Commissioning K-12 Schools

The reasons to commission K-12 schools are the same as the reasons for commissioning any facility. However, the primary benefits that most K-12 schools are hoping to gain from the commissioning process are as follows:

• Verify and document safe indoor air quality

• Energy savings

• Training and documentation for operations personnel

What can be more important than providing our children with a healthy environment in which to learn and grow? As a reaction to serious, highly publicized, and highly litigated indoor air quality problems in schools over the past few years, very few school districts are skimping on the design of HVAC systems these days. They are able to raise money in the name of providing healthy facilities that promote learning, and they know that their funding sources - the community in general and parents in particular – will be checking up on them.

Meeting expectations typically includes providing a minimum of ASHRAE 62 ventilation rates to all occupied spaces, controlling maximum relative humidities, and doing it all in the most energy conservative manner possible. This is often achieved with HVAC equipment, systems, and controls the likes of which the building operators have never seen before – nor have the design engineers and contractors, in some cases.

The verification/validation aspect of commissioning is critical for schools, as is the training required to maintain and document on-going proper operation over the life the facility. Schools in some jurisdictions are required to prove that they have maintained healthy indoor environments during occupied hours, and there are people - primarily parents – checking those records.

What is intriguing and disturbing at the same time is the fact that, in our commissioning assignments, K-12 schools have been notoriously “deficient” during the first round of testing. It’s as if the contractors weren’t in tune with the critical nature of their work and didn’t take seriously the fact that the owner would, indeed, be checking their work. The following are sample findings from actual verification test reports from an elementary school. These are typical of the type of things we are finding when the construction project is “complete and ready for demonstration.” What happened to quality control, quality assurance, and pride in a job well done?

OPERATION:

• The outside air damper failed to open when the air handler was switched to occupied operation.
• There is no airflow measuring station (AFMS) on the outside air duct. The design sequences of operation are based on an AFMS in the outside air duct.
• The discharge air temperature reset schedule is not programmed for the gym air-handling unit per the design documents.
• The supply and return smoke dampers remained open when the unit was shut down.
• The relief fan continued to operate when the AHU was stopped in the unoccupied mode. The outside air dampers were commanded fully closed, but the relief fan should have stopped to prevent the space from becoming negatively pressurized.
• In unoccupied mode the fan-powered VAV fan continued to operate. The fan is not programmed into the automation system at all. The only reason the fan was on in the Occupied Mode test was because the controls contractor manually turned it on before the test. The system does not know the fan exists. As far as we could tell, the fan had never run during occupied mode up until this point.
• The occupancy sensor did not work. The room was full of people, but the occupancy sensor indicated the room was unoccupied.

DOCUMENTATION

• The DDC computer graphics user interface (GUI) is incorrect in several instances. For example: the exhaust air damper position incorrectly displays the relief fan VFD commanded speed (%); the GUI indicates a Discharge Air Temperature Low Limit Shutdown, when in fact the value in the field is a heating valve override setpoint; “Duct Static Alarm Value” is displayed on the GUI but the value displayed is actually the space temperature: and the adjustment feature for the High Limit Space Temperature alarm was not functional.
• We reviewed the as-built control schematics and noted several discrepancies between them and the actual air handling unit configuration. For instance, a chilled water coil is incorrectly shown in the air handler; an airflow measuring station is incorrectly shown in the outside air duct; the mixed air temperature sensor is shown downstream of the filters; and the relief damper is incorrectly shown down stream of the relief fan.

 

COMMISSIONING: GETTING IT RIGHT

Engineered Systems, March, 2003

Rebecca Ellis, PE, LEED AP, CCP, CxA
President
Questions & Solutions Engineering
1079 Falls Curve
Chaska, MN  55318
rteesmag@QSEng.com