Program Administration

Funded by California Energy Commission's Public Interest Energy Research (PIER) Program

Rooftop Unit Diagnostics

Problem Statement
The product developed in this project will enhance packaged air conditioning equipment controllers used in commercial buildings. It will be based in part on research conducted under PIER Contract 400-99-011. In addition to the controller's normal control functions, the combined system will provide diagnostic and performance information. It will be integrated into packaged units with or without economizer and demand-controlled ventilation controllers. The building automation system could provide for data communication and customer access to web-based reports as well as email alerts quantifying equipment performance and identifying equipment problems needing attention. There will be a technician interface at the unit for diagnostic information and immediate feedback on repair effectiveness.

The project goal is to supply the marketplace with a product offering within 24 months that provides important diagnostic and performance information with a compelling business proposition for achieving significant energy and demand savings in commercial buildings. The product will be an automated data acquisition system with sensors embedded in rooftop packaged air conditioners that will report out alarms and operating data. The alarms and data will be transferred to remote servers for web- and email-based reporting.

Honeywell is the commercial partner and will provide substantial financial support and prospective customers for pilot demonstration of this new technology. Honeywell is the market leader for packaged unit controls for small commercial buildings and has the resources to successfully market this technology. The intent is to integrate this capability into Honeywell's building controls systems and operation centers. The product will allow for condition-based maintenance, remote energy efficiency monitoring and immediate equipment failure alarms. It will be unique because no other product provides on-line performance monitoring with enough detail for well-informed remote management.

Diagnostic features include:

Refrigeration Cycle Diagnostics for improving the operating efficiency and reliability of rooftop unit mechanical cooling systems, including identifying the following faults:
- Abnormally low or high evaporator heat transfer (e.g. fan, duct, filter problems),
- Low or high refrigerant charge either due to incorrect setup or an ongoing leak,
- Air in the refrigerant system,
- Abnormally low condenser heat transfer (e.g. condenser fan or fouling problems),
- Too much or too little refrigerant flow restriction (e.g. plugged filter or expansion device, incorrect orifice size), and
- Low compressor pumping efficiency.
Economizer, DCV and Control System Diagnostics to ensure that these components are working properly to provide the expected energy savings, comfort, IAQ and HVAC equipment operation.

Performance information includes estimates of capacity and efficiency indices for current performance relative to manufacturers' specifications and overall statistics associated with the indoor environment (e.g. temperature and CO2 distributions).

Benefits of this product include:

Reducing scheduled preventative maintenance costs through condition-based monitoring and decision making,
Providing customers reports quantifying the condition of their equipment and building environment,
Reduced utility costs through improved performance (e.g. proper functioning economizers and air conditioners that perform closer to design efficiencies),
Reduced downtime,
Improved reliability, comfort and IAQ resulting from performance monitoring and proactive service practices,
New business sales opportunities through monitoring and proactive responses to equipment "calls for help", and
Reduced environmental impact due to early detection of refrigerant leaks and better operating efficiencies.

Diagnostic features will be tested sequentially using the following tools:

Existing and improved computer simulations.
Units installed in the laboratory or on a bench operating under controlled conditions.
Units installed on buildings where we have easy access.
Field test sites established during a recently completed PIER project.
Pilot sites on final platform.

Current News:

Currently, 35 units are being tested in the field in California, Georgia, and Pennsylvania.
FDSI has branded the embedded diagnostic tool the ACR_x Sentinel
An additional 60 units will be installed in California as part of the expanded field testing and development program.
Development continues on the refrigeration diagnostics, communications protocols and approach, and financial algorithms.
FSDI is interested in working with OEM’s to achieve the highest value and impact of the diagnostics.

Updated August 25, 2004