Application Data; Location; Water Circuits - York YMC2 Manual

Application Data

JOHNSON CONTROLS
The following discussion is a user's guide in the application and installation of YMC² chill-
ers to ensure the reliable, trouble-free life for which this equipment was designed. While
this guide is directed towards normal, water-chilling applications, a Johnson Controls
sales engineer can provide complete recommendations on other types of applications.

LOCATION

YMC² chillers are virtually vibration free and may generally be located at any level in a
building where the construction will support the total system operating weight.
The unit site must be a floor, mounting pad or foundation which is level within 1/4" (6.4
mm) and capable of supporting the operating weight of the unit.
Sufficient clearance to permit normal service and maintenance work should be provided
all around and above the unit. Additional space should be provided at one end of the unit
to permit cleaning of evaporator and condenser tubes as required. A doorway or other
properly located opening may be used.
The chiller should be installed in an indoor location where temperatures range from 40°F
to 104°F (4.4°C to 40°C). The dew point temperature in the equipment room must be be-
low the entering condenser water temperature to prevent condensing water vapor inside
of the VSD. Applications using cooling sources other than evaporative or closed loop air
exchange methods need to request a factory-supplied temperature control valve to pre-
vent condensation inside the VSD. Other areas susceptible to water vapor condensate
are outside of the condenser shell and condenser water boxes. Example applications
include cooling condenser water using chilled water, wells, river, or other low temperature
fluids.
For outdoor applications, please contact the Large Tonnage Application Team.

WATER CIRCUITS

Flow Rate – For normal water chilling duty, evaporator and condenser flow rates are per-
mitted at water velocity levels in the heat exchangers tubes of between 3 ft/sec (3.3 for
condensers) and 12 ft/sec (0.91 m/s and 3.66 m/s). Two-pass units are also limited to 45 ft
H20 (134 kPa) water pressure drop. The three pass limit is 67.5 ft H20 (201 kPa). Variable
flow in the condenser is not recommended, as it generally raises the energy consumption
of the system by keeping the condenser pressure high in the chiller. Additionally, the rate
of fouling in the condenser will increase at lower water velocities associated with variable
flow, raising system maintenance costs. Cooling towers typically have narrow ranges of
operation with respect to flow rates, and will be more effective with full design flow. Ref.
Table 1 for flow limits at design conditions.
There is increasing interest to use variable primary flow (VPF) systems in large chilled
water plants. VPF systems can offer lower installation and operating costs in many cases,
but do require more sophisticated control and flow monitoring. YMC² chillers will operate
successfully in VPF systems. With a minimum allowable evaporator tube velocity of 1-1/2
fps (0.5 m/s) for standard tubes at part-load rating conditions, YMC² chillers will accom-
modate the wide variation in flow required by many chilled water VPF applications.
FORM 160.84-EG1 (617)
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