I am posting this to try and save lives or property. I bought a stoker coal stove on December 23, 2016 that has an Intermatic C8835 mechanical timer. This timer unit is a 30 minute timer that normally rotates in a clockwise direction and completes one revolution every thirty minutes. Around the perimeter of the timer wheel are slots which receive small metal "tripper" keys. As the timer wheel rotates these tripper keys then activate a normally open microswitch that in turn activates the coal stoker drive motor which pushes unburnt coal from the coal hopper onto the fire grate and this pushes the burnt coal ash off of the grate and into an ash bucket below.
On January 16th, 2017 when I returned home from work the temperature in my house was 100 degrees and the stoker was feeding continuously. And yes the thermostat had met the room set temperature. At that time on my investigation I thought that the Intermatic timer wheel had simply stopped turning with the normally open microswitch in the closed position. So I de-energized the stove and then re-energized the stove and the timer returned to service and was turning in it's normal clockwise rotation. So everything was good, or so I thought.
However, on February 3rd, 2017 on my return home from work the room temperature was up to 84 degrees and the thermostat had met the call for heat. I turned the thermostat down but the stoker drive motor was continuing to drive the stoker unit. When I opened the cover of the Intermatic timer I noted that the timer had the normally open microswitch in the closed position and the stoker unit was continuing to run. The timer wheel was again not turning. I once again de-energized and re-energized the stove. However the Intermatic timer wheel did not resume normal clockwise operation as it had the first time (Jan 16) this happened. When I manually advanced the timer wheel in a clockwise direction and disengaged the micro switch the stoker drive motor stopped as it was supposed to do. I then monitored the unit for a while and I discovered that the timer unit wheel was turning counterclockwise which is backwards from its normal clockwise operating direction. As at the time of my initial observation of the timer micro switch I had found trippers engaged and the micro switch closed, I decided to manually turn the timer wheel (clockwise of course) to once again re-engage the micro switch. I then observed that with the reverse direction (counter clockwise) rotation of the timer wheel the micro switch lever would jam against the adjacent "tripper" (key or tab) and then the timer wheel would not turn and would not disengage the micro switch controlling the stoker drive motor. This of course leading to continuous feeding of coal by the stoker drive motor and the overheating of the house. Even with multiple reset cycles of de-energizing and re-energizing the power to the stove I was not able to get the Intermatic timer unit to return to normal clockwise rotation direction and I had to replace the timer with a used loaner from my local hardware store off of their showroom display model.
Note that the next day I tested the faulty Intermatic timer unit and found it then to be turning in the correct clockwise direction. As the unit at the time of this test was not mounted on the stove I am thinking perhaps the mounting location of the timer on the body of the stove could possibly be causing the failure due to heat. But I cannot confirm that as I returned the faulty timer to my local hardware store that I purchased the coal stove from.
So if you have a stoker unit with one of these units I would suggest that you replace it with another unit and also add an over-ride thermostat unit to de-energize the entire stove unit if there is a problem and your unit begins to overheat the room as mine has now twice done. FYI the stove manufacturer says that there is a second micro-switch that supposedly shuts the stoker drive motor off if the temperature of the stove climbs above 200 degrees. However that safety over ride is not working on my stove either. Bottom line is I want anyone and everyone that has an Intermatic C8835, 30 minute mechanical timer, with a 125 volt AC, 60 hertz drive motor to be aware of this as soon as possible since it will probably take a few months before the NFPA can investigate this and make a determination on the safety hazard of this motor.
These OEM Intermatic timers are also apparently used to control some pool filter units but this problem would not necessarily create a life safety hazard as the coal stoves do by overheating and potentially causing a fire.
The stoker manufacturer has advised me that there has been some issues with this Intermatic timer switch unit since Intermatic began sourcing them from a manufacturing facility in Mexico. Which makes this the second electrical item in my house in the last two months that was made in Mexico to have an fire safety hazard electrical fault that has occured. A Samsung TV "blew out" the transformer with a loud electrical crack/snap and a puff of smoke.
And yes I have contacted the coal stove manufacturer but I have also contacted Intermatic as well. So please if you have one of these units be aware of this issue and take necessary precautions until this issue is corrected.