Forced Air Heating Basics

1. Your thermostat(9) sends a message to your furnace that it’s too cold.
2. Burners(1) in your furnace ignite. Flames from the burners are fueled by the gas supply and oxygenated(2) air from outside.
3. This heats up the heat exchanger(3). This heating process produces carbon monoxide(4) that gets drawn up out of the heat exchanger through the flue to the outside.
4. The blower(5) actives. Cold air is pushed by the warm air and pulled by the blower(5) via the return-air(6) vents in the house through the filter(7).
5. The filter(7) removes a portion of the dust and allergen particles.
6. The blower(5) then pushes this air across the hot heat exchanger(3) warming it.
7. This warm air(8) continues through your duct and vents into your home. This flow of air continues until the thermostat(9) sends a message to your furnace that it is warm enough.

That’s really nice, right. But what does all of it mean to you?

This means there are many opportunities for in-efficiencies and safety concerns.

Some Heating Problems:

1. The Thermostat

Some require batteries to operate. If the batteries are not changed at least once every year they can cause erratic behavior in your furnace and/or air conditioning.
Because thermostats operate on electrical power there is a possibility of wire and connection corroding or shorting out.
Lower end thermostats are often disrupted by static electricity. There is a performance difference between retail store and HVAC professional thermostats.

2. The burners

When there is a flame there is a potential for carbon buildup. This buildup can reduce the size of the flame requiring more gas usage to compensate.
During the off-season the tubes that make up the burners are cozy little places for spiders to hang out. A web inside one of the tubes can block the flow of gas. This can lead to a repair bill or even a fire.

3. The oxygenated or combustion air

A flame needs oxygen rich air to burn properly. When the combustion air source is obstructed the flame may not burn properly and again uses more gas to compensate.
If the flame is poor enough one of the safety mechanisms can shut down the system. This must be repaired.

4. The heat exchanger

Over time of system use or due to defects in manufacturing a heat exchanger can develop a crack. This causes carbon monoxide that would normally be drawn out through the flue to be pushed into the home. This can be a dangerous situation.
Some levels of carbon monoxide concentration and what they can cause:
- 50ppm - OSHA maximum allowable concentration for continuous exposure in any eight-hour period.
- 200ppm - Slight headache, tiredness, dizziness, nausea after two to three hours
- 400ppm - Frontal headaches within one to two hours, life threatening after 3 hours.
Your reading should be 0ppm. If your reading is more than zero you need to have your system inspected. This inspection may find that the system can be repaired or it may need to be replaced.

5. The flue

Making a change to your system like adding an air-conditioning unit or replacing a water heater can result in in-adequate flue draw. The carbon monoxide is not drawn up the flue to the outside but gets pushed into the home. This must be repaired.
An obstruction in the flue. Occasionally our feathered friends deposit themselves or debris into the flue creating an obstruction. The carbon monoxide is not drawn up the flue to the outside but gets pushed into the home. Again this must be repaired.
A 90% efficient system causes considerably more condensation, which can freeze and obstruct the flue. This can trigger a safety mechanism that shuts down your system. Some these mechanisms can be reset but will weaken each time they are triggered. Others are one-time use and must be replaced. Either way this must be repaired.

6. The blower

As you can see from the diagram on the previous page the filter can only remove a portion of the dust and allergen particles. The remainder of those particles get pulled into the blower. Here there are plenty of places for those particles to get trapped in the motor, causing it to work harder and use more electricity. This also causes additional wear and tear on the motor and can shorten its life span.
In a new home sheetrock dust can be a major contributor to the particles being pulled into your blower.

7. Return air

As the air circulates through your home it collects additional dust and allergen particles to be passed through the system. This becomes important in the next section.
In-adequate return airflow passes less air through the heat exchanger, creating less warm air to be pushed into your home. With less warm are in the home your system will operate for longer periods of time using more gas and electricity. Operating a system for longer periods also creates additional wear and tear and can shorten its life span.
In-adequate return airflow can trigger a safety mechanism that shuts down your system. Some these mechanisms can be reset but will weaken each time they are triggered. Others are one-time use and must be replaced. Either way this must be repaired.

8. The filter – believe it or not this is a tricky one

First we will address the obvious. A dirty filter reduces the return airflow and by now you know what types of problems this can create.
The tricky part. Thick, dense, heavy duty, high quality, allergen reducing filters definitely reduce the particles traveling through your system. Of course in order to accomplish this the return airflow is also reduced. With the information you now have, this one is for you to decide what you want to do.

Some Heating Solutions:

1. Change or clean your filter regularly. A standard filter should be changed at least every two months during system use. Yes that means during the cooling season as well. The thicker, denser, heavy duty, high quality, allergen reducing the filter is the more often it will need to be replaced or cleaned. If you have hair fur-bearing pets inside the home the filter should be cleaned or changed more often.

2. Indoor air quality can be improved without compromising the operating efficiency of your system by opting for electronic or ultra-violet air cleaners.

3. Have your system professionally cleaned and inspected (tuned-up) annually. Make sure this cleaning and inspection is very thorough. It should at least address each of the potential problems mentioned here.