15
Part Number 550-142-320/0720
GWA
Series 3
Gas-Fired Water Boilers –
Boiler Manual
4 Water piping — multiple zones
continued
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 tem-
perature
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 Williamson-Thermoflo
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.
Primary/secondary (preferred)
Bypass piping method
Primary/secondary
bypass piping is preferred because
the flow rate and temperature drop in the heating circuit(s)
is determined only by the heating circuit circulator(s). So
adjustment of the bypass valves in the boiler circuit will not
cause a change in the heating circuit rate and temperature
distribution.
Figures 12 or 13 on page 16
, show suggested bypass ar-
rangements using primary/secondary bypass piping (pre-
ferred) for low temperature systems such as radiant heating
systems or converted gravity systems. For alternatives, see
pages 17 and 18.
The bypass valves (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 display 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 minimum of 130°F. If this
gauge is not available however, adjust the valves such that
the boiler-mounted temperature/pressure gauge reads at least
150°F when the system return water is cold (approximately 60°F
water temperature).
Valve adjustment
(Figures 12
and 13 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 temperature 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 water. Valve
7b
regulates the amount of system water flowing through the
boiler secondary loop.
Water piping — low temperature systems
