12/24V DC On Demand Pump Relay

longpvo · January 31, 2022, 3:38am

Hi guys,

I am setting up my 4 zones system with a Rachio 3 Pro in SEA. Already got a good 220-240V to 24V AC output for the Rachio controller. I am trying to figure out how to get a pump relay box to work with those small 12/24V DC on demand diaphragm pumps (my locally accessible ones are SEAFLO units, I am looking at the highest throughput one which is the 51 Series).

My municipal STATIC pressure is only hovering around 25 to 30 PSI during peak hours, it can be 35 PSI during off-peak.

Doing the math with flow and scheduling, I highly doubt the pressure is enough for my system (which are all 30 PSI regulated, 3 drip line zones and 1 medium sprinkler zone).

Those relays I see available such as ORBIT 57009 are 110/220 AC output only. My reason for the smaller on demand diaphragm pump is I need something smaller. Can’t see myself installing a bigger delivery pump in a 14x20 valve box. SEAFLO does have 110/220 AC units, but they’re not easy to source apparently.

DLane · January 31, 2022, 4:43pm

@longpvo - I might use a Single Pole Single Throw (SPST) relay with contacts rated for the maximum amps that the pump would pull in combination with a power supply that will supply the needed amperage. Use the Rachio M terminal to close the relay by connecting it to the relay coil with the other side of the relay coil connected to the Rachio C terminal. Connect one side of the power supply to the pole on the relay with the other side of the relay going to the pump and the other side of the power supply going to the pump. If one wanted to switch both leads coming from the power supply then the relay could be changed to a Double Pole Single Throw (DPST) or a Double Pole Double Throw (DPDT) relay which may be easier to find - just don’t connect up the normally closed contacts on the DPDT relay to anything.

Gene · January 31, 2022, 8:40pm

My recommendation is to get rectifiers with regulators included, which will provide a more steady 12 or 24VDC output from an AC source. Something like this:

Amazon.com: 2Pcs AC/DC to DC Step Down Buck Converter AC 5-30V DC 5-48V 24V 36V 48V to DC 2.5-35V 12V Voltage Regulator Board 2A Adjustable Volt Power Supply Module Delinx : Electronics

What my fried @DLane will work as well, just wanted to provide a self powered alternative.

DLane · January 31, 2022, 8:54pm

@Gene - depending on the model of pump @longpvo chooses, they pull up to 17 amps from the quick search I did on the manufacture’s website →

That would be more amperage than the Rachio can source if I understand the proposed solution.

Gene · January 31, 2022, 9:03pm

You are right, I’ve read the part about pumps being small and didn’t do the research, you are right about my suggestion being greatly underpowered.

longpvo · February 1, 2022, 8:23am

Thanks guys. Let me take a look at Gene’s.

If I can source a 220V AC unit (Max Draw ~ 1.7 A), it’s a fairly simple setup using a relay like Orbit 57009, correct?

DLane · February 1, 2022, 4:14pm

@longpvo - correct. A pump start relay is basically a large double pole single throw relay with a 24 VAC coil circuit. The Orbit device should work fine. Some pump start relays pull too much amperage through their coil for Rachio supply. With 1.7A draw you won’t need a heavy duty pump start relay.

longpvo · February 28, 2022, 12:15pm

Hi guys,

Can someone let me know what is the tip size for the rachio power input? I need to find a right angle adapter to make the 220V AC/AC fits nicely.

Gene · March 1, 2022, 4:20am

5.5mm x 2.1mm
5.5 mm is the outer diameter, 2.1 is inner.

longpvo · April 16, 2022, 7:05am

Hey guys,

This is a WIP. So I got the outdoor enclosure for the Rachio unit, also an off shelf power transformer called DB-25VA EI 57*35 (25W 220VAC to 24VAC 1A). Now I am deciding where to mount the transformer inside the enclosure behind Rachio.

I am not too sure if fastening it on the back surface is ideal due to heat dissipation, it’s quite close like back to back with the Rachio back side. Alternatively I can have it lie down on the bottom surface with one end fastened (would have to bend one side in order to fit).

Gene · April 16, 2022, 2:41pm

Heat should not be much of an issue.
I do not recommend back mounting in case you are installing it outdoors as this can lead to leaks into the enclosure.
Great solution, nicely done

DLane · April 17, 2022, 11:51pm

@longpvo - if the transformer will fit in the lower left hand corner that is where I’d put it to shield off the high voltage wires. Just my $.02. Should be enough ventilation with the top hole where the plug went.