Project Report
Southern California Edison
Coachella Valley
Duct and HVAC
Retrofit Efficiency Improvement Pilot Project
Prepared for: Southern California Edison
Report Dated: July 3, 1995
By: Proctor Engineering Group, San Rafael, CA., Boston, MA
Contributors: John Proctor, P.E., Michael Blasnik, Tom Downey
Abstract
In 1994, Proctor Engineering Group investigated opportunities for improving air conditioning system performance in existing houses in Southern California Edison's service territory. This investigation involved field testing duct systems, air conditioners, and building shells in 30 houses; hiring and training contractors to repair duct leakage and correct deficiencies in air conditioners; and detailed modeling of the energy and peak demand impacts from these improvements.
The investigation found substantial deficiencies in most of these systems. Duct leakage caused an average effective capacity loss of 35%. (44% under peak conditions). Air conditioners often had insufficient air flow across the indoor coil and could not be brought to the correct amount of air flow without substantial modification of the duct system design and/or sizing. The improvements made by contractors led to substantial reductions in duct leakage and improved air conditioner performance in most houses. The retrofits are predicted to provide significant energy and peak demand savings while improving occupant comfort and satisfaction.
The key findings of this study include:
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Houses must be pre-screened for combustion safety or accessibility problems that preclude inclusion in the program (31% of the houses failed the combustion safety screen and 43% of the homes had insufficiently accessible ducts.)
- Duct leakage and existing duct insulation levels caused an average loss of 49% in overall cooling
efficiency.
- Existing duct systems in pilot homes have an average efficiency loss at peak of 62%.
- The effectiveness in sealing ducts was dependent on the contractor used.
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In homes that have accessible duct work the modeled cooling energy savings from the repairs in this pilot averaged 22% using the most effective contractor. The average cost of these repairs was $615 ($375 for ducts and $240 for AC repairs).
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Using the most effective contractor, the modeled diversified peak reduction under baseline assumptions is 0.46kW at system peak and 0.49 at residential peak.
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With the most effective contractor, the effective capacity (cooling capacity actually delivered to the house) of the air conditioners was increased by an average of 60% under peak conditions.
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Customers were highly satisfied with the program (95% rated the program good or excellent) and 45% indicated an willingness to pay for the service.
Southern California Edison has a potentially worthwhile option for improving cooling effeciency, reducing peak demand, and increasing customer comfort. Proper program design, contractor selection, training, and quality assurance are critical issues for actually achieving these improvements.
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