Filter
Top Products
FILLING THE BOILER
HOW A HOT WATER SYSTEM OPERATES
The entire heating system (boiler, piping, and radiation units) is filled with water. As the water in the boiler
is heated, it is circulated from the top of the boiler through the supply main to the radiation units. The cooler
water in the radiation units flows back through the return piping through the return main into the boiler. This
arrangement provides positive and rapid response to the thermostat.
FILLING THE SYSTEM WITH WATER
OPTION #1 - This method utilizes the boiler piping as shown in the figure on the previous page.
a) Close the main shutoffvalve, isolation valves, and zone valves (if applicable). If bypass piping is
installed, also close the two throttling valves. Leave the boiler service shutoffvalve (if installed) and the
balancing valves to each heating zone fully open.
b) Ooen the following valves in order: the drain valve for power purging, isolating valves before and after
the boiler circulator (if applicable), both throttling valves (if applicable), and then open the fill line
shutoff valve. Water will fill the bypass piping and push the air through the piping and out the power
purging drain valve. When the power purging drain valve runs air free, close the bypass piping throttling
valve (leaving the throttling valve to the supply piping f_lly open).
c) Next, ooen the isolation valve (or zone valve) to the first zone. Water will fill the piping and push any air
out the power purging drain valve. When the power purging drain valve rims air free, close the isolation
valve or zone valve). Repeat this procedure for the remaining heating zones.
d) Once all zones are filled with water and purged of air, close the power purging drain valve and fill line
shut off valve, open the main shutoff valve, and adiust the throttling valves and balancing valves as
required.
OPTION #2 - Close the air vents on all radiation units. Open the valves to the radiation units. Make sure
the boiler drain valve, expansion tank drain cock, and the air bleed screw "on the expansion tank drain fitting
are closed. Open the fill valve on the piping to the expansion tank. Open the water inlet to the boiler and
leave it open. Open the air vent on the lowest radiation 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 until finishing with the
highest radiation unit. If the heating system has automatic vents, this manual venting is unnecessary but it
will speed up the proper filling of the system.
If the system is a closed expansion tank system, an automatic fill valve is needed. Leave the automatic fill
valve open to refill the system automatically as needed. Note the initial fill pressure on the boiler's
temperature / pressure gauge, which should be 10-15 psig. Any lowering of the pressure from its initial fill
pressure indicates a loss of water due to leakage. The automatic fill valve should then compensate for this
water pressure loss. If it does not, manually open this valve to refill the system until the needle is again
pointing to the same pressure reading. Instructions are packaged with the valve.
19