B.
1.A mixing valve arrangement is a method of controlling house temperature that is different than traditional American systems. In the average hydronic system, circulating or not circulating water of a fairly high and relatively constant temperature to radiation controls temperature in the house or zone. The thermostat used in such a system is a simple switch to a relay, which turns the circulator on and off. In a mixing valve controlled system, the circulator runs continuously, and the temperature of the water flowing to the house is varied by the mixing valve, which adds more or less cooler return water to the
A system controlled by a mixing valve has several advantages over a conventional off/on system.
∙Fuel savings of 20%
∙Longer boiler life due to elimination of thermal shock to the boiler caused by surges of cold return water at circulator
∙A quieter and more comfortable house, because heat is more even. Rather than having the heat turn completely on and completely off in response to heating demands, causing fluctuation in the house temperature, the heat is always “on” with the temperature of the radiation adjusting gradually to respond to the house’s needs.
In addition, a mixing valve arrangement has very important advantages for solid fuel burning hot water systems. Because there is constant circulation, there is always some heat being drawn from the boiler. Since a solid fuel is always generating a certain amount of heat, such a system will dispose of this heat efficiently. In conventional system, there is a grater possibility of the boiler overheating (when there is no circulation) and creosote formation (caused by the fire burning too slowly). A mixing valve system minimizes the possibility of either of those problems occurring, thus increasing both the safety and efficiency of the solid fuel system.
Mixing valve arrangements can be added to any of the systems described in this section or, in fact, to any conventional heating system as well. We recommend the
The following outlines a typical installation of a mixing valve controlled distribution system with a 3WOOD boiler in a system planned for solid fuel firing with
1.The line from the 3WOOD boiler supply tapping goes to the oil/gas boiler supply pipe. Install a “tee” with a 1” branch in the line as close to the 3WOOD boiler as possible. This branch tee should point up and will route the piping to the “dump zone”. There must not be a valve or any potential restriction between the boiler and this tee.
2.Immediately after the
3.In the boiler supply piping install an air purger and expansion tank sized to handle the water in the distribution system as well as the 3WOOD boiler.
4.Pipe the
5.Install a tee with a 1” branch for the dump zone in the return tapping as close to the 3WOOD boiler as possible. Point the branch of the tee up.
6.The 3WOOD boiler circulator should be installed from the other
7.The 3WOOD boiler circulator may be controlled by an outdoor reset controller operating the mixing valve, the oil/gas boiler relay or a Honeywell R845 or equivalent if the mixing valve is manually operated. This relay is controlled by the 3WOOD boiler Aquastat.
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