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?