Mental wrestling with a 9 year old ...Tarm Solo 30

[Jim Post]

Greetings-

We have been struggling to keep our 3-zone radiant baseboard heated house warm this Fall due to frequent overheat trips on our 2005 installed Tarm Solo 30 wood boiler (no storage). When the overheat trip occurs the draft fan is disabled until one of us notices cool temps in the house and investigates. We then reset the Tarm by pressing that little white button under the cap on the control panel. In the meantime, it seems the return water from the house loops drops low enough to cause the Thermovar to restrict flow into the wood boiler loop. This seems to be causing the wood boiler loop to get to an overheat condition rapidly and the whole cycle starts over again.

In order to get the temps in the house up, I must manually stop the circulator for the zones so that the return to the wood boiler temp increases...once that happens I open the zones one at a time from smallest to largest...waiting each time to ensure the return temp at the thermovar is hot to the touch. Once all the zones are flowing the supply to the house struggles to get above above 160F and sometimes hovers around 130F...this is a new symptom this year...

After babysitting the boiler every couple hours last night, I got the whole system up to 190F by this morning and the house was getting comfortable again...then we got another overheat trip and the cycle repeats although much less problematic if I am here to catch it in time...

I am sure both circulators are functioning properly and the Tarm seems to be working as designed,....my suspicions revolve around the thermovar but I have heard that ..."when they fail they fail closed and you know it."

So based on this long winded description of the symptoms can any of you wood heat boiler gurus suggest a cure or at least methods to diagnose the underlying cause. ...(storage is not an option for us at this time) ;-)

Thanks,

JP in WI

 

[Clarkbug]

For the termovar, do you have a bypass with a ball valve on it? What is that ball valve set at? Any changes in that valve position this year?

I agree that it sounds like you definitely have an issue with the near boiler water circulation. The termovar should restrict some flow from coming back, but you should still be pumping enough water that the Tarm knows its getting too hot and can cycle off. If you are sure your pumps are all working fine (just because they are spinning the motor doesnt mean the impeller is OK), check your valves and then the termovar. Its coming up on 10 years old, might be worth a swap out just for peace of mind.

 

[BoilerMan]

I agree, check boiler circulator impellers by isolating and removing the cartridge. Also remove the element from the Termovar, put it a pot on the stove and watch it as the water heats up, a candy thermometer is helpful. I'd just get a new element and keep the old one if it's good. Something is amiss with near boiler circulation, either with a pump or the Termovar.

TS

 

[Jim Post]

Thanks for the responses...I took the guts out of the Termovar and put it back together....I will be able to swap in the new parts when they arrive...I tested the thermostat in a pan of water on the stove and it did open up around 150F. Still decided against using it. I am questioning the need for it since the system is more responsive than it's ever been. I really dreaded tearing into it with the forecast low tonight for 13F, but it went pretty smoothly. I had to cut into my piping 'cause the guy (me) that put it together back 2005 didn't anticipate the need for servicing....and mounted it overhead above a washing machine and sink. Today I added a ball valve and union which will make it easier next time. I should have the new parts from Tarm by Wednesday. Looking forward to a good night sleep and so relieved to put my hand on a baseboard and feel the heat. Thanks again for taking the time to respond. Stay warm!