Tarm 2000 fan not restarting

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New Member
Feb 1, 2023
central NY
Hello All-
I'll put the real problem in bold if you want to skip the back story...
I rent a place and inherited a Tarm 2000 multi-fuel boiler. I try and use wood primarily as I have sufficient access to it and it is cheaper then the oil side. It has a Custom Controls panel which as the name implies, is custom built. No one around me will touch it as they have never seen one before. But it seems I am slowly rebuilding it as each weak link fails and in the process becoming more aware of how it works than I really wanted to be. I have recently replaced the Guard dog low water sensor. And I have replaced the fan a couple years ago. As well as have replaced the fan switch module in the panel. And the wood is having no problem feeding downward towards the gassifier. (I mention these since they relate to the current issue I'm having.)
The problem is that when the boiler gets up to full temp (190-200) the fan kicks off and often doesn't kick back on when it drops below 150. The solution every time thus far is to simply flip the power off and on to the furnace. This kicks the fan on every time.
During the day I go outside and do that (tedious obviously). During the nights, I can usually guarantee that the house will be cold in the morning since the fan will shut off after it gets to full temp and will not kick back on.
At first I thought it was because of low demand during the "shoulder seasons" but it is still happening and we are in the teens at night. I try and leave my heat on at 70 inside the house at night (higher then we would prefer) just to keep the demand up. But inevitably, during the late hours of the night there must not be enough demand to cycle the fan back on because it drops and doesn't turn back on. I've even gone out at 3:00am on cold nights to flip the power off and on to restart the fan. We've lived here 4 years and this year has been the worst for getting it to come back on when it should.
I am thinking of replacing the wall power switch (red light switch) with a digital timer switch from Home Depot that will kill the power to the furnace at pre-scheduled times. Maybe it turns the power off and on at 2:00 am and 4:00 am. (Kind of Rube Goldberg but I can't seem to find the real problem.)
Any thoughts or experience on what it could be? Aquastat wearing out? Some temp sensor corroded/creosoted? I did a major clean of the entire unit in the fall, so I had high hopes of how efficient it would run this winter, but I can't seem to get on top of this problem.
It's also causing me to burn through a lot of unnecessary wood just to try and keep the demand up so that it doesn't "time out" and not come back on. I really like the idea of how it is supposed to work and would love to have it operating at its former glory... whatever that might have looked like. Any help would be greatly appreciated (except "call the landlord and tell him to fix it". That won't help me.) I have a inquiry into BioMass about it too, so maybe they will have the solution.
On my Tarm solo plus there is a dial on the back side of the control panel to adjust the temp of fan operation. I have no idea if yours is the same or not. Also mine has a safety thing that acts like a circuit breaker if you get it too hot you have to manually reset it after it cools to start the fan. Just a guess that these things could have anything to do with it.
Thanks so much for your suggestion. Mine does have a temperature dial that is connected to the chimney temp probe.
A technician from Biomass got back to me and suggested that this probe could be what is bad. Or he said it might be the internal timer on the control panel. His recommendation was to replace them both if I wasn't sure how to trace it with a volt meter. So I decided to order both parts. I might try one part at a time so that I can have a clearer sense of what it might be. I will be sure to post the results in case it helps someone else too.