Piping — low temperature systems
4d
24
Part Number
550-110-290/0219
CGt
GAS-FIRED WATER BOILER — Series 2 —
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.
Bypass piping
Figures 19 and 20
, page 25, show suggested bypass ar-
rangements using bypass piping for low temperature
systems such as
radiant heating systems
or
converted
gravity systems
.
Primary/secondary bypass piping is required because
the boiler circulator must install on the return line and
be used to provide domestic water priority. Adjustment
of the bypass valves in the boiler circuit will not cause a
change in the heating circuit flow rate or temperature
distribution.
The bypass valves in
Figures 19
and
20
(items
7a
and
7b
) provide mixing of hot boiler outlet water with
cooler system return water — set to assure a minimum
return water temperature (at least 130°F) to the boiler.
Set the valves as explained below.
Temperature gauges
•
Gauge
4a
is suggested, but optional on any system.
•
Gauge
4b
is optional on converted gravity systems,
but
required
on radiant heating systems — to dis-
play the water temperature being supplied to the
radiant tubing.
•
Gauge
8
is
required
on all systems to assure the
return water temperature is accurately set for a mini-
mum of 130°F. If this gauge is not available however,
adjust the valves such that the boiler-mounted tem-
perature/pressure gauge reads at least 150°F when
the system return water is cold (approximately 60°F
water temperature).
Valve adjustment
(Figures 19 and 20 only)
1. Set the valves while the system is cool, setting for the
coldest expected water temperature (usually 60°F
since the system will often drop to room tempera-
ture between cycles).
2. Start with valve
7a
fully closed and
7b
fully open.
3. Gradually open valve
7a
while closing valve
7b
until
the temperature at gauge
8
reads 130°F when gauge
4a
reads 60°F.
4. Note that valve
7a
regulates the amount of hot water
from the boiler supply which mixes with return wa-
ter. Valve
7b
regulates the amount of system water
flowing through the boiler secondary loop.
