Assuming existing motors are old and due for replacement.
There are only a few existing motors on site, and with the exception of the refrigeration compressors, they are relatively small. Replacing the small motors would be of little value with a very long payback. It is recommended that high efficiency motors be installed when an existing motor fails and needs replacing.
It is recommended that high efficiency motors be installed when an existing motor fails and needs replacing.
Past experience shows that even large motors have to be running on very long schedules to justify replacing them with high efficiency equivalents. And in any case, the efficiency difference between standard and high efficiency motors is quite small in the higher horsepowers. As with the small motors, we recommending waiting for motor failure or until the third rewind would be needed before replacing with a new high efficiency equivalent. It is recommended that high efficiency motors be installed when an existing motor fails and needs replacing.
Install motors having the highest economical efficiency.
This is one of the most important and most widely applicable energy conservation measures. Needs more attention in new construction. In existing facilities, replace failed motors with more efficient models.
Issues and Concerns
This recommendation is in accordance with Measure HV14 of the CMHC manual on Energy and Water Efficiency in Multi-Unit Residential Buildings and with Section 7.5 Electric Motors of the ASHRAE Standard on Energy Conservation in Existing Buildings.
The CMHC manual on Energy and Water Efficiency in Multi-Unit Residential Buildings can be found online at www.hwbinc.com/495-1003/introduction.html.
ASHRAE Standard ANSI/ASHRAE/IESNA 100-1995 – Energy Conservation in Existing Buildings is an approved standard of the American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc., the Illuminating Engineering Society of North America and the American National Standards Institute.
The best method is to meter the existing motors using a Megger, and refer to published data for new motors. If you can’t do that, for motors that have not been rewound, use a 3% efficiency improvement. For motors that have been rewound, use a 6% efficiency improvement.