High Efficiency Furnace Pressure Switch Problems

Problems a furnace pressure switch can develop.

High efficiency furnace pressure switch problems.

Pressure switches may act up for several reasons including. 4 a dirty or stopped up draft inducer. A partially clogged flue vent condensate line or a clog at the condensate collector box near the inducer fan will often trip the furnace s pressure switch. 1 a restricted vent pipe 2 too long of vent piping and too many turns which exceeds manufacturer s recommendations 3 a stopped up condensate drain line if you have a high efficiency condensing furnace.

You can disconnect the pressure switch tubing so it will not get damaged and suck the condensate drain line out with a wet vac. Holes tears or other damage to the diaphragm. Using a cloth and a wire brush remove any blockages and dirt from the secondary exchanger and the inducer. A bad switch or a tripped switch is a common cause of furnace malfunctions.

The most common problem on high efficient furnaces would be frost or water in the vent. First off the furnace being high efficient will produce water due to low vent temperatures and condensation in the vent pipe. A crack in the heat exchanger could also be at fault. Some other things that cause furnace pressure switch problems are.

If your pressure switch is stuck it is most likely a problem in the running of the furnace. Pressure switch fail open first and most obvious would be failed ventor motor check 110 volts to motor and if it has seized. Coated or stiffened pressure switch diaphragm. Of course the pressure switch may also shut down if the motor is old and running too slow to satisfy the switch or the hose from the fan to the switch is pinched or broken or the switch itself is bad.

Water in the vent due to a sag in the piping could cause a pressure switch not to close. If the condensate drain is blocked by debris or frozen condensate or it simply drains improperly the pressure switch may open preventing ignition. Old age which can cause inaccurate readings and faulty furnace cycling.