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RELIEF VALVE
You must have a relief valve on your boiler. Water expands as it is heated. If there is no place for the water to expand into,
water pressure will build up inside the boiler and system. Should this happen, the relief valve will automatically open at a
pre-determined pressure. This will relieve the strain on the boiler and system. Run a pipe from the relief valve outlet (pipe
must be same size as outlet and the open end must not be threaded) to an open drain, tub or sink, or other suitable
drainage point not subject to freezing. Failure to do so may cause water damage or injury should relief valve release.
EXPANSION TANK
In a properly assembled system, the expanding water flows into a expansion tank. This tank should be of the correct size.
The tank is filled with air. As the water expands it compresses the air in the tank to form 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 a water, even in the highest radiation unit of the system. It also prevents blowing off of the relief valve.
The air in the tank in the beginning (with system filled with cold water) is sufficient for proper operation. The tank also
serves as a trap for excess air in the system. The air would cause gurgling in the pipes and inefficient circulation in the
radiators if left in the system. It is possible for a tank to become "water-logged" (filled with water). It can also become
overfilled with air. This can happen after filling the system with new water. Fittings provided on the tank and in the line to
the tank are for bleeding off excess water or air. When installing this tank, it is important: 1) That the tank be higher than
the boiler top. 2) That the pipe to the tank continuously rises up to the tank (so that air can "bubble" up to it).
DIAPHRAGM TYPE EXPANSION TANK
The diaphragm type expansion tank (EX-TROL) takes the place of the conventional expansion tank. Carefully read the
instructions packed with your EX-TROL tank assembly. The EX-TROL tank comes to you with a 10-12 pounds per square
inch air charge. This is the same as the pressure produced in the system by the automatic fill valve. When the system is
first filled, the EX-TROL tank will contain little or no water. As the water is heated its pressure increases. It expands into the
EX-TROL tank, compressing the air in the tank. This compressed air cushion permits the water in the system to expand as
the temperature changes. The diaphragm type tank can be mounted on the air purger fitting or at any convenient place in
the supply or return line.
AIR ELIMINATING FITTING (AIR PURGER)
An air purger is used to remove excess air from the system. It is installed in the supply line. It will eliminate air from the
water before it reaches the radiators and bleed off this air.
MAIN AIR VENT FOR DOWN FLOW SYSTEMS OR DIAPHRAGM TYPE EXPANSION TANK
Before a system isfilled with water, there isair in the pipes and radiation units. Some of it will be trapped as the system is
filled. It is possible to eliminate most of this air through the air vent on the radiation units. A main air vent will speed and
simplify this. It should be installed on the highest point in the supply main when all radiation is below top of boiler.
AUTOMATIC FILL VALVE
For safe, efficient operation, a hot water system must be completely filled with water. Adding new water, when needed
can be done manually (by use of a hand valve in the water supply line). This requires regular attention to the system's
needs. An automatic fill valve accomplishes this without attention. It is installed in the supply line on hot water boilers only.
The valve operates through water pressure differentials. It does not require an electrical connection.
DRAIN VALVE
This manual valve Provides a means of draining all water from the boiler and system. It is often installed in the %" tapping
at the bottom of the end boiler section. Or it can be installed in a tee where the return line enters the boiler.
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