Part number 550-143-010/1021
19
GV90+
series
2
gas-fired water boiler – boiler manual
Figure 22
Single-zone radiant heating or
heat pump system
Single-zone radiant heating or heat pump
Radiant heating systems and heat pump systems usually require system
supply water temperatures below 140°F. But the boiler outlet water
temperature will be at least 150°F to 160°F during most operating
conditions. So the piping must include a method of reducing the sup-
ply water temperature to the system.
Figure 22 uses two balancing valves to manually adjust the supply water
temperature. Follow the instructions below to adjust these valves. Install
the supply temperature limit control (item
14
) as shown to protect the
system from over-temperature conditions. Note also that this piping
requires a separate system circulator, as shown, because of the higher
flow rates of radiant and heat pump systems.
Manual adjustment of the supply temperature is limited to single-
zone systems because multi-zone systems will cause varying loads,
making it unlikely an acceptable valve setting could be found. See
for multi-zone systems.
You may also apply the suggested piping of either
if you want automatic supply temperature regulation
or outdoor reset temperature control.
For additional information and alternatives in piping for radiant heat-
ing systems, contact Weil-McLain.
The system circulator must be supplied by the in-
staller.
Adjust balancing valves
Use valves
17
and
18
to mix boiler supply water with system return
water, reducing supply water temperature to the system.
1. Subtract the design system supply temperature from 150°F. Call
this number the
temperature difference
.
2. Open valve
17
and close valve
18
.
3. Start the boiler and system.
4. Let the system warm up for about 15 minutes.
5. Note the temperature at gauge
9
(system supply) and gauge
8
(boiler
supply).
6. Slowly close valve
17
while opening valve
18
until gauge
9
reads
lower
than gauge
8
by at least the
temperature difference
found
in step 1.
7. Example: For a design supply temperature of 100°F, the
tempera-
ture difference
would be 150°F minus 100°F, or 50°F. Set the valves
until gauge
9
reads at least 50°F lower than gauge
8
.
MINIMUM
Boiler loop pipe
size
GV90+3/4
GV90+5/6
1”
1¼”
Install water piping
(continued)
Legend
1 Isolation valves
2 Automatic air vent (with diaphragm-type expansion
tank), or connect to tank fitting (closed-type expan-
sion 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
.)
5 System circulator
7 Hose bibb purge valve
8 Boiler pressure/temperature gauge
9 System supply temperature gauge
10 Return temperature gauge
14 Supply temperature limit control — Set at a tempera-
ture below the maximum allowed for the system or
as directed by the system designer.
16 Cold water fill line — see
for typical
components
17 Balancing valve
18 Balancing valve
