Dunkirk Q95M-200 Modulating Condensing Boiler - Manual (Page 14)

14
Differential Air Pressure
Differential air pressure switch is a safety device which
prevents boiler from firing if there is an air intake, boiler
heat exchanger or vent blockage.
To check differential air pressure:
1. Turn off service switch or lower thermostat setting.
2. Remove vinyl caps from tee.
3. Install testing lines as shown to inclined manometer
or differential pressure gauge with ability to read
0.01” increments to at least 6.0” w.c.
4. Turn on service switch and set thermostat to call for
heat.
Boiler Status Diff. Pressure Switch Contacts
Not Running 0”
3.5” Closed
0.14” Open
Running with
Blockage
Greater Than or
Equal To Setpoints
3.5” Open
0.14” Closed
Running w/out
Blockage (approx.)
Min. Fire: 0.3” 3.5” Closed
Max. Fire: 2” 0.14” Closed
If manometer readings do not correspond with chart
above, check for possible causes:
• Blockage or moisture in suction lines to switch.
• Blockage in air intake or vent pipes.
• Undersized air intake or vent pipes.
• Loose blower wheel on motor shaft.
• Incorrect pressure switch or pressure switch setpoint
When pressure reading is correct and pressure switch
is operating properly, remove testing lines and reinstall
vinyl caps to Tee and 3-way connector.
Checking the Differential Air Pressure
9 - TROUBLESHOOTING
DANGER
Electric shock hazard! Following procedures may
expose you to dangerous line voltage. Use caution
to avoid touching live electrical contacts. All service
must be performed by a trained, experienced service
technician. Failure to follow these instructions WILL
result in death or serious injury
!
CAUTION
WHAT TO DO IF YOU SMELL GAS
• Do not try to light any appliance.
• Do not touch any electrical switch; do not use
any phone in your building.
• Immediately call your gas supplier from a
neighbor’s phone. Follow gas supplier’s
instructions.
• If you cannot reach your gas supplier, call the fire
department.
!
WARNING
Fire, Explosion. Shut off gas at a location external
to appliance should overheating occur or gas
supply fail to shut off. Do not turn off or disconnect
electrical supply to pump. Do not use the boiler
if any part of the gas control system has been
underwater.
Only a qualified service technician should inspect
the boiler and replace any part of control system
and any gas control which has been underwater.
Use only your hand to turn gas control knob. Never
use tools. If knob will not turn by hand, don’t try to
repair it.
Failure to follow these instructions could result in
death or serious injury.
!