19
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 top of the boiler. The connecting pipe from the
boiler to the expansion tank shall rise continuously
up to the expansion tank so that air can rise into the
expansion tank.
An expansion tank is partially 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 “waterlogged” (filled
with water). It can also become overfilled with air when
filling the system with new water. Fittings 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.
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 fill partially with 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
EQUIPMENT AND ACCESSORIES
supply or return line. It is recommended to locate the
diaphragm type expansion tank in the supply line with
the circulator located after the expansion tank. 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.
MAin AiR VenT:
(not provided)
Before a system is filled with water, there is air in
the pipes and radiation units. Some of the air will
be trapped as the 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 process. The main air vent should be installed on
the highest point in the supply main.
AuToMATiC FiLL VALVe
(not provided)
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 or pressure
reducing valve accomplishes this without attention. It
is installed in the supply line on hot water boilers only.
The valve operates through water pressure differen-
tials. It does not require an electrical connection.
AQuAsTAT ReLAy ConTRoL
(provided)
The water temperature limit control in the aquastat
relay is adjustable. See Aquastat instructions for how
to set the limit temperature.
dRAin VALVe
(provided)
The drain valve is a manually operated valve that pro-
vides a means of draining all the water from the boiler
and heating system. It is installed in the casting below
the burner door.
