62 MOTORS AND DRIVES
Fig. 3 Electrical power consumed by pump at partial loads is significantly less than with valve or on/off control.
Fig. 2. The main components of an HVAC system; air circulation, water cooling circuits and water heating circuits.
➠
controls the speed of the pump and fan by changing the electrical energy supplied rather than damping the air- or water flow. It is like reducing the speed of a car by pressing less on the accelerator instead of using the brake to slow down the speed. The payback time of an ac drive is typically one year or less. Other benefits of using ac drive to control the speed
of fan or pump are:
n Smooth ramp up and -down causes less stress to the mechanics of fans and pumps and to air ducts and water piping.
n Slowing down the speed rather than damping the output will result in lower noise levels.
n Tuning the HVAC system during and after the commissioning is easier when the flexibility of an ac drive is used
Compressors in HVAC are often used in chillers for cooling water, which again is used for cooling air. Utilising ac drives in compressor applications will potentially bring energy savings compared to on/off control.
Energy savings are achieved
by optimising the system setup of compressor, chilled water circulation and condenser water
Fig. 4. The Vacon 100 HVAC is designed to meet the stringent requirements of the
energy-intensive HVAC sector.
circulation. The optimum set point for chilled water temperature and condenser water temperature is based on outdoor and indoor temperature and humidity.
Energy savings
The energy savings are most effectively achieved by tuning the system rather than optimising individual functions. The ac drive gives the flexibility of tuning the setup
of the system to operate in the most energy efficient operational point. Other benefits include:
n Reduced number of starts and stops reduces the wear of the compressor.
n The piping and mechanics are stressed less in ramp up or -down situations.
n Reduced noise level in low load situations. n Possibility to use high speed compressors.
Summary
Forty per cent of all energy in Europe and North America is consumed in buildings. The biggest share of this energy is consumed in HVAC applications. With the
rising energy cost and concerns about the CO2 levels and global warming, it is crucial to use all means available to reduce the energy consumption in HVAC applications. The savings potential is big. The key thing is to start looking more at lifetime
costs of heating, ventilation and air conditioning system, where energy cost plays a big role, rather than the initial investment in HVAC system. To give an example, 90 per cent of the lifetime costs of the pump or fan is energy. n
Enter 62 or ✔ at
www.engineerlive.com/ede
Olli Tevä is a Director, Product Marketing, Multipurpose Drives, Vacon Group, Finland.
www-vacon.com
www.engineerlive.com
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60 |
Page 61 |
Page 62 |
Page 63 |
Page 64 |
Page 65 |
Page 66 |
Page 67 |
Page 68 |
Page 69 |
Page 70 |
Page 71 |
Page 72 |
Page 73 |
Page 74 |
Page 75 |
Page 76 |
Page 77 |
Page 78 |
Page 79 |
Page 80 |
Page 81 |
Page 82 |
Page 83 |
Page 84