Bryan Boilers Triple-Flex 150, 250, & 300, 200 service manual Air Flow Switch

NOTE:

The low fire displacement final adjustment should be made at low fire only.

3.Main gas pressure regulating and shutoff valve actuator. The pressure regulating actuator provides slow opening fast closing safety shutoff and air/gas ratio control. The actuator controls the pressure difference across the gas limiting orifice valve (Figure 7 item 26) as a function of the pressure difference across the furnace section so that the air to gas ratio remains constant irrespective of air volume changes. There is no need for an upstream constant pressure regulator when the supply gas pressure does not exceed 56 inches of water column. A minimum of 14 inches of water column must be supplied at the gas inlet connection (Figure 6 item 1). The supply pressure can be measured at the test port (Figure 7 item 28).

NOTE:

The supply pressure is not static. The supply pressure is at the maximum full flow of gas through the burner.

4.Manual main gas shutoff valve.

5.Pilot ignition transformer.

6.Manual pilot gas shutoff valve.

7.Pilot gas pressure regulator. This regulator provides a constant gas pressure to the pilot when the solenoid valve is energized. The pressure can be adjusted by removing the cap and adjusting the slotted screw clockwise to increase the pressure and counter-clockwise to decrease the pressure. The pilot gas supply is taken upstream of the main gas cock so the pilot may be lighted and adjusted with the main gas cock closed.

8.Low pilot gas pressure switch (Manual Reset)

9.Pilot spark igniter assembly. For further detail see Figure 9.

10.Pilot gas solenoid valve.

11.Flame scanner.

12.Main gas manifold pressure test port (1/4” NPT).

13.Main high gas pressure switch (Manual Reset). This switch should be set 1” of water column above the maximum gas manifold pressure.

14.Pilot gas pressure test port (1/4” NPT). This

14

Date: 8-4-2010

Revision: 0

Form: 2396

port is also used to record the furnace pressure.

15.Boiler water flow switch. The boiler water flow switch is adjustable within the parameters listed in the table.

Settings	Mode Of Operation
	Switch	Switch
	Closed	Open
Minimum	30 gpm	12 gpm
Maximum	52.1	46.1
	gpm	gpm

Table 4 Water Flow Switch Settings

16.Low Water Cutoff (Manual Reset Probe Type).

17.Combustion air-flow switch. An airflow switch is provided to prove that air is being provided to the burners before main flame can be established. The airflow switch can be adjusted by turning the screw (Figure 8 item A) clockwise to increase the pressure setting and counter-clockwise to decrease the pressure setting. The switch will open on pressure drop. When the blower is running there should be continuity between the common and the normally open contacts (Figure 8 item B and C). When the blower is interrupted the switch should open and cause a safety shutdown.

A

B

C

Figure 8 Air Flow Switch

18.High burner air pressure switch manual reset. This switch will trip when the air pressure in the burner rises above the set- point, indicating that the burner has become plugged with dust or other foreign matter.

19.Gas and air mixer assembly.

20.Main 3-phase power connection and fuse