Recommendation for 3 way (SP3T) motor contactor

I have a motor with three winding taps. One for high, medium, and low. I want some sort of contactor module that can switch one line in between each of these windings, obviously only one at a time.

I’ve thought about using two relays. when power is off to both, then the middle winding would get power, the first one would ‘divert’ power to the low speed winding, and the second would divert to the high speed. But that seems rather hacky and it won’t retain memory, which I kind of want.

The motor is in my HVAC indoor air handler. I want to reduce speed on the indoor air handler when the heat pump is running. UNLESS the electric furnace is also running, in which case I want it at medium ( as it currently is hard-set-to). And maybe in the summer I’ll kick it into high during AC mode for extra air movement.

This relay module needs to switch 220VAC ideally. And if it runs on 220 as well that would be fantastic. Otherwise I need to pull a neutral to my air conditioner, which it doesn’t normally have.

A couple of clarifications… load (amps/KW/HP)? I suspect it’s a blower motor you’re talking about, so likely not very high?

Memory? In a contactor? Or are you referring/suggesting/hoping to use something like a latching relay?

Off the top, I’m not aware of any contactors other than very-special purpose integrated things you would not be able to get. Using three contactors seems like the best solution. If it was my setup, I would put in a 220V-24VAC transformer to run the contactor coils, and buy two of the contactors with aux contacts and use them as lockouts, so you can’t possibly have more than one contactor closed at a time.

A two channel insert and two relays should do the job. and interlocking between channels.

no power to channels and two relays in series pass power to low.
power channel 1, turns off 2 and it power medium, and cuts out one relay , removing power from low.
power channel 2, turns off 1, and relay is cut, no low power and power is high.

If you use dp relays you can do interlocking of channel 1 and 2 as safety override.(if 1 and 2 are powered system shuts down.)

Memory would be store in insert switch states.

Zooz makes a 3-relay zwave device (2x 15A, 1x20A) that can handle 240V. It needs a separate 12 or 24v power supply it says it works with vera.

Great device. I wish it existed a similar one on European frequencies.

I would point out that this device does not do interlocking, And with vera’s random glitches it could turn on two/three channels at a time. So i would still probably add some relays to do interlocking.

1 Like

You would definitely want to turn off a channel before turning on another, and likely want logic in the events that won’t turn on channel 3 until channel 1 &2 are off. (and vice versa)

Yeah, its a shame there is no shared 900mhz frequency across countries. I sometimes wish zwave had used 433mhz, but I am told the antennas can get too big.

I would not rely of logic alone, you really need a physical interlock.

1 Like

I agree. This is not perfect (for this case) and I hope @Agnes.Zooz may consider this in a future revision of this device.

apparently you can interlock r1 and r2 but not r3 with latest firmware, go figure

Parameter 24

If r3 is the 20A that kind of makes sense.

I don’t know about ‘makes sense’ but if they had to pick two to work together (they didn’t) then the two identical ones would be logical.

Far better choice in my opinion would be to make r1, r2, and r3 SPDT. @Agnes.Zooz that would greatly increase the value and would be a much more fool proof lockout. I’d buy a couple of these just to have around as spares at any given time if they were spdt.

Actually, come to think of it. I bet the relays on the circuit board of the zooz are spdt already. I take apart all sorts of electronics and it’s really rare to find a mechanical relay that’s single throw… If i just drilled some holes through the zooz case and soldered wires on that might work…

would make sense to have all three be able to be interlocking.

They do give option of NO or NC, just not both, A few extra pence on DT relays and interlocking on all, then these would be an excelent devices.

Best Home Automation shopping experience. Shop at getvera!

© 2020 Vera Control Ltd., All Rights Reserved. Terms of Use | Privacy Policy | Forum Rules