How to troubleshoot a gas furnace?

A gas furnace is a piece of equipment that takes in cold air, uses an air filter to clean it, heats it with the help of a gas burner and distributes the warm air through the ductwork. The heated air helps to increase room temperature during the cold winter days. Furnaces come with different efficiencies. However, once in a while these appliances may not work quite right and you may have to troubleshoot them. 

Let's look at the most common problems you may have to face with a conventional furnace.

Gas Furnace does not produce any heat:

Possible causes:

1. Thermostat not working
2. Propane or natural gas control valve is closed
3. Circuit breaker or fuse that is controlling the gas furnace is tripped or blown

Best possible repairs:

1. Check if the thermostat has the right temperature setting
2. Try to move the dial setting down or up a few degrees
3. Clean contacts in a non-digital thermostat
4. If the circuit breaker has tripped, reset it
5. Relight the standing pilot light

Blower is always running:  

   

Possible causes:

1. Thermostat has been fixed to run fan continuously
2. Defective control switch for fan limit

Best possible repairs:

1. Change the fan setting on the thermostat
2. Replace or reset furnace fan control switch

Gas furnace produces less heat

Possible causes:

1. The air filter is dirty
2. The gas burner is dirty or requires adjustment
3. Air flow is blocked to the combustion air chamber

Best possible repairs:

1. Clean or replace the dirty air filter
2. Call a professional service provider to get the burners adjusted.
3. Make sure the furnace has enough combustion air.

Noisy operation of gas furnace

Possible causes:

1. A "squealing" sound caused by slipping motor or shaft bearings or blower belt that requires oiling
2. Slight "rumble" when the burner is off may be caused due to wrongly adjusted pilot light.
3. Slight "rumble" sound when the burner is on is caused by dirty gas burners.

Best possible repairs:

1. Use a light weight oil to lubricate the blower motor lubrication ports located at the end of the shaft
2. Check for correct belt tension. If it’s loose, make sure you tighten the belt.
3. Adjust pilot light
4. Replace frayed belt
5. Call a technician to get the burners cleaned or adjusted.

Pilot light is out

Possible causes:

1. Dirty orifice, a strong draft, or dirt inside the gas tube can lead to a pilot light going out.
2. A faulty thermocouple may also shut off the supply of gas.

Best possible repairs:

1. Ensure that your thermostat is on "Heat" mode.
2. Find the pilot.
3. In case you have a pilot that has a red Reset button, turn "Off," the gas valve to "Pilot."
4. In case you have a pilot that has no red button, turn the dial from "Off" to "Pilot."
5. Depress the knob or hold the button and light the pilot using a lighter.
6. After the furnace burners ignite, regulate the thermostat to the preferred setting.

Sometimes your gas furnace may act out and may require repair. You can follow the tips mentioned above or call a technician to fix the problem. If the issue seems complicated, it is best to seek professional help.

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.

Thermostat:

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.