Lochinvar 000 - 2 Installation And Service Manual page 42

Hydronic Heating Boilers and
Domestic Water Heaters
CLEANING AND
MAINTENANCE
Figure 43 - Air Pressure Switch
Turn the adjustment screw on
the air shutter to open or close
shutter.
Figure 44 - Adjusting Air Shutter
Set Up Procedure
To the left of the fan is an air pressure switch with a large and
a small tube delivering pressure from points inside the unit (see
Figure 43). The pressure in the large tube is the chamber
pressure. The pressure in the small tube is the burner pressure.
They act together to make the pressure switch. By
disconnecting the caps from the tees in the pressure switch
hoses and connecting them to either side of a manometer, you
can read the differential pressure to the switch.
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The " (+)" connection on the manometer connects to the tee in
the tubing from the units front chamber and the " (-) "
connection on the manometer connects to the tee in the small
tubing from the burner.
Upon a call for heat, the fan will run for about 90 seconds
before going into soft lockout. If necessary, turn the power to
the unit OFF and then back ON again to recycle the fan.
Note: If the unit has been firing recently, allow the unit to cool
for five minutes with the fan running before beginning the
adjustment procedure.
Note: Retain the plastic caps removed from the tees for
reinstallation when complete.
Figure 45 - Combustion Air Adjustment with a Manometer
to set Differential Pressures
Adjustment Procedure: 495,000 - 1,255,000 Btu/hr
Models
1. Remove the upper front jacket panels from the unit to
access the upper chamber.
2. Locate the air shutter on the side of the fan housing (see
Figure 44). Turn the adjustment screw on the air shutter to
open or close the shutter. Increase air shutter opening to
increase air pressure. Decrease air shutter opening to
decrease air pressure.
3. Adjust the air shutter until the differential pressure is
nominally 1.2 - 1.35 inches water column for models
495,000 - 745,000 Btu/hr and 1.1 - 1.3 inches water
column for models 985,000 - 1,255,000 Btu/hr. Note: The
air chamber pressure is 1.2 inches water column for
liquefied petroleum (L.P.) and 1.4 inches water column
for natural. See Figure 45 on installations up to 2000 feet
altitude. Contact the factory for high altitude pressure
settings.
4. Once the adjustment procedure is complete, reconnect the
caps to the tees in the hoses to the pressure switches and
check all tubing and wire connections for a snug fit. Test
fire the unit. Reinstall upper panels.
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