by Brian Stack
This article could relate to anything that we install, but I want to focus on proper installation of hot water and steam boilers. Today’s boilers could easily cost twice as much to install as a single high efficiency furnace and because of this, our clients expect these new boilers to last twice as long as a furnace. The key to maximizing the life of the boiler is proper installation.
The internet is full of pictures of equipment that was not installed properly or safely for that matter. While I enjoy looking through these pictures to see what new ways people have come up with to install equipment horribly wrong, I am also concerned with the number of people who refuse to open the manual and follow the manufacturer’s instructions.
We frequently get calls from potential clients who are upset that the new system they had installed does not seem to be functioning as well as the old steam boiler they had or that the new high efficiency hot water boiler does not seem to be working right. What we almost always find is that the new boiler was not installed per the manual. I am able to open the manual and show the client a beautifully drawn schematic detailing exactly how the boiler should be installed versus the display in front of us. The manufacturer supplies an installation manual with every boiler for a reason! They have done the homework for us and are letting us know that this is how their equipment needs to be installed for proper operation and maximum longevity. Sure there are some other things to consider, such as water quality and the condition of the existing piping system, but the manual is a great place to start.
Steam Boilers
The main problem we see with steam boilers is that the near boiler piping is incorrect. Steam boilers are not the same as hot water boilers! Too many times we see them piped straight up from the supply tapping to the house supply. A properly sized riser, header, and equalizer are paramount to the efficient operation of the steam boiler. The correct installation of these three components allows for separation of the water droplets and steam before heading out to the home. “Dry” steam has more latent heating capacity than “wet” steam. Without the proper near boiler piping, “wet” steam will be sent out to the home causing issues, such as water hammer, spitting main line vents, and higher energy bills. The life of the boiler will also be shortened due to uneven water levels and surging inside the boiler. I have seen energy bills actually increase when a new steam boiler replaced an 80 year old coal converted model!
Mid-Efficiency Hot Water Boilers
While these boilers may seem like the easiest to install, they also take the most effort to install correctly. Depending on the type of hot water system you are installing them on, certain precautions must be made to ensure a long and efficient life. Cast iron and copper fin hot water boilers will work with any system as long as you understand what piping modifications need to be done. A boiler connected to an old system with cast iron radiators needs to be protected from low water temperatures at start up, as well as during mild outdoor temperatures. The instruction manuals usually shows some sort of bypass piping between the supply and return piping near the boiler. This allows some of the hotter supply water to mix with the return water to bring the water temperature up before being returned back into the boiler. A boiler connected to copper fin tube baseboard will most likely not required any special piping due to the relatively higher water temperatures required and the smaller volume of water that can be heated quickly. A radiant floor heating system will required mixing valves and sensors to prevent continuous return water temperatures below 135 degree F from entering the boiler.
High Efficiency Boilers
These boiler are definitely more forgiving when it comes to water temperatures and various system designs, however they too must have correct piping. Most high efficiency boilers require what is known as primary/secondary piping or hydraulic separation of the boiler flow from the system flow. The smaller heat exchangers in these boilers require a certain amount of flow to ensure not only proper operation, but to ensure longevity of the boiler. Too little flow can cause short cycling and overheating while too much flow can cause poor heat transfer and erosion. The easy fix to this is to install the circulator pump the manufacturer specifies for the boiler loop and install a hydraulic separator.
There are many other issue we see such as flue gas venting, air separation from the water, expansion tank sizing, and steam system venting to name a few. Good topics for future articles! Remember to “Read the Manual” and avoid many of the headaches that plague the hydronics industry!
Author's Note: Brian Stack is president of Stack Heating & Cooling in Avon, OH, and a member of the ACCA Board of Directors.