What a standard boiler has to do is relatively simple: use oil or gas to heat large volumes of water that is then distributed via piping to some form of radiation unit such as a finned tube or a flat panel in each room of your building. There have been significant advances in boiler efficiency, resulting in lower costs to heat interior spaces.
Modern high-efficiency boilers adjust their water temperature in order to meet the heating requirements of their environment. Older systems adjust environmental temperatures by restricting water flow rather than temperature. With high-efficiency units, water temperature is adjusted to compensate for ambient conditions; as it gets colder outside, higher-temperature water, rather than a higher volume of water, is sent -- and vice versa for warmer ambient temperatures. This leads to a more consistent comfort level for your employees by maintaining a more even room temperature.
Condensing boilers are designed first to allow the heat to rise upward through the primary heat exchanger. Then, at the top the gases are diverted over a secondary heat exchanger. These boilers can reduce the flue gas temperature to about 130°F. This reduction of temperature causes the water vapor that is formed during the combustion process to condense, and as the droplets of water form, they fall by gravity to collect at the base of the flue manifold.
The remaining gases are expelled to the outside environment through a fan-assisted balanced flue. The condensation produced within the unit is drained away. It is only possible for a condensing boiler to work to these very high efficiencies if the flow and return piping is also kept below 130°F. The flow and return temperatures need to be maintained for the heat transfer to occur from the flue to the water.
Efficiency and Advantages
Businesses often neglect to look at the possibility of installing a new, more efficient boiler where savings materialize quickly and the investement is recouped quite quickly. Today's high-efficiency boilers can achieve efficiency ratings of 97 percent, compared with 65 to 70 percent ratings for old boilers. High-efficiency boilers have typical annual fuel utilization efficiencies (AFUE) ratings of 85 percent or greater, with some boilers scoring as high as 92 percent AFUE.
The efficiency of a typical non-condensing or traditional boiler is around 75 percent, but with high-efficiency or condensing boilers it can be over 87 percent. This increased efficiency is due to the extraction of heat from the otherwise wasted gases that go up the chimney. The majority of boilers have a single combustion chamber enclosed by the waterways of the heat exchanger through which the hot gases can pass. These gases are eventually expelled through the flue, located at the top of the boiler, at a temperature of around 180°C.
There are several advantages to having a high-efficiency boiler. Traditional chimneys are not required, as high-efficiency boilers are typically direct vent systems. The cost to operate a high-efficiency boiler is considerably less than a conventional boiler.
Season-to-season efficiencies of 85 to 95 percent can be achieved whereas the efficiency of conventional boilers may only be 55 to 65 percent. Reducing heating requirements also has an indirect effect that often is not considered: with the reduction in exhaust gas, there are less greenhouse gas emissions. Adding to that, there may be financial incentives such as grants and discounts from manufacturers that make new boiler investment a viable consideration.
Practice Boiler Safety
Safety is always a consideration for any type of boiler but becomes more critical as the boiler gets older. The best way to ensure a boiler is running safely is to get it serviced on a yearly basis. Don't wait until the unfortunate winter breakdown.
Servicing the boiler will ensure that it is burning correctly and carbon monoxide is not produced. Carbon monoxide is odorless and colorless, making it a lethal killer and a threat to you and your employees. It is a good idea to have a carbon monoxide sensor installed and maintained along with scheduled boiler servicing.
Safety is further enhanced with devices located in the boiler system. The safety valve is the most important safety device in a boiler. It is designed to relieve internal pressure if various failures occur within the system. It is a simple device, but something as simple as corrosion or restricted flow within the valve and the related piping can affect boiler operation.
Other safety devices are water-level controls and low-water fuel cutoffs. Many systems combine these two discrete safety functions into one unit. They are designed to ensure the water level within a boiler never falls below a set amount. If that situation occurs, the system is designed to shut down the boiler by cutting off its fuel supply. For these safety devices to function properly, there must be no buildup of sludge or scale within the system that would interfere with its operation.
There are many reasons to upgrade if a boiler is old or causing a significant amount of money to operate. Using a modern boiler brings benefits to energy consumption, the environment, and employee safety.
Jerry Barber is founder and president of Boilersupplies.com. A division of Power Plus International, based in McDonough, Ga., Boilersupplies.com is a distributor of boiler controls, gaskets and rope, gauges, condensate pumps, steam traps, level controls, valves, and tube bundles.