The term "Water tube boiler" is used to refer to a boiler with a specific type of heat exchanger where the water travels through tubes that are surrounded by the hot combustion gases. Water tube boilers may or may not utilize induced draft systems. An induced draft system utilizes a fan that either pushes or pulls the combustion air through the combustion chamber. Water tube boilers utilize a large primary combustion chamber that contains the fuel and air while combustion is taking place. After the fuel is burned, the hot gasses contact the water tubes. As the hot combustion gasses travel over the water tubes, the heat of the combustion gasses is transferred to the tubes, and then in turn transferred to the water flowing through the tubes. Some water tube boilers utilize only one "pass" of the combustion air over a single row of water tubes, while others utilize multiple "passes" of the combustion air over water tubes where the combustion gas passes over one tube to then come in contact with the next.
Water tube boilers can have a wide range of efficiencies. Some Water tube boilers reach efficiencies up to 96%, while others are in the range of 70%. Water tube boiler manufacturers consider several variables when designing the boilers. While combustion air condensation is indicative of high efficiencies, if the boiler is not designed to properly handle the condensation, the boiler's components may be damaged. In some circumstances, boiler manufactures need to alter the design of the boiler, to avoid problems caused by condensation. This reduces the efficinetcy of the boiler, but some times this needs to be done. Water tube boilers that are designed to obtain high levels of efficiency, like the Burnham Alpine Boiler, utilize stainless steel heat exchangers to deal with the corrosive attributes of the acidic condensation produced during the heat transfer process, while other water tube boilers like the Quietside boiler shown in the image to the left of this text utilize copper water tubes.
The design of water tube boilers offers some benefits and disadvantages compared to other types of boiler designs. One benefit of water tube boilers is that they are often able to rapidly deliver hot water due to the fact that the capacity of water in a water tube boiler tends to be much lower than that of other boiler types. With water tube boilers, the water in the boiler resides in the pipes, while with a fire tube boiler, the pipes hold only the combustion gases while the water is housed all around the fire tubes. Because every modern, high efficiency boiler either utilizes a fire tube heat exchanger or a water tube heat exchanger, something like a high efficiency tank less water heater must be either or. When utilizing a modulating burner to control the discharge water temperature, the burner system is able to heat the water in the boiler very rapidly because there is not much water in the boiler.
Water tube boilers tend to have poor water flow characteristics, when compared to other boiler designs. Because the heat exchanger in a water tube boiler is comprised of a series of tubes, the water must either pass from the inlet header through a tube to the outlet header, through a series of tubes (one to another) with 180 degree bends connecting every tube, or some combination of the two. The water flow characteristics of a boiler are important for several reasons. Firstly, when installing a boiler with poor water flow caritoristics, the total job cost may go up if oversized pumps need to be used to overcome the water flow issue. Also notable is the fact that in situations like the utlization of a boiler with poor water flow characteristics as a water heater (for domestic hot water), the pressure of the system will tend to drop when more hot water is used.
The repair of a water tube boiler tends to be less difficult than that of a fire tube boiler. Because a fire tube boiler passes hot combustion gasses through the tubes, it is nessisary to use steel or stainless steel tubes. While some water tube boilers may also use steel or stainless steel heat exchangers, often copper tubes are used. Copper may be brazed with very little difficulty, however, the replacement of steel tubes often requires a complicated "rolling" process in which the entire tube is replaced and the ends of the tube are rolled backwards to create a compression seal against the boiler's header. While steel and stainless steel tubes will rust and fail, generally speaking, copper tubes seem to be more resilient to corrosion and thermal expansion fatigue.
If you live in the State of Michigan and need boiler repair, boiler installation, boiler service, or just a good boiler repair company, give us a call. We have two decades of experience working on boilers and hydronic heating systems, our rates are competitive, and we always treat our customers the way that we would like our families to be treated if they were in your shoes. If you would like to learn more about some of the work that we have done, and look into some of our references that are local to you, just navigate to our contact page and click on the link to your township or city. We have listed a few references from several areas in Macomb and Oakland Counties that are organized under their respective township/city and area codes.
