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?