Dunkirk XEB-2 Installation Instructions Manual page 21

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 (Optional)
In a properly assembled system, the expanding
water flows into an 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 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 "waterlogged"
(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 (Optional)
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.
AIR ELIMINATING FITTING (AIR PURGER)
(Optional)
An Air Purger is used to remove excess air from
the system. It is installed in the supply line. It will
help to 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 (Optional)
Before a system is filled with water, there is air
in the pipes and radiation units. Some of it will
be trapped asthe system is filled. It is possible
to eliminate most of this air through the air vents
on the radiation units. A Main Air Vent will speed
and simplify this. It should be installed on the
highest point in the main when all radiation is
below top of boiler.
AUTOMATIC FILL VALVE (Optional)
For safe, efficient operation, a hot water system
must be 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 3J4,, tapping at the bottom of the left boiler
section. Or it can be installed in a tee where the
return line enters the boiler.
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