25
17 - EQUIPMENT AND OPTIONAL ACCESSORIES
EXPANSION TANK
Expanding water
fl
ows into expansion tank. Tank
should be correct size. Tank is
fi
lled with air. As water
expands it compresses air in the tank to form air
pressure cushion. This “spring-like” cushion serves to
maintain correct operating water pressure regardless
of water temperature. This assures “full measure”
of water, even in highest radiation unit of system.
It also prevents blowing off of safety relief valve.
Air in tank in beginning (with system
fi
lled with cold
water) is suf
fi
cient for proper operation. Tank also
serves as trap for excess air in system. Air would
cause gurgling in pipes and in ef
fi
cient circulation in
radiators if left in system.
It is possible for tank to become “waterlogged” (
fi
lled
with water). It can also become over
fi
lled with air.
This can happen after
fi
lling system with new water.
Fittings provided on tank and in line to tank are for
bleeding off excess water or air.
When installing this tank, it is important:
Tank be higher than boiler top.
1.
Pipe to tank continuously rises up to tank (so
2.
air can “bubble” up to it).
DIAPHRAGM TYPE EXPANSION TANK
Diaphragm type expansion tank takes place of
conventional expansion tank. Carefully read
instructions packed with your tank assembly.
Tank comes with 10-12 pounds per square inch air
charge. This is the same as pressure produced in sys-
tem by automatic
fi
ll valve. When system is
fi
rst
fi
lled,
tank will contain little or no water.
As water is heated its pressure increases. It expands
into tank, compressing air in tank. Compressed
air cushion permits water in system to expand as
temperature changes. Diaphragm type tank can be
mounted on air purger
fi
tting or at any convenient
place in supply or return line.
AIR ELIMINATING FITTING (AIR PURGER)
Air purger is used to remove excess air from system.
It is installed in supply line. It will eliminate air from
water before it reaches radiators and bleed off this
air.
MAIN AIR VENT FOR DOWN FLOW SYSTEMS OR
DIAPHRAGM TYPE EXPANSION TANK
Before system is
fi
lled with water, there is air in pipes
and radiation units. Some of it will be trapped as
system is
fi
lled . It is possible to eliminate most of
this air through air vent on radiation units. Main air
vent will speed and simplify this. Install on highest
point in supply main when all radiation is below top
of boiler.
AUTOMATIC FILL VALVE
For a safe, ef
fi
cient operation, hot water system must
be
completely fi lled
with water. Adding new water,
when needed can be done manually (by use of hand
valve in water supply line). Requires regular atten-
tion to system’s needs. Automatic
fi
ll valve accom-
plishes this without attention. Install in supply line on
hot water boilers only. Valve operates through water
pressure differentials. It does not require electrical
connection.
DRAIN VALVE
Manual valve provides means of draining all water
from boiler and system. It is often installed in 3/4”
tapping at bottom of end boiler section. Or it can be
installed in tee where return line enters boiler.
WATER TEMPERATURE CONTROL
Water temperature limit control in relay is adjustable
and may be set as necessary. It may be set as low
as 140°F (60°C), or as high as 240°F (116°C). This
depends on type and amount of radiation involved
and weather conditions.
CIRCULATING PUMP
Every forced hot-water system requires circulating
pump. Separate pump or zone valve is required for
each zone, if you have a two or more zone system.
Pump must have capacity to provide circulation
required by your system. Pump is connected into
main just ahead of boiler. It is also wired to electrical
system.
VENT DAMPER
This product is automatic, motorized stack damper
developed to increase ef
fi
ciency of heating system
by reducing standby losses from heating apparatus
and conditioned air space. Damper closes chimney
vent when burner is off and fully opens it when
combustion is required.
