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WOODMASTER OUTDOOR FURNACES • OWNER'S MANUAL
Adding Antifreeze to Outdoor Furnace System
Most outdoor furnaces are installed without antifreeze when an existing
heating system is in place and there is no anticipation of leaving the outdoor
furnace unattended for extended periods of time (10 days or more). If the
building being heated has an alternate heat source, system water may be
kept from freezing by running the circulating pump(s) and drawing heat
from the existing furnace or boiler in the building.
To prevent freezing if the outdoor furnace is not fired for extended time
periods or if lengthy power outages are anticipated during cold weather,
a nontoxic propylene glycol may be used in the system. Some types of
antifreeze that contain various inhibitors have been known to create
problems like coagulation and jelling. To prevent potential problems, do
not use propylene glycol that is premixed with inhibitors. MolyArmor 350
is compatible with (raw) propylene glycol. It is important to use MolyArmor
350 with straight propylene glycol for corrosion protection. If adding
antifreeze to the system, it is imperative that the entire system contain at
least 30% antifreeze concentration mixed with softened, reverse osmosis
or deionized water to prevent bacterial growth and minimize minerals
in the system. Bacterial growth is likely to occur with low antifreeze
concentrations and can cause corrosion in the furnace water jacket and/or
clogging of heat exchangers. To confirm the antifreeze solution is adequate
and to kill bacteria, immediately heat the system up to 170˚ F, allow the
pumps to circulate for at least 24 hours and then obtain a sample of the
system water. Using an antifreeze tester, the solution must be protected to
10˚F (-12˚C) or below.
NOTE: If using antifreeze, test the pH and Moly levels once each month . If the
bacterial issues occur, the pH will decrease .
NOTE: Be sure to adhere to all warnings and precautions on the antifreeze label .
NOTE: Do not use automotive or RV types of antifreeze .
