Instruction manual

Part number 550-142-056/0411
21
GWC gas-fired water boiler — Boiler Manual
Figure 25 Auto return temp regulation — circulator
zoning
Piping snow melt systems or combination
snow melt/space heating systems
Combination snow melt/space heating systems can have return water
temperature below 60°F, and the return temperature will fluctuate. So
these systems require automatic return water temperature as shown in
Figure 25 (zone-valve zoning) or Figure 26 (circulator zoning).
Select an automatic temperature control valve or motor-operated valve
which can be adjusted to provide a return water temperature of at least
60°F. Any setting higher than 60°F will also be acceptable.
Zone-valve zoning — The suggested piping uses a separate circulator
for system circulation to assure good temperature distribution in the
system when the return water temperature is low.
Circulator zoning — The GWC internal circulators must not be re-
moved. Provide a separate circulator for each zone.
The return water temperature to the boiler must be
at least 60°F. Provide and apply means to regulate the
return temperature. Failure to do so can result in boiler
control operation problems, causing possible significant
property damage.
Zoning with zone valves — Each zone in the piping
diag
rams
in this se
ction
is sho
wn
w
ith
an isolat
ion
v
alve
on each side. Substitute a memory-stop valve for one of
t
hese
i
n
e
ach
z
one
i
n
o
rder
t
o
u
se
t
he
m
emory-stop
va
lve
for balancing flow as well as isolation.
Provide
a s
eparate
2
4-volt
t
ransformer
t
o
p
ower
t
he
z
one
v
alves.
S
ize
t
he
t
ransformer
t
o
h
andle
t
he
t
otal
r
ated
l
oad
o
f all connected zone valves.
Zoning with circulators — The GWC internal system
circulator cannot be removed from the boiler for use as
one of the zone circulators. It must remain as shipped
from the factory to allow proper flow control inside the
boiler. You will need a circulator for each zone. Provide
circulator relays or circulator zone controller.
The sys-
tem circulator must be supplied by the installer.
MINIMUM
Boiler loop pipe size
GWC-070/105
GWC-140/175
1”
1¼”
MINIMUM
Boiler loop pipe size
GWC-070/105
GWC-140/175
1”
1¼”
Legend
1 Isolation valves
2 Automatic air vent (with diaphragm-type expansion tank), or
connect to tank fitting (closed-type expansion tank).
3 Diaphragm- or bladder-type expansion tank, if used (For closed-
type expansion tank, pipe from top of air separator to tank fitting
as in Figure 15, page 14.)
4 Zone valve
5 System or zone circulator
6 Flow/check valve
7 Hose bibb purge valve
8 Boiler pressure/temperature gauge
9 System supply temperature gauge
10 Return temperature automatic mixing valve
11 Differential pressure by-pass valve
16 Cold water fill line — see Figure 15, page 14 for typical components
Figure 26 Auto return temp regulation — zone valve
zoning
Install water piping (continued)