Furnace and alteranative heating system information.

Forced air furnace

80% Furnace

Percentage ratings refer to how efficient the unit is. In other words, out of the total heat that can be produced, how much actually makes it into the home. In this case it is 80%. The other 20% is eliminated through the flu pipe as evaporation. This may sound like a lot of wasted heat, but if your furnace was made 20 years ago, it is probably only in the 60% efficient range. 80% units typically have one gas burner to heat the incoming air. In addition, modern furnaces do not have a pilot light. They have electronic ignition. This means that when it is not running, there is no gas being burnt. An electric igniter will light the burner when the thermostat calls for heat.

90% Furnace

Based on what we learned above, this unit puts 90% of the heat produced back into the home. It is able to do this by having two burners instead of one. The second burner evaporates the water vapor a second time removing nearly all the heat the vapor has to offer and puts it back into your home.

Differences

The biggest difference, besides the obvious efficiency rating is the way they are vented. An 80% unit is typically vented straight up through the house and out of the roof. The pipe from which it is vented can be in a flu or chimney, or it can stand alone. A specially rated pipe must be used for the venting.

80% units are less expensive than 90% units. Many experts believe that it will take approximately 5 years to recoup the cost difference between the 80% and 90% unit. The length of time you plan to stay in your home may play a significant role in deciding which furnace to purchase.

A 90% efficient furnace is vented through the side of a house. Typically the vent pipe is PVC. Because so much heat is extracted from the exhaust vapor, a fan is needed to push the exhaust out of the vent. It is not hot enough to draw to the colder exterior air. This fan is located inside the housing. A drain is required for the condensed water vapor. This is normally drained into a floor drain in the basement or into the crock. There are pumps available to pump the water to other locations if a drain is not readily available.

Both 80% and 90% units offer either single stage or two stage units.

Single stage

Stages are sometimes confused with blower speed. The blower speed does change during different stages but stages refer to the burn rate of the fuel. A single stage is either all the way on, or it is all the way off. When it is on, it burns at 100% of it’s capacity. This creates larger temperature swings(up to 3 degrees). This results in the house feeling chilly before the furnace starts its cycle and then feeling hot when it completes the cycle.

Two stage

With a second stage, the unit can run at 60% capacity most of the time. This provides a slow heat up time. This allows the air in the home to circulate better which lowers the temperature swing. It’s also great for moderate temperatures. It takes the chill off without running at 100%. When the days are really cold and the furnace is drawing in the cold air, it fire up to the second stage which the burners will then operate at 100% capacity. Because of the second stage the temperature swing will be less noticeable making the home more comfortable.

Check out this website by the American council for an Energy Efficient Economy. It has a lot of useful information about heating systems such as whether or not you should replace yours, charts for determining the size you need, how much cost savings you can expect and other information.

Electric furnace

The advantages of electric heat is there are no combustible fuels in your home. Since there is no fuel being burnt, there is no gas bi products such as carbon monoxide. This makes the furnace very safe.

The disadvantage, generally speaking, is that electric furnaces are more expensive to operate than a gas furnace.

Heat pumps

Although heat pumps can get there heat source in many different forms, the most common sources are: Air, Water, and Ground. Depending on the type of heat pump system chosen, it can deliver heat via a forced air system, or a radiant floor system. Heat pumps are also known as being environmentally friendly because they do not burn fuel.

Heat pumps can be costly to install. Some people believe they are not a good choice for heat in colder climates. There is a lot on information available at this website. It explains several different heat pump systems in more detail.

Electric baseboard heat

Some disadvantages are they will most likely be more expensive to operate than other heating systems. They are not compatible with central air. An alternative cooling solution will have to be employed, or separate duct work will need to be ran for central air.

Radiant floor heat

Gas systems use a complex system of pipes. A boiler heats water that is ran through the pipes. Like electric, these pipes are laid on the floor and are encased in mortar. In either system, flooring is installed over the mortar. The heat then radiates up through the floor.

The benefits of radiant heat is that there is no temperature variation. It is a constant enveloping type of heat, much like wood burner heat in my opinion. It is an efficient heating system and your floors are always warm to walk on. It can be used throughout the home or in specific rooms such as the bathroom.

It can be expensive to install and it is not compatible with central air conditioning. Separate duct work will have to be run for the central air or alternative cooling systems will have to be employed. Another down side to a radiant heat system is that it takes longer to initially heat a home than a gas furnace. So if you come home from vacation and the house is cold, it may take a couple hours or more to heat the home.

Electric systems will require no fuel lines, or venting. Hot water systems will require the boiler be vented and have a fuel line.

An interesting note: some people have this type of system installed under there drive ways and walk ways so that no shoveling is required in the winter.

For detailed information about in floor heating systems, check out the links listed below.

Energy council - radiant floor heating Radiant floor heat

Hot water (boiler) system

Some disadvantages are, this system is not compatible with central air. It also has a slow heat up time. Baseboard units can make it hard to place furniture against the wall. You will also have to be careful of long drapes which could trap the heat.

For more detailed information on boilers, check out this Link.

Wood furnaces

The disadvantage is that you have to insert the logs and make sure you have fire at all times. Most homes have a back up heat source when using wood furnaces. If you leave the house for several days, you will need an alternate heat source.

Another disadvantage is the amount of wood you will need to store to heat the home throughout the winter. This will take up a large amount of space. You will either have to purchase the wood or cut it yourself.

The second type of wood furnace is an exterior unit. The way it works is it has a boiler that heats water. The water is pumped into your home into a coil that is installed in your existing forced air furnace. Air is pushed through this coil extracting the heat and forcing it into your home. This system can also provide hot water for kitchens and baths as well. Since it is attached to your existing heat source, back up heat is already in place.

The same disadvantages stated above apply to an exterior furnace as well.

Fore more detailed information on wood stoves and other alternative wood heating systems, check out this web site.

As always, if you have specific questions that were not addressed here, please contact me for the additional information you need. Tanner Phillips installs forced air furnaces and central air conditioners. Please feel free to contact us for a free quote.