Rachio 3 Pump Start Function

Is anyone else having issues with pump start issues? My 3 will not start my irrigation pump from a schedule. I irrigate with lake water through a pump so I have connected terminal M and set the system for this connection, but I get a Fault Zone error message and the pump won’t start.

Have you connected the pump directly to the M terminal by any chance? Do you have a pump relay?

Yes, I am using a Munro MSR24 Start Box that worked perfectly with my Hunter controller. When I replaced the Hunter with the Rachio 3, scheduled runs won’t work. Rachio says the Start Box may be drawing too much power, but Muro says it will work with a very low power draw. Everything is set and connected correctly. BTW, the start box works on Quick Run!!!

@Crocboy I spoke with our hardware engineers and they believe that relay is pulling over 2A to get that fault, which will more than likely damage our power supply. They recommend purchasing a lower current relay.

I’m working with our customer success team on recommended pump relays that draw less power.


I talked with Munro and they told me they sell a low power Start Box that draws 50mA. It is model #MPSR242W22. They said the Munro model I was using, the MPSR24 requires 360mA. This information should be made really clear in the Rachio product info as the MPSR24 is the standard box used by a lot of landscapers when connecting pumps. I doubt I’m the only one with this issue. Thanks for the reply.

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Would it be too much to ask for a couple of pictures? One of the Gen 3 wiring and the other of the inside of the relay box? At this point it sounds like there is a short going on somewhere, I wonder if pictures would show any indication of it.


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Not 100% sure how much difference it makes (having never used such a relay box), but official manual shows Common (white) on the left and feed (black) on the right:

If there is some sort of connection between the Earth GND and the left terminal, it could explain the short if the common is Grounded elsewhere in the system.

I recommend you try to switch where the Black and White wires are connected to the relay.

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.