Looking for a ZWave "Latching" or "BiStable" relay switch


#1

I’m looking for a mechanical ZWave “switch” that physically stays in it’s “state” when power is lost or the device fails.

If folks recall from the X10 days, a X10 outlet was actually a mechanical switch inside that would flip on or off with a solenoid. There was no relay. And it consumes the same power in either state. Only uses the coils during a state change.

The only device claiming this behavior is a WiDom Universal Relay Switch but I’m not sure it does what I want and not easy to find in the USA.

The reason I want this is, I want it for a Furnace and I have it On for 6 months and Off for 6 months. But occasionally would like to turn it off or on remotely.

I don’t like the idea of an Coil needing to be “Active” to Keep it ON for 6 month or OFF for 6 months.
Coils will and can fail. And it would be a real pain if it failed. It seems all ZWave switches have failure reports and I can deal with that. But I want it to fail in the state it was last left.

One way to test if a device is a mechanical switch is, if you turn it on, you’ll hear a Click for almost any device that isn’t solid state or a dimmer. But if you remove power (while “On”), do you hear another click (coil releasing the relay contact)? What I’m looking for, it would NOT click when you remove power. Nor would it click again to restore state when power is restored (because it mechanically stayed in the correct state).

I highly suspect such devices exist, but the descriptions are vague.

There are “Active” latching (or BiStable) relays that use a feedback circuit to hold the relay in it’s state (without a signal). These are often used when you want a Momentary signal to turn it On or Off. But still requires an active coil to hold that state. But that is not what I’m looking for, and I suspect the WiDom unit might be that type of device. But it claims it’s the only “Latching” Relay.

I’ve looked at the GE 40 Amp Relay 12726, NuTone NFS20Z, Remotec Dry Contact Relay, Aeotec Nano Switch , Quibino Switch (last 2 look similar to WiDom switch) and I cannot tell from the descriptions what these actually do inside.


#2

The Fortrezz Mimolite can be set to either latched or momentary operation. I don’t know if it requires current to maintain the state, though. You could write them and ask.

https://support.smartthings.com/hc/en-us/article_attachments/205404346/User_Manual_MIMOlite.pdf


#3

Thanks I have two MIMOLites for smoke alarm integration with Kidde relays.

There are different applications of Latching. That is a setting that allows the the input signal to directly drive the relay (no zwave) and has the option of the input signal being momentary (and latched) versus a continuous input signal to hold the relay state.

The relay still has to be actively held with current when closed.


(Mike Maxwell) #4

I would use a general purpose micro switch to drive a real latching relay.
Pulse the micro to change the latch state.

I doubt you will find a zigbee or zwave latching relay, and if you did it would be stupid money.


(Ray) #5

I think it goes the same for mechanical contacts for failure as well. If you are operating the switch a couple times a year then the failure rate is very low. I have switches that operate at least 10 times a day for a couple of years now without issue. If you are really worry about having your furnace accidentally switch on then maybe a smart thermostat is something to think about.


#6

I already have WIFI thermostats.

It’s a forced hot water system with hot water.
Even with not calling for heat it uses fuel on standby.

I’ve been shutting it off and on for 13 years manually.

Coil contacts are not really designed for 24/7 energized. You’d usually use normally closed and energize to shut off. But then if it fails it it will turn on. And I flip it’s “normal” state seasonally.

There are devices made for this type of purpose. They are called bistable relays.

I know I could make one by using a bistable relay that is controlled by a momentary contact Zwave device like a MIMOLite. But I would not get feedback on the furnace circuit. But I could add another dumb Zwave device on the furnace side to monitor power.

That’s expensive and overkill. And I suspect a device might already exist. All X10 outlets were made that way.


#7

Right, might have to do that.

I don’t want to do that if it exists and why I’m asking first.

If anything did, it might be that GE 40A switch. I don’t mind spending a couple hundred if a nice device exists.


#8

I tested GE 40 relay and it’s not (mechanically) Bistable.

I did find this one that is surely the exact behavior I want. But it’s 50hz 230V only.
http://www.ubisys.de/en/smarthome/products-s1.html


(Brian Gemberling) #9

Did you ever find that latching switch. I have been surfing around for quite a few weeks and have found nothing. I am looking for two different flavors (1) a solenoid operated by zwave that flips a solid state three way switch. I don’t want to have to replace all the devices and rewire to make smart lighting work.
(2) I want a 30A variety that will allow me to turn on and off the water heater. It does make sense to hold in contacts 24/7. As stated previously if the coil is going to stay energized to hold it in any give state for a prolonged period of time it doesnt make sense.
Let me know if you found the magic bullet


#10

Nope. I sort of gave up for now.

I even requested info on several on Amazon and the engineers replied for that GE one and said it was. I bought one and it clearly wasn’t. Got lots of replies “Why do you need that”.

I think I posted about this, but the only one I found was in Europe but looks like it was for 220V only. Looked real nice too. And clearly documented as true mechanical bistable switch.

I wanted it for a heating system that nobody is at during winter and I just don’t trust anything that isn’t a true mechanical bistable switch and have a power failure glitch or something not restore state correctly.

Also all these non bistable switches they keep a coil energized 24/7 when “ON”. Or is a solid state FET. I assume you knew all that or you wouldn’t be hunting like I did.


(Renato P. de Bulhoes) #11

Hi friends. I think have you been looking for this…?

http://www.morssmitt.com/industry/heavy-industry/industrial-plug-in-power-relays/latching-bistable-heavy-duty-power-relays/kdn-series-latching-relay-bistable-mechanical-latch/


#12

That’s the correct type of relay but it needs to a zwave interface to control it, reasonable price and readily available.

I suspect that relay is very expensive too. There are other similar relays out there. But none designed for zwave or end consumer.


(Kevin [Yorkshire UK]) #13

I found a Bluetooth version…


#14

Getting close. How about s link.


(Kevin [Yorkshire UK]) #15

Was just trying to find it again…
http://www.tinyosshop.com/tslr0511
I wonder if you could replace the BT module with the XBee equivalent…


#16

That’s a nice little package.

There might be a zwave/zig bee bridge device out there.

Unfortunately its relay can only handle 5A.

It’s really surprising there isn’t more stuff like this out there.


#17

I know the following won’t fit a lot of these cases, and I’m not sure if it will fit yours, but I did want to mention that there is now a battery operated switch cover which is bistable because it physically moves the switch underneath, rather than being wired in to the mains.

If you don’t want it to be battery operated you would have to modify the power supply. (The good news is that it runs on two AA batteries, so it should be easy to use dummy batteries with a plug-in pack instead.)

It’s intended for light switches and there is both a toggle version and a rocker version.

So for someone who happens to have a Device which could be wired to a regular toggle switch you could then fit this zwave device over the top of it, giving you a bi-stable Z wave controllable set up. And you don’t have to worry about matching voltage as it’s just going to physically move the switch underneath. :sunglasses:

So again, not a match for every use case of this type, but it just came on the market last year and I thought it was worth mentioning.


(Mark) #18

Was the rocker version ever released?


#19

Yes, twice!

The first time it was released under the name “Decora“ but that is actually a trademark of Leviton, so they had to withdraw it and re-release it under the generic “rocker“ name.

They appear to have sold most of the rocker stock to ADT, where it is sold as the “ADT Pulse easy install rocker switch.” it is sold through authorized installers at what appears to me to be almost double the original price. :disappointed_relieved:

( I don’t know anything about this particular dealer, this is just a typical listing. )


(Mark) #20

guess that explains why I haven’t been able to find it anywhere that doesn’t routinely mark up device prices by an absurd amount :angry:.