32 Low-heat pressure switch did not close or reopened

What the control is telling you

The low-heat pressure switch (LPS) did not close or opened. If open more than 5 minutes the inducer shuts off for 15 minutes before retry. Also the expected result of the pressure-switch safety check with the inducer unplugged.

Applies to: 59TP6A two-stage variable-speed ECM multipoise condensing gas furnace, all sizes (040-10 to 120-22)

Likely causes

• Improper vent sizing or restricted vent
• Air leak between vestibule and blower compartment
• Low inlet gas pressure (if LGPS used)
• Disconnected or obstructed pressure tubing
• Defective or miswired pressure switches
• Excessive wind
• Plugged condensate drain
• Water in vent pipe (sagging pipe)
• Defective inducer motor
• Low inducer voltage (115 V)

Test and repair steps

1. Warning: If the hot surface igniter glows while the inducer is disconnected, shut the furnace down immediately.
2. Warning: Shut off 115-V power and gas, and lock/tag out before working inside the furnace; there may be more than one power source.
3. Check vent sizing and length against Tables 15-17 and look for restrictions or sagging pipe holding water.
4. Check the condensate trap and drain are clear.
5. Inspect pressure tubing and switch wiring.
6. Check the vestibule/blower compartment seal for air leaks.
7. Measure inducer supply voltage (115 V) and confirm the inducer runs properly.
8. Check inlet gas pressure (minimum 4.5 in. W.C. natural gas) if a low gas pressure switch is used.
9. Verify switch values from the label break +/-0.05 in. W.C. of nominal, max make 0.10 in. W.C. above max break.

Settings for these units

• Filter sizes by casing width and filter cabinet · 59TP6A
• Minimum clearances to combustibles · 59TP6A