Carrier 30HK - Manual (Page 4)

3. A specific head pressure must be maintained.
Set water regulating valve to maintain design
head pressure. Do not adjust to compensate for
high head pressures caused by fouled condenser
tubes, excess refrigerant or the presence of non-con­
densables. Due to changes in water temperature, it
may be necessary to adjust valve seasonally. After
adjusting for design head pressure, shut unit down.
Water regulating valve should shut off flow of water
in a few minutes. If it does not, raise head pressure
setting. Make sure that capillary tube from water
regulating valve is connected to condenser purge
valve.
Instead of water regulating valve(s), a bypass
arrangement may be used. This permits leaving
condenser water to mix with condenser supply
water, in order to maintain entering chilled water
temperature above 70 F or an appropriate tem­
perature necessary to maintain a specific head
pressure.
CAl ;' a ;\; keliglr.e:: ali condenser ixuui bolts
before filling system with water. Torque bolts to
a maximum of 45 ft-lb.
Water leaving condenser is under pressure and
should not be connected directly into sewer lines.
Check local codes. A 3/ 8-in. drain plug is located in
the head at each condenser end.
Refer to PRESSURE RELIEF DEVICES and
CHECK VALVE, page 8, concerning piping con­
nections for these components.
COOLER DESCRIPTION
The cooler is a direct-expansion type with
removable heads and is partitioned for multi-pass
refrigerant flow. Water flow across the tube bundle
is directed by baffles designed for minimum water-
pressure drop. The tubes have integral internal fins
for maximum heat transfer efficiency.
Viewed from unit front, the return chilled water
enters at left end of cooler and leaves at right end.
The sensing bulb for the water temperature con­
troller is in the return-water nozzle, the return-
water temperature being the control point. The
sensor for the low water-temperature cutout is
located in the leaving-water nozzle.
The cooler is insulated with a flexible, closed­
cell plastic foam insulation of suitable thickness.
Water vapor cannot penetrate the cellular structure
to condense either within cells or on the cooler
shell. Thus, the insulation itself is a vapor barrier.
Because of the toughness of insulation, a protective
sheet metal covering is not necessary.
The standard cooler can be used for all glycol
brines down to -20 F. However, for calcium or
sodium chloride brines, it is improtant that the
proper inhibitors be carefully selected for protection
of the copper tubes. Refer to publications of the
Calcium Institute or the Mutual Chemical Division
of Allied Chemical Corporation for information on
corrosion control in calcium or sodium chloride
systems.
COOLER PIPING
Plan piping for minimum number of changes in
elevation. Install manual or automatic vent valve at
high points in line. Maintain system pressure by
using a pressure tank or combination relief and
reducing valve.
See Carrier System Design Manual, Part 3,
Piping Design, for chilled-water piping details.
Install thermometers in entering and leaving
water lines. Provide drain connections at all low
points to permit complete drainage of system.
Connect shutoff valve to drain line before oper­
ating unit. Install shutoff valves near entering and
leaving water connections. Use flexible connections
to reduce vibration transmission.
Insulate piping after leak testing to prevent heat
transfer and sweating. Cover insulation with
moisture seal.
A chilled water flow switch is factory installed in
the line entering the cooler. Sec Table 3 for min­
imum recommended cooler and condenser flow
rates and loop volume.
^ Table 3 — Minimum Cooler and Condenser
Water Flow Rates and Minimum Loop Volume
UNIT
MINIMUM FLOW
(GPM)
T
PRESSURE DROP
(ftwg)
MINIMUM
VOLUME!
(Gal) Cooler ContSenser*I Cooler Condenser
30HK,HL015 '~25~ 34 3,2 2,1 47
020 32 34 5.1 2,1 60
025 38 41 5,5 2,1 81
030 38 41
I, 5.5 2.1
88
'Applicable to 30HK units only.
tMlnimum system water volumes:
Gallons = V X ARi Capacity in Tons APPLICATION
Normal Air Conditioning
Process Type Cooling'
Low Ambient Operation
NOTE: Minimum condenser water flow based on 3 ft/sec to minimize
condenser fouling. Flow rates below 3 ft/sec may require more frequent
tube cleaning.
Step 5 — Make Electrical Connections
All field wiring must conform with local code
requirements. Control circuit is 115 volts on all
60-Hertz units. Control power is supplied from a
separate source, thru a !5-amp fused disconnect.
Inside the control box, provisions are made to
connect the ground wires which must be installed
with each field power supply.
The 30HK,HL015 units are factory supplied with
across-the-line start at all voltages and cannot
be converted to part-winding start. The 30HK,
HL020,025,030 units are factory supplied with part­
winding start at 208/230 volts and across-the-line
start at 460,575 volts.
1090