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9AQ4 Manual
3 Operation
3.1 First time start up
It is important to verify proper operation of the power
vent motor before commissioning the system:
1. Slowly turn on cold water supply and check for
any leaks at newly installed flow switch and piping.
2. Plug power vent motor into 120VAC outlet.
3. With the gas supply to the water heater turned off
(see water heater manual) turn on a hot water
tap. The power vent motor should come on. Verify
the back-draft flapper is open and air is being
blown out of the power vent hood. If not, see the
troubleshooting tips in Chapter 5.
4. Turn off hot water tap.
Note: The AQ4 power vent fan motor is equipped
with a 45 second post purge cycle. The fan motor
should continue to run for this length of time after
the hot water flow has been shut off.
5. Open gas supply to the water heater and follow
the lighting instructions in water heater
installation manual.
3.1.1 Draft test
1. Check for proper combustion and ensure there is
no spillage by holding an recently extinguished
match or other visible smoke source in front of
the draft divertor. The smoke from the extinguished
match should be quickly sucked into the opening
and up the exhaust venting. If the smoke is blown
back, there is a blockage in the vent or the vent
motor is not operating properly.
3.1.2 Safety interlock test
1. Open the gas supply to the water heater.
2. Block the back draft flapper from opening from
the outside.
CAUTION:CAUTION:
CAUTION:CAUTION:
CAUTION: The metal of the back draft
flapper will be hot when conducting this
test.
3. Turn on the hot water supply to allow the burner
to activate. Hot flue gasses will spill from the
draft diverter momentarily. In less than three (3)
minutes, the linear spillage switch should trip,
opening the the heater safety circuit and halting
the flow of gas to the heater.
NOTE:NOTE:
NOTE:NOTE:
NOTE: If spillage switch does not shut off the
gas, check that you have made the proper safety
circuit connections. If the switch still does not
trip, contact Bosch Water Heating.
4. After the burners shut off, turn off hot water
supply and wait 2-3 minutes...then push the reset
button on the linear spillage switch.
5. Depending on model, light the pilot or run hot
water and repeat Safety Interlock Test, (Step 1-4)
6. Ensure back draft flapper moves freely and
closescloses
closescloses
closes
properlyproperly
properlyproperly
properly before operating once test is complete.
4 Maintenance
The vent system must be inspected at regular 3-month
intervals. Points of inspection are as follows:
1. Screened opening of the vent hood should be free
from foreign material and cleaned as necessary.
2. Check all vent system connections for leakage and
reseal where needed with high temperature
silicone sealant. If any vent pipe component shows
signs of deterioration, replace immediately.
3. Inspect proper closure of the back draft flapper
accessory. If the flapper does not properly close,
there is a risk of freezing air crossing the heat
exchanger that may cause the pipes to freeze and
burst. This condition is not covered by the water
heater warranty. See Fig. 11A for a properly closed
back-draft flapper.
4. Conduct safety interlock test and operation of
backdraft flapper once a year (Chapter 3.1.2).
Operation
Fig. 11A Properly closed backdraft flapper
Fig. 11B Improperly closed backdraft flapper