Schriever Air Force Base, Colorado Springs, CO
Retro-Commissioning – JNTF Building (2000)
Retro-commissioning is the process of testing, troubleshooting, and adjusting systems in an existing building to achieve the original design performance.
Identify the Problem
A long history of comfort complaints and maintenance problems in a facility, combined with high energy bills. EMC provided retro-commissioning services for the building systems at the JNTF building at Schriever AFB. The JNTF building is a three-story building that contains high-level security operations such as administrative, computer lab and laboratory in support of U.S. Air Force Space Command. The building is served by over 49 AHUs and 350 VAV/VAVI terminal units.
Troubleshoot the Problem
Retro-commissioning services were required primarily to correct comfort and maintenance problems in the buildings, including:
- Evaluated heating and cooling load studies.
- Created functional tests to determine if the terminal units were properly sized and operating according to original design intent. The results of the test are shown in the table below.
- Identified numerous failed mechanical components, such as DDC controllers, temperature sensors, damper actuators, fan speed controllers, dampers, and pressure sensors.
- Provided 40 hours of air and water balance training, and 40 hours of DDC system controls training to technician and engineering staff so the on-site staff could continue to maintain systems in the future.
| Troubleshoot the Problem |
| Problem |
Energy Wasted |
|
Simultaneous heating and cooling
of air through AHUs.
|
Energy was being used to first preheat outside air to 70°F, then cooled down to 50°F.
|
AHUs operate 24 hours/day. Most areas unoccupied at night. Only ER, ICU, ORs required air flow during unoccupied periods.
|
Fan, coil energy was being used unnecessarily to provide comfortable space conditions during unoccupied periods.
|
|
Multizone temperatures reset according to fixed outside air temperature.
|
Air was being excessively heated and cooled. Multizone AHUs were not being controlled to meet needs of the worst-case zone.
|
| Correct the Problem |
| Solution |
System Response |
Customer Response |
|
Modification to the existing fan powered VAVI units and controls
|
VAVI units regained control of the conditioned space temperatures.
|
Comfort was restored to occupants. |
Customer complaints regarding stagnant air and drafts were eliminated.
|
Maintenance calls and costs were down. |
|
Hot spots throughout the building were reduced.
|
Reduced comfort-related maintenance calls. |
| Hot spots throughout the building were reduced. |
Improved employee productivity. |
| Re-balancing of airside system |
Airflow to the conditioned air space was reduced by 60%. |
Energy savings obtained by reducing fan energy use. |
| Redundant AHUs were shut off. |
Energy savings obtained by reducing fan energy use. |
| Outside air/exhaust air systems were balanced to maintain building pressurization. |
Achieved improved IAQ and HVAC control. |
| Re-balancing of waterside components |
Chilled water requirements for central plant pumps were reduced by over 40%. |
Energy savings obtained by reducing pump energy use. |
| Less chiller energy required to serve chilled water system |
Energy savings obtained by reducing chiller energy use. |
| Less heating energy was required for the MAUs. |
Energy savings obtained due to reducing heating. |
Energy Savings
As a result of retro-commissioning, comfort and maintenance problems were
resolved and significant energy savings were realized. Energy savings is
summarized
by the following areas:
| Energy Savings |
| Savings Opportunity |
Energy Savings In: |
Potential Energy Savings |
| Re-balancing airside systems (VAVI) |
AHU Supply Fan |
$150,000 to $190,000 |
| Re-balancing waterside systems (VAVI Coils) |
Central Plant Cooling |
$25,000 to $40,000 |
| Re-balancing waterside systems (Pumps) |
Chilled Water Pumps |
$5,000 to $8,000 |
| Modify control of preheat coils in MAUs |
Central Plant Heating |
$2,000 to $4,000 |
| Modify control sequence of evap. cooling - MAUs |
Evap. Cooling Pump |
$500 to $1,000 |
| Total Annual Estimated Savings |
|
$180,000 to $240,000 |
| Simple Payback |
|
< 2 years |
|
 |
|
