Question
HI Robert,
appreciate your time.
I recently purchased a house which has a lawn and garden irrigation system run by a Richdel 500PR timer/program system.  There is a rain sensor on the house with the wiring making it to the Richdel, but it is not connected to the unit.  I have not been able to find information on what part of the Richdel unit to attach the rain sensor wiring to.  The rain sensor wiring looks like speaker line (2 wires running parallel).
Any assistance/guidance would be appreciated (I want to save that valuable resource called 'water'!!)

thanking you

regards

Chad

Answer
Chad

The following will be the easiest way of wiring in the rain sensor.  Split the rain sensor wire inside the controller and remove the wire that is connected to the "common" or C terminal.  Wire nut that wire to one of the rain sensor wires and take the other sensor wire and insert that into the "common" or C terminal.  By doing that the timer will work as designed but it will now send the electric signals through the sensor before they able to reach the valves. So when the sensor is working the timer will display as normal but the signal never reaches the valve so the zones will not turn on. There will be no way to bypass the sensor so you will have to wait until the water evaporates inside the sensor before the system will operate.  When you wire it in i would pour water onto the sensor to ensure it is functional or if it is too high just use a hose to reach it.