EZS-495-11 – UNIVERSAL FURNACE PRESSURE SWITCH (0.15″ – 2.0″ W.C.)

SUPCO EZ Set universal air pressure switch. It proves draft or airflow before the ignition sequence is allowed to continue, and its SPDT contacts can be wired for positive, negative or differential pressure. The set point is field-adjustable from 0.15″ to 2.0″ w.c. with an allen key, so it can be dialed in to the OEM switch it replaces – set it to the pressure the equipment manufacturer specifies, since a switch set too low will not detect a blocked flue.

Specifications published by the manufacturer. Source: manufacturer documentation.

Specs

• ManufacturerSUPCO
• TypeField-adjustable universal air pressure switch
• Set point range0.15" to 2.0" w.c.
• SensingPositive / negative differential pressure
• ContactsSPDT
• Temperature range-40 F to 190 F
• Rated life100,000 cycles
• Air sampling connectionAccepts 3/16" ID flexible tubing
• AdjustmentAllen key set point adjustment

Cross-reference numbers

This part replaces the following OEM and aftermarket numbers:

• S1-02435271000
• 024-27630-000

Not sure if your number matches? Call (214) 340-9421 or bring the old part in — bench-testing is free.

What does the furnace pressure switch prove?

It is a normally open switch on a hose running to the inducer housing or the heat exchanger. When the inducer spins up and pulls enough negative pressure, the contacts close and the board is allowed to light the burners. A switch marked -0.75 in. W.C. closes at three quarters of an inch of water column of vacuum. That is the furnace verifying draft before it makes fire.

Mine will not close. Do I need a new switch?

Usually not, because these do not fail all that often. On a 90 percent furnace look at the condensate trap and drain line first - water backing up into the secondary heat exchanger is the most common cause we hear about. After that, the hose (cracked, kinked, or full of crud and water), the port on the inducer housing, the flue and intake for a bird or wasp nest, and the inducer itself for weak amp draw or a chewed up wheel.

How do I pick the right one?

Read the setpoint off the switch body. It is printed or stamped right there, along with whether it is a single or two-stage switch. Do not guess by looks - the same housing gets built at a half dozen different pressures, and -0.75, -0.80 and -0.85 in. W.C. are indistinguishable on the shelf. Bring the old switch or a clear photo of the label.

Can I jump it out to get heat tonight?

No. That switch is what keeps a blocked flue from pushing combustion gas into the house instead of out the roof.