Been lurking here more than a year. The information on this site helped me decide to buy a Biomass 25 last winter when the electric utility decided to eliminate the Residential Thermal Storage rate that I enjoyed for many years. Thanks to all for the help!
When I went with the RTS system many years ago I decided to go with a pressurized water storage system for several reasons. The more common ceramic systems would sometimes overheat a house with clear weather due to the cold nights and daytime solar gain. Also with a closed system there should be fewer problems with corrosion than with an open system. Another reason was my thought that if and when the sweet deal electric rate went away, I would have in place a distribution system and I could just heat the water a different way. That day has come.
I had always supplemented my heating with wood but I wanted to use the wood more efficiently and the Biomass certainly delivers on that one. So, I piped the boiler into the existing storage tanks and have been tweaking ever since to the point now that it works quite well. A few more things are in order but by and large the system works very well.
Which brings me to my point. Over and over again I read about adding more storage by increasing the volume of water. There is another way that I believe should get more attention and that is the temperature differential in the storage system. My RTS system was designed to store enough energy to heat the house for 10 hours during the day with the lowest temperatures we get here, I have the paperwork for the heat loss calculations etc but I believe that temperature was -20 degrees F.
My system was designed to heat the upstairs only I believe (1000 sq ft) but I had also added basement rooms so that the total was 1500 sq ft. Even after adding this, we had a very cold day onetime that was theoretically below what the system was designed for. The electric utility called us on that day to let us know that we could turn on the override function and they would not bill us for that but we never did it because we didn't need to.
The storage system consists of 2 112 gallon well insulated tanks that resemble water heaters. The way this system is able to do so much with so little is by the temperature differential it uses. The baseboard radiators are sized to be able to heat the house with a water temperature of 120 degrees and the max temperature for the tanks is 235 degrees. The temperature of the water flowing into the radiators is moderated by a thermostatic mixing valve.
My question is, why don't the makers of these systems design them to run up to a higher water temperature? I ran the system last winter as it was but the max temp of 195 degrees was OK but not enough. I was not getting anywhere near the BTU capacity my system was designed for. I contacted Zenon and he told be I could increase the max temp by putting a resistor in parallel with the temperature sensor so I did that, carefully selecting a resistor value that raised the temperature 10 degrees when near the maximum temperature. This helped quite a bit but more would be better.
In the winter I can burn the system once a day and get some idling at the end of a burn but by the time it gets to that point most of the wood gasses are gone so I don't think it's a big deal. During the milder weather I can even skip days!
So back to my question, why is there not more emphasis on the temperature differential?
When I went with the RTS system many years ago I decided to go with a pressurized water storage system for several reasons. The more common ceramic systems would sometimes overheat a house with clear weather due to the cold nights and daytime solar gain. Also with a closed system there should be fewer problems with corrosion than with an open system. Another reason was my thought that if and when the sweet deal electric rate went away, I would have in place a distribution system and I could just heat the water a different way. That day has come.
I had always supplemented my heating with wood but I wanted to use the wood more efficiently and the Biomass certainly delivers on that one. So, I piped the boiler into the existing storage tanks and have been tweaking ever since to the point now that it works quite well. A few more things are in order but by and large the system works very well.
Which brings me to my point. Over and over again I read about adding more storage by increasing the volume of water. There is another way that I believe should get more attention and that is the temperature differential in the storage system. My RTS system was designed to store enough energy to heat the house for 10 hours during the day with the lowest temperatures we get here, I have the paperwork for the heat loss calculations etc but I believe that temperature was -20 degrees F.
My system was designed to heat the upstairs only I believe (1000 sq ft) but I had also added basement rooms so that the total was 1500 sq ft. Even after adding this, we had a very cold day onetime that was theoretically below what the system was designed for. The electric utility called us on that day to let us know that we could turn on the override function and they would not bill us for that but we never did it because we didn't need to.
The storage system consists of 2 112 gallon well insulated tanks that resemble water heaters. The way this system is able to do so much with so little is by the temperature differential it uses. The baseboard radiators are sized to be able to heat the house with a water temperature of 120 degrees and the max temperature for the tanks is 235 degrees. The temperature of the water flowing into the radiators is moderated by a thermostatic mixing valve.
My question is, why don't the makers of these systems design them to run up to a higher water temperature? I ran the system last winter as it was but the max temp of 195 degrees was OK but not enough. I was not getting anywhere near the BTU capacity my system was designed for. I contacted Zenon and he told be I could increase the max temp by putting a resistor in parallel with the temperature sensor so I did that, carefully selecting a resistor value that raised the temperature 10 degrees when near the maximum temperature. This helped quite a bit but more would be better.
In the winter I can burn the system once a day and get some idling at the end of a burn but by the time it gets to that point most of the wood gasses are gone so I don't think it's a big deal. During the milder weather I can even skip days!
So back to my question, why is there not more emphasis on the temperature differential?