58 Product Manual PM WSC/WDC
Machine Room Ventilation
In the market today centrifugal chillers are available with either hermetic or open type motors. Hermetic motors
are cooled with refrigerant and dissipate their heat through the cooling tower. On the other hand, open motors
circulate equipment room air across themselves for cooling and reject the heat to the equipment room. McQuay
chillers have hermetic motors and DO NOT require additional ventilation.
For chillers with air-cooled motors, good engineering practice dictates that the motor heat be removed to
prevent high equipment room temperatures. In many applications this requires a large volume of ventilation air
or mechanical cooling to properly remove this motor heat.
EXAMPLE: 1000 tons x 0.6 kW/Ton x 0.04 motor heat loss x 0.284 Tons/kW = 7 tons (24 kW) cooling
The energy and installation costs of ventilation or mechanical cooling equipment must be considered when
evaluating various chillers. For a fair comparison, the kW used for the ventilation fans or if mechanical cooling
is required, the additional cooling and fan energy, must be added to the open motor compressor energy when
comparing hermetic drives. Additionally, significant costs occur for the purchase, installation, and maintenance
of the ventilation or air handling units.
Equipment room ventilation and safety requirements for various refrigerants is a complex subject and is updated
from time to time. The latest edition of ASHRAE 15 should be consulted.
To Next Page
Loading...
Need help?
General
