As the heating season comes to an end and people consider boiler replacements before the beginning of the next heating season I’d like to offer some advice. This is a few of things I’ve recently seen that were not thought through when preparing for a few projects. Start with a clear list of objectives for the replacement. The list should include past, present, and future. Each category should include the following;
1) Cost and frequency of maintenance and repairs (past, present and future)
2) Cost and quantity of fuel and electricity (past, present and future)
3) Changes to the system and building (past, present and future)
Cost and frequency of maintenance should consider labor, cleaning consumables, fuel filters, seals, nozzles, and gasket. Most large boilers should be tuned three times a year for maximum efficiency. Don’t forget the cost of water treatment, especially for steam.
Cost and frequency of repairs should consider labor hours and parts. Also consider down time and availability of parts. Fewer sectional boilers are installed we see less parts for them on the shelf at the supply house. Burner manufactures are going out of business or changing their product line and we’re finding many parts hard or impossible to replace.
Cost and quantity of fuel should obviously be a major consideration if not a justification for change. It can also it can be used to determine how changes to the building or usage of the building may have changed. There is historical data available to factor in temperature and humidity differences from year to year. Also consider changes in the occupied period or set points that may have caused a change in fuel consumption. Recalculating the fresh air requirements and adding CO2 sensors to minimize excess outdoor based on current occupancy could have a huge impact on the total BTU requirements.
Changes to the system and building include the obvious like additions or space usage changes. Other changes to be aware of are piping changes, past or proposed. Would it make sense to reconfigure the piping to primary secondary or has it been done? Would it make sense to remove three way valves and add VFD’s to the secondary pumps or was it already done? Is there a boiler sequencer panel for multiple boilers? Would it be better to eliminate that panel and incorporate those functions into the BAS so that one microprocessor is coordinating the total building demand?
I like to see multiple high efficiency boilers with the extra capacity of a spare boiler equal to the others. A good example is a school we did over 10 years ago with 4 boilers that are 1 million BTU’s each at 95 % efficiency. We removed 2 boilers that were 3 million BTU’s each at 78% efficiency. Prior to the boilers replacement the windows were replaced and some additional baseboard heat was added. We also replaced heat only unit ventilators with dual temp unit ventilators and air handlers. We made some changes in the boiler room so that we have 3 secondary loops. One for is for radiant baseboard heat that basically works off outdoor air but can maintain unoccupied set points during most of the heating season. This minimizes outdoor air infiltration though dampers. Another is for heating only coils in the air-handles and VAV boxes that serve temperature and humidity sensitive areas. Each of these loops has its own reset schedule based on outdoor air and calculated demand. The third loop is actually a dual temperature loop with water cooled chillers and auto change over capabilities.
When the system was installed an expansion was in the future and we added the extra capacity to add two more boilers. By the time the addition was build we determined that through additional equipment changes and building envelop changes additional capacity wasn’t required. That addition, a theater, band rooms and art classes has been complete and occupied for over five years with no additional capacity and no major boiler repairs since installation.
We pride ourselves on what we do well, the experience we gain and the ability to incorporate those positive aspects of mechanical and control installations into future successes. Hearing the answers is as important as asking the right questions. Fixing the building is more important than replacing a piece of equipment.
