Residential and light commercial boilers serve as an alternative to forced air furnaces and heat pumps. Boiler heating systems require a distribution network that is installed during the construction phase of the project. Heated water is pumped through a piping grid, and thermal energy is released into the various rooms of the building during the recirculation process. In older systems, radiators, convectors and grilles are used to deliver heated air. Modern radiant heating applications employ the floor itself as a heat sink.
When given a choice, most homeowners prefer radiant heat because the warmth is spread evenly throughout the building. The slow, even release of heat helps reduce drafts and eliminates annoying air noise.
Radiant Heat Generation
Most radiant heating systems use a boiler to heat water or a special liquid antifreeze. Older boilers used steam as a transfer mechanism, but steam generators were very noisy and inefficient. Unfortunately, older piping systems were not made to carry liquid, and the cost of re-piping an entire building can be cost prohibitive. While steam boilers are no longer utilized in new construction, later models offer better comfort, improved efficiency and lower noise levels.
Gas boilers are popular because of their simplicity and economical operation. Most residential neighborhoods have a natural gas infrastructure available to the surrounding offices and homes. The operating principles for gas and oil boilers are similar, but the design of the combustion chamber is less complex in a gas model.
When the thermostat is triggered, a valve in the boiler opens, and natural gas flows into the combustion chamber. An electronic ignition system ignites the gas, and the heat exchanger transfers the thermal heat energy to the water, which is circulated through the radiant heating coils or piping network.
In an oil hot water boiler, a pump draws heating oil from a storage tank and forces it through a fuel line. The oil enters a specially designed nozzle, and the pressure creates a fine mist that is sprayed into the combustion chamber. The atomized oil is mixed with air, and a spark from the ignition system ignites the resulting vapor. The hot gas flows through a series of tubes inside the heat exchanger, and the energy is transferred to another set of tubes containing water. When the thermostat engages, the heated water is circulated through pipes or coils and returns to the boiler to be reheated. The water continues to circulate until the interior of the building reaches the desired temperature.
Condensing boilers provide the ultimate in efficient operation since they recover a portion of the energy that is usually lost during the venting process. A condensing boiler incorporates a second heat exchanger that extracts latent heat from the waste gas. Water vapor produced during the combustion stage is condensed back into a liquid and drained from the system. Condensing boilers are offered in efficiencies up to 98 percent.
Choosing an Oil or Gas Boiler
Since a boiler is the heart of every radiant heating system, it is important to select a model that provides excellent efficiency and durability. Most boiler purchasing decisions are based on the homeowner’s budget, local fuel availability and monthly operating costs. There are several important factors to consider before buying a new boiler including:
* Maintenance: Every HVAC equipment component requires regular service, but oil boilers are maintenance intensive when compared to their gas counterparts. Heating oil is a sticky liquid, and it tends to clog the injection nozzles over time. The combustion chamber must be cleaned frequently by a knowledgeable service technician who can remove the residue byproducts that accumulate during the burn cycle.
* Efficiency: Gas and oil boilers are rated according to the Annual Fuel Utilization Efficiency (AFUE) standard. In general, gas fired boilers are more efficient than oil based boilers when measured at the same level of heat output. A higher AFUE rating indicates a more efficient unit.
During the selection process, it is helpful to check your local costs for both gas and fuel oil. In most areas of the country, natural gas is substantially cheaper than heating oil. However, there are certain regions where fuel oil is very competitive because of a large established user base. Energy costs are unpredictable, and the price of fuel can change rapidly in a short period of time.
* Storage and Conversion Costs: Fuel oil must be stored in a tank, which will eventually have to be replaced. Since this is an expensive process, many homeowners consider converting to natural gas when it is time to replace an aging oil boiler. The conversion process can be expensive, especially if a contaminated underground tank needs to be removed. If natural gas is available, the piping must be large enough to deliver enough gas to satisfy the BTU requirements of the new boiler.
Comfortable, Efficient Heat
Radiant heating systems provide controlled, comfortable and economical warmth that is distributed evenly through the entire indoor environment. A qualified heating contractor can explain the many benefits of a modern gas or oil boiler.