CMFRT4: Dual-stage compressor

Purpose

Dual-stage HVAC compressors offer increased efficiency over standard single-stage compressors. These compressors are able to vary their output to provide longer runtimes, which helps control indoor humidity levels and allows for increased filtration of indoor air.

Criteria

All cooling equipment must have a dual-stage (or two-stage) compressor for improved humidity removal and increased efficiency. The higher stage compressor must comply with the maximum 15% oversizing criteria as required for all cooling equipment.

Clarifications 

• When a dual-stage compressor is used for a heat pump to lower the balance point, size the air conditioner at design conditions for the lower fan speed only. The second stage shall not come on at design temperatures. Use the second stage to size the heat pump at design heating conditions. 
• If a system is designed and installed with a variable speed compressor, this requirement will not apply to a project.

Confirmation

The EarthCraft Technical Advisor will visually confirm compliance of criteria at final inspection.