OPERATING YOUR BOILER (continued) PAGE 37
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MODES OF OPERATION (continued)
• WOOD BURNING WITH AUTOMATIC BACK-UP (“AUTO BACK-UP”)
When set to this mode, “AUTO BACK-UP”, (or after reset), the control logic is as follows:
When starting a cold boiler, the wood combustion draft fan will run until the wood fire
causes the boiler water to attain a temperature of 180° F (L8124C “HI” setting). The fan
will then cycle off and on trying to maintain boiler temperature (170° F to 180°F). Should
the wood fire die out and, therefore, not make enough heat, then the wood draft fan will
stop (as in item “3” under “WOOD BURNING ONLY” on page 34 and 36) and the oil or
gas burner will turn on. The oil or gas burner will then bring the boiler temperature back
up to 180° F. When no heat storage tank is used and when the boiler control is set to the
“AUTO BACK-UP” mode, the oil or gas burner will fire to keep the boiler at Operating
Temperature (170°F to 180°F). When a heat storage tank is used the burner will also be
responding to the settings on the L8151A aquastat located on the tank, i.e., once the
heat storage tank gets up to 175°F (L8151A “HI” setting) the burner will not fire again
until the tank cools back down to 155°F (L8151A “LO” setting minus the 10° F.
differential). The wood combustion draft fan will remain off until reset. To reset, switch
the boiler Control Panel power switch to the position “OFF/RESET” and then back to
“ON”. A power failure will also reset this control.
USE OF THE BY-PASS DAMPER
The by-pass damper must always be opened before opening the loading door. This will
minimize smoking and puff-backs. The by-pass should always be locked tightly in the closed
position when the boiler is in operation. Failure to close the by-pass damper tightly may lead to
puffing and incomplete combustion!
INSTALLING THE 339N PROBE THERMOMETER
The 339N Probe Thermometer is to be installed just downstream of the boiler flue collar. Drill a
¼” hole in the top of the pipe and insert the probe all the way in. The thermometer gives you
an indication of how well the wood is burning and when it is time to brush the heat exchange
tubes. If you are burning dry wood that is well split, you should achieve temperatures of 600°F
or more on the probe thermometer. If you are not achieving temperatures this high, check the
following things:
1. Is the by-pass damper latched tightly closed?
2. Are the vanes of the fan clean and not filled with ash?
3. Are the primary air channels open?
4. Is your wood dry?
In most instances, low stack temperatures are an indication of wood that is not dry. If you have
been operating with temperatures of 600°F and then notice the temperatures are higher, it is
probably an indication that it is time to brush the dust from the heat exchange tubes.
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