Danfoss VSH 008 Application guide
Energy Performance Comparison of Fixed Speed, Danfoss VSH 088, and
Mechanically Modulated Compressors When Cooling and Dehumidifying
100% Outdoor Air to 55 F for 8760 Hours per Year in 8 US Cities.
Prepared May 4, 2011
S. A. Mumma, Ph.D., P.E.
Executive Summary: VSH 088 vs. Fixed Speed annual energy consumption
Energy consumption necessary to cool and dehumidify 100% outdoor air (OA) to 55 F
was modeled using hourly US weather data for eight (8) select cities. The three (3)
compressor types simulated included: fixed speed, Danfoss VSH 088 variable speed, and
mechanically modulated.
The VSH 088 performed much more energy efficiently than the fixed speed for all flow
rates and US cities analyzed, and was relatively insensitive to over sizing or geographic
location. Overall for all conditions analyzed, the VSH 088 used 37% less annual energy.
Depending upon air flow rates and location, the energy savings ranged from about 56%
to 19% compared to the fixed speed arrangement.
1
Energy Performance Comparison of Fixed Speed, Danfoss VSH 088, and
Mechanically Modulated Compressors When Cooling and Dehumidifying
100% Outdoor Air to 55 F for 8760 Hours per Year in 8 US Cities.
Prepared May 4, 2011
S. A. Mumma, Ph.D., P.E.
Executive Summary:
VSH 088 vs. Mechanically Modulated annual energy consumption
Energy consumption necessary to cool and dehumidify 100% outdoor air (OA) to 55 F
was modeled using hourly US weather data for eight (8) select cities. The three (3)
compressor types simulated included: fixed speed, Danfoss VSH 088 variable speed, and
mechanically modulated.
The VSH 088 performed more energy efficiently than the mechanically modulated for all
flow rates and US cities analyzed. However the VSH displayed significantly better
energy performance compared to the mechanically modulated for oversized applications,
reducing energy use by as much as 50%. In the absence of over sizing, the VSH 088
used between about 10-20% less energy than the mechanical modulating arrangement.
Overall for all conditions analyzed, VSH 088 used 21% less annual energy than the
mechanically modulating.
2
Energy Performance Comparison of Fixed Speed, Danfoss VSH 088, and
Mechanically Modulated Compressors When Cooling and Dehumidifying
100% Outdoor Air to 55 F for 8760 Hours per Year in 8 US Cities.
Prepared May 4, 2011
S. A. Mumma, Ph.D., P.E.
Objective
Compare the energy consumed by 3 compressor arrangements when cooling and
dehumidifying 100% outdoor air (OA) for eight selected US cities. The 3 compressor
arrangements included: fixed speed, Danfoss VSH 088 variable speed, and mechanically
modulated.
US Cities selected
The 8 cities selected for analysis include: Chicago IL, Raleigh NC, Denver CO,
Washington DC, Austin TX, Sacramento CA, Long Beach CA and Atlanta GA.
Compressor performance maps
The performance maps for the 3 arrangements are illustrated by the figures below:
Fixed Speed Compr essor s
14,000
12,000
10,000
8,000
6,000
Power in, Watts
4,000
2,000
57,720; 12,940
13,750; 6,470
57,720; 6,470
0
0 20,000 40,000 60,000 80,000 100,000 120,000 140,000 160,000
13,750; 0
Load, Btu/hr
144,300; 12,940
3
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