This report contains an evaluation of the heating, ventilation, and air conditioning systems located in the middle school and high school buildings. Existing plans have been studied along with a site visit to develop an understanding of the existing systems and their condition. The purpose of this report is to make recommendations that will keep the school’s mechanical system operating comfortably and efficiently for at least another 15-20 years. It identifies deficiencies and recommends replacement options along with associated costs and phasing options.
Building Conditions & Deficiencies
The middle school and high school buildings encompass approximately 44,500 square feet including the band room. This original brick/masonry building was constructed in 1966, and with the exception of a few minor changes, the building’s layout is nearly the same as it was when originally constructed. In 1978, the vocational shop building was constructed to the west of the school and is outside the scope of this report.
The school is heated via hot water through a steam to hot water heat exchanger located in the high school mechanical room. Steam is delivered via a tunnel system from the central boiler plant which is fueled by propane gas. The steam heat exchanger was installed in 1988 when the central boiler plant was constructed.
The heat exchanger is four years past its useful life. The condensate pump package is also beyond its useful life and should be replaced.
Hot water is delivered to the building in three piping zones via three Bell & Gossett brand heating water pumps and one Taco brand backup pump. One pump delivers heat to the high school, one to the middle school, and one to the band room. This existing zoned pumping system is inefficient and some of the major piping around the pumps is showing signs of wear. Hot water is piped to perimeter finned tube/baseboard radiation and classroom unit ventilators to heat the rooms.
All ventilators are original and beyond their useful life. Replacement parts for these old 1966 Nesbitt brand ventilators are impossible to locate and the St. Labre maintenance staff has disabled some non-essential units for parts to keep essential classroom units operating.
In 1992, the outdoor air intake on each unit ventilator was blocked as part of an air conditioning retrofit project. The supply and return ductwork appears to be in good condition. Approximately five VAV boxes that serve the east wing of the middle school have been retrofitted with reheat coils and Johnson Controls digital controllers.
Two separate hot water/chilled water unit ventilators were installed for the band room in the 1992 retrofit project.
The cooling tower that is serving the chiller is in poor condition and is in need of replacement. The absorption chiller was installed when wood chips was the fuel source, however, with propane gas as the current fuel source, this no longer makes financial sense. The school could save some $27,000 per year by replacing the absorption chiller.
Temperature controls are primarily pneumatic with the exception of two Temtrol air handling units and five VAV boxes that were retrofitted with reheat coils. The two air handling units are equipped with stand-alone Johnson Controls controllers that appear to be working but have no connection to a central monitoring control system and are at the end of their useful life along with all the pneumatic controls in the building. Maintaining thermal comfort is performed by hand with a “hit-or-miss” strategy because service and parts for this system are obsolete. The school is also using much more electricity and propane because of this aging control system.
Summary of Deficiencies
- Unit ventilators are beyond their useful life, noisy, and at risk of failure that will lead to inadequate classroom heating and potentially requiring closure of the school.
- Pneumatic controls are obsolete, inefficient, and in need of replacement.
- The existing Johnson Controls digital controllers are over 20 years old and not connected to a viewable front end control system.
- The zoned heating water pumping system and pump is beyond its useful life.
- The steam heat exchanger and condensate pump are beyond their useful life.
- The band room ventilators are essentially manually controlled and questionable.
- VAV boxes designed without reheat coils are problematic for school use.
- The building’s chilled water cooling system is nearing the end of its useful life.
Breakdown of Recommendations & Phases of Implementation
It is estimated that the entire project will be extended across two school years for completion of all five phases.