Is there any existing thermostat shutoff device for when a pellet stove goes on UPS?

[whit]

A pellet stove vented straight out the wall, as we know, will put some smoke in the room if the power (and its fans) go off. Putting the stove on a good computer-grade UPS gives time to simply shut it off at the thermostat, and the fans run on the backup power for plenty of time to clear the stove. Doesn't work when you're not home.

Now, the UPS will typically have a USB output on which it can signal when it goes to backup power (among other things). That could easily be hooked up to a "wall wart" Linux computer to receive the UPS's messages (probably using NUT). Such computers start under $50. But to complete the project that tiny computer would need to control a switch added to the thermostat's line. Such things exist. Don't know where to find them. Wall wart computer + switch it can control (preferably USB pluggable) with both plugged into UPS for power, and connected to the UPS by USB, with the thermostat line running through that switch = a straight-vent system where you'll get no smoke in the house during an unattended power failure. If the switch can be had for $20 (wild guess) and the wall wart and USB cables add another $50, with the software free and easily copied onto new units once configured for one, seems like it could be a nice little product for someone.

Which makes me wonder if anyone's already done it.

 

[CJ-SR4ever]

Not that I know of. Would be a neat idea though. If I lose power in my home, I disconnect the thermostat and just run the stove straight out. Im not a fan of the thermostat for my pellet stove but my wife was the one who insisted we needed it. LOL. How long are you able to run your stove off of the UPS?

 

[whit]

How long are you able to run your stove off of the UPS?

Basically it can run the fans and augur for a long time. But as soon as it starts an new cycle and powers up the heater under the firepot to start a new fire, that drains it pretty fast. I can do that maybe once, if lucky.

So the best strategy, come to think of it, would be to first bypass the thermostat and set the stove to being constantly on - let it think the thermostat is never satisfied. Then monitor the UPS for when battery reserves start to run low, and shut down the call for more pellets at that point. That way the starter would never get called, and the augur and fans would get their maximum run off the UPS, putting max heat into house before shutoff.

 

[kofkorn]

Easiest thing I can think if would be to wire a relay that plugs into your wall outlet and switches your thermostat line. When the power goes out, it opens up the thermostat connections, and assuming you have a stove with an On/Off mode, it will shut your stove down.

You can find 110V DC relays pretty easily, if you wire one with a couple of diodes and a small capacitor, it should work very well. It would save you the whole issue of setting up a separate system.

 

[whit]

You can find 110V DC relays pretty easily, if you wire one with a couple of diodes and a small capacitor, it should work very well. It would save you the whole issue of setting up a separate system.

That's elegant. Don't know enough to select the right parts and put them in the right configuration. A soldering iron I'm fine with. But only with spec'd parts and a diagram. It's not just easy to find relays. Grainger has for instance 1785 relay switches.

I see a vaguely similar project to what you propose here - vaguely in that it's wildly complex and to a different purpose, but similar in that there's a relay being used to switch a thermostat off and on. It has a 5V wall-wart-style transformer powering a 24V AC relay, such that when the transformer loses power the relay is open. I take it 24V AC is the standard for thermostats (at least the ones that aren't directly in the 110 circuit - as are sometimes used with electric radiators), and my Quad's on a standard thermostat. He mentions that the relay cost $2, but that being the IEEE site, although he specs several other parts exactly, he says nothing more about which relay he used. If you're reading anything there you're assumed to know already on a thing like that. Sure would work though.

Update: Here's someone spec'ing a 5V relay.

 

[Boom]

I think this is a great idea and expect it to be an option on some stoves in the future. Seems stove companies do not implement technology until it is mature. No iPhone/Android change your temperature or start your stove from your car apps except one european stove that does not offer those features in the US. :'(

What stove companies appear to recommend most is a few feet of vertical exhaust vent to create draft. Vertical stove pipe draft pulls smoke out of the stove until the fire is out electricity or not. It is what I have always used to keep smoke out of my house.

Jay
PS, nice avatar kofkorn, I thought you were me for a moment!

 

[Murphy118]

Whit,
What I believe you are proposing could easily be done with only a 110 volt relay that will open the tstat on power outage. If I can figure out how to include a diagram in my post I will,,,,,relay from grainger should be cheap and then only a box to put it in and a plug to you house power and your good to go,,,,,,,,,lemme go onto graingers site and pick one out..don't even need the bix if you put it in the basement or out of the way somewhere.

John

 

[Murphy118]

Relay#5zh99 and socket#4kn18 from grainger should do the trick,,,,,,

John

 

[DBCOOPER]

https://www.hearth.com/econtent/index.php/forums/viewthread/78773/P22/

 

[whit]

https://www.hearth.com/econtent/index.php/forums/viewthread/78773/P22/

Thanks. My search attempts here didn't find that. You say there "Well I found the relay I want to use. About 60 bucks but it looks like it will do what I want it to do." Which isn't too much to pay for the feature. Except a < $2 relay (677-OJE-SH-105DM) that runs on 5V plus a 120V-to-5V transformer at around $5 (or free if I dig one out of my box of old wall wart transformers) comes in even cheaper.

Anyway, you've implemented and it works?

 

[whit]

Relay#5zh99 and socket#4kn18 from grainger should do the trick

Thanks for the research. So that's < $16 plus shipping. Won't require soldering. Won't waste as much power as a wall-wart transformer. I like it.

 

[DBCOOPER]

https://www.hearth.com/econtent/index.php/forums/viewthread/78773/P22/

Thanks. My search attempts here didn't find that. You say there "Well I found the relay I want to use. About 60 bucks but it looks like it will do what I want it to do." Which isn't too much to pay for the feature. Except a < $2 relay (677-OJE-SH-105DM) that runs on 5V plus a 120V-to-5V transformer at around $5 (or free if I dig one out of my box of old wall wart transformers) comes in even cheaper.

Anyway, you've implemented and it works?

The relay I used impliments a time delay in it so if say the power takes 5 hits in three minutes it won't keep restarting the stove. I don't know what would happen if it tried to start over and over with short duration power hits. Thats why I used the relay I used. It works fine. Watched it work a bunch of times during last weeks snow.

 

[whit]

The relay I used impliments a time delay in it so if say the power takes 5 hits in three minutes it won't keep restarting the stove. I don't know what would happen if it tried to start over and over with short duration power hits. Thats why I used the relay I used. It works fine. Watched it work a bunch of times during last weeks snow.

What happens if it tries to start over and over with my Quad - which I've seen when adjusting the thermostat - is that it ends up with more pellets in the pot than on a normal start. So it's a higher fire for the first minute or so when it finally does fully start. That can happen when the thermostat adjusts itself too, say at night when it's set to drop 10*. If it was already dropping pellets for a new cycle and the thermostat ends the call, then on next startup it'll overfire at first. Don't see any danger in it, but probably a slight drop in efficiency, and additional heat stress in going from cold to hotter so fast.

Realized the most convenient place to mount the relay's probably inside the stove. At first was thinking by the thermostat, but one end of the wire's as good as the other.

 

[whit]

Relay#5zh99 and socket#4kn18 from grainger should do the trick

Got 'em. Cute little thing. Now to interpret what the pin out is, and how that corresponds to the socket screws. We've got a double-pole, double-throw relay here. I'm wanting to put house wire to a couple of the screws, and run I presume just one lead of the thermostat to and from a couple of the others. The pins are labeled:

1    4
5    8
9    12
13   14

Then the socket has screws on two levels at each end. Is the convention for the upper level screws to be connected to the outside pins, and the lower level to the middle ones?

The diagram on the side of the relay shows something about like:

(1)12             (4)42
    o----             o----
        |                 |
(5)14   |          (8)44  |
     |  |              |  |
     /--               /---
     |                 |
(9)11             (12)41
           _
(13)A1  --|_|--  (14)A2

So the DPDT switch is on the middle set of pins. But beyond that I get fuzzy. Just wiring it by trial and error seems like it might fry something. Advice will be most welcome.

 

[kofkorn]

Here's what I can make out:

The AC connection goes to the relay coil, #13 and #14. Polarity shouldn't matter.

The thermostat wires should go to the Normally Open contact #8 and the common contact #12. This way when the coil is no longer receiving energy, the contacts will open, shutting off your stove.

You only need to use the contacts on one side of the relay. It doesn't matter which side. (except for the input coil of course)

Let me know if you have any other questions.

Test the relay with something simple just to confirm before attaching it to your stove, just to be sure.

 

[whit]

Let me know if you have any other questions.

Very nice. Thanks. Now, what's the convention for the socket? It's shaped like a pyramid, with two screws either end on the top level, and two screws either end on the bottom. If I were designing the socket I'd have the top-level screws wired to the outer pins, and the bottom-level screws wired to the middle pins. (But if I were designing wire I'd have the hot wire be white and the neutral wire be black, so I can be totally backasswards compared to the common sense of an electrical engineer.)

 

[kofkorn]

No Problem.

Image from the data sheet attached below:

Datasheet: http://www.ia.omron.com/data_pdf/data_sheet/my_dsheet_gwj111-e1-03.pdf

Good luck!

 

[whit]

These instructions are exactly perfect. The next time the power goes off at 3 am, I don't need to remember to wake up and go shut down the thermostat. Ah, this modern world.

Ended up screwing the socket down to a small piece of wood and just setting it behind the stove by the thermostat-line terminals. Other than that it's just stripping a few wire ends and tightening down the screw on them - once I'd been clued on which screws to use. Couldn't have been simpler if it had come packaged as a dedicated device in a blister pack.

Thanks guys.

 

[killayaw]

Any way to do accomplish this if you're currently using a thermostat? I love this idea, but I'm not sure how it would work given that I have a thermostat wired up to those contacts.

 

[whit]

Any way to do accomplish this if you're currently using a thermostat? I love this idea, but I'm not sure how it would work given that I have a thermostat wired up to those contacts.

I have the relay and socket above wired up using my thermostat. Basically, I screwed the socket down to a small block of wood, attached a lamp cord with AC plug to the screws indicated above, to be plugged into the surge-protected but not battery-supplied plug on the back of my UPS. (A wall socket would work as well.) I then unscrewed one of the two wires running to the thermostat from the terminal on the back of the stove, and attached that wire to an appropriate screw on the relay socket. From the other screw, I connected a short length of wire from the other relay screw back to the thermostat terminal. Then as the last step I plugged in the AC line. Essentially it's just making one wire of the thermostat line run through this device on its way to the terminal on the back of the stove.

What the relay is is a small electro-magnet that pulls a switch one way when there's power to it. The switch is spring-loaded to switch the other way when the power goes off. In this case it's being wired to be on when there's power to it, and off when there's not. So where there's no AC from the house, it disconnects the thermostat, which effectively shuts off its call for heat. The thorough diagrams above to show me which screws to use were greatly helpful.

 

[Murphy118]

Whit,
Glad to see ya got it all figured out,,,I got contraptions like that all over my house,,,,sump pump,,,furnace,,,lights,,,
It's neat to make this stuff solve problems for yourself

John

 

[killayaw]

Awesome.. thanks!