I have a Weso 125 ceramic tile stove with an automatic thermostat. The automatic function no longer works and I can't find a replacement. The stove still functions fine on manual thermostat over ride. I purchased this stove in the eighties and I really like it. My question is does anyone know where an aftermarket thermostat can be had and if not is there a good quality overheat alarm that I could acquire. I left the stat open and got the stove pretty hot so I need to do something to keep that from happening again. Thank you for any input.
Weso automatic thermostat
- Thread starter 2old2run
- Start date
-
Active since 1995, Hearth.com is THE place on the internet for free information and advice about wood stoves, pellet stoves and other energy saving equipment.
We strive to provide opinions, articles, discussions and history related to Hearth Products and in a more general sense, energy issues.
We promote the EFFICIENT, RESPONSIBLE, CLEAN and SAFE use of all fuels, whether renewable or fossil.
I thought that was probably the case. Do you know of any good quality stove or flu overheating alarms?
Okay thank you. If anyone on this forum makes one I would be interested in buying one from them. Is there a place on here to give a thumbs up for replying to a post?
![[Hearth.com] Weso automatic thermostat](https://www.hearth.com/talk/data/attachments/308/308462-acf846f1476d7e875a9c81c1361963e3.jpg?hash=dr7fsV9KxR "[Hearth.com] Weso automatic thermostat")
![[Hearth.com] Weso automatic thermostat](https://www.hearth.com/talk/data/attachments/308/308463-cf4e89baa1cf45720539ef3563aa560c.jpg?hash=i7uazhrZ6O "[Hearth.com] Weso automatic thermostat")
![[Hearth.com] Weso automatic thermostat](https://www.hearth.com/talk/data/attachments/308/308464-342c639a89cc58af215a6aec0d6a427f.jpg?hash=-6va_TrOOO "[Hearth.com] Weso automatic thermostat")
With attention, the stove could be run by manually controlling the thermostat as long as the linkage is still in place.
![[Hearth.com] Weso automatic thermostat](https://www.hearth.com/talk/attachments/screen-shot-2023-01-25-at-6-09-12-pm-webp.308543/ "[Hearth.com] Weso automatic thermostat")
The Auber AT200 has an alarm function. We have one and like it.
Thermometer for Stove Pipe,Chimney,Outdoor Wood Boiler,w/ Alarm Thermometer for monitoring temperature on stove, chimney, or outdoor wood boiler [AT200CHIM] - $79.99 : Auber Instruments, Inc., Temperature control solutions for home and industry
This thermometer kit can be used for monitoring the temperature in stove pipes, chimneys, and outdoor wood boilers. This thermometer reads a thermocouple probe, shows the temperature on its red LED display, and makes a buzzing sound when temperature rises above the pre-set alarm temperature. For...
www.auberins.com
I have a hard time believing WESO made that part and that would mean they very well may have purchased a standard available part from another manufacturer. I have never taken the door apart to look at mine but if I found myself in your situation I would do that and photograph and measure what is there before starting a search. I think Vermont Castings uses a similar part but it may not fit. If I manufactured the stove, I'd have bought that part. Why reinvent the wheel. I have the same stove and have thought about this situation but never looked into it seriously. It is a shame to junk a nice stove.
I have my stove open today to clean it out a bit and while it's open I decided to remove a few cover panels and see how the control works. I was expecting a simple bi-metal arm or bi-metal coil being activated by the heat level coming off the outside of the ash door. The control unit is bolted to the ash door and then covered by a cast iron panel. What I found is a pivoting arm but it does not appear to be bi-metal. There is a screw that goes through the arm to the base of the unit on the end opposite the damper flapper. This appears to set up a pivot point. About 1.5" to the right of that there is a coil spring behind the arm. In between the spring and the screw is where the control knob shaft is threaded through a bracket and the inboard end is against the arm. It appears the adjustment knob shaft is what controls how far out the spring can push the arm. The farther out the arm moves, the more air the stove gets. Great, what we have so far is a simple means of manual adjustment. What makes it automatic is a small two-part brass cylinder on the front side of the arm, opposite the spring. This cylinder has a thermo-couple attached to the back end of it. The thermo-couple wire feeds through the ash door with the end attached to the inside of the door, next to the front clean-out grate of the firebox. It appears the adjustment knob limits how far the damper disc can open and the thermo-activated cylinder pushes it closed based on firebox temperature. I am unsure how the little cylinder works. Could it be some type of bi-metal actuator operating off of a thermo-couple or perhaps it is filled with mercury and the expanding mercury is doing the actuating. Attached is a sketch of what I described. I pointed a butane lighter flame at the thermo-couple sensor and the damper did close. If that happens, I'd say it is working. If it doesn't close I'd guess the thermo-couple sensor or the cylinder are bad. If the damper is closed all the time, I'd guess the spring broke or fell out. I hope this may help another WESO owner.
![[Hearth.com] Weso automatic thermostat](https://www.hearth.com/talk/data/attachments/317/317315-14187a2880801beb3a639cb53fc5673a.jpg?hash=RP_dlMsVMM "[Hearth.com] Weso automatic thermostat")
Looks like that cylinder may be what is called a thermal actuator piston. I have been unable to determine if they were a standard product from some manufacturer or something WESO had made to spec by a manufacturer.
Do you have any pics of the cylinder? I wonder if it’s a wax capsule? They might not be able to handle the heat though.
I saw some websites with the wax filled actuators but the ones I saw did bot deal with temperatures as high as a coal firebox gets. Perhaps some do. Being able to find a substitute replacement for that part would be a very handy thing. Here is a photo showing a side view of the unit.
![[Hearth.com] Weso automatic thermostat](https://www.hearth.com/talk/data/attachments/317/317520-a3d9334354cbcaa31032b5f15fedab98.jpg?hash=FXSklzq4S9 "[Hearth.com] Weso automatic thermostat")
I've been thinking that what I referred t as a wire from the sensing bulb to the actuator must actually be a capillary tube allowing fluid heated in the bulb to transfer heat to the actuator. That said, while the bulb may be reading 600 degrees, the temperature at the actuator end of the capillary may be much lower and in the acceptable range of a wax motor. With the actuator being close to the pivot point and the center of the damper disc being about about 5" farther out the arm, the distance the damper moves would be greater than the distance of the max wax motor stroke. I have this question, if the actuator stroke is enough to push the damper disc closed at the highest setting, where does the excess expanded wax/oil (or whatever is in there) go when you are set on a midrange setting and the damper is already halfway closed? Unless of course the expansion amount is less at the temperatures generated when the stove is on a lower setting. PS: If that is a fluid filled capillary tube, pinching it would cause the expansion cylinder to not operate. For the person whose automated damper was no longer working, try heating the bulb and watch to see if the actuator is moving the arm.
![[Hearth.com] Weso automatic thermostat](https://www.hearth.com/talk/data/attachments/317/317646-c94f24af26493d1e18989a0492e53dab.jpg?hash=TVwspXma-2 "[Hearth.com] Weso automatic thermostat")
the wax would be fully contained so it won’t leak out. It expands and contracts at a known rate so it would be fully expanded when the stove is hot, expanded half way when running at midrange, and at its smallest size when the stove is cold.
It has been very warm here in Southeast PA for late October, so my stove is not fired up. Once I get it burning again I plan to use my infrared thermometer to check the temperature of the sensing bulb located inside the the ash bin door and also the temperature of the actuator on the outside to see what those temperatures are. I watched a video this morning about wax motor actuators which have no electric heaters built in. That manufacturer's max temperature was 300 degrees F. My unit woks but the day may come when it doesn't and I'd sure like to have a source for a replacement. It's the remote sensing bulb that creates the unknown. Is the temperature of the bulb the same at the actuator end?
American stoves use a bimetallic spring that pulls a chain to open the air door closed by gravity.
European stoves use similar to yours that use hydraulic action via a capillary tube. This same theory is used on conventional oven thermostats to control the oven temperature with the sensing bulb end and capillary tube connected to thermostat.
They use a very light oil in the tubing that expands, building up pressure at the sensing end. This puts hydraulic pressure through the capillary tube on one side of a diaphragm. (It doesn’t heat the thermostat control end) The other side of diaphragm has a spring controlled by rotating thermostat that puts opposing pressure on the other side of diaphragm. By turning it up, that manual pressure side of diaphragm pressure opens air door, as capillary heats, fluid pressure on other side tries to close it.
The hydraulic system is more sensitive than bimetallic and normally only fails when fluid leaks out. Some have the sensing bulb under heater (Surdiac, Efel) in the circulating return air airflow, and can be moved to adjust how much heat affects the oil.
Many capillary tube systems use a sensing bulb with tube end connected to a diaphragm that works a micro switch turning an electric controlled system on or off with temperature rise or drop. Newer electronic controls use thermistor sensor connected by wire instead of mechanical / hydraulic control.
I happen to have a Weso stove sitting in my front yard right now. some parts are not usable, but I believe the door with the thermostat is still good.
Similar threads
