Rachio 3 Pump Start Function

Will do! And I’ll let you know what happens. Thanks

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I was headed out to change the connections when I remembered that Munro said the MSRP24 draws 360mA to start the pump and Rachio says the Gen 3 gives an error at 300mA. Munro recommended and Rachio has agreed that I switch to a low-power start relay. I don’t want to damage the Rachio for sure by demanding too high of a load for it.

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Thanks for the update (I’ve missed the part where Rachio would give an error at 300mA). The contact positions would probably not make a difference (they usually don’t in the AC systems).

This is the relay I am being told will definitely work.



My pump is 3hp and this relay is for up to 2hp. I have ordered the low-power Munro Start Box rated for up to 5hp. Thanks for the research!

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I installed the Munro MPSR242W22, which is the low power pump start relay and had a scheduled run work without the Zone Fault Error! I think the Munro MPSR24 relay commonly in use for irrigation systems using 220v pumps requires more amperage (360mA) than the Rachio 3 will deliver (300mA). The low power relay has a component built into it that lowers its power demand to function to 50mA. It looks like it is working, but the system hasn’t run a full cycle yet of all zones and that will be the real test. I’ll report when that happens. Rachio has been good to work with through this difficult process and has made the frustration, time and expense worth it. We all know now how to deal with this issue.


Did the controller run a full schedule without errors? I am considering a Rachio Controller for our lake house. Thanks

I’m getting a zone fault interruption message, and the timer starts, but the pump will not start, so it runs the program, but does not water. It does not happen every time. I can fix it by stopping the cycle, then restarting it using a manual cycle. Getting a little irritating, especially having to wake up at 4 am to see if the system is working. I am learning a lot about the system, however.

Hi, after reading all this I also purchased and installed the Munro MPSR242W22 and I have a 5hp motor but now I can’t get the pump to turn on now. Any ideas?

I’m sorry, but I don’t know what could be wrong. It works fine on my 3hp pump so maybe check the starter on the pump itself. That Munro relay just accepts the lower mA signal from Rachio and then steps it up to the normal signal required by the pump. That’s my understanding.

Also, did you enable the pump through the app? Can you tell us more about how you have it all connected (maybe pictures)?

I do have the pump enabled through the app. I replaced the munro start box MPSR24 I just wired the same wires to the same places in the MPSR242W22.

This is the 5 hp pump

Good to know it is on within the app. When you turn a zone on, do you hear the PSR click from the relay? Do you have a multimeter that you can check voltages? in other words, when the pump should be on, you should see the 24VAC and should see the 120VAC on both ends. When the pump should be off, you should not see the 24 and only one place with 120. Of course, you should always be careful around especially the higher voltage.

Looking at the pump lawn controller wiring diagram, it says the largest motor is a 3hp. Could that be the problem? When I ordered the MPSR242W22 it clearly stated that it was compatible with a 5 HP.

Possibly. When I looked at the spec for that model, it does say 5 HP.

After checking power with the multimeter, I always have power going out the pump whether rachio is on or off. I have power on all 5 black wires at all times.

That does not sound right. How about the 24 VAC?

24VAC is working correctly. Thanks for the help. I appreciate it. This is really frustrating and I hope I didn’t burn up the motor. Not sure what to do now.