Manual

EQUIPMENT AND OPTIONAL ACCESSORIES
RELIEF VALVE (provided)
Each low pressure hot water heating boiler is provided with a relief valve for over pressure
protection of the boiler and heating system. The relief valve will open when the pressure in
the boiler rises to 30 psig. Each relief valve is provided with a lifting device for testing and
should be tested monthly during the heating season. Discharge piping should be provided
from the outlet side of the relief valve so as to prevent scalding or other hazardous
situations. The discharge piping must remain full size and end at a safe point.
CONVENTIONAL EXPANSION TANK (not provided)
In a properly assembled system, the expanding water flows into an expansion tank. The
expansion tank should be sized correctly, because an improperly installed or sized expansion
tank may result in frequent lifting of the relief valve or other heating system problems. It is
important to install the tank higher than the boiler top and that the connecting pipe rise
continuously up to the tank so air can bubble itself up through it.
An expansion tank is filled with air. The air compresses as water expands, thus forming an
air pressure cushion. This "spring-like" cushion serves to maintain correct operating water
pressure regardless of water temperature. This assures a "full measure" of water, even in
the highest radiation unit of the system. The tank also serves as a trap for excess air in the
system. The air can cause noises in the pipes and inefficient circulation in the radiators if left
in the piping system.
It is possible for a tank to become "water-logged" (filled with water). It can also become
overfilled with air when filling the system with new water. Fittings provided on the tank and in
the line to the tank are for bleeding off excess air and water.
DIAPHRAGM EXPANSION TANK (not provided)
The diaphragm type expansion tank takes the place of the conventional expansion tank.
Carefully read the instructions packed with your tank assembly. The expansion tank should
be sized and installed correctly, because an improperly installed or sized expansion tank
may result in frequent lifting of the relief valve or other heating system problems.
The tank typically comes with a 10-12 psig air charge. This is the same as the pressure
produced in the system by an automatic fill valve set to fill the boiler to 10-12 psig with fresh
water. When the system is first filled, the tank will contain little or no water. As the water is
heated, and system pressure increases, the water expands into the tank and compresses
the air in the tank. This compressed air cushion permits the water in the system to expand
as the temperature changes and assures a "full measure" of water, even in the highest
radiation unit of the system.
The diaphragm type expansion tank can be mounted on the air purger fitting or at any other
convenient place in the supply or return line. It is recommended to locate the diaphragm type
expansion tank (a) in the supply line with the circulator located after the expansion tank or
(b) off the 3/4" tapping provided on the top of the rear casting with the circulator mounted
directly off the boiler's supply piping connection. This configuration allows the circulator to
"pump away" from the expansion tank for improved air elimination and system performance.
The air eliminator fitting or air purger is not provided. The air eliminator fitting or air purger is
used to help remove air from the system before it reaches the radiators. It should be
installed in the supply line. Air left in the system can cause noises in the pipes and inefficient
circulation in the radiators.
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