Weil-McLain CGi Series 3 Installation And Maintenance Manual page 22

CG i
GAS-FIRED wATER BOILER- sERIEs a -
Boiler Manual
4c
22
Water piping - multiple zones
Piping multiple zones
Follow instructions on pages 20 and 21 to install near-
boiler or single-zone piping. (Also refer to Piping for
radiant heating systems or converted gravity sys-
tems, below, if applicable.)
See Figure 18 or Figure 19 to complete installation.
Zoning with circulators (Figure 18)
(return temp over 130•F)
1.
Size each circulato r to individual circuit require-
ments.
2. Do not install circulator on boiler (except fo r
primary/secondary piping).
3. Install isolation (balancing) valves to adjust flow
to distribute heat to all zones.
Piping for radiant heating
systems or converted gravity
systems
Converted gravity (or steam) systems
Whenever possible, use the primary/secondary piping
shown in Figures 20 o r 21 on page 25. This piping de-
sign allows changing boiler flow rate without affecting
primary circuit flow rate.
If Figures 20 or 21 cannot be used, use the boiler-by-
pass piping shown in Figure 22 or Figure 23 o n page 27.
You can also use the piping shown in Figure 24 o n
page 29 (system-bypass), if the reduced flow rate in
the heating system will not cause heat distribution
problems.
4. Install and wire a separate relay fo r each zone
circulator.
I&
WARNING!
Failure to prevent low return water
temperature to the boiler c. o uld
cause corrosion of the boiler sec-
tions or burners, resulting in severe
personal injury, death or substantial
property damage.
Zoning with zone valves (Figure 19)
(return temp over 130•F)
t.
Install isolation (balancing) valves to adjust flow to
distribute heat to all zones.
2. Provide a separate 24-volt transfo m1er to power the
zone valves. Size the transformer to handle the total
rated load of all connected zone valves.
Radiant heating systems
Preferably, use primary/secondary piping, as shown
in Figures 20 or 21 on page 25. Alternatively, use the
method of either Figure 22 or Figure 23 o n page 27.
Do
not use the piping of Figure
24
(system-bypass),
because this method does not control radiant system
supply temperature.
lA
CAUTlON
I
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 va1ve 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.
If radiant system tubing has no oxygen barrier, a heat
exchanger m ust be used.
I&
WARNING!
Radiant heating system piping sho uld 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 tem
perature will be
adequately controlled using the methods
shown in this manual provided the system supply temperature is relatively constanL
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
Weii-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 dan1age.
Part
Number
550-142-780/0712