By Tom Secondino, Technical Sales Support Specialist for U.S. Boiler Company
We hope you all are as excited as we are about the release of the new SteamMax boiler! As with all our products, we strive to assist contractors before, during and after the installation. This month’s tech tip is a brief synopsis of the information found in our past steam boiler articles and steam webinars.
>> FYI, we have a variety of steam boiler webinars available here!
Sizing a Steam Boiler
First and foremost, let’s size the boiler correctly. As opposed to water boilers, steam boilers are not sized by the BTU loss of the home/facility. Steam boilers need the capacity to develop enough steam to adequately serve the radiators while maintaining sufficient water volume to avoid flooding. Undersized boilers may run constantly while not adequately heating the building, leading to excessive fuel consumption and unhappy customers. Conversely, an over-sized steam boiler creates a host of other issues such as short cycling, potential issues with condensate in the flue, excessive fuel consumption, and other unwanted dynamics that can also lead to angry customers.
Bare steam mains often end up being some of the largest radiators in the house. While this makes the floors nice and toasty, it can be problematic for the boiler. Uninsulated piping can cause delayed heating due to excessive condensation in the steam mains, elevated pick-up loss, system noise and again, elevated fuel consumption. See a pattern? The tech team always recommends that the piping be insulated properly prior to installing a new system. Some contractors will figure the piping loss into the boiler sizing. We will nod and smile politely and say that you should insulate the pipes.
The takeaway: Accurately size the radiator square footage and make sure the steam supply piping gets insulated!
>> For more, here is an informative webinar about steam boiler sizing.
Investigate existing returns and water quality
Next, interview the customer. Ask if there are areas of the house that are over or under heating. Is the system single or two pipe? Are there buried returns that are 70 years old? They may be plugged or leaking. At a minimum, best practice is to flush and clean old returns or, better yet, replace them. Leaking returns will cause excessive make up water to be added, which will greatly shorten the life of the new boiler.
U.S. Boiler strongly suggests using a feeder with a digital feed counter or an inline water meter to monitor water usage. Maximum allowable make up water is listed in the manual. If make up water volume exceeds the max value listed in the boiler, look for leaking returns or bad air vents. In a two-pipe system with a receiver, look for blown traps causing steam to leak from the receiver vent.
To avoid having debris from the system wash back into the new boiler, consider installing a strainer on the return piping. While on the topic of make-up water, do not use softened water to feed a boiler. A good practice would be to have the make-up water tested. Certain areas of the country have municipal water, which is extremely high in chlorides. High chlorides will contribute to early deterioration and failure of the boiler block.
The takeaway: Check for existing problems, determine corrective actions, and create a system that will allow the boiler to do its job for a long time!
Venting and clean combustion
Our next consideration will be venting. If the chimney is masonry and exposed to the exterior, there may be issues with condensate forming in the chimney. Chimneys with even one wall exposed may require a liner. Confirm if a liner is required before quoting or installing a new boiler.
Next, verify the internal dimensions of the flue as well as the overall height. We all know an undersized chimney can be a problem, but an oversized chimney may also negatively impact the draft dynamics. Chimney sizing for various BTU inputs can be found in the NFPA code books. A little reading or a call to your local building inspector can eliminate a lot of anxiety after you install the boiler and find out that the installation does not meet current codes or constantly locks out due to a tripped spill switch.
Look at all devices that can generate negative pressure inside the house such as, but not limited to, clothes dryers, range hoods, bathroom exhausts, ERV/HRV units that are unbalanced, workshop vent fans, etc. Devices pulling air out of the house can cause the flue to compensate and the result can be the dreaded downdraft. This situation is aggravated by today’s efforts to seal houses so tight they could float.
Also, discuss future renovations with the customer. Are the windows and doors getting replaced soon? Additional sealing? Is the basement getting turned into a rec room and the boiler being boxed into a closet? All these things can and will have a dramatic impact on draft and should be considered.
Combustion air and venting overlap to some degree. Current codes require a minimum of 50 ft3 for each 1,000 BTU of input, and that the house is reasonably able to breathe. If the house is of exceptionally tight construction or the available area for combustion air is <50 ft3/1000 btu input, measures must be taken to ensure adequate combustion air. Solutions exist, such as appropriately sized louvers near the floor and ceiling, interlocked powered louvers, an interlocked combustion air fan, and others. Again, NFPA is our friend and will provide all the necessary data to properly size louvers or fans. Keep in mind that a 48’ x 56’ basement with a 8’ ceiling provides 21,504 ft3, enough to support a very large boiler, but not when 90% of the basement is filled with boxes stacked 6’ high! We need free, open area.
The takeaway: Even if the air volume requirements are met, if a house is very tight and/or has a large volume of air being pulled from the house by appliances, steps must be taken to ensure that sufficient air is available to the boiler for clean combustion and proper draft.
Near boiler steam piping
After we’ve determined we can install a properly sized boiler that will have sufficient air and good draft, we can start the removal and installation process. ALWAYS note and record the existing water line (this assumes someone has not replaced the boiler already and altered the original water line). Be sure the normal water level of the new boiler matches the old water line. Most of the old timers knew their trade and we do not want to start rethinking their math. Changing the water line can cause issues with condensate return and hammering pipes. No one wants a call from a customer that starts with, “It never did that until you replaced the boiler!”
Piping should be one of the simpler aspects of steam boiler installation but is frequently the source of great contention. Near boiler steam piping can be tricky, but U.S. Boiler provides very detailed piping drawings in our boiler installation manuals. We recommend you follow these diagrams carefully, including the notations. Header height above the water line, number of risers required, location of the system piping riser and other specifications have been carefully thought out by our engineering team and can have a dramatic impact on system performance and longevity. While okay for use on returns, do NOT use copper pipe on the steam main piping. For more involved projects involving receiver tanks, pumped returns, vacuum systems, etc., contact your distributor, local rep, or give tech support a call before starting your piping. We would much rather help you properly plan your piping arrangement than help you fix it after problems arise.
The takeaway: Follow manual piping recommendations and/or contact tech support for additional steam boiler piping assistance prior to installing.
For gas-fired steam applications, make sure the gas line is sized appropriately and will supply enough volume to not only maintain inlet pressure above the listed minimum, but also to avoid excessive drop when the boiler is starting. If possible, find out if the area has issues with low gas pressure during the winter months. Old gas mains can struggle to feed areas where a high volume of homes or businesses have been added to an old main. We have talked with many frustrated contractors who were having ignition issues due to a low static gas pressure that was adequate during the summer months.
Skim the boiler thoroughly following the recommendations in the manual. If you are unfamiliar with the skimming process, please contact us, review our webinars, or read this steam boiler skimming tech tip. Skimming is critical to a stable water line and will be ineffective if not performed properly.
For commercial products, our engineering team has included a document for a combination LWCO/pump controller. Be sure to pipe the control as directed, mount at the proper level and install tees or crosses to allow rodding and flushing of associated piping. Remember to add manual lockout LWCO and pressure controls as required by code.
Paying close attention to detail and careful planning should result in a steam boiler installation that will serve the customer well for years to come. Although we are all in the heating business, it is imperative to make our customers happy. Unhappy customers do not generate residual business or help build buzz about your company. Some forethought in the early stages of a steam boiler replacement can lead to happy customers instead of a Mad Max! As always, we hope you and your family are staying safe and healthy. Should you have any questions regarding this article, please reach out to me on the tech line or at firstname.lastname@example.org.