Project Report

Investigation Of Peak Electric Load Impacts
of High SEER Residential HVAC Units

Prepared for: Pacific Gas & Electric Company, Department of Research and Development, 3400 Crow Canyon Road, San Ramon, California 94583
Project Manager: Ash Agboatwala, P.E., Senior Research Associate
Final Report: May,1994
Prepared by: Proctor Engineering Group
Contributors: John Proctor, P.E., Zinoviy Katsnelson, Ph.D., P.E., George Peterson, P.E., Ann Edminster

Abstract

The design parameters that affect power draw under these conditions were investigated. Four modified air conditioner designs capable of reducing peak draw by at least 500 watts were created and tested with a computer simulation.

Major air conditioner manufacturers were contacted regarding the proposed modifications. The manufacturers indicated that in principal it was possible to build units that meet the design criteria.

By providing a better understanding of air conditioner performance on peak, this study will help PG&E ensure the effectiveness of residential air conditioner peak load reduction programs. This study found that SEER rating is not an accurate predictor of peak kW or kVA.

Executive Summary

1. To determine the peak kW and kVA characteristics of standard and high efficiency air conditioners
2. To investigate the air conditioner design parameters that affect the performance at high outdoor ambient temperature.
3. To determine potential future design changes in residential central air conditioners that can improve peak performance.

The study had four components:

1. Manufacturers, distributors, utility (PG&E) program managers, and AC design experts were contacted to obtain information on market penetration and air conditioner performance. High volume models were analyzed for performance at high ambient temperatures and design features that effect performance at high temperatures.
2. Industry experts were contacted to discuss the current air conditioner designs, possible future changes, their recommendations on how to lower kVA at high ambient temperatures, and cost.
3. Proposed design changes were modeled with a computer simulation program. After over 300 simulations, four new air conditioner designs were modeled. The four new designs were based on existing technologies. No breakthrough technology is used in the designs.
4. Experts from inside and outside the manufacturing companies were queried on the feasibility of the new designs and the cost estimates.

Conclusions

• Based on manufacturer supplied data on current high market penetration air conditioners, the SEER rating is not an accurate predictor of peak kW or kVA.
• Oversized units are likely to produce a higher kW and kVA than properly sized units (under a number of peak conditions this increase will be substantial).
• A number of techniques currently employed by the AC manufacturers to increase SEER are also effective at reducing peak draw.
• A number of techniques currently employed by the AC manufacturers to increase SEER are ineffective at or detrimental to reducing peak draw.

  These include:

  • Increased condenser area and efficiency
  • Increased evaporator area and efficiency
  • Improved condenser fan/motor efficiency (sometimes with increased air flow)
  • Improved evaporator fan/motor efficiency

• A number of techniques currently employed by the AC manufacturers to increase SEER are ineffective at or detrimental to reducing peak draw. These include:
  • Two speed compressor
  • Variable speed compressor*
  • Scroll compressor
  • Evaporator fan time delay
  *Current variable speed units have a low power factor and high current harmonic distortion.

• It is possible to build a 3-ton residential air conditioner with existing technology that will have a diversified local peak of .4 to .5 kW less than existing SEER 1 0 units. The reduced peak kW (RPK) unit would have a peak kW draw less than current SEER 12 designs. The incremental cost increase should price the RPK unit at or below the cost of current SEER 12 units. These designs would have a SEER between 12 and 14.

  The incremental cost (at the contractor) of the RPK design would be:

  • between $300 and $600 per local area peak kW (diversified)
  • between $400 and $800 per system peak kW (diversified)

Based on this investigation, Proctor Engineering Group makes the following recommendations:

• PG&E enter into discussions with ARI on rating methods to assure peak reduction. For the utility, a direct rating of steady state kVA at a high temperature would be most effective. The cost effectiveness of one air conditioner over another is determined by both demand and energy considerations.
• Properly size new and replacement units to reduce peak kVA.
• Monitor the actual indoor conditions (temperature and hun-ddity) of a sample of air conditioned residences in PG&E's service territory. This would substantially add to the current information and assist development of a low peak kVA unit. Little is known about the latent capacity needs in hot dry climates. Some effective design changes to reduce peak may result in reduced latent capacity. Whether a reduction in latent capacity would effect comfort or energy use in hot dry climates has not been tested.
• Through an alliance with the manufacturers, build and lab tests the most promising RPK designs. Based on the results undertake a limited field test of the designs.
• Lab test alternative cabinet designs matched to more efficient blowers. This could result in substantial efficience gains at a low cost.

Also see Energy Efficiency Research

Bound copies of this entire report are available for $30 each.
For details about obtaining a copy see How To Order Project Reports