Boilers vs Furnaces and Best Furnace/Boiler Fuel

To determine your needs — regardless of whether they are for a residential home or building, for a company or campus, or for an industrial complex, — understanding your options is a critical component of making the most appropriate and cost-effective choice with regard to a heating system. 

Even more important than the specific features of a particular type of heating system, knowing which heating system best serves your big-picture needs will make the difference with respect to heating efficiency and cost savings. 

There are two types of heating systems, not including electric baseboard heating and wood burning stove. (Woodburning stoves are still extremely popular — and probably will be because of the ambiance they produce. However, they are the least practical and least efficient of all the heating systems.)

One heating option is a boiler. Another is a furnace. The engineering designs of both are different. Both heat a home, building or complex in a different manner. And, therefore, both have different space, installation, and maintenance requirements. 

Not only are the systems different, there are different options for fuel as well. Number 6 diesel — aka, heating oil or bunker fuel — is extremely popular in many parts of the country. So are other grades of distillate fuels. But, they are not as common for furnaces as they are for boilers. Natural gas and propane are options for both boilers and furnaces, though using gas fuels for furnaces is more common. Electricity is rarely used for boilers. Electricity simply isn’t cost efficient enough to use for a boiler heating system.

Traditional options include coal and wood. Coal is still used to fire some boilers. Not often furnaces, however. Coal is more efficient. But anymore, coal is only used on a very large scale anymore. 

Before deciding on a fuel type, it is typically best to decide which heating system best serves your needs. That requires knowing the differences between the three types.

What is a Boiler and How Do Boilers Work?

As the name implies, a boiler boils water. Water from a holding tank or feed line enters the boiler, heats to the point of becoming a gas — steam, — then circulates throughout a home, building or complex. The steam within the piping system heats radiators distributed around an edifice which in turn heat the ambient air in rooms and open areas. 

While in principle a simple concept, a boiler is relatively complex in relation to furnaces. Boilers produce large amounts of pressure in addition to heat. Those two variables in conjunction mean inexperienced people cannot generally operate or manage a boiler. At least a small degree of training is required to oversee the system processes of a boiler.

There are about a dozen essential components to a boiler system. Raw make-up water lines, boiler feed pumps and piping, the boiler casing (tank), the boiler heating element, pressure reducing valves, safety relief valves, purge vents, overflow traps, and scrubbers are all elements that play a vital role in a boiler system. 

There are two types of types of boilers: water tube boilers and fire tube boilers. The fundamental difference between the two is how they heat water into steam — or don’t. 

Water Tube Boilers

Water tube boilers are used for large industrial applications. Water pumped through tubes within a boiler heats and converts into steam before being pumped into the piping system of the building or complex. Advantages of water tube boilers include:

  • higher operating pressures
  • higher temperature output
  • safe, dependable design
  • precise load fluctuation handling
  • superheated steam generation
  • fast heat recovery
  • better turn down

Water tube boilers are not bad systems for smaller buildings and residential homes, it simply that a water tube boiler — the pressure and heat they generate — are not necessary. For a family home or small office building, water tube boilers are typically overkill. 

Fire Tube Boilers

While called boilers, fire tube boilers produce a very small sum of steam. Most of the heat fire from fire tube boilers is generated from hot water, not steam. As a result, they do not generate as much heat as water tube boilers. However, fire tube boilers are extremely efficient and work exceptionally well in smaller buildings and residential homes. 

The advantages of fire tube boilers include the following: 

  • Compact construction
  • Efficient, straight tube design
  • Lower total cost of ownership
  • Easier access and maintenance
  • Good load surge handling @ pressure
  • Simple operation

What is a Furnace and how do Furnaces Work?

Rather than water or steam, furnaces use hot air to heat a home or building. Furnaces are not typically associated with large industrial complexes or corporate buildings. Furnaces are more often used to heat residences and smaller offices. In relation to boilers, furnaces are not complex, but do a sufficient job at keeping a living or work space warm.

In the heating and conditioning industries, furnaces are often referred to as forced-air heating systems. Furnaces are thermostat controlled. Once the temperature of a room or workspace falls below a certain level, the thermostat sends an electric signal to a relay in the furnace. 

The burners in a furnace run around the clock, so when the relay opens the gas delivery valve and turns on the furnace blower, the furnace begins to burn fuel in the combustion chamber. The heat from the combustion chamber warms the air and the blower moves the hot air into and through the duct system. 

Advantages and Disadvantages of Furnaces and Boilers as Heating Systems

Both heating systems have their pros and cons. Advantages of furnaces include flexibility, size, and heating rate. There is a variety of different furnace makes and models. The flexibility of furnace options means that regardless of how you heat your home, office, or workspace — what fuel you use — there is a furnace that will fit your needs.

The varieties of sizes of furnaces are also an extremely attractive aspect of furnaces. Furnaces the sizes of economy water heaters are available. Additionally, furnaces can heat an area quickly, much faster than a boiler. And finally, the initial costs of installing a forced-air heating system — in relation to the initial costs of installing a boiler heating system — are low. 

There are distinct advantages to boilers as well. 

For one, boilers can heat very large buildings extremely efficiently. Boilers have low operating costs because they are extremely efficient in relation to electric heating systems and furnaces. When compared to furnaces — which require large duct systems — boilers leave a small footprint because the pipes are only a few inches in diameter as opposed to a few feet. 

Also, though it may sound counter-intuitive given that boilers are more complex heating units, because of the fact boilers use pipe instead of ducts, boiler heating systems are easier to install than forced-air heating systems. Without an understanding of how to bend and fasten sheet metal, it is virtually impossible to install your own furnace heating system.

Deciding on a Fuel Type for a Furnace or Boiler

There are several factors to consider when deciding on a boiler fuel type. One factor is cost. Is the cost of one fuel type significantly different than another so as to justify using a lower quality fuel or a fuel that is less stable? A second factor is ease of use and safety. How much maintenance can you expect a furnace or boiler to require over its lifetime? A third consideration is the life of a boiler that takes a given fuel type. How long will a furnace or boiler that takes one type of fuel last in relation to one that takes a different type of fuel? Fuel emissions are also a factor that certainly should not be ignored. 

Cost of Boiler and Furnace Fuels

The cost of boiler fuels depends on a number of variables, but the location is the most influential. In places like the Northeast, fuel oil is typically the preferred boiler fuel type because, among other things, it is less expensive than natural gas, propane, and coal. But, in other parts of the country, that is not always the case. In the Desert Southwest, natural gas and propane are less expensive. Along the East Coast and the southern states, coal is often less expensive. 

Ease of Use and Safety Boiler and Furnace Fuel Comparisons

The type of fuel you choose will determine, to a large degree, just how easy your furnace or boiler is to use. More importantly, the type of fuel plays a critical role in the safety precautions you must take in order to use and maintain a boiler. Propane and natural gas are extremely volatile. 

That means if there is a leak in a line or in the furnace or boiler, you must exit your home or place of business and call an expert to conduct repairs. If there is a leak, it is almost always suggested that you call the fire department as well. 

Fuel oil and coal are extremely stable fuels, exponentially more stable than gas fuels and gasoline. If there is a fuel oil leak, even people who do not have the expertise to repair the issue are in no real danger. No. 6 bunker fuel, the most stable of fuel oils, is only slightly more volatile than motor oil. Even No. 3 – No. 5 diesel fuel oils are extremely stable.

The stability of fuel oil means it is much easier to make your own simple repairs, an effort that saves both time and money. 

Coal is the most stable of all fossil fuels. Getting coal to ignite and combust is a far greater worry than a coal fire. Unless there is a substantial amount of methane — natural gas — buildup in a storage unit the odds of an explosion associated with coal are virtually nil whereas it is an inherent danger with gas fuels. 

Life of a Furnace or Boiler

One of the most valuable aspects of a fuel oil or coal furnace or boiler is its life expectancy. A fuel oil boiler or furnace typically has twice the life of a natural gas or propane furnace. And, the initial costs of a fuel oil boiler or furnace is only slightly higher than that of a gas powered unit. 

The cost of replacing a natural gas or propane furnace or boiler every 10 to 12 years is something that must be taken into account when determining which type of boiler or furnace is most economically efficient. 

Emissions from a Furnace or Boiler

There are two ways to look at boiler and furnace emissions, on a micro scale and on a macro scale. If you are only concerned with the number of emissions your furnace emits around your home, then it is best to go with a gas or fuel oil furnace or boiler. Reducing the emissions associated with burning coal is extremely hard to do.

However, if you are concerned for the wellbeing of the planet as a whole, a coal-fired furnace may be something to consider. The emissions from coal combustion are higher than that of natural gas, propane, and fuel oil. But, throughout the entire life cycle of coal, the sum of emissions coal generates in relation to other fossil fuels — particularly natural gas — is highly debatable. 

Natural gas is 90 to 95 percent methane. Methane has a global warming potential that is 25 times greater than the global warming potential of carbon dioxide. And, estimates of across-the-board fugitive methane leaks vary anywhere from 10 to 15 percent in the Western World and even greater in developing countries. 

Fuel oil and coal are extremely stable fuels which means they produce little to no pollution prior to combustion.

Reducing Boiler and Furnace Emissions with Rentar Fuel Catalyst

For those who choose to use fuel oil, there are means of reducing emissions and pollution dramatically while — at the same time — decreasing fuel consumption and increasing savings. The Rentar Fuel Catalyst, for example, is a pre-combustion device that both increases energy production — which means cost savings — while reducing emissions dramatically. 

The Rentar can reduce boiler and furnace fuel oil consumption by up to 30 percent. There is a direct correlation between fuel consumption and fuel expenses. In other words, a 30 percent reduction in fuel consumption means a 30 percent increase in savings. 

But more importantly, the Rentar Fuel Catalyst reduces emissions significantly. The sum by which the Rentar reduces emissions cannot be overstated. The Rentar reduces greenhouse gas emissions by more than 19 percent. With respect to cancer-causing volatile organics, the Rentar reduces emissions by between 19 percent and 58.7 percent. Volatile organics include chemical compounds like acetone, acetaldehyde, benzene, tri-methylbenzene, toluene, and xylenes. 

Most spectacularly of all, maybe, is the fact that the Rentar Fuel Catalyst can reduce the black smoke associated with furnaces and boilers by up to 44 percent.


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