York YR Owner's Manual page 21

nected in series and condenser water circuits connected
in parallel. All of the chilled water flows through both cool-
ers with each unit handling approximately one-half of the
total load. When the load decreases to a customer se-
lected load value, one of the units will be shut down by a
sequence control. Since all water is flowing through the
operating unit, that unit will cool the water to the de-
sired temperature.
FIG. 2 – SERIES EVAPORATORS
PARALLEL CONDENSERS
BRINE APPLICATIONS
The YR Screw Chiller, utilizing the Frick Refrigeration com-
pressor, is a good match for the high head requirements
of low temperature brine applications. This is particularly
true of thermal ice storage systems, typically requiring 22°F
(–5.6°C) to 24°F (–4.4°C) leaving brine temperatures. This
performance is enhanced with the standard thermal stor-
age control mode described on page 6.
Particular attention must be paid to the application of
two or more chillers with evaporators in parallel or se-
ries when the brine temperature is below 32°F (0°C).
The brine MUST NOT flow through the evaporator of
the idle chiller, because it can cause the condenser wa-
ter to freeze. A bypass or other type of arrangement is
required that shuts off flow to the idle evaporator. When
units are applied in series with lead/lag capability, the
units should be identical.
REFRIGERANT RELIEF PIPING
Each chiller is equipped with pressure relief devices.
The purpose of the relief devices is to quickly relieve
excess pressure of the refrigerant charge to atmosphere,
as a safety precaution in the event of an emergency
such as a fire. They are set to relieve at an internal
pressure of 235 psig (1620 kPa) and are located on the
condenser, evaporator and oil separator; and are pro-
vided in accordance with ASHRAE 15 Safety Code and
ASME or applicable pressure vessel code. Under these
circumstances the relief devices may be relief valves,
YORK INTERNATIONAL
overflow valves or type tested Safety Pressure switches
or a combination of these devices.
Sized to the requirements of applicable codes, a vent
line must run from the relief device to the outside of the
building. This refrigerant relief piping must include a
cleanable, vertical-leg dirt trap to catch vent-stack con-
densation. Vent piping must be arranged to avoid im-
posing a strain on the relief connections and should
include one flexible connection.
SOUND AND VIBRATION CONSIDERATIONS
A M E chiller is not a source of objectionable sound
AX
and vibration in normal air conditioning applications. Neo-
prene isolation mounts are furnished as standard with
each unit. Optional level-adjusting spring isolator assem-
blies designed for 1" static deflection are available.
M E chiller sound pressure level ratings will be fur-
LD00508
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nished upon request.
Control of sound and vibration transmission must be taken
into account in the equipment room construction as well
as in the selection and installation of the equipment.
THERMAL INSULATION
No appreciable operating economy can be achieved
by thermally insulating the chiller. However, the chiller's
cold surfaces should be insulated with a vapor barrier
insulation sufficient to prevent condensation. A chiller
can be factory insulated with 3/4" (19mm) or 1-1/2"
(38mm) thick insulation, as an option. This insulation
will normally prevent condensation in environments
with dry bulb temperatures of 50°F to 90°F (10°C to
32°C) and relative humidities up to 75% [3/4" (19mm)
thickness] or 90% [1-1/2" (38mm) thickness]. The in-
sulation is painted and the surface is flexible and rea-
sonably resistant to wear. It is intended for a chiller
installed indoors and, therefore, no protective cover-
ing of the insulation is usually required. If insulation is
applied to the water boxes at the job site, it must be
removable to permit access to the tubes for routine
maintenance.
VENTILATION
The ASHRAE Standard 15 Safety Code for Mechani-
cal Refrigeration requires that all machinery rooms be
vented to the outdoors utilizing mechanical ventilation
by one or more power-driven fans. This standard, plus
National Fire Protection Association Standard 90A,
state, local and other related codes should be reviewed
for specific requirements.
FORM 160.81-EG1
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