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Part Number 550-142-300/0520
18
CGa Series 3 Gas-Fired Water Boiler — Boiler Manual
Water piping — multiple zones
Piping multiple zones
Follow instructions on pages 16 and 17 to install near-
boiler or single-zone piping. (Also refer to Piping
for radiant heating systems or converted gravity
systems,
below, if applicable.)
See
Figure 11 or Figure 12, page 19, to complete in-
stallation.
Zoning with circulators (Figure 11)
(return temp over 130°F)
1. Size each circulator to individual circuit require-
ments.
2. Do not install circulator on boiler (except for
primary/secondary piping).
3. Install isolation (balancing) valves to adjust flow to
distribute heat to all zones.
4. Install and wire a separate relay for each zone
circulator.
Zoning with zone valves (Figure 12)
(return temp over 130°F)
1. Install isolation (balancing) valves to adjust flow to
distribute heat to all zones.
2. Provide a separate 24-volt transformer to power the
zone valves. Size the transformer to handle the total
rated load of all connected zone valves.
DO NOT connect directly from
3-wire zone valves to the T-T termi-
nals on the boiler
. When using 3-wire
zone valves, install an isolation relay.
Connect the zone valve end switch wires
to the isolation relay coil. Connect the
isolation relay contact across the boiler
T-T terminals. Failure to comply can
result in damage to boiler components
or cause unreliable operation, resulting
in severe property damage.
3c
Piping for radiant heating
systems or converted gravity
systems
Converted gravity (or steam) systems
Whenever possible, use the primary/secondary piping
shown in Figures 13 or 14 on page 21. This piping de-
sign allows changing boiler flow rate without affecting
primary circuit flow rate.
If Figures 13 or 14 cannot be used, use the boiler-bypass
piping shown in Figure 15 or Figure 16 on page 23. You
can also use the piping shown in Figure 17 on page 25
(system-bypass), if the reduced flow rate in the heating
system will not cause heat distribution problems.
Failure to prevent low return water
temperature to the boiler could cause
corrosion of the boiler sections or burn-
ers, resulting in severe personal injury,
death or substantial property damage.
Radiant heating systems
Preferably, use primary/secondary piping, as shown
in Figures 13 or 14 on page 21. Alternatively, use the
method of either Figure 15 or Figure 16 on page 23.
Do not use the piping of Figure 17 (system-bypass),
because this method does not control radiant system
supply temperature.
If radiant system tubing has no oxygen barrier, a heat
exchanger
must be used.
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 in 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.
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