Selecting a Natural Gas Furnace As A Heat Source

In this country there are few places where you can live without needing a heating system or a cooling system at some point during the year. These systems are the biggest consumers of energy in your home as they require more power than any other appliance or item of machinery that the average person is likely to use in their home. Therefore it is essential that you know what the different types of natural gas heating systems are and that you are able to choose one that will not waste too much of your money.

When selecting a natural gas furnace you will need to know about things such as AFUE, which is basically a unit of measurement that tells you how much energy goes into your home in comparison to how much of that energy in fact is used to heat your home. For example a high AFUE of 90% means that 90% of the money that you are paying to run your natural gas furnace is being turned into heat for your home. The higher the AFUE, the better. Different systems provide differing levels of efficiency.

Types of Natural Gas Heating Systems

There are a number of different natural gas heating systems on the market. They tend to vary from to the next in a number of key ways. These ways include:

  • Configuration: This has to do with the structure of the furnace and how it is laid out and controlled.
  • Size: The size of the natural gas furnace that you end up selecting has to correspond to the size of your home. If the furnace is too big it will switch on and off unnecessarily and frequently, thereby wasting power. If it is too small it will have to run practically all the time in winter in order to keep the home warm enough, once again wasting power.
  • Types: The main types of heating systems are central heating systems, forced air systems, condensing furnaces, water-based (or hydronic heating systems), and room or supplemental space heaters.
  • Efficiency ratings: The efficiency rating refers to the amount of heat you get for the amount of money you put in, as well as the amount of power the system uses in comparison to the amount of heat you get. Clearly the more efficient the gas furnace is, then, the more money you will save when you use that gas furnace.

Central HeatingNatural Gas Furnace

Central heating systems consist of three main parts. These parts are:

  • A unit where heat is created
  • A system that distributes the heat that the previous unit creates (this is called the “delivery system” and can be air, gas, or water based)
  • A control system that allows you to turn the distribution system on an off

The unit where the heat is created is usually a secure cabinet. In this cabinet you will find:

  • A natural gas burner
  • A heat exchanger

The heat exchanger is the component that is responsible for moving he heat form the cabinet to the delivery system. When heat is required the gas burner in the cabinet is switched on by a standing pilot light (or, in some cases an electronic ignition switch – these are the more modern options). The heat is moved to where it is needed.

To control the burner and the delivery system you will use the thermostat. The thermostat:

  • Turns the system on
  • Turns the system off
  • Allows you to control the actual temperature

The systems often come with other control mechanisms as well, as well as vents that move the byproducts out of the home. In addition it is often possible to provide different temperatures for different rooms in the home.

Forced Air Systems

These are by far the most common systems used in homes at present. They range in AFUE from about 78% to 97% making them among the most efficient options for you to choose. 78% is the absolute lowest AFUE efficiency rating that any new natural gas furnace is allowed to have, so forced air systems are well within regulations. The system functions in two main steps:

  • Cool air is drawn into the heat exchanger where t is warmed up
  • An electric fan pushes the no warm air into ducts throughout the home

Air is needed in these furnaces to mix with gas in the combustion chamber. This air can come from either in the home or from outside the home, with the second option being more preferable as you do not lose air from inside the home that is already warm. The other way in which air is used is, of course, to heat the home by moving through it.

Natural draft furnaces simply require a vent r chimney high up to get rid of by products as hot air rises. More efficient and modern systems, however, are not as natural and require that a fan pushes the byproducts out.

Condensing Furnaces

Condensing furnaces have the highest AFUEs. Any condensing furnace that you buy will have an AFUE of over 90% consistently, so you can be certain that you are getting the best value for your money as possible. This is probably more important than you realize. To reiterate, the higher the AFFUE< the more money you will save when you purchase and then use this furnace. This is quite possibly the most important thing to consider when selecting a natural gas heating system, so it is important that you know what to look out for and what questions to ask. Condensing furnaces are therefore among the best options. These furnaces are of such high efficiency in terms of converting most of the power you use into heat for your home that they take enormous quantities of heat out of the flue gasses. What happens then is that the gasses or vapor actually turn back into liquids. That is now efficient the furnace is. In order to vent these liquids, which are just like the byproducts mentioned in the previous sections and therefore need to be removed from the home, the manufacturer will specify a plastic vent material that needs to be used with that system to remove this liquid.

Water-Based or Hydronic Heating Systems

These kinds of natural gas furnaces use water instead of air to give you warmth. Water is heated and vaporized into hot steam which is circulated through your home. Radiator systems work in this way. When the vapor loses its heat it is allowed to condense and return to a liquid form. So radiators are one type of hydronic heating system. You also get under floor heating systems: Here hot water is pumped through pipes embedded in the ground to keep the home warm. Other systems work differently:

  • A baseboard unit produces heat
  • The convector within the base board warms up as water runs through creating radiant heat
  • At the same time warm air rises off the convector
  • This warms the room

In all these systems water returns to the boiler after giving off heat. These types of heating systems also require byproducts to be efficiently removed; hence they too come with vents.

A hydronic system that is of very high efficiency is also referred to as a condensing system because it works in the same way.

These heating systems are usually stored somewhere where they will not be in the way. Basements and utility rooms are ideal places to keep the boiler of this kind of system.

Room or Supplemental Space Heaters

Sometimes there is a room in your house that is not used often and therefore does not need to be affected by the central heating of the home. In some cases there may only be one or two rooms in the house that you use frequently where heating is required. In either of these cases you will want a room or supplemental space heater. These heaters usually come as panels that can be mounted and that will warm the person or object directly in its path by using convection currents to heat the air. The air is then moved wither by:

  • Natural air current within the room, OR
  • A small fan or blower that comes with the system

If you are not at home frequently or if your heating needs are highly specific, these are the kinds of heaters that you should purchase. They can be switched on only when necessary and, because they are only heating one room at a time, they will not require nearly as much power. However if your need or intention is to heat the entire house frequently and for long periods of time you should consider one of the other systems mentioned above as these will be more appropriate for your needs.

Venting Options

Practically all of the systems mentioned above require venting in order to get rid of the byproducts created in the heating process. Some furnaces do not require venting as they are internal and use air within the home to combust. Because of the inherent dangers in using air form within the home to heat the home, these systems will have an air-depletion sensor included in them which will automatically cause the system to shut down altogether and the gas to switch off if it detects that there is too little air in the room. In addition the system will be unable to start up again until the air is sufficient and it is restarted manually.

However these are not legal in all states or areas, so you should find out what the specifications are for your area before choosing a gas furnace of this kind. There are several different venting options:

  • You can use a conventional chimney
  • You can use flue vents
  • You can have the byproducts directly vented through a wall

Because byproducts can be dangerous appropriate venting is necessary. Be sure to ask about ventilation options when selecting a system, and make sure that the installers know where and how to connect them before allowing them to get started.


The size of your system is important. The right size for your home depends on:

  • The size of your home
  • The construction of your home
  • The insulation of your home
  • The way you use your home
  • The most severe temperatures your home is subject to in your area

To determine the exact figures for the above parameters you will require a specialist’s help. Once you have the correct numbers a calculation can be done to determine the most appropriate size for your furnace.

Don’t base the purchase of your new system on the size of your old one. Many older boilers installed in older homes are not necessarily the correct size. Rather have a specialist make the required calculations. You will also need these calculations to determine what AFUE you need from your furnace in order for it to function at its most efficient within your home.

It is essential that you have a working knowledge of what the AFUE rates are for each of the gas furnaces that you are looking into purchasing. There are plenty of options out there, but if you make the wrong decision you could well end up wasting a substantial amount of money in the process.

Cost Comparisons

There are two main factors to take into account when comparing the prices of the various units that you are interested in purchasing:

  • The initial cost to buy and install
  • The average annual operating costs

Get a copy of the Energy Guide fact sheet and use your local gas rates to do the calculations. This will help you find a furnace that s of a reasonable price.

The climate you live in will affect whether a high-efficiency or low-efficiency unit is a better buy:

  • If you live in a very cold climate you should go for the more expensive high-efficiency units. This is because your cost will be paid back to you in savings on energy bills in a very short period of time.
  • If the climate you live in is milder you should go for a lower efficiency and cheaper model as you will not use the furnace often enough to benefit fully for the energy savings.

Another thing to take into account is whether or not you plan to stay in your home long enough to benefit from the long-term energy savings that a more expensive and more efficient unit will give you. Calculate and compare how much you will save over the long-term.

Proper Use and Maintenance

There are a number of things that you should do to ensure that your system is well maintained:

  • Have your system checked by professionals ion a yearly basis to ensure that everything is working well and that the boiler is still safe.
  • You should also do your own basic inspections in between professional inspections. There are several things that you will notice just by looking, such as if the flame is the wrong color, or water is collecting near a boiler or a vent.
  • Be sure to keep all vents and chimneys clear of blockages.
  • Do not try to bypass any safety measures as they are all there for a very good reason: to protect you.
  • Keep objects such as aerosol cans and anything flammable away from the gas equipment to avoid explosions and fires.
  • Forced-air systems have filters and these filters need to be cleaned regularly, sometimes even replaced. Keep ahead of this. This should be done about once a month during those times of year where you are required to heat your house frequently, i.e. winter.
  • Keep all registers, radiators ad baseboards clear.

The older your natural gas furnace is, the more likely it is to be one that is not terribly efficient. Most older furnaces that use a boiler system only have an AFUE of around 65% or lower. Most of the newer systems that are fresh on the market have far higher AFUE rates. The newer your system is the more likely you are to be saving money on it. There are several different kinds of furnaces and each of these different kinds have differing levels of efficiency. They are also generally chosen for slightly different reasons, so the choice you make will depend largely on what you need to use the furnace for. Selecting the right natural gas furnace for your home depends on a number of different parameters. The amount of factors that need to be taken into account when making your selection may seem daunting at first, but once you have sifted through the information and considered the size and location of the home that you need to heat, you will soon realize that the choice is not that difficult, and that it is worth the effort of looking through all the information in detail.