User's Information Manual Bosch 96% AFUE Gas Furnace | 7
Bosch Thermotechnology Corp. | 11.2018
Data subject to change
4 Operating Your Furnace
4.1 Furnace Start-Up
1. Close the manual gas shutoff valve external to the furnace.
2. Turn off the electrical power to the furnace.
3. Set the room thermostat to the lowest possible setting.
4. Remove the burner access panel.
WARNING:
This furnace is equipped with an ignition device which
automatically lights the burner. Do not try to light the burner
by hand.
5. Push the gas valve switch to the OFF position (See Fig. 2).
Figure 2
HIGH FIRE COIL TERMINAL (HI)
COMMON TERMINALS (C)
COAXIAL COIL
TERMINAL (M)
ON/OFF SWITCH
INLET PRESSURE
TAP
MANIFOLD PRESSURE
TAP
REGULATOR VENT
LOW FIRE
REGULATOR
ADJUSTMENT
HIGH FIRE
REGULATOR
ADJUSTMENT
6. Wait fi ve minutes to clear out any gas. Then smell for gas including near the
fl oor.
7. If gas can be smelled following the fi ve minute waiting period, repeat step 6.
If you have waited more than 10 minutes and still smell gas, check for leaks
using a soap and water solution.
8. If you do not smell gas after fi ve minutes, push the gas valve switch to the
ON position (See Fig. 2).
WARNING: FIRE AND EXPLOSION HAZARD
Never test for gas leaks with an open fl ame. Use a
commercially available soap solution made specifi cally for
the detection of leaks to check all connections.
9. Replace the burner access panel on the front of the furnace.
10. Open the manual gas valve external to the furnace.
11. Turn on the electrical power supply to the furnace.
12. Set the room thermostat to slightly above room temperature. This signals
the furnace to start (the inducer motor starts and the hot surface igniter
energizes).
13. After 17-21 seconds, the gas valve energizes, letting gas fl ow to the
burners, where it is then ignited.
If fl ame is not detected, the furnace control goes into the “retry”
sequence. The “retry” sequence provides a 60-second wait following
an unsuccessful ignition attempt (a fl ame not detected). After this wait,
the ignition sequence is restarted with an additional 2 seconds of ignitor
warm-up time. If this ignition attempt is unsuccessful, one more retry will
be made before the control goes into system lock out.
14. If the burner fl ame is proven, the blower motor is energized on HEAT-H
speed 30 seconds after the gas valve is energized.
15. Set the room thermostat to the desired temperature. The furnace is now
running correctly and will be controlled by the thermostat.
There is an approximate 48 second delay between thermostat energizing
and burner fi ring.
4.2 Furnace Shutdown
In case of furnace malfunction, you may need to shut it down. Use the following
procedure to do this.
1. Set the thermostat to OFF or it's lowest temperature setting.
2. Turn off the electrical power supply to the furnace.
3. Turn OFF the main gas supply to the appliance at the manual valve, outside
of the appliance cabinet.
4. Remove the burner access panel.
5. Move the appliance gas valve switch to the “OFF” position (See Fig. 2).
6. Replace burner access panel.
7. If the furnace was shut down due to malfunction, contact your contractor
immediately.
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