Hi to All. I have been reading the forum posts for some time now and am amazed at the knowledge of the forum members. I wish I had more hydronic heating background when I bought my Tarm MB55 Solo in 1980 and I built our 2100 sq ft. home. At that time, I was undecided on the type of system--a wood furnace or a boiler. I decided on an air source heat pump as primary and the wood boiler as a backup. I also have a 5 KW generator in case of a power failure to supply power to the boiler circulator, air handler fan, and other essentials such as lights, refrigerator, etc. This will be the 38th year I have used the MB55. I have also added a 40 Gal Amtrol Boiler Mate to heat our domestic water. This past cold snap, I heated continuously for over two weeks. The coldest winter we ever had was -20 Deg F. There was no problem keeping our home at 70 Degrees.
The biggest unknown for me was the design of the two row hot water coil that I had installed above the heat pump air handler. I contacted a representative at McQuay company with my home size and we came up with a 21” X 27” coil. My two row coil, has the coils in parallel with water flow through both coils in the same direction. If I had some of the information that is on this Forum, I would have had the coils configured so that the supply water would enter the top coil on one side and enter the bottom coil on the other side. Now the supply water and return water are both on the same side. With mild weather (around 30 degrees), I have the water flow reduced resulting in one side of the coil hot and the other side cold. As a result, the registers on one side of the hot air plenum receive warmer air than the registers on the other. No big deal, but I could have done better.
My basic flow control to the water coil consists of two valves in parallel, a ten turn Hoke trim valve and a hydronic zone valve with a balancing cock in series with the zone valve for flow adjust. The zone valve is controlled by a thermostat in the main living area. This valve modulates the flow by increasing or decreasing the total flow through the water coil. I always have a minimum flow through the Hoke trim valve. I open the Hoke valve based on the outdoor temp--3 turns at 30 Degrees, 5 turns at 25 Deg, and wide open at 20 Deg. With this set up, my heat loss to the outside is equal to the heat output from the boiler. I run the boiler temp at 175 Degrees. The Samson draft regulator does a fantastic job of controlling the boiler water temp. When using the wood boiler, to heat our house, the temperature is more constant than when I use the heat pump.
For domestic hot water, I have three configurations using three valves to supply hot water to the house--The Electric hot water tank only, Amtrol Boiler Mate only, or a combination where the Boiler Mate preheats the water input to the Electric water tank. In this last mode, I have an independent circulator loop that only circulates water through the air handler water coil and the Boiler Mate water coil. This mode is useful in the spring and fall when the heat pump compressor is most efficient. The heat pump will raise the incoming 40 degree water temp to 80-90 degrees in the Boiler Mate. The Electric water tank will then raise the temp to the final 110 degrees.
I know the trend today is to go with an efficient gasifier type boiler to reduce wood consumption. My MB55 is less efficient, but I have an abundance of wood, the most being ash. Each spring, I have a “fresh fall” of trees (courtesy of the Emerald Ash Borer). I am happy with the simplicity of the MB55 controls; a mechanical draft regulator and no electronics to fail. I have not replaced one single part in the boiler in the 38 years I have had it heating my home! Also, I am surprised that I only have to clean my chimney and MB55 once a season. Creosote forms in the boiler but when it gets thick enough and the fire gets hot enough it burns and flakes off in the boiler. I get very little creosote in the chimney (loose & flakey) which I clean once a year.
John M.
The biggest unknown for me was the design of the two row hot water coil that I had installed above the heat pump air handler. I contacted a representative at McQuay company with my home size and we came up with a 21” X 27” coil. My two row coil, has the coils in parallel with water flow through both coils in the same direction. If I had some of the information that is on this Forum, I would have had the coils configured so that the supply water would enter the top coil on one side and enter the bottom coil on the other side. Now the supply water and return water are both on the same side. With mild weather (around 30 degrees), I have the water flow reduced resulting in one side of the coil hot and the other side cold. As a result, the registers on one side of the hot air plenum receive warmer air than the registers on the other. No big deal, but I could have done better.
My basic flow control to the water coil consists of two valves in parallel, a ten turn Hoke trim valve and a hydronic zone valve with a balancing cock in series with the zone valve for flow adjust. The zone valve is controlled by a thermostat in the main living area. This valve modulates the flow by increasing or decreasing the total flow through the water coil. I always have a minimum flow through the Hoke trim valve. I open the Hoke valve based on the outdoor temp--3 turns at 30 Degrees, 5 turns at 25 Deg, and wide open at 20 Deg. With this set up, my heat loss to the outside is equal to the heat output from the boiler. I run the boiler temp at 175 Degrees. The Samson draft regulator does a fantastic job of controlling the boiler water temp. When using the wood boiler, to heat our house, the temperature is more constant than when I use the heat pump.
For domestic hot water, I have three configurations using three valves to supply hot water to the house--The Electric hot water tank only, Amtrol Boiler Mate only, or a combination where the Boiler Mate preheats the water input to the Electric water tank. In this last mode, I have an independent circulator loop that only circulates water through the air handler water coil and the Boiler Mate water coil. This mode is useful in the spring and fall when the heat pump compressor is most efficient. The heat pump will raise the incoming 40 degree water temp to 80-90 degrees in the Boiler Mate. The Electric water tank will then raise the temp to the final 110 degrees.
I know the trend today is to go with an efficient gasifier type boiler to reduce wood consumption. My MB55 is less efficient, but I have an abundance of wood, the most being ash. Each spring, I have a “fresh fall” of trees (courtesy of the Emerald Ash Borer). I am happy with the simplicity of the MB55 controls; a mechanical draft regulator and no electronics to fail. I have not replaced one single part in the boiler in the 38 years I have had it heating my home! Also, I am surprised that I only have to clean my chimney and MB55 once a season. Creosote forms in the boiler but when it gets thick enough and the fire gets hot enough it burns and flakes off in the boiler. I get very little creosote in the chimney (loose & flakey) which I clean once a year.
John M.