Input required -Switching 2 relays for 240V pool pump

Hi, thinking about next year pool season already.

I am looking to control my pool pump which runs off 240VAC (14/3 cable which has 2 hot and 1 neutral + 1 ground)

I have some heavy duty 30A high current relays, but not sure about using 2 separate relays (one for each hot wire) I’m worried what would happen if only one relay tripped, would it damage the pump etc.

is there such thing as a double pole/throw relay which would ensure both relays trip together?

Otherwise my current plan would use 1 gpio on my rpi to trigger both relays which should hopefully work.

Anyone switching any devices that have 2 hots and 1 neutral?


i control my 3-phases pool pump with something that is called “schütz” in germany. not sure how this is called in your language, perhaps “magnetic contactor” or sth like that.

in openhab i control quite a normal actor as i use for other lights or sockets for example. this actor switches the magnetic contactor. the magnetic contactor is available in different versions, you have to search one that closes at least two lines when activated.

i would not recommend to use two separate relais because if anything is going wrong and only one realy is closed this may damage your pump. for magnetic contactors there are additional savety-components available that can cut off power when one line is missing to protect the pump (but i know this savety-components only for 3-phases-motors, not for 2-phases)

Thanks so much for your reply, I will do some searching using the info you shared!

I’ll post back any further leads I come up with.

So you must be very careful when designing an electrical system.

A contactor is a multiple channel relay but not all channels are rated the same.
Make sure you use the correct channels for the hot wires they are likely the ones with the bigger screws and terminals.

Take note of the coil voltage as this is the voltage you have to use to switch the contactor on and off. You can use another relay to drive the contactor (interfacing relay)

Thanks, completely agree. After more thought, I might just opt to use a mechanical timer that I have which is designed for pool pumps and won’t be automated. (Perhaps it even has a remote turn on input such I could drive with a relay)

Currently I run my pump 24 hours a day so not really a big deal if not automated.

While I’m comfortable working with mains power, I don’t want anything remotely unsafe or unconventional.

I might focus instead on pool temperature and heater on/FF control. I already have the pool lights on/off.

The Aeon zw078 handles 220 V / 40 a and has two hots. It works well for my water heater, though I only have one hot for that.

@openhab2 , I’ve got one of those ZW078’s running my Sprinkler Pumps. Works perfectly, and I think would work for pool pump as well.

Another idea, a hack, is this one: disassemble your mechanical timer and take the relay/contactor from it. When I installed the ZW078 I had to remove the old mechanical timer, so I disassembled it. Usable part was just the relay/contactor.

I’m thinking of reusing that relay/contactor with a ESP8266 board to remote control my pump. The disadvantage compared to a ZW078 would be that the ZW078 measures the power consumption, which is always good to know.