Outdoor Wood Furnace Info
All-Purpose OWF Discussions => Electronics => Topic started by: Gunpowder on December 20, 2016, 06:36:48 AM
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Installing my OWB. It appears using two thermostats so your furnace can work as a backup is pretty common. Some experienced quirks depending on furnace design. (air conditioner coming on, etc.)
There are a few posts where people are successfully using a surface mounted Honeywell aquastat on the incoming line before the heat exchanger. This allows one to use only one thermostat and the aquastat determine if the furnace burner comes on or not depending on the temp of the OWB water. This is my preferred but my CB OWB parts supplier had never heard of doing this. Sent me home with an extra thermostat.
Have seen people attempt to use a sincgle multi-stage thermostat but appears no one was successful.
Since the 2-thermostat arrangement seems common was curious if the other method is becoming popular.
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I use to have the two thermostat method, wife kept turning the wrong one up >:(
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I have a strap on aqustat on my supply line coming in from the owb. It is set to trigger the oil boiler to start up if the incoming water temp drops below 130. It acts like an automatic switch that breaks the power to the oil burner when there is sufficient temp to heat the boiler. When it closes the loop the oil burner resumes it's original function and takes over. Only trouble is that water to water heat exchangers work both ways so some heat is going back outside and heating the boiler water , thus more demand on the oil boiler. But very little chance of freeze up over an extended period.
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Single thermostat for each zone (different levels of a split level) which controls the oil boiler like the wood boiler isnt even there. I run a temp controler (aquastat would do the same thing) the cuts power to the burner of the oil boiler and lets the house circulating pump turn on and off like normal. As long as my incoming water from the wood boiler is above 130 or so (dont remember where its set) my oil boiler never fires but the pump still runs and works like it should. If the temps from the wood boiler drop, the controler kicks open and the oil boiler fires and heats like it would without the wood boiler there.
Here is the temp controler Im running : https://www.amazon.com/gp/aw/d/B00OXPE8U6/ref=sxts1?ie=UTF8&qid=1482332641&sr=1&pi=AC_SX236_SY340_FMwebp_QL65
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I prefer two thermostats but not wired in series. Not sure why you would want to do that.
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I generally like a two thermostat system. Simple, just turn up the one you want. Most people can figure that out.That said, we just did a job with three heatpumps with wifi t-stats and used a ranco aquastat on the incoming line and switched all three units. Simple switch turns off the ranco when going back to air conditioning.
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Nest. :thumbup:
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I generally like a two thermostat system. Simple, just turn up the one you want. Most people can figure that out.
Neve met my wife have yah?
She likes the look of just one thermostat on the wall since I’ve gone with the aqua stat.
Wish I had known of it 16 years ago. It literally took ALL NIGHT to get that stupid second thermostat hooked up. Only had two wires to start with, so I thought easy cheesy, tape the new multi wire thermostat line to the old and pull it out and things turned to crap from there.
The old wire was actually fastened in a groove in the lathe and plaster behind the paneling. Took a while to get the trim off without breaking any. Found the wire went down to the floor and was in another groove. This groove went off at an angle until it went under the wall?!?!?! Came out on the other side then down thru the floor. Seriously WTF?? They did this to avoid drilling thru a 14x14 beam in the basement. Drill the stupid beam already!!! I had it all apart anyways and the carpet pulled up, I routed the new wire the same.
Of course if I had an Aquastat then, I would still have had to mess with that nightmare later when adding the central air to the house.
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Well, I voted for 2 thermostats but now switched over to a single.
I had the humidifier controller mounted down by the furnace and I don't think it was very accurate there. I started looking for a thermostat with humidity control so I didn't have to add a 3rd box on the wall and there weren't many decent options that I liked. I eventually found one that I liked and could do everything I wanted.
There are 3 different brands that are the same. Johnson Controls, Venstar and Start to Finish. I went with the Start to Finish since it was the cheapest.
It can be set from 1 to 10 degrees before the backup comes on and also a delay can be set so if you raise the temp setting it won't turn on the gas right away.
It does make the blower cycle a lot more than it used to though. I am guessing the old thermostat was just letting the temperature swing a lot further.
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Well, I voted for 2 thermostats but now switched over to a single.
I had the humidifier controller mounted down by the furnace and I don't think it was very accurate there. I started looking for a thermostat with humidity control so I didn't have to add a 3rd box on the wall and there weren't many decent options that I liked. I eventually found one that I liked and could do everything I wanted.
There are 3 different brands that are the same. Johnson Controls, Venstar and Start to Finish. I went with the Start to Finish since it was the cheapest.
It can be set from 1 to 10 degrees before the backup comes on and also a delay can be set so if you raise the temp setting it won't turn on the gas right away.
It does make the blower cycle a lot more than it used to though. I am guessing the old thermostat was just letting the temperature swing a lot further.
Good to know, I’m using a Nest atm, controlling the humidifier with it as well. I like the wifi capability, if the wife and I are gone on the way home I can turn the heat back up from the iPhone.
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Good to know, I’m using a Nest atm, controlling the humidifier with it as well. I like the wifi capability, if the wife and I are gone on the way home I can turn the heat back up from the iPhone.
This one has wifi too.
I just read the manual again and there is a fix for the short cycling. It can be set to let the temp drop before coming on and you can limit the number of cycles per hour.
You can also send messages to the thermostat from the phone app. Not sure why you would want to do that. Maybe to tell your wife to leave it alone? ;D
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RSI, so which did you install, I see they have three
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I got the sfthrtsh742
It is the same as the Venstar t5900. The newest version of the Venstar is the t7900 which is only slightly different and didn't seem to be worth the extra. The T7900 doesn't need a separate wifi key like the T5900 and the sfthrtsh742. (I bought mine as a package deal that included the wifi key)
It looks like the Johnson Controls is sold as the T-8000 series.