Weil-McLain CGA25SPDN Boiler User Manual


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GOLD CGa Gas-Fired Water Boiler — Boiler Manual
22
Part Number 550-101-009/0107
Failure to PREVENTLOWRETURNWATERTEMPERATURE to the boiler could cause corrosion of
the boiler sections or burners, resulting in severe personal injury, death or substantial
property damage.
Radiant heating system piping should include a means of
REGULATINGTHEBOILERRETURN
WATERTEMPERATURE
and the SYSTEMSUPPLYTEMPERATURE (such as provided by an INJEC
TIONPUMPINGCONTROL
).
"OILERRETURNWATERTEMPERATUREWILLBEADEQUATELYCONTROLLEDUSINGTHEMETHODSSHOWN
in this manual provided the SYSTEMSUPPLYTEMPERATURE is RELATIVELYCONSTANT
DO NOT apply the methods of this manual if the system is equipped with an OUTDOOR
RESETCONTROL
Instead, PROVIDECONTROLSANDPIPING which can REGULATETHEBOILERRE
TURNWATERTEMPERATURE
at NOLESSTHAN& regardless of system supply temperature.
#ONTACTYOUR7EIL-C,AINREPRESENTATIVEFORSUGGESTEDPIPINGANDCONTROLMETHODS
Failure to
PREVENTCOLDRETURNWATERTEMPERATURE to the boiler could cause corrosion
damage to the sections or burners, resulting in possible severe personal injury, death or
substantial property damage.
BOILER-bypass piping
method
This piping method (&IGURE or , page 23) is called
a
BOILERBYPASS because part of the circulator flow is
bypassed around the boiler (through valve A). This
method reduces the flow rate throughout the boiler, in
order to raise the average water temperature in the boiler
ENOUGHTOPREVENTmUEGASCONDENSATION"OILERBYPASS
PIPINGISEFFECTIVEFORSOMEBOILERSINCLUDINGTHE#'A
— provided the flow rates are adjusted according to the
instructions following.
&IGURES and  are alternative piping suggestions
for
CONVERTEDGRAVITY (large water content or steam
systems) or RADIANTHEATINGSYSTEM — for use when
primary/secondary piping can’t be applied. (&IGURE,
page 25, is another alternative, using system bypass in
place of boiler-bypass piping. &IGURE however, is
not suitable for radiant heating applications because it
does not protect the radiant system from possible high
water temperature.)
"OILERBYPASSPIPINGKEEPSSYSTEMmOWRATEASHIGHAS
possible and temperature drop as low as possible, help-
ing to equalize the building heat distribution.
Temperature gauges
'AUGEA is optional if the bypass valves will be ad-
justed using cold (or room temperature) return water
to the boiler. (When setting the valves without gauge
A installed — using cold or room temperature water
— assume the return water temperature to be 60°F. Set
the valves so gauge
reads at least 120°F.
'AUGE
B is optional on converted gravity systems,
but REQUIRED on radiant heating systems — to display
the water temperature being supplied to the radiant
tubing.
'AUGE
is REQUIREDon all systems to assure reliable
adjustment of the bypass valves. The boiler-mounted
temperature/pressure gauge can be used if a separate
temperature gauge is not installed.
Valve adjustment
1. Start with valve A fully closed and B fully open.
 'RADUALLYOPENVALVE
A while closing valve B
until the temperature at gauge reads 60 °F higher
than gauge
A. A minimum 60°F temperature rise
through the boiler assures a low enough flow rate
and high enough average temperature to prevent
condensation even with low system return water
temperature.
 6ALVE
A regulates the system flow rate, while valve
Bregulates the boiler flow rate.
4. The boiler-mounted temperature/pressure gauge
may be used in place of a separate gauge
.
Piping — low temperature systems (continued)3d
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