Armstrong World Industries 123, 243, 302, 242 Pressure Switch Specifications, 18 Pressure Switch

Service Reference Manual UNIT COMPONENTS

5-21

Pressure Switch (*57)

These are Normally Open switches that react to a difference in pressure on an internal diaphragm. It will not allow ignition to start if the induced draft blower cannot produce sufficient negative pressure relative to atmospheric pressure or pressure in a sealed burner box. Its electrical contacts will open in reaction to inadequate negative pressure resulting from excessive venting system restriction or a failed induced draft blower, thus providing protection from a change in safe, stable furnace operation.

The Armstrong part number is stamped on the body of the switch. A label on the switch carries the manufacturer’s model number. Always verify the proper switch number from the parts list.

Common Terminal

Pressure Switch Specifications

Manufacturer: Tridelta Industries Electrical Rating:

SPDT Elec. Load: 28 VA Pilot Duty @ 24VAC 3 FLA, 18 LRA @ 24VAC

SPST Elec. Load: 5 A Resistive @ 24VAC

Electrical Switch: Single Pole, Normally Open, Snap Acting Contacts

Electrical Connectors: Common (C), Normally Open (NO) 1/4" x .032" thick quick connect terminals Maximum Pressure: 3" W.C.

Operating Temperature Range: – 40° to 190°F

Sample Line Connector: Negative; barb type for use with 3/16" or 1/4" I.D. tubing with .016" +/– .004" bleed hole

Normally Open

Terminal

Connect to Port on

Induced Draft Blower

Electrical Switch

FIGURE 5-18 Pressure Switch

SRM-HW/HWC 2/99