Hydronic Heating Boilers and Domestic Water Heaters
CLEANING AND MAINTENANCE CONTINUED
The " (+)" connection on the manometer connects to the tee in the tubing from the units front chamber and the "
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 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.
4 |
3 |
2 |
1 |
0 |
1 |
2 |
3 |
4 |
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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