Boiler choke point
The Glitch:
Due to its low efficiency and high emissions, an installer is asked to replace the outdoor wood-fired furnace shown in Figure 1, with a new cordwood gasification boiler.
ENLARGE
FIGURE 1
The new boiler has a rated output of 150,000 Btu/h. The outdoor furnace is located about 100 feet from the indoor mechanical room. Two runs of 1” PEX connect the outdoor furnace with the remainder of the system. Due to existing landscaping, the installer plans to reuse the existing underground piping.
The new “near-boiler” is shown in Figure 2.
ENLARGE
FIGURE 2
When the boiler is put into operation its temperature quickly climbs to the high limit setting of 200° F, the combustion fan turns off, and the air shutter closes, leaving a large amount of wood to smolder in the combustion chamber. All the circulators are nominal 1/25 HP and are running fine.
Can you determine why this is happening and propose a correction?
Are you an ace troubleshooter?
Within the pages of this magazine, PM’s Hydronics Editor John Siegenthaler, P.E., will pose a question to you, our readers, to review a system’s schematic layout and discover its faults, flaws and defects. Discover archived “The Glitch & The Fix” exercises at its radiant-focused website, www.radiantandhydronics.com. Good luck!
