Specifications

Part number 550-142-120/0113
WM97+ gas-fired water boiler — Boiler Manual
– 92 –
Startup — final checks (continued)
If combustion at either high or
low fire is outside the range given
in Figure 101, follow the proce-
dure given on page 92 or page 93
for adjusting the throttle screw
on the venturi. If throttle screw
adjustment does not correct the
problem, then shut down the
boiler and contact your local Weil-
McLain representative. Throttle
screw adjustment must be done
only by a qualified technician,
using calibrated test instruments.
Failure to comply could result in
severe personal injury, death or
substantial property damage.
7. Measure natural gas input:
a. Operate boiler 10 minutes. Turn off other ap-
pliances.
b. At natural gas meter, measure time (in seconds)
required to use one cubic foot of gas.
c. Calculate gas input:
3600 x 1000
= Btuh
number of seconds from step b
d. Btuh calculated should approximate input rat-
ing on boiler rating label.
8. Use the WM97+ control display to navigate to
Manual test mode (see Figure 93, page 83) and force
the firing rate to MIN (low fire).
9. Look at the flame through the flame inspection
window. The low fire flame should be stable and
evenly distributed over burner surface with a uni-
form orange color.
10. Repeat the combustion test as instructed in the
previous steps.
11. Use the WM97+ control display to navigate to
Manual test mode (see Figure 93, page 83) and
force the firing rate to AUTO (normal operation).
12. Reinstall the flue gas temperature sensor. When
replacing the sensor, remove the rubber grommet
from the probe. Insert the rubber grommet into
the flue pipe, then insert the probe into the rubber
grommet.
You must reinstall the flue gas tempera-
ture sensor to prevent flue gas spillage
into the boiler enclosure. Failure to com-
ply could result in severe personal injury,
death or substantial property damage.
Throttle screw adjustment
WM97+70 or 110 ONLY
DO NOT attempt to adjust the throttle screw unless by a quali-
fied technician, and with the use of calibrated combustion
test instruments. Adjust the throttle screw only as needed to
meet the combustion values given in Figure 101.
1. Throttle screw adjustment is
only necessary if specified elsewhere in
this manual or if combustion tests indicate the need, as explained under
“ Check flame & combustion with instruments,” page 90.
2. Boiler behavior that might indicate a need to check combustion values
at high fire (as per page 90) to verify boiler is in adjustment include:
difficulty igniting, poor flame stability at low fire, combustion noise
or high carbon monoxide values.
3. Combustion readings must be taken at both high fire and low fire. DO
NOT attempt an adjustment of the throttle screw at low fire. Just check
the combustion values.
4. See Figure 100 for location of the
WM97+70 or 110 throttle screw.
Remove the cover screw to access the throttle adjustment screw.
Figure 100
WM97+70/110 Throttle screw (ONLY for use by a
qualified technician, using calibrated combustion test
instruments)
Throttle adjustment screw
Gas inlet pressure test port
Adjust the throttle screw in small movements. Turning the
screw too far will cause the adjustment to reverse behavior.
5. See Figure 89, page 79. Make sure the Max firing rate is set to the
maximum given in the table. If not, adjust as necessary. Then navigate
to DIAGNOSTICS — Manual test mode (see Figure 93, page 83) and
force the firing rate to MAX (high fire). After the boiler has had time to
stabilize, take a CO
2
reading. If result is not acceptable, do the following:
a. Turn the throttle screw either direction very slightly. Allow the
boiler to stabilize and take another CO
2
reading. Note whether CO
2
increases or decreases.
b. Turn the screw slightly in the direction needed to increase or
decrease reading as needed. Allow the boiler to stabilize and take
another reading. Continue until CO
2
is acceptable.
6. Lock the boiler into low fire. Check the combustion readings. If results
are acceptable at low fire, verify high fire readings again. Restore firing
rate to AUTO. DO NOT adjust throttle on low fire.
7. Consult your local Weil-McLain representative if acceptable results
cannot be obtained for both high and low fire.