There are 3 main fuel sources which are commonly used. They are:

• Gas (natural city gas or propane)
• Fuel Oil
• Electric

Outdoor Wood Boilers are another alternative to gas or electric.
There are many variations in style, size, capacity or floor or wall mounted design,
various efficiencies, open burning or sealed combustion, etc. . .

Exhaust Venting of boiler systems
The exhaust venting applies to gas and fuel oil boilers. The boiler is designed
to direct the burned fuel out of your home through a pipe venting system
called aflue. Some boilers are designed for a gravity vented piping design and
have a metal style pipe flue which exits through the roof of your home.
Other styles may have a powered fan which pushes the burned combustion
gases out and is usually vented out a sidewall of the home.
NOTE: Not all boilers are designed to be sidewall vented.

Expansion Tanks
This is a device that is piped into the water piping system.
The reason for an expansion tank is to hold a cushion of air at all times.
As water is heated it expands and takes up more room. Without an expansion tank in the
system the pressure would increase and rise to unsafe levels in the piping.
Two types of expansion tanks are open tank and bladder style tank.
The open tank was used more in the past and is placed usually at a high point in the
piping and located above the boiler. Through a series of special valves and design considerations,
an air column of approx. 1/3 of a tank of air is kept in this expansion tank.
NOTE: It is important to realize that there is no physical seperation from the
water & air in the open tank style and only gravity works with it.
The bladder style tank is along the same concept except a rubber balloon is installed
into a tank with an external access to add air into the bladder as needed.