I am about to get an sprinkler system installed. The pump will be down at the lake, connected to an existing 240V circuit that was run by the previous owner. The breaker is a two pole 20A. I will need to install a 24V pump relay, but the ones I have found at the improvement store are 15A. I have a few questions
1) On my previous house, I had a well and the pump had a Franklin control box. Is that also normal on shallow water pumps? I have never seen them on pool pumps, so I assume it is something specific of well pumps.
2) Many moons ago, in my previous life, on the other side of the east pond I would have installed a relay with thermal protection built it. They were called contactors and where not expensive. What is considered a normal setup for a shallow water 2-3HP pump ?
3) Would it be acceptable by code to install a 15A (Rainbird) relay fed by a 20A breaker? I have been told that the 3HP pump (still wandering why a 2HP will not cut it, but that is another story) would be 240V/15A.
Any relay or contactor that is rated for the motor HP will work. Assuming this is a single phase 230 volt motor, a one pole relay is code compliant, but I'd use a two pole.
The motor needs to be thermally protected, but almost all single phase pumps have protection built into the motor.
The Franklin control box might have a relay in it, most smaller ones do not. They do have a start capacitor, and a start switch. Some also have a run capacitor. An above-ground pump has all these built into the motor.
If the pump doesn't have the HP listed on the nameplate, you can figure a 2 HP will be around 10-13 amps, and a 3 HP will be 14-18.
The 15 amp relay in question would be code compliant only if it was rated for the motor HP.