National Products BW3 - Manual (Page 14)

PROCEDURE 9—CIRCULATING PUMP
Every forced hot water system requires a circulating pump. A separate pump or zone valve is required for each zone if there are 2 or more zones.
This pump must have the capacity to provide circulation required by system. The pump is connected into return main just ahead of boiler and wired
to electrical system.
PROCEDURE 10—BLOWER (DRAFT INDUCER)
The blower provides a means for pulling air through boiler and exhausting flue gases into vent system. The blower shuts off when burners are not
firing. This keeps heat in the house rather than losing it up the chimney.
PROCEDURE 11—PRESSURE SWITCH
The air pressure switch works on a negative pressure. When blower comes on, the air pressure switch operates intermittent pilot and gas valve.
The air pressure switch is factory set and only works when blower operates properly. It prevents boiler from starting if blower does not generate
enough pressure or if venting system is blocked.
The factory-set pressure switch setpoint is as follows:
-0.4 in. wc for 2-5 section boilers
-0.5 in. wc for 6-7 section boilers
PROCEDURE 12—ROLLOUT SWITCH (FLAME ROLLOUT SAFETY SHUTOFF)
The rollout switch is a temperature-sensitive fuse link device. It is located on boiler base just outside fire box. In the event of heat exchanger
flueway blockage causing flame to roll out of fire box, the fuse blows shutting down flow of gas to main burners. The fuse does not change in
appearance when blown.
If rollout switch blows, it must be replaced with an exact replacement. Check heat exchanger flueways for blockage when restoring system to
operating condition. Do not operate system without a rollout switch.
STARTING BOILER
PROCEDURE 1—HOW A HOT WATER SYSTEM OPERATES
The entire heating system (boiler, piping, and radiation units) is filled with water. As water in boiler is heated, it is pumped from top of boiler
through supply main to radiation units. The cooler water in them flows back through return main to boiler. This provides positive and rapid
response to thermostat.
PROCEDURE 2—FILLING SYSTEM WITH WATER
To fill:
1. Close air vents on all radiation units. Open valves to these units.
2. Make sure boiler and expansion tank drain cocks are closed. The air bleed screw on tank drain fitting should be closed.
3. Open valve in line from boiler to expansion tank. Refer to Maintaining Boiler section for additional information.
4. Open water inlet to boiler and leave it open.
5. Start with LOWEST radiation unit. Open air vent on this unit. When all air has escaped and water starts to flow from vent, close air vent.
6. Proceed to next lowest radiation unit and repeat process outlined in item 5. Repeat until every radiation unit in system has been covered.
End with highest unit in system. If units have automatic vents, this manual venting is unnecessary but speeds up proper filling of system.
If system is a closed expansion tank system, there may be an automatic fill valve. It may be left open to refill system automatically as needed.
Check temperature-pressure gage. Note position of hand indicating pressure. This should be between 10 and 15 lb. Any lowering of this movable
hand below 10 lb indicates loss of water due to leakage. The automatic fill valve should compensate for this. Instructions are packaged with valve.
CAUTION: Never run water into a hot, empty boiler.
FOR YOUR SAFETY READ BEFORE OPERATING
WARNING: If you do not follow these instructions exactly, a fire or explosion may result causing property damage,
personal injury, or loss of life.
This appliance is equipped with an ignition device which automatically lights burner. Do NOT try to light burner by hand.
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