Thursday, 24 March 2016

Troubleshooting a high efficiency furnace

A high efficiency furnace is a high technology machine that enables you to heat your house while consuming low energy. However, like any machine it can at times stop working, and when this happens it normally requires calling a ventilating and heating repair shop.

However, before calling an expert, there are a lot of things that you can check or repair on your own.


The thermostat that controls your high efficiency furnace should be the first thing you check. You must check to see if the machine is operating properly. Some of the possible problems include:

  • Fuse blown or circuit breaker is tripped
  • Dirty thermostat components
  • Loose wires
  • Bad battery

Clogged filter:

A severely blocked furnace filter can create a lot of damage.  It can also cause the machine to overheat and frequently cycle the safety switch on and off. Check the filter which is either a paper media or a fiberglass furnace filter or a state of the art pleated paper media filter and make sure you replace it if necessary.

Once you have replaced the clogged furnace filter, turn off the furnace switch for a few minutes and then turn the switch back on. This will help in resetting the furnace electronics.

High limit switch:

A high temperature limit switch is basically a safety device that screens the temperature of the internal furnace and shuts down the gas valve if temperature limits exceed. As soon as the temperature decreases to the lower limit, the gas valves are turned back on turning on the burner.

It is possible for the high temperature limit switch to suffer damage if it is subjected to frequent tripping because of low air flow and overheating. You can use a multi-meter to test the switch.

  • Set the multi-meter to resistance.
  • Evaluate the wires travelling to every switch terminal.
  • In case the resistance is 0 Ohms then the switch can be regarded as good. On the other hand, if the resistance is infinite the switch needs change.
  • It is easy to replace the switch. All you have to do is unscrew the switch plate and change the replacement part.

Obstructed vent pipe:

Another problem that can stop the furnace from functioning properly is an obstructed or clogged flue vent pipe. An obstructed flue gas vent pipe can also make the pressure switch to trip.

Make sure the pipe is sloped properly and is free of obstructions.

Hot surface ignition:

In normal conditions the hot surface ignition will last for three to five years. However, it will have to be replaced eventually, quicker if the oils from your skin get on the element by improper handling.

The HSI achieves 1,800°F to 2,500°F of heat. Once the right temperature is attained, the gas valve opens, introducing gas to the burner which is then ignited by the HSI. Once the flame sensor senses a proper flame, the HSI shuts down.

Knowing your furnace will help you keep it in the best condition possible. However, it is important to get in touch with experts if you find it hard to correct the issues.