Power Burner Boilers
The term "power burner boiler" is used to refer to a boiler with a specific type of burner assembly. A typical power burner boiler utilizes a blower which has a constant RPM, dampers to control the amount of air which enters the inlet side of the blower assembly, an actuator, and a linkage assembly which moves the damper assembly to open and close the air damper. Often a power burner boiler has a modulating gas valve or a butterfly valve which controls the flow of gas into the combustion compartment. While boilers with variable speed fan driven induced draft burner assemblies may technically be called a power burner, they are not referred to as such by boiler makers in the State of Michigan. When someone asks a Michigan boiler maker about a power burner, the picture on the left is what pops into his mind.
Power burners where developed to provide a means of modulating the fuel and air going into the combustion chamber of a boiler for the purpose of allowing multiple burn rates. Because the use of inverter technology, which allows for the full modulation of electric motors, is relatively new (within the last ten years), burner manufacturers have used power burners in the past, and still continue to use power burners today. Traditional power burners with single speed blower motors are still used today, although, in many instances inverter driven combustion blower assemblies have replaced the less advanced single speed blower motor of a power burner system.
Adjusting or configuring a power burner can be very stressful work, particularly because power burners are usually only used on bigger boilers. A properly configured power burner is set up to have smooth and even transitions from high burn to low burn, and from low burn to high burn. The stressful aspect of a power burner is that it is very easy to configure the boiler improperly so that the amount of oxygen drops to 0% while the boiler is in operation. If linkage adjustments are being made "on the fly", or while the boiler is in operation, which is typical during set up or adjustment of the linkages, it is possible to produce explosions inside the boiler. David Johnson's uncle has told him stories about men being killed by linkage shafts being shot out from the burner assembly like an arrow, due to explosions while the linkages where being adjusted. When the level of oxygen in the fuel air mixture drops to 0% at the point of combustion the boiler begins to fill with unspent fuel. If a large amount of oxygen is added to the combustion chamber, the unspent fuel will burn very rapidly, which may produce an explosion.
Power Burner Maintenance and Service
Power burners require regularly scheduled maintenance. The moving parts on a power burner, the linkages and air damper, are often exposed and vulnerable to damage from outside influences and interferences. The pictures to the left show a neglected, but still operational power burner on a very large boiler in Royal Oak, Michigan. David Johnson, the owner of Johnson Heating and Cooling, LLC, was hired to get the boiler in good working order, and what he found was astonishing. The power burner's air damper had actually became stuck closed. When the boiler's power burner would fire, the linkages would move and the gas valve would open, but the damper always remained in the same position. The linkage shaft connected to the damper arm would simply slip through the linkage attachment. David found that the boiler was producing carbon monoxide in excess of 5,000 parts per million, which is enough carbon monoxide to make someone sick simply from a few breaths, and enough carbon monoxide to kill a man within minutes. The high carbon monoxide production of the boiler was not the most dangerous aspect of the boilers poor operation. As stated above, boilers with 0% oxygen in the combustion camber are able to explode given the right set of circumstances. Had the boiler been running and the damper suddenly opened, the boiler could have had an internal explosion.
What Causes Incomplete Combustion in Boilers With Power Burners?
As should be obvious after reading the preceding paragraphs, poor combustion with a power burner boiler is dangerous, but it is also wasteful. Perfect combustion produces CO2, and when a boiler's combustion is too "rich", or doesn't get enough air, carbon monoxide and possibly even Carbon build up is produced because there is not enough oxygen present to produce CO2. Typically, boiler manufactures set the maximum allowable amount of carbon monoxide at 100 parts per million, however even one part per million of carbon monoxide is indicative of incomplete combustion. If boilers do not get enough oxygen (or air), the condition is not only dangerous but also wasteful. It is important to adjust power burners properly when servicing or setting up a boiler. Manufactures allow small amounts of carbon monoxide in the combustion gasses because it is sometimes difficult for burner and boiler manufactures to design systems that obtain perfect combustion, although many do. The science behind burner and boiler design has been a work in progress from the time before Noah's Ark.
If adequate air is supplied to the fuel air mixture, imperfect combustion may still be present if there is flame impingement, or if there is an uneven mixture of fuel and air at the point of combustion. While flame impingement is a very common cause of incomplete combustion of fuel in a natural draft boiler, it is not as common in a boiler with a power burner because the typical design of a boiler with a power burner has ample room in the combustion chamber to accommodate the entire burn of the flame. When adequate air is supplied to the flame of a boiler with a power burner, but the combustion is still imperfect or incomplete, usually the problem is due to an uneven distribution of fuel and air mixture at the point of combustion. The picture to the left is a very good illustration of how the flame, which is being forced away from the sight glass, is not uniform, even though this boiler does run very well. With incomplete combustion the yellow parts of the flame have a lack of oxygen in that part of the flame, while the blue parts of the flame have adequate O2, and consequently, perfect or near-perfect combustion. The yellow color of the flame is not always indicative of carbon monoxide production, and in fact the burn shown to the left is quite good, with a total carbon monoxide of around 0 parts per million.
Flame impingement is the condition that occurs when the flame comes in contact with a surface. As stated above, flame impingement issues are not very common in boilers with power burners because boiler manufactures are careful to ensure that the combustion chamber is of adequate size to accommodate the entire flame. If flame impingement is present in a boiler with a power burner, it is likely that the boiler burner is firing at a rate in excess of the design of the boiler.
What is Excess Air?
After reading the preceding paragraphs covering the consequences of a lack of oxygen in the combustion of a boiler, one may be thinking "I'm going to make sure that my boiler has more than enough air in the combustion gasses". This way of thinking, while understandable, is not correct. Adding too much air to the combustion gasses is not desirable, will reduce the efficiency of the boiler, and can actually lead to the production of carbon monoxide. There are several reasons why excess air in the combustion gas mixture is undesirable. Firstly, adding excess air may cause the flame to reach the back of the combustion chamber, causing flame impingement. Secondly, excess air actually drops the temperature of the flame. Thirdly, excess air causes the combustion gasses to travel through the boiler faster then they should, increasing the stack temperature and dropping the efficiency of the system. Fourthly, excess air may cause the flame to come into contact with the internal surfaces of the boiler, which may cause thermal-fatigue of those surfaces. The image to the left shows a boiler with a power burner that has too much excess air. As can be seen in the image, the yellow spot in the picture is where the flame is hitting the rear of the boiler.
I have a boiler with a power burner, what should I be doing, and what is profitable?
If you have a boiler with a power burner, and you are reading this page, you are already beginning to do the right things concerning your boiler, you are becoming educated and understand that your boiler with a power burner is worth your attention. Boilers should never be neglected or forgotten about because they are dangerous pieces of equipment that require the supervision and the attention of a qualified, experienced, and skilled boiler maker. Boilers are safe to operate and are excellent devices, however, the parts on a boiler, that ensure the boiler's continued safe operation, fail on a regular basis because they contain moving parts. Many people fail to realize that even circuit boards contain moving parts that are all but guaranteed to fail after a certain number of cycles. Generally speaking most boilers have multiple safeties that ensure a certain level of redundancy, however, conditions which cause destructive and dangerous boiler failures are always as simple as saying "if X device fails, and then Y device fails, and then condition Z occurs, the boiler will explode and destroy this part of the building, killing or injuring anyone in the vicinity". Often times, while doing the State of Michigan required, CSD-1 boiler inspections, tests, reports, and maintenance, we will find that "X device has failed" or "X and Y device" has failed, but "condition Z" has not occurred. The State of Michigan requires that certain procedures, inspections, maintenance, repairs, and reports be performed on all commercial and industrial boilers, to protect the safety of the general public. As a man who believes in individual rights, small government, less regulation, and freedom in general, David Johnson, the owner of Johnson Heating and Cooling, LLC, supports the State of Michigan 100% regarding it's adoption of regulation concerning the safe operation of commercial and industrial boilers. As per the regulation adopted by the State of Michigan, the owners and operators of commercial and industrial boilers are responsible for their boilers. The boiler maker has certain responsibilities concerning what he must do, however, he is not responsible for your boiler's operation unless he conducts himself or his work in a negligent mannor.
When it comes to boilers with power burners, what must be done according to State of Michigan law, and what is profitable to do are often the same things. Because boilers with traditional power burners are usually only used on larger boilers, it is often profitable for the boiler owner to have his boiler serviced regularly. Inefficiencies with boilers cost money! The good news is that if a boiler maker, who does his job properly (and many do not), performs the State of Michigan required CSD-1 reports, testing, maintenance, and required repairs on your boiler, he is likely to cause your boiler to operate more efficiently. At Johnson Heating and Cooling, LLC, we find that often times, while conducting the State of Michigan required boiler CSD-1 boiler inspections, testing, reports, and maintenance, that we are able to increase a boiler's efficiency by so much that the customer actually realizes a net profit by hiring us to do what the State of Michigan says has to be done anyway.
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.
Boiler Service and Maintenance
- CSD-1 Reports