, a 3/4" conduit fitting might have worked to actually attach conduit directly to it, BUT inside there is a plastic tunnel that meets it and is part of the controller assembly. It serves to keep the low voltage seperate from the line voltage stuff that is already there. The tunnel takes the low voltage cables past that section into the top left of the controller where the low voltage section is, ie the connection points, microprocessor, etc. With the tunnel there, you can't get to the backside of the hole in the box to put a nut on. I guess I could take the seal out, shove a conduit fitting into it and just not put a nut on the inside, but again, that would seem less Kosher to me than just runnning the direct burial cable out the hole without a conduit, like it was designed for.
If I did run conduit from 1/2" or so below the box, do you feel that is a lot better than using underground direct burial sprinkler wire? I can see it would make it easier to replace the cable someday, but since it's low voltage, not deep, only goes 3 feet, etc, didn't seem to make that much improvement to me.

On the pool pad, once the cables leave the weathertight box, there is no need for conduit or flextight as wire ties can fasten them to the pool eqpt piping and they only go a couple of feet.
As always, thanks for all the help and input.
Clearly, the controller is not meant to have conduit attached, just low voltage cables popped through the rubber seal. IMO, anything beyond that such as pvc or carflex, is just an improvement. I wouldn't be concerned about water getting into the conduit, as any conduit underground gets filled by condensation anyway. You can always put some silicone around it to make it look pretty. You could even get a gland type rubber cord fitting, but that's probably a bit over the top
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A related question. What do you use for low voltage splice boxes indoors? Just a regular plastic outlet box with cover that you'd use for AC?
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On Fri, 20 Aug 2010 05:45:07 -0700 (PDT), snipped-for-privacy@optonline.net wrote:

A lot of times they just use a LV ring and the splices are loose in the wall. I like the shallow PVC boxes.
As for your problem of 2 cables, use a "T" conduit body on the exposed pipe and bring the second wire in there. I had the same thing on my pool.
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