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HOW A HOT-WATER SYSTEM OPERATES
Your entire heating system (boiler, piping and radiation units) is filled with water. As the water in the boiler is
heated, it is pumped from the top of the boiler through the supply main to the radiation units. The cooler water
in them flows back through the return main to the boiler. This provides positive and rapid response to the
thermostat.
FILLI"NG SYSTEM WITH WATER
Close the air vents on all radiation units. Open the valves to these units. Make sure the boiler and expansion
tank drain cocks are closed. The air bleed screw on the tank drain fitting should be closed. Open the valve in the
line from the boiler to the expansion tank. Open the water inlet to your boiler and leave it open. Start with the
lowest radiation unit. Open the air vent on this unit. When all the air has escaped and water starts to flow from
the vent, close it. Go to the next radiation unit, and repeat this process. Repeat until you have covered every
radiation unit in the system (ending up at the highest unit in the system). If your units have automatic vents,
this manual venting is unnecessary but it will speed up the proper filling of your system. If your system is a
closed expansion tank system, you may leave it open to refill the system automatically as needed. Check the
temperature pressure gauge. Not the position of the hand indicating pressure. This should be between 10 and
15 Ibs. Any lowering of this movable hand below 10 Ibs. Will indicate loss of water due to leakage. The
automatic fill valve should compensate for this. Instructions are packages with the valve.
WARNING - Never run water into a hot empty boiler.
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