25
Part Number 550-110-732/0703
GWS
Gas-Fired Water Boilers –
Boiler Manual
12 Troubleshooting
Figure 14
Checking pressure switch
Label all wires prior to disconnection when
servicing controls. Wiring errors can cause
improper and dangerous operation.
Never jumper (bypass) rollout thermal fuse element
or any other device except for momentary testing as
outlined in “Troubleshooting” charts, pages 26-32.
Severe personal injury, death or substantial property
damage can result.
Burner access panel must be in position during boiler
operation to prevent momentary flame rollout on
ignition of main flame. Severe personal injury or
substantial property damage will result.
Before troubleshooting:
1. Have the following items:
a.
Voltmeter that can check 120 VAC and 24 VAC.
b.
Microammeter with a minimum scale range of 0-10.
c.
Continuity checker.
d.
U-tube manometer and inclined manometer (with 0 – 2" w.c.
range).
2. Check for 120 VAC (minimum 102 VAC to maximum 132
VAC) to boiler.
3. Make sure thermostat is calling for heat and contacts
(including appropriate zone controls) are closed. Check for
24 VAC between thermostat wire nuts and ground.
Check the following:
1. Wire connectors to control module are securely plugged in
at module and originating control.
2. Gas pressures:
a.
With boiler off — 13" w.c. maximum natural or propane gas
pressure upstream of gas valve.
b.
With boiler on:
•
5" w.c. minimum natural gas pressure or 11" w.c. propane
gas pressure upstream of gas valve.
•
3.5" w.c. minimum natural gas pressure or 10" w.c. propane
gas pressure downstream tapping on gas valve — Can be
adjusted by regulator on gas valve.
Check pressure switch setting
Make sure boiler water temperature is 100 °F or
cooler before starting procedure to obtain appropriate
readings.
1. See Figure 14 and Table 8.
2. Remove both air pressure switch hoses from air pressure
switch.
3. Install tees and tubing as shown in Figure 14 to inclined
manometer.
4. Turn off gas valve and set thermostat to call for heat. Inducer
will run but burners will not ignite.
5. Check for 24 VAC between both air pressure switch terminals.
6. If manometer reading is above the setpoint of the switch (see
Table 8), but there is not 24 VAC between both air pressure
switch terminals — replace air pressure switch.
Troubleshooting air pressure reading
1. If manometer reading is lower than the setpoint of the switch
(see Table 8) — check for possible causes:
•
blockage in hoses
•
obstruction in inducer housing outlet
•
loose inducer wheel on motor shaft
•
inducer motor not in proper rpm
•
inducer back plate not sealed properly
•
blockage in block assembly
•
blockage in flue pipe or termination
•
incorrect pressure switch
Return to normal operation
When pressure reading is correct and air pressure switch is
operating properly — remove tees and reinstall hoses to air pressure
switch.
The boiler will not operate correctly unless pressure
switch hoses are correctly located. The red hose
connects from the right side (negative) hose barb to
the flue collector. The white hose connects from the
left side (positive) hose barb of the switch to the
connector box (between flue collector and inducer)
as shown in Figure 14.
Table 8
Pressure switch setpoint (for elevations
above 2,000 ft, contact your local supplier for
details.)
Boiler model number
Inches W.C.
GWS-063
1.79
GWS-095
1.48
GWS-127
1.22
GWS-158
0.95
