Let’s start with what a boiler is; a boiler is a device in which water is being heated to support heating and other needs. Boilers vary mostly in efficiency, output, fuel type, and application of use. A boiler transfers energy from combustion or electricity to water. A boiler is a vessel for heating water or generating steam.
 

The first step towards water heating is believed to be dated back as far as 300 C.E. Evidence of the Romans building large baths with heated water, was one of the first steps that lead to the invention of the steam-generating boiler in 1867. Although highly debated many people believe that the founding fathers of the steam generating boilers were Steven Wilcox and George Babcock. This patent was known as a breakthrough and aided the progress of civilization and the birth of the power industry. Over time this method has been re-applied with a slight change in the fuel source to better accommodate the consumers.

Fuel Sources of Boilers

Most boilers used today are the “conventional” type in which the liquid is being heated by natural gas. Other variants to this device include heating the water by burning wood, coal, and oil. Another way to heat the water is with electricity (electric steam boiler), which uses immersion type heating elements. Boilers have always been a popular source for heating the water in any system, and with so many different ways to apply the heating method, it’s no surprise.
 

Natural Gas – These types of boilers use the most popular fuel type in the world. These units turn the water into either hot water or steam. Boilers are used to create hot water for domestic needs as well as heating applications including snow melting.
According to a study in 2012 by the Center for Climate and Energy Solutions, natural gas boilers consumed 25% of America’s energy.  

Pros: Low fuel price, constant source of fuel
Cons: Initial installation costs (Minimum of a few thousand dollars) and safety, monthly payments, annual maintenance.

Propane – Propane is commonly used where a natural gas boiler cannot be installed due to a lack of natural gas lines in the area. Rural areas are more prone to installing propane fueled boilers. Propane boilers are used in the same way as natural gas boilers.

Pros: Boiler can be installed anywhere, easier to shop for competitive fuel pricing.
Cons: Manual refueling must be done, safety and annual maintenance

Oil – Oil fired boilers are mostly used in areas where there is limited or no access to natural gas. These boilers offer their consumers options such as using heating oil blended with bio-diesel to run their system. Boilers that are fueled by oil are often designed to work with another fuel source as well, giving the consumer the ability to choose. These boilers are usually set up in an area where other types of boiler installation are too costly. Oil-fired boilers are used in the same ways as natural gas boilers.

Pros: Long lifespan, can operate on various types of fuel, easier to shop for competitive fuel pricing.
Cons: Maintenance must be done by experts, inhabits large space.

Electric - Electric boilers are easy to install and can take up very little space in a confined area. These boilers heat water with electricity. Electric boilers are used in the same way as gas boilers.

Pros: Unlimited source of energy, safest type of boiler, eco-friendly, can benefit from nuclear powered, solar and/or wind powered electricity generation.
Cons: Annual maintenance, high price of electricity.

Wood - Usually installed outdoors, these units can work at an efficiency rate of 85-90%. Through the burning of wood these boilers can be used in the same way as gas boilers. These units are usually installed as a second source of heat in areas that have frigid weather conditions, and rural areas consisting of woods.

Pros: Can be the least expensive fuel source, renewable fuel.

Cons: Installation cost must be manually fed at least once a day (except where pellets are automatically fed) and annual maintenance.

Condensing and Non-condensing Boiler

Basically, condensing boilers are hot water heating systems that run so efficiently that condensation (water) forms in the heat exchanger and/or exhaust flue (pipe). These types of boilers can be up to 98% efficient. Condensing boilers can recover up to 12% more energy than a conventional boiler. 

Basically, non-condensing boilers, also known as conventional boilers, avoid condensation accumulation by moving and exhausting combustion products before water vapor can develop. Unfortunately, these boilers are less than 90% energy efficient.

Boiler Efficiency 

As you read, please be aware that efficiency standards and codes change. Local codes and local officials must always be consulted before you try to decide on purchasing boilers or other equipment.  Texas and California often update standards faster than other states. This information is designed to educate you about basic principles concerning energy efficiency and various types of equipment.
Efficiency Ratings- Every distributor of water heating equipment had to follow a certain standard to ensure their products follow a certain guideline. The efficiency rating provider is the AFUE (Annual Fuel Utilization Efficiency); which is a thermal efficiency measurer of combustion equipment such as boilers, furnaces, and water heaters. The AFUE rates high efficiency natural gas boilers at over 90%. The AFUE minimums for these boilers are as follows; 80 percent for gas-fired steam boiler, 84 percent for an oil-fired hot water boiler, and 82 percent oil-fired steam boiler. Non-condensing boilers offer efficiencies of 80-88 percent while condensing boilers offer that of 88 percent and higher. Wood fuel boilers have efficiency ratings of 71% and higher.

Boiler Sizing

Basically, the sizing method of a boiler is usually matched up to a few specific components. Boiler efficiency, heat loss and area to be heated are key factors in the equation that determines boiler selection.

Details concerning insulation, windows and home construction dramatically affect boiler sizing. A well-insulated building usually requires a smaller boiler than a poorly insulated building.  

High efficiency boilers provide more usable energy and usable energy (output) is what determines the necessary boiler size. Example: Sometimes, a high efficiency 80,000 BTU boiler might replace an old less efficient 100,000 BTU boiler. Often, a new high efficiency 100,000 BTU boiler might be too large when replacing an old 100,000 BTU boiler.

Over sizing a boiler will result in wasting energy, premature boiler failure and wasting money. If you need convincing and more details, watch for future articles provided by Mike Quick.

Under sizing can be dangerous and may not generate enough heat. Also, under sizing can cause premature failure.  

Proper sizing (not too big and not too small) a boiler is extremely important.

Boilers are only a portion of a heating system, and must be properly installed with pipes, pumps, valves, an output source for the heat, and the control equipment. To ensure proper function of a boiler, it must be properly sized, installed and maintained.

Electric Boiler Efficiency

Some residential households are inclined to install electric boilers due to the unavailability of natural gases to fuel their boiler. This method of heating water is extremely efficient at a whopping percentage range of 95 to 100 according to the AFUE. Although the heat efficiency output is at an all-time high, the cost of electricity in the area may not make this a reasonable choice for home owners.
An electric boiler does not require a chimney or other exhaust pipe or connection. They are also considered much safer than other boilers, and require less maintenance due to less condensation and fewer contaminants.

ENERGY STAR Label on Your Boiler 

The label ENERGY STAR can be located on all types of products including boilers. This term is an international standard for energy efficient consumer products. Finding this term on any product correlates to the product using 20-30 percent less energy than required by the federal standards. This term is one followed on an international scale, and is highly considered when purchasing home electronics, appliances for heating and cooling systems, imaging equipment, and many other appliances.

Boiler Heating System

A boiler heating system can produce hot water or steam. Normally, a boiler heats up to 180 degrees for hot water, and 210 degrees for steam (depending on boiler pressure).

Hot water is usually circulated through baseboard heaters, kickspace hydronic heaters, radiators, radiant tubing, heating coils and other heating equipment using a circulator pump.  All these devices are managed at a control point by valves and thermostats to ensure the proper functioning of the system.

Steam boilers operate and provide heat much differently than hot water boilers. Watch for future articles concerning steam boilers.

Components typically found in a residential boiler system:

■ Boiler- The heart of the system, heats water.
■ Circulator Pump - This device is used to circulate water in a cycle from its original location around the loop and back to the boiler to be reheated..
■ Manifold - This is the base of some heating systems, through this component the zones and loops can be manually or automatically controlled.
■ Shutoffs valves - Shut-off valves are used to stop flow within a piping system. These valves are used to turn off parts of or the whole system.
■ Relief valves - These valves release pressure in a system that has pressure too high or temperature too hot.
■ Pressure Reducer - These valves reduce pressure to a safe level for the heating system and boiler (sometimes this valve is called a “feed valve”).
■ Back Flow Preventer - This valve, one of the most important valves, is designed to protect the potable (drinking) water from water that is not safe to drink.
■ High water/Low water cut-off valve - This valve has frequently been used to control a steam boiler. Usually, this valve feeds water to a steam boiler and shuts down the burner if water gets too high or too low on a steam boiler.
■ Thermal Expansion Tank -This tank is necessary to provide space for water to go as it is heated. Water expands when it is heated.  When water is heated in a closed system, an expansion tank is required.  
■ Air Eliminators - Air eliminators are used to remove collected air from a system. Air circulating in a system in which it does not belong can lead to the destruction of a boiler system, loss of heat, noise and other problems.
■ Thermocouple - Thermocouples monitor pilot lights. If a thermocouple fails to sense a pilot light, complete or partial burner shut down will take place.
■ Thermopile - is a type of thermocouple that can generate enough electricity to actually enable controlling the burner and some thermostats.   
■ Burner Control - This component of the system is required to control the flame that is used for combustion.
■ Zone Control - Controlling zones (heated areas) can take place using “zone valves” and/or individual pumps. Zone control allows the user to use multiple and variously located thermostats and/or aqua stats.
■ Gauges - Gauges are used to read important information pertaining to the boiler such as the pressure and temperature.
■ Boiler Header - Boiler headers are usually set up in a boiler room, and act as a hub to the system. They can distribute the system load if the boiler is overwhelmed.
■ Dirt Separator - Installed between the boiler’s supply outlet and the circulator pump these devices are used to extract dirt, scale, and other particles from corroding the system.

We hope you realize how important it is to always check local codes and other regulations before making any boiler decisions. This article was designed to help you understand and ask better questions. Safety is always most important.