Part Number 550-142-300/0520
24
CGa Series 3 Gas-Fired Water Boiler — Boiler Manual
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
injection
pumping control
).
Boiler 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 return water
temperature
at
no less than 130°F
regardless of system supply temperature. Contact your
Weil-McLain 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.
Water piping — low temperature systems
(continued)
SYSTEM-bypass piping
method
This piping method (
Figure 17
, page 25) is called a
system-bypass
because part of the circulator flow by-
passes the system (through valve
7a
). This bypassed hot
water from the boiler outlet mixes with cooler system
return water temperature in order to provide minimum
130°F return water to the boiler. Valve
7b
will most often
be full open, but may need to be slightly closed on some
low pressure drop systems in order to cause enough flow
through valve
7a
.
Figure 17
is an alternative piping method that provides
return water temperature control for boilers installed
on
converted gravity systems
(large water content
or steam systems).
DO NOT
apply the piping of
Figure 17
on
radiant
heating systems
. It provides no method of regulat-
ing the water temperature provided to the system and
could result in excessive water temperature in the radi-
ant tubing.
System-bypass piping as shown in
Figure 17
can be used
with either zone valve or circulator zoning. When used
with circulator zoning however, the boiler circulator
(item
3
), must be piped as shown. It cannot be used as
one of the zoning circulators.
DO NOT
apply system-bypass piping if the reduced
flow in the system could cause poor heat distribution.
That is, system-bypass piping reduces the flow in the
system and increases the water temperature supplied to
the system. This can cause increased heat from radiators
at the beginning of the system and reduced heat from
radiators near the end of the system.
Valve adjustment
1. Start with valve
7a
fully closed and
7b
fully open.
2. Gradually open valve
7a
while closing valve
7b
until
the temperature at gauge
8
reads at least 130°F at all
times.
3. Valve
7a
regulates the amount of boiler supply water
mixed with return water. Valve
7b
causes a pressure
drop in the system needed to balance flow through
valve
7a
and the system.
4. The valve adjustment should be done with the
system at the coldest expected temperature (60°F
for converted gravity systems or high mass radiant
systems).
3d
