Dunham-Bush HRSC - D, HRSC50, HRSC60, HRSC75, HRSC100 Operating & Maintenance Instructions
...
HRSC - D
Remote Condenser Packaged Chiller
Installation, Operation &
Maintenance Instructions
Table of Contents
Description Page No.
Introduction & Product Identification ................................................................................. 1
Inspection, Storage & Rigging............................................................................................. 2
Location, and Clearance & Foundation ............................................................................... 2
Vibration Isolation .............................................................................................................. 2
Water Piping .............................................................................................................2, 3 & 4
Refrigerant Piping ............................................................................................................... 5
Electrical Connections ......................................................................................................... 5
Operation .....................................................................................................................5 & 6
Maintenance ....................................................................................................................... 6
Slide Valve Unloading System ............................................................................................. 7
Control Settings ............................................................................................................8 & 9
Sequence of Operation ...............................................................................................9 & 10
Optional Microcomputer Controller ..................................................................... 10 thru 16
Electrical Data (60 Hz) ...............................................................................................17 & 18
Typical Power Wiring ......................................................................................................... 19
Typical Control Wiring (Electro-Mechanical ....................................................................... 20
Typical Control Wiring (Optiomal Microcomputer Controller) ................................... 21 & 22
Typical Piping Schematic ................................................................................................... 23
Capacity Control ............................................................................................................... 24
Physical Data..................................................................................................................... 24
Evaporator Pressure Drop ................................................................................................. 25
Rigging (Sizes 50 thru 150) ............................................................................................... 26
Rigging (Sizes 180 thru 300) ............................................................................................. 27
Spring Vibration Isolation Data......................................................................................... 28
Rubber-in-Shear Vibration Isolation Data.......................................................................... 29
Troubleshooting Guide ..................................................................................................... 30
Start-up Check List ............................................................................................................ 31
FORM 5504
INTRODUCTION
This manual is designed to provide all the necessary information for installation, operation and maintenance
of the latest generation of the Dunham- Bush small
screw compressor remote air-cooled packaged chillers.
Your Dunham-Bush package has been manufactured
under a careful quality control system. If the package is
installed,
PRODUCT IDENTIFICATION
050
060
075
100
110
120
135
150
180
210
225
240
255
270
300
operated and maintained with care and attention to
the instructions contained herein, it will give many
years of satisfactory service.
It is assumed the user of this manual and those who
install, operate and maintain this equipment are experienced and qualified air conditioning equipment personnel.
VOLTAGE
AK = 200
AN = 230
AR = 460
AU = 400 (50 Hz)
1
GENERAL
Packaged chillers are designed to cool water or other noncorrosive liquids. Water is circulated through the direct expansion cooler where it is cooled to the desired temperature
then circulated to cooling coils for air conditioning, or to
other types of heat exchangers for process cooling.
Care should be taken to see that the equipment is properly
installed and adjusted. An installer or operator should first
become familiar with the information contained in this
manual.
INSPECTION
When the equipment is delivered, it is important that the following inspection be completed in the presence of the carrier’s
representative.
LOCATION & CLEARANCE
Location of the equipment and the size of the equipment
room require careful consideration of the following factors:
1. Route by which the chiller will be moved within the build
ing to the equipment room. Make sure there are adequate
clearance and floor strength through doors and passage
ways.
2. Space required for final connections and for normal equipment maintenance. Sufficient clearance should be allowed,
between unit and walls, to permit cleaning or repair of
cooler tubes.
3. Effect of location on piping sizes and piping layout.
4. Location of service facilities; power supply, water and
approved drainage.
5. Motor starting restrictions of local power company.
1. Check all crates and cartons received against the Bill of
Lading/Shipping Papers to be sure they agree.
2. Check the model number and the electrical characteristics
on the nameplate to determine if they are correct.
3. Check for freight damage, shortages or other discrepan
cies and note them on the delivery receipt before
signing.
In the event that any damage is found, a damage claim should
immediately be filed by the purchaser against the delivering
carrier as all shipments are F.O.B. Factory.
STORAGE
The HRSC unit is designed for indoor use and should be
stored indoors and/or protected from the elements.
RIGGING
General - Each unit has been carefully tested and crafted at
the factory where every precaution is taken to assure that
the unit reaches you in perfect condition. It is very important
that the riggers and movers should use the same care and
precaution in moving the equipment into place. Make sure
that chains, cables, or other moving equipment are placed
so as to avoid damage to the unit or piping. The refrigerant
piping must not be used as a ladder or as a hand hold. Do
not attach a chain hoist sling to the piping or equipment.
Move the unit in an upright position and let it down gently
from trucks or rollers.
Another consideration which must be taken into account is
that the unit should be mounted away from noise sensitive
spaces and must have adequate support to avoid vibration
and noise transmission into the building. Units should be
mounted over corridors, utility areas, rest rooms or other
auxiliary areas where sound levels are not an important factor. Sound and structural consultants should be retained for
recommendations on critical installations.
FOUNDATION
A flat concrete foundation or floor, which can support the
weight of the equipment, must be provided. The unit must
be level for proper operation and functioning of controls.
VIBRATION ISOLATION
Under certain critical conditions, it may be necessary to install vibration isolators under the base of the Packaged Chiller.
Rubber-in-shear or spring vibration isolators are offered as
optional items. When spring isolators are used, flexible connections must be installed in the water piping system and in
the refrigerant lines of split systems. Note: These flexible connectors must be suitable for the fluid and pressures involved.
All piping which is external to the packaged chiller must be
supported by spring mounted hangers and any piping which
goes through the wall, ceiling or floor should be properly
sheathed to prevent transmission of piping vibration to the
structure.
Rigging and Moving - Any unit mounted on skids may be
moved with a forklift, but care must be taken not to damage
the unit with forks. The skids should not be removed until
the unit is at its final location.
The HRSC units are to be rigged thru the holes in the base
side rails. In all cases, spreader bars must be used between
rigging lines to prevent damage. The unit must be lifted
using All Rigging Points. Refer to Rigging Instructions on
pages 29 & 30.
When spring isolators are used, electrical service to the unit
must also be flexibly connected, by means of a 36" section of
flexible conduit.
PIPING CONNECTIONS
Water Connections, Chilled Water Piping - After the unit
has been leveled, the external water piping may be made
up. Be sure water piping is connected to the correct fittings.
The water out connection is closest to the expansion valve
(R-in) end. A chilled water flow switch must be installed in
the external chilled water outlet piping.
2
It must be located in a horizontal section on the pipe where
there are at least five (5) pipe diameters on both sides of the
flow switch before any other connections. The flow switch
paddle must be adjusted to the size pipe in which the paddle
is installed. Consult the wiring diagram accompanying
the unit for the electrical connections to interlock the flow
switch with the control panel.
Water flow through the cooler must remain constant for
proper chiller operation. Water pressure gauges are recommended to check the water pressure and flow rate in the
system, before and after the cooler, and to determine if variations occur in the cooler and system.
Method B. Install units the same as Method A, but add a
third thermostat in the return water, as shown in Figure 1 E.
This thermostat will be set to cycle off one of the units when
the load drops below 40%. When this condition is reached,
leaving mixed water temperature will rise, causing the return water temperature to rise and the unit operating will
load up. The “off” unit is sequenced to start again before
full system load temperature is reached.
This system will not provide as stable an operation as Method
A, but in normal air conditioning applications, this is not
detrimental. The advantage of Method B is a better part load
efficiency.
When installing pressure taps to measure the amount of
pressure drop across the water side of the cooler, the taps
should be located in the water piping a minimum of twentyfour (24) inches downstream from any connections (flange,
elbow, etc.).
There are many piping and control systems which may be
used to assure constant water flow through the cooler. A
typical system is shown in Figure 1 A. It uses a three way
motorized valve which operates in response to the discharge
air temperature of the cooling coil.
Another system which is sometimes used consists of a two
way modulating control valve, which also responds to the
discharge air temperature of the cooling coil, used in conjunction with a spring loaded bypass regulating valve as
shown in Figure 1B. The bypass valve must be set to assure
the full flow of circulating chilled water when the modulating valve is completely closed.
Other systems are noted in the ASHRAE Handbook and may
serve equally well. Whatever system is selected, water flow
must be constantly maintained through the chiller.
If the system is arranged for the dual purpose of cooling in
the summer and heating in the winter,
THE COOLER MUST
BE VALVED OFF DURING THE HEATING SEASON SO THAT
HOT WATER WILL NOT PASS THROUGH THE COOLER. THIS
MAY BE EITHER A MANUAL OR AUTOMATIC CHANGE-OVER
OPERATION. There are also times, such as early spring and
late fall, when both heating and cooling are required. This
should also be considered when designing heating and cooling systems. For various piping arrangements, consult the
ASHRAE Handbook.
Water Connections - Multiple Packaged Chillers - Multiple unit packaged chillers have been successfully applied
to parallel and series piping systems for years. Special attention, however, must be given to the particulars involved for
each application or serious operational problems can result.
Series Chilled Water Flow Units - Units should be equally
sized. The upstream unit will carry a larger load because it
cools higher temperature water. The controllers are to sense
leaving water temperatures (see Figure 1D). The number 1
unit controller should be set to start the unit at system design leaving water temperature plus 50% of the minimum
loading of the number 1 unit times unit number 1 design
temperature differential [example: system design supply
water temperature is 45°F, design temperature differential
is 12°F; Unit #1 minimum loading is 15% and the design
temperature difference is 6.5°F: (.5 x 12) + (.15 x 6.5) +45
= 52°F]. The number 1 unit controller should be set to cycle
the unit off at system supply water temperature plus number 2 unit design temperature differential times .9 [example:
45°F + (.9 x 5.5) = 50°F]. These settings will ensure enough
load on the number 1 unit to prevent short cycling.
The above series flow controller set points are for the electromechanical units. Contact the factory for microcomputer
controlled units.
Water Quality - Coolers used in these packages are made of
steel, copper and brass and are suitable for operation with
well-maintained water systems. However, if the water used
in cooler is corrosive, high in mineral content or entrained
solids, the water can cause reduced performance and even
failure of heat exchangers. Therefore, it may be necessary to
obtain the services of a water treatment consultant and to
provide and maintain water treatment. This is particularly
important with glycol systems.
For information concerning the installation, operation and
servicing of Dunham-Bush coolers, consult the latest revision
of Form 8110.
The following are guidelines which should be followed for
multiple unit application. NOTE: A constant chilled water
flow rate is assumed to be maintained through all coolers.
Parallel Chilled Water Flow Units - Method A. Both units
operate simultaneously, modulating with load variations.
Each packaged chiller operating controller senses leaving
water temperature using standard controls (see Figure 1 C).
The set point of each controller will be set to maintain the
desired unloading.
3
TYPICAL CHILLED WATER PIPING
TYPICAL MULTIPLE PACKAGED CHILLER WATER CONNECTIONS
PARALLEL FLOW
SERIES FLOW
PARALLEL FLOW
4
HRSC SYSTEM REFRIGERANT PIPING
• Horizontal lines must pitch 1/2" per 10 feet in the direction of refrigerant flow.
• Each refrigerant circuit must be piped independently.
• Lines must be sized according to latest edition of ASHRAE Handbook. Liquid lines should be sized based on 100°F liquid
subcooling at the condenser.
• Maximum of 50 linear feet of refrigerant line length (contact factory if application requires longer runs).
• All installations require authorized Dunham-Bush start up.
• Factory is to review all field piping.
ELECTRICAL CONNECTIONS
All units are wired as completely as possible at the factory
prior to delivery. The connections which must be made by
the installer are to the main power source, control power
source, remote condenser, and interlocking the satellite
equipment. In connecting power wiring to the unit, the following precautions should be taken:
¥ All field wiring is to be in accordance with the National
Electrical Code and state and local codes.
¥ Due to transport & rigging all wiring is to be checked
for damage and all terminal connections tested for tightness. Unit terminal blocks are to be connected with copper conductors only, sized per ampacity listed on unit
data plate.
¥ The power supply should match the unit nameplate in
volts, phase and Hertz. Voltage must be within ± 10% of
name-
plate value and voltage imbalance between
phases must not exceed 2%.
¥ For minimum circuit ampacity and maximum fuse
size, see Unit Nameplate.
Refer to the unit nameplate data for the minimum circuit
ampacity and maximum allowable dual element fuse size.
The factory supplied field power block is sized to accept
wires sized per NEC, 75C (3-in-conduit) up to 500MCM as
required. When multiple wires per pole are required to stay
at or below 500MCM, the power block supplied will have
multiple wire per pole capability.
A separate 15 amp 11 5V field power supply is required to
power the main control circuit (which includes the compressor sump heaters) unless the control transformer option is included.
GENERAL
The unit should be started up only by a refrigeration technician who is familiar with accepted operation practices for refrigeration systems.
Use small screw unit start-up report, Form NS1157 to record
all temperature, pressure, electrical readings and control set-
tings. A copy must be forwarded to Dunham- Bush, Inc., North
American Service, Harrisonburg, Virginia before the warranty
will be honored.
HRSC REMOTE AIR COOLED CHILLER START-UP
The unit is ready for start-up when the following procedures have been completed.
1. Water piping for the cooler is installed and tested.
(If cleaning agents are used to clean system, be sure to
select an agent that will not harm the chiller or other
system components. Do not allow water to stagnate and
corrode.
OPERATION - HRSC
2. Electrical connections are made and properly fused.
3. Unit has been leak tested, leaks corrected, and charge completed.
Compressor crankcase heater(s) has been energized for a
4.
minimum of 24 hours.
5. Calibrated refrigerant gages have been connected to the
suction and discharge.
6. Turn on the chilled water pump, check direction of rotation
and adjust the water flow through the cooler to the specified flow rate. Bleed off all entrained air.
7. Manually energize the fan starters and check the fan rotation. Fans should pull air through the condenser coil and
discharge vertically upwards.
8. Check all refrigerant valves to be sure they are open.
9. Proceed to System Start-up.
SYSTEM START UP
1. Request for Start-Up Representative - Start-up service is an
option for these units and is requested when the unit is
5
ordered. If you purchased start-up service, then after the
installation has been completed and checked, Form 9180
must be filled out and sent to the local Dunham- Bush
representative who sold the unit. Following receipt of this
signed form, a representative will be sent to the customer.
The purchaser should have competent service and operating personnel in attendance to assist in the work involved, and also to be trained in the operation and maintenance of this unit.
The representative will inspect the installation to determine whether it meets Dunham-Bush, Inc. requirements,
perform the initial start-up of the installation, determine
whether it is in satisfactory operating condition, and instruct specified customer personnel in its operation and
maintenance for the length of time specified in the purchase contract.
NOTE: Sump oil heaters should be energized a minimum
of 24 hours and the oil sump temperature must be at a
minimum of 100°F (38°C) prior to arrival of start-up representative. This will ensure that the oil is warm enough
to vaporize any dissolved refrigerant and that the oil is
within the normal operating temperature range.
3. Start compressor(s), check the gages and note if the
pressures are within the prescribed limits.
4. Check the refrigerant sightglass at the TX Valve to be sure
it is free of bubbles. If not, charge as required to clean
sight glass.
5. Stage unit down until all compressors are off and check
the compressor crankcase sight glass for oil level. It should
be 1/2 to 3/4 of the compressor sight glass. If not, see procedure for adding oil on page 7.
6. Restart the compressor. After an hour of operation, the
expansion valve superheat setting should be checked, it
should be between 9°Fand 12°F at full load design conditions. In some instances, it will be necessary to lower the
superheat setting to ensure proper distribution. Turn the
TX valve adjustment stem clockwise to increase the superheat setting and counterclockwise to decrease the setting.
Be sure and allow ample time between each adjustment
for the system to re-balance.
7. The electrical control settings should be checked and, if
necessary, reset to those settings indicated on the wiring
diagram. Safety controls are factory set and must be maintained at settings indicated on the wiring diagram.
2. Before starting the compressor(s), check all three phases
of supply voltage, of all legs of the motor. They must be
within ± 10% of the nameplate voltage. Check to be sure
compressor is not running backwards.
MAINTENANCE
COMPRESSOR
1. OIL LEVEL - The oil level in the compressor(s) should be
checked periodically, with the compressor stopped. Stage
the unit down until all compressors are off and check the
compressor crankcase sight glass for oil level. If the oil level
is below one half (1/2) the sight glass, oil must be added.
2. A. RECOMMENDED OIL FOR R-22 MACHINES
Compressor Model Series SSC
charged with DB Karlube #10 Oil.
Compressor Model Series SSCB - The compressor is factory charged
with DB Karlube #21 Oil.
Do not mix above oils or attempt to operate the screw
compressor with any other oil. It is suggested that a gallon
or more of the appropriate oil be obtained and kept at the
job site.
DB Karlube #10
DB Karlube #21
B. RECOMMENDED OIL FOR 407C MACHINES
DO NOT USE DB Karlube #10.
Compressor Models SSCA use DB Karlube #16 Oil.
Compressor Models SSCB use DB Karlube #21 Oil.
Contact factory for price.
The above-listed oils are synthetic lubricants of the Polyol
Ester (POE) type. Due to the complex nature of the POE,
great precaution must be taken to prevent any moisture
from entering the system when servicing or adding oil. POE
oil has a greater solvency for water. Water reacts chemically with the ester to form acids and alcohols in a process
called “hydrolysis”. POE molecules attract moisture. Moisture removal by evacuation is more difficult because the
POE “holds water more tightly” than mineral oil. Moisture
causes corrosion and copper plating at an unacceptable,
high level. This reaction occurs where temperatures are the
highest within the compressor.
To prevent moisture entering the system and contaminating
the oil, extra care is necessary. Follow the enclosed procedure to add or remove oil from the system.
A - The compressor is factory
8. The temperatures of the chilled water both in and out,
should be checked to insure the unit is operating within
the desired temperatures.
The holding tank must be clean and free of any moisture. (Evacuate tank to 200 microns). The holding tank
can be a receiver or reclaiming tank of a size large enough
for the total oil change and must be able to withstand
the operating pressure of the system. When adding oil, it
should be transferred from the container supplied to a
holding tank and then evacuated through the vapor port
down to 100 microns with no more than a 50 micron rise
per hour. Do not allow the container to vent to the atmosphere as the transfer must be done through a closed
loop. An oil pump will be required.
PROCEDURE FOR ADDING OIL
Manually close liquid line service valve. Lower return wa-
ter T-stat (4TAS) setting to start the compressor. Run compressor until unit shuts down on low pressure. Place the
control circuit on/off switch in the off position. Locate
the high pressure port adjacent to solenoid valve UL-3
(see drawing page 8) and remove the cap. Attach oil pump
to holding tank high pressure port. Pump oil into this
port until the oil level is 1/2 of the sight glass.
Replace the port cap, open the liquid line shut off valve
and place the control circuit on/off switch in the on position. Set the operating T-stat to the normal operating
temperature and reset the low pressure switch.
Oil can also be added, through the suction port of the
compressor, while running the compressor.
3. COMPRESSOR REPAIRS (internal) - Contact factory or an
authorized DB Service Agency if a compressor malfunction is suspected.
4. COMPRESSOR REPAIRS (External) - Proper operation of
unloaded start, loading, and unloading is controlled by
solenoid valves UL-1, UL-2 and UL-3. Any of these three (3)
solenoid valves may be repaired or replaced in the field,
as required. Also the compressor crankcase heater may be
replaced.
5. Standard oil acid test kit is not compatible with synthetic
oil. See DB color chart for oil condition.
6
SLIDE VALVE
UNLOADING SYSTEM
The DB screw compressor capacity control system for infinite
modulation consists of a slide valve and hydraulic piston/
cylinder operator internal to the compressor, plus three hydraulic solenoid valves (UL-1, UL-2, & UL-3) piped externally.
the oil return (low pressure) line. The slide valve will move
to the right (unloading) whenever UL-2 opens the oil supply
(high pressure) line, since the force of the oil exceeds that of
the discharge gas.
The slide valve forms a portion of the chamber wall in which
the rotors turn; thus, its position with respect to the rotors
determines the effective rotor length and thereby the percent of full load capacity.
Upon compressor start-up, UL-3 is opened (energized). This
allows oil pressure to act upon the hydraulic piston, holding
it in the fully unloaded position. After 30 seconds, during
which time full oil flow is established to all bearing surfaces,
UL-3 is closed (de-energized). At this point, temperature controller is free to open or close UL-1 and UL-2 in response to
the supply water temperature.
The slide valve will move to the left (loading) by force of
discharge pressure, whenever UL-1 opens to permit flow to
The temperature controller sends a series of electrical “pulses”
to the appropriate solenoid to adjust to load conditions. The
further the supply water temperature is from the controller
set point, the longer is the duration of the pulses. The series
of pulses will continue until the controller is satisfied. As the
water temperature approaches the set point, the pulses become quite brief to prevent overshooting the set point.
This method of compressor unloading, in conjunction with
supply water sensing, minimizes action/reaction lag time and
overshoot resulting in an exceptionally precise and stable
control of supply water temperature.
7
HRSC CONTROL SETTINGS
PRESSURE ACTUATED LEGEND FACTORY SETTING
High Pressure Control HP 1-4 Cut-Out 365 PSIG
(Manual Reset)
Low Pressure Control LP 1-4 Cut-In 55 PSIG
(Auto Reset) Cut-Out 35 PSIG
Low Pressure Freeze Control LPF 1-4 Cut-Out 54 PSIG
PRESSURE ACTUATED LEGEND FACTORY SETTING
Low Chilled Water Temperature Thermostat
(Manual Reset) T2 Cut-Out 37°F
il Temperature Safety Control
(Adjustable) OTS 1-4 Cut-Out 240°F
Manual Reset
W7100 Controller Settings T1 Control Point Set at 44°F
Note: For special units supplied with the NC25-4 microcomputer controller, refer to the “Operations Guide” Form
6874.
UNIT OPERATING LIMITATIONS
1. Maximum allowable cooler water pressure is 200 PSIG.
2. Maximum allowable operating water temperature to cooler is 85°F.
3. Minimum allowable water temperature from cooler is 42°F. If lower temperatures are required, a glycol
solution must be used.
4. Unit should not be installed where it may be subjected to freezing temperatures. Provisions should be
made to maintain the ambient air temperature at least 37°F, to avoid possible damage from freezing.
5. Line voltage should not vary more than the voltage tolerances listed for the unit. Refer to the Electrical
Data table.
SAFETY CONTROLS
The unit is protected by the following safety controls.
1. High Pressure (HP)
2. Low Pressure (LP)
3. High Discharge Temperature (OS)
4. Compressor Solid State Module (CSTM)
5. Low Water Temperature (T2)
6. Phase Loss Monitor (PLM)
7. Control Circuit Breaker (CB1)
If any of these devices should open due to abnormal conditions, the compressor(s) automatically stop. All
controls must be manually reset, except the phase loss monitor (PLM).
8
CONDENSER HEAD PRESSURE CONTROL
General
All units require some means to keep the condensing pressure high enough to insure adequate expansion valve feed
to the cooler to prevent low side pressure trips, particularly
during cold starts.
THE RECOMMENDED SPD-SD REMOTE AIR COOLED CONDENSER
Standard Factory Installed Fan Cycling
This commonly applied scheme cycles condenser fans “on”
and “off “ in response to head pressure to maintain the head
pressure within an acceptable range for proper system operation. This method will permit starting and sustained running to 30°F ambient.
FAN CYCLING CONTROL SETTINGS
CUT-IN/CUT-OUT)PSIG)
UNIT FCP1 FCP2 FCP3 FCP4
070 260/160 275/175 285/210 295/235
140
FCP1 & 2 FCP3 & 4 FCP5 & 6 FCP7 & 8
260/160 275/175 285/210 295/235
The minimum ambient shown above reflects the performance
of the condenser surface exposed to the operational fan(s)
as well as that portion of the surface rejecting heat by natural convection with related fans “off”. To further assist low
ambient starts, all fans are held “off” until the head pressure
reaches 260 psig. This alone cannot insure sustained operation if the system load is not high enough to produce the
minimal pressures required.
Operational Variable Speed Fan Control
This scheme utilizes fan cycling but also adds speed control
to the lead fan of each refrigerant circuit. This feature not
only serves to stabilize the head pressure between normal
fan staging but also allows for virtually “no fan” operation
down to 0°F ambient.
SPD-SD
HRSC100-150
SEQUENCE OF OPERATION (TYPICAL) MODELS
The following sequence of operation is typical for all Electromechanical HRSC models. Refer to the wiring diagram furnished with the unit for specific information.
Important Note!
With all the control circuit switches (SW1-SW3) in the “off”
position and the staging thermostat (T1) to its highest temperature, there must be a 115 volts supplied to the compressor crankcase heaters (CCH1,2) for a minimum of 24 hours.
Preliminary Sequence
Close the main power disconnect switch. Check to see that
the red indicating light on the phase loss monitor (PLM1) is
lit. (Note: There will be two phase loss monitors, (PLM1) and
(PLM2) on dual power block models). This light must be on
to indicate proper phase rotation for the compressors. If the
light is not on, disconnect the main power and reverse any
two phase legs at the Main Incoming Power Terminal Block.
(Warning! DO NOT REVERSE THE LEADS ON THE PHASE
LOSS MONITOR FOR THIS WILL ALLOW THE COMPRESSORS
TO RUN BACKWARDS, CAUSING SEVERE DAMAGE, AND
WILL VOID THE COMPRESSOR WARRANTY!).
The crankcase heater relay contacts are closed and are supplying power to the compressor crankcase heaters.
Control power goes through the control panel circuit breaker
(CB1) and customer supplied control (if supplied).
Start up the chilled water pump. An auxiliary contact on the
chilled water pump closes. The water flow is confirmed when
the water flow switch completes the electrical circuit. Set
the thermostat (T1) to the desired leaving water temperature (e.g. 44°F.). Set point Adjustment is accomplished directly on the control.
Place the three (3) control circuit switches (SW1-SW3) in the
“On” position, thus energizing the balance of the control
circuit. The system will be in the “Time-In” mode for five
minutes before the first compressor will start.
The low temperature freezestat (T2) must also be satisfied to
allow compressor operation.
Stage 1 Loading
Upon demand for cooling, the first step of the staging thermostat (T1) will close energizing relays (R1) and time delay
(TD1). If all the safety controls and switches are closed, (see
“Safety Controls” section for more detail) the control circuit
for Compressor No. 1 will energize, allowing the compressor
to start. Power is supplied to condenser fan interlock terminal CT19 and CT2 to enable the remote condenser fan circuit. Relay (R5) will energize, closing the normally open set
of contacts, which energizes the liquid line solenoid valve
(SOL1). Another set of normally open contacts on (R5) provide a series interlock with all the safety and operating controls, which will lockout the compressor if any safety trips
during normal operation. (See Note 6 on Wiring Diagram).
The last set of normally closed contacts on (R5) open and deenergizes (CCH1).
Time Delay (TD1) has two (2) sets of contacts: The first set of
(TD1) normally closed contacts provides a 30 second jumper
around the low pressure control (LP1) to prevent short cycling during start-up. The second set of (TD1) normally closed
contacts powers the unloader solenoid (UL3-1) which holds
the compressor in the full unload position for 30 seconds.
After (TD1) times out (30 seconds), the contacts for the
unloader solenoid (UL3-1) open and the normally open contacts close, which energizes the relay (R3). Upon energizing
relay (R3) the normally open contacts of relay (R3) are closed,
allowing the thermostat (T1) to energize the load (UL1-1)
and the unload solenoid (UL2-1) upon demand.
9
Stage 2 Loading
Subsequent to the start of Compressor No.1 an approximate
five minute time delay is incorporated into the microcomputer. After this time delay, and a further call for cooling, the
second step of the staging thermostat (T1) will close. This
will energize relay (R2) and time delay (TD2). If all the safety
controls and switches are closed, (see “Safety Control’ section for more details) the control circuit for compressor No.2
will energize, allowing the compressor to start. Power is supplied to condenser fan interlock terminal CT20 and CT2 to
enable the remote condenser fan circuit. Relay (R6) will energize, allowing the liquid line solenoid valve (SOL2) to energize. Relay (R6) will energize the safety controls the same as
compressor No.1 circuit.
SHUTDOWN SEQUENCE
Time delay (TD2) will provide a 30 second jumper around
the low pressure control (LP2) and will energize the full unload solenoid (UL3-2) for 30 seconds then energize relay (R4).
Upon energizing relay (R6), the crankcase heater (CCH2) is
de-energized and the normally open contacts of relay (R4)
are closed, allowing the thermostat (T1) to energize the load
solenoid (UL2-1) and the unload solenoid (UL2-2) upon demand. Relays (R1) and (R2) will interlock the water pump
starters.
Stage 2 Shutdown
After both compressors have unloaded fully and the leaving
water temperature is still lower than the set-point, the second step of the thermostat (T1) will open and de-energize
relay (R2), providing an approximate five minute time delay,
again integral with the microcomputer to the start of Compressor No.2. This will close the liquid line solenoid (SOL2)
condenser fan control contactor and turn off Compressor
No.2. Compressor No.1 will load and unload as required.
Compressor No. 2 will not be able to restart for five minutes
due to integral time delays.
STAR-DELTA STARTING
OPEN TRANSITION
Time delay relay (TD1) closes, energizing start contactor (S1)
and the five second transition timer (TD9). Contactor (S1)
closes, tying the center legs of the motor windings together
into the “Star” (wye) configuration. (S1) N.O. auxiliary contacts close and energize motor starter (C1), starting the compressor motor. This motor starter is then “held in” by (C1)
N.O. auxiliary contacts.
MICROCOMPUTER CONTROLLER
1. General Description
Your Dunham-Bush HRSC is controlled by an NC25 microcomputer system. The computer system is composed of a
main microcomputer board, several types of input/output (I/
O) boards, and sensors. The I/O boards are connected to the
microcomputer by ribbon cables. These hardware components are controlled by the software program in the microcomputer. The software determines the state of the output
relays based on the input values.
There are two types of inputs to the computer system. A
digital input indicates whether or not voltage is present at
the input. This could be used to determine whether or not a
contactor is pulled in, a water flow switch is made, or the
status of other on/off devices. Another type of input is an
analog input. An analog value is one that varies continuously, such as temperature, pressure, current, etc. An analog input must be converted to a digital value with an analog to digital (A/D) converter board before the computer can
process the data.
The computer system outputs are relays that switch the 115
VAC control devices such as contactors and solenoids.
The software for the computer is stored in three different
types of computer memory chips. The two EPROM chips
Stage 1 Shutdown
If the leaving water temperature is still lower than the setpoint, the first step of the thermostat (T1) will open and deenergize relay (R1). This will close the liquid line solenoid
(SOL1) condenser fan control contactor and turn off Compressor No.1 as long as it has run for approximately three
minutes. Compressor No.1 will not be able to restart for five
minutes.
After five seconds (TD9) N.O. contacts close, de-energizing
“Star’ contactor (S1) and energizing run contactor C2 through
(S1) N.O. auxiliary contacts. The compressor motor now runs
in the “Delta” configuration.
There is an instant of time (the “open transition”) between
the opening of (S1) power contacts and the closing of (C2)
power contacts, in which power across the motor windings
is interrupted.
(Electrically Programmable Read Only Memory) store general operating procedures (algorithms) and are the same for
all packages. The EAROM chip (Electrically Alterable Read
Only Memory) stores the program that defines the logic for a
particular unit. This software is called the data base. Both of
these chips retain their content when power is removed. The
third type of memory is battery backed RAM (Random Access Memory) and is used for temporary storage.
Information can be retrieved from the NC25 and displayed
on a video display terminal. The RS232 communications port
is used. Refer to FORM 6372 for more information.
2. Microcomputer Hardware Precautions
The following precautions must be taken while working with the microcomputer system.
2.1 Do
2.2 Cover the computer components completely when
2.3 Strip wires away from microcomputer to prevent
not lay the solder side of a computer board on a
metallic surface. This may damage the battery on
the board.
drilling sheet metal near the computer.
strands from falling on components.
10
2.4. Do not allow the component boards to get wet,
(direct contact with water or condensation).
2.5 Disconnect power to the NC25 when plugging
in or unplugging a ribbon cable connector.
2.6 Disconnect power to the NC25 when changing a
chip on the board. Check to make sure that pin 1
of chip is in upper-left corner and that the chip is
inserted fully before reconnecting power.
2.7 Route ribbon cable and sensor wires away from
control and power wires.
2.8 Handle boards with care.
3. Operation of LCD Display NC25-4
The following instructions are for operation of the
NC25- 4 microcomputer with 2 x 40 character LCD
display.
To Display data from the menu
3.1
1. Press the MENU key.
2. Use the up or down arrow keys to select the
type of information desired. The main menu
items are: DATE & TIME SET
ALARMS
DIGITAL SENSORS
CONTROL POINTS
SETPOINTS A & B
AUTHORIZATION
ANALOG SENSORS
3. Press the ENTER key.
4. Use the up or down arrow keys to select the
desired data. For control points, additional
data can be viewed with the right and left
arrow keys. Press the right arrow key to
sequence through the following screens:
A. LAST ON/OFF - RUN T/Y - CYC
TIME TIME TIME TIME COUNT
LAST ON/OFF gives the time of day that the
control last turned on or off. The last on time
is not updated if a screw compressor is started
manually.
RUN T/Y gives the accumulated time that the
control point has been on today (T) since midnight and the accumulated run time during
yesterdays(Y) twenty-four hour period.
TOTAL CYCLES gives the number of cycles
since a memory clear was performed. This
records up to 65,000 cycles.
C. -- CURRENT -- -- TARGET —
VALUE VALUE VALUE VALUE
The values under CURRENT and TARGET give
different operating analog input values and
setpoints for different types of control points.
Screw compressor control points give current
and target leaving water temperature and
percent full load capacity. Fan type control
points give the current analog value and
target turn on and turn off setpoints.
NOTE: When displaying analog sensors, the PAGE
MODE key can be pressed to display two new
analog inputs after each arrow key is pressed. Press
PAGE MODE again to return to displaying one new
analog input.
To Reset All Control Points to Computer Control
3.2
1. Press the RESET key. The display will show RESET
ALL CPs to COM MODE? N Y
2. Press the right arrow key to select Y.
3. Press the ENTER key. The reset will not be
accepted if a lockout control point is active.
Resolve the problem and reset again.
3.3
To Display Alarms
.
1. Press the MENU key.
2. Use the up or down arrow to select ALARMS.
3. Press ENTER. The day, time, and alarm code is
displayed.
4. Alarm 1 is the most recent alarm.
5. Press the down arrow to view previous alarms.
6. Check the data label to obtain the name of the
alarm. If the data label is not available, display
the digital input that corresponds to the alarm
number. If the digital input name is SPARE, then
display the control point that corresponds to
the alarm number. EX: If alarm code 29 has
occurred, then display digital input 29 or
control point 29 to determine the failure.
CYC gives the number of times that the control
point cycled off since midnight. It a feedback
digital input is associated with a control point
(EX: compressor) the digital input cycles are
recorded.
B. TOTAL RUN TIME = COUNT
TOTAL CYCLES = COUNT
TOTAL RUN TIME gives the number of hours the
control point has been on since memory clear
was performed. This records up to 65,000
hours.
11
To Become Authorized
3.4
1. Select AUTHORIZATION on the main menu.
Press ENTER.
2. The current status will show VIEW, press the
authorization code (64) on the number keys.
3. Press ENTER. The current status will change to
PROG (program) if accepted. If no keys are
pressed for five minutes, or if the Authorization screen is re-displayed, the authorization
to change setpoints is removed and the above
procedure must be repeated to log in.
To Alter Setpoint Data
3.5
1. You must be authorized and in the PROG
mode. See section 3.4.
2. Select SETPOINTS A & B on the main menu.
Press ENTER.
3. Use the up or down arrow keys to select the
setpoint to be changed. Press ENTER. A
cursor will flash over the setpoint A value.
4. a) If you want to change setpoint A, press
in the desired new value and press
ENTER. If the new value is within limits,
it will be stored in memory. The cursor
will then move to setpoint B.
b) If you do not want to change setpoint
A, press ENTER.
5. Repeat Step 4 for Setpoint B.
To Calibrate Temperature and Pressure Sensors
3.6
NOTE: Pressure calibration should only be
done by a qualified refrigeration
technician. Calibrate amps with
potentiometer on filter board.
NOTE: For units with SI display option, the
critical temperature and pressure
calibration values are stored in the
setpoints corresonding to the sensor
names or numbers.
1. You must be authorized and in the PROG
mode. See Section 3.4.
2. Display the analog sensor to be calibrated on
the top line of the display.
3. Press ENTER to show ZERO CALIBRATION
value.
4. Use an accurate gauge to measure the
analog value when it is stable and near
design conditions.
5. Determine the revised zero calibration
required as follows: Meter Reading - Al
Display + Zero Calibration = New Zero
Calibration. The new zero calibration must be
rounded to the nearest whole number.
6. Press ENTER to place the cursor on the zero
calibration value.
7. Enter the new value from Step 5. Negative
values are entered by pressing LOWER
FUNCTION +/- before the number.
8. Press ENTER to store the revised zero calibra-
tion.
For example, if a suction pressure gauge
shows 58 psig and the computer displays
60.3 psig with a zero calibration of -1, then
new calibration would be 58 - 60.3 + (-1) =
-3.3 (-3). So the zero calibration should be
changed to -3.
3.7
To Set Date and Time
1 . You must be authorized. See Section 3.4.
2. Select DATE & TIME SET on the main menu.
Press ENTER to display current date and time.
3. Press ENTER key to move cursor to each date/
time item.
4. As each item flashes, use the number keys to
enterrevised data if necessary. The day of
week, SUNday through SATurday, is selected
by number keys 1 through 7, respectively.
5. Press ENTER to continue. The last ENTER will
store the new date and time.
12
WARNING: Setting the clock will cause a system
reset. The entire unit will shut down and start over
again. If the change was started inadvertently,
press MENU key before completing the change.
3.8
To Display Data without Accessing Menu
1. Press LOWER FUNCTION.
2. Press function desired (blue sub-script)
3. Press item number to be displayed.
4. Press ENTER.
EX- To display analog input #5, press LOWER
FUNCTION, ANALOG INPUT, 5, ENTER.
3.9
To Revise Unit Schedule of Operation (Optional)
If a seven day time schedule of unit operation is
desired, the internal real time clock of the
microcomputer can be used. When the SCHEDULE
control point is ON, the unit is allowed to operate.
The following procedure is used to modify the
operating schedule.
1. Perform the authorization procedure (See 3.4).
2. Press MENU key.
3. Use Up and Down to select CONTROL POINTS.
4. Press ENTER.
5. Use Up and Down to select SCHEDULE control
point.
6. Use --> to display the first schedule. The
standard display screen would show:
CP 17 SCHEDULE GRP:1 SCH:1 0000 2400
DAYS: *** ALL DAYS ***
This indicates that control point 17 named
SCHEDULE is controlled by schedule group
(GRP) #1. The first schedule (SCH:1) turns on
at 0000 hours and off at 2400 hours (military
time) every day of the week. Thus it is on all
the time.
7. To change this schedule, press ENTER. The
cursor will flash over the turn-on time. To
move to the next schedule, press the right
arrow key.
8. Use the number keys (0-9) to enter the revised
turn-on time using military format.
9. Press ENTER. The cursor will move over to the
turn-off time.
10. Use the number keys to enter the turn-off time
in military format.
11. Press ENTER. The cursor will move to DAYS
during which this schedule is active.
12. To change the days for this schedule, press one
or more of the following number keys: 0 Clear all current days; 1 - Sunday(S); 2 Monday(M); 3 - Tuesday(T); 4 - Wednesday(W);
5 - Thursday(R); 6 - Friday(F); 7 - Saturday(A);
8 - *** ALL DAYS’**.
13. Press ENTER. The revised schedule number is
now stored.
14. To add another schedule, press the right arrow
key and repeat steps 7-13.
15. To delete a schedule, clear all of the days by
pressing 0 at Step 12.
The schedule group turns on when any of the individual schedules turns on. The turn-on time does
not have to be earlier than the turn off time.
Schedules turn on by time and day, but turn off
by time alone. For example, a schedule from
1900 to 0700 Saturdays would turn on at 7:00 PM
Saturday (time and day) and turn off at 7:00 AM
Sunday (time only).
Example: If a unit is to operate at all times except
between the hours of 1:00 AM and 6:00 AM, the
following schedule would be entered:
CP 17 SCHEDULE GRP:1 SCH:1 0600 0100
DAYS: *** ALL DAYS ***
Another example: A typical building may require
cooling from 6:00 AM to 7:00 PM Monday - Friday
and from 7:00 AM - 3:00 PM on Saturdays. The
schedules would be entered as follows:
CP 17 SCHEDULE GRP:1 SCH:1 0600 1900
DAYS: MTWRF
CP 17 SCHEDULE GRP:1 SCH:2 0700 1500
DAYS: A
4. HRSC Package Control
In order to start a unit, the following conditions must
be met:
-- chilled water pump running
-- chilled water flow switch made
-- customer control contact closed
-- control switch and compressor switch on
-- main unit power on
-- all safety conditions satisfied
-- reset pressed on microcomputer keypad
-- the compressor has not started within the last 15
minutes
-- leaving chilled water temperature 20°F or more
above set point
The NC25 computer system performs the following
functions on small screw compressor packages:
1. Capacity control of compressors
2. Staging of compressors
3. Compressor current limiting
4. Ramp control
5. Manual lead/lag
6. Compressor start delay
7. Power loss reset
8. Anti-recycle timing
9. Low pressure safety
10. High pressure safety
11. Freeze safety
12. High Oil Temp Safety
13. Alarm output
14. Fan control
15. Customer control interlock
16. Hot Gas Bypass option control
17. Compressor power control (No-stop alarm)
18. Sensor alarm shutdown
19. External shutdown indication (No-run alarm)
20. Fast Unload Solenoid Control (HRSC 50 thru 225)
21. Low suction / discharge differential pressure alarm
22. High Motor temperature safety
23. Low chiller flow alarm
A description of each of the functions follows:
4.1.
Capacity Control of Screw Compressors
The capacity of a compressor can be controlled
manually or automatically.
The status of a compressor can be observed by
displaying the compressor control point (1/CP, 4/CP,
7/CP or 10/CP). One of the following messages will
be displayed where # is 1, 4, 7 or 10 for compressors 1, 2, 3 or 4:
CP# COMP LOAD COM Computer load
CP# COMP CURRENT STATUS: LOAD Manual load
CP# COMP HOLD COM Computer hold
CP# COMP CURRENT STATUS: HOLD Manual hold
CP# COMP UNLD COM Computer
CP# COMP CURRENT STATUS: UNLD Manual unload
CP# COMP OFF COM Off on a normal
CP# COMP COFF COM Off on timer
CP# COMP LOFF MAN Manual off or
Automatic Control
4.1.1
The computer calculates the operating percent capacity of a compressor by measuring
discharge pressure and amps. This operating
percent capacity is then compared to a target percent capacity. If the operating
capacity is outside of a
+ 3% deadband, the
load or unload solenoids are pulsed to
match the operating and target percent
capacities. Since all compressors have
the same target, their percent capacities are
balanced.
The target percent capacity is given a fixed
value when a compressor starts or stops.
This value is then increased or decreased
based on how far the leaving water temperature (TLW) is from setpoint and also on
how fast the TLW is approaching setpoint.
The target percent capacity will not change
if the temperature is within a temperature
deadband around the setpoint.
Some packages may have logic that prevents
loading if the leaving water temperature is
falling (negative derivative) at a certain rate.
The desired leaving water temperature is
typically stored in setpoint 1 A.
Calibrations of Amps Calculation at Full Load
The amps calculation is calibrated at the
factory and does not normally need to be
altered. If a compressor is replaced or
improper operation is observed, the amps
values can be calibrated as follows:
1. Check calibration of discharge pressure,
and amps. NOTE: Calibrate amps with
13
potentiometer on filter board.
unload
control shutdown
(clock off)
safety shutdown
2. Manually load the compressor(s) to full load.
This can be done one compressor at a time if
necessary.
3. Locate the amps and full load amps (FLA)
analog locations from the analog input menu
for the compressor being calibrated.
4. When the compressor(s) are at full load and
conditions are close to design, record the
amps and FLA analog values.
5. If the values do not match within 2-3 amps,
do the following calculation: AMPS - FLA
6. Locate the amps calculation A setpoint for the
compressor from the setpoint menu.
The setpoint is labeled FLA # CON, where
is 1 through 4 for each compressor number. 7.
7. Add the value obtained in step 5 to the amps
calculation A setpoint value from step 6.
8. Change the amps calculation setpoint to the
new value.
9. Verify that amps and FLA now match closely.
10. Manually unload the compressor all the way.
11. Locate the percent full load capacity (%FLCP)
for the compressor from the analog input
menu and record the value.
12. If the value is 25% ±3%, no change is required. If the value is less than 22% or greater
than 28%, locate the %FLA # CON setpoint B.
If the setpoint is equal to 25.0, change it to
the value observed in step 11 and proceed to
step 13. If the setpoint is not equal to 25.0,
change it to 25.0 and repeat steps 11 and 12.
13. Repeat this procedure for each compressor.
4.1.2
Manual Control
Screw compresors can be controlled manually
with the key pad. A compressor can be turned
on, off, or placed in computer control. When a
compressor is controlled manually, it can be commanded to load, hold, or unload. If current limit
is active, it will not accept a load command.
To place a compressor in manual control,
which turns it on, use the following procedure:
1 . Log in for authorization.
2. Address desired compressor (1, 4, 7, or 10
control point).
3. Press ENTER to modify status.
4. Use up or down arrow keys to select ON
MAN.
5. Press ENTER. The compressor will start or
continue to run in hold state.
6. Press 0 to return to computer control, 1 to
hold, 2 to load, 3 to unload. Note:
Compressors will not load past amp limits.
7. Use menu key or arrows to access other
data.
If a safety condition is exceeded while operating manually, the compressor will shutdown.
To put all compressors back into computer
control from a locked off state, press RESET.
14
CAUTION: Anti-recycle timer is bypassed by
manual control. DO NOT start a compressor more
than once every 15 minutes.
NOTE: All compressors will revert back to auto-
matic control if the computer is not given a
load, unload or hold command at least once
every 15 minutes. A command can be repeated
to meet the 15 minute requirement for manual
control.
4.2.
Staging of Compressors
The staging of compressors is based on leaving
water temperature and the capacity calculations
mentioned in section 4.1. When the percent
capacity target gets up to full load and temperature is above deadband, a time delay of one or
two minutes is initiated before starting the next
compressor. When the capacity target falls below
a stored setpoint and temperature is below the
deadband, a compressor is turned off.
The percent capacity values that the computer is
calculating can be displayed by addressing the
analog input menu.
Compressor Current Limiting
4.3.
The amp limit B setpoint on the unit control data
sheet is the amp value at which the compressor
will be prevented from loading. The amp limit A
setpoint is the amp value at which the compressor will be given an unload command until the
current drops below the A setpoint.
If the values are changed, the difference between the hold and unload points should not be
decreased below 10% of compressor RLA so that
oscillations will not occur.
4.4.
Ramp Control
Ramp control can be implemented with the
microcomputer. Whenever the unit starts with
leaving water temperature greater than 5°F
above setpoint, a ramp up is generated. The
ramp start B setpoint specifies the percent
capacity target at which the ramp begins on the
first compressor. This can be set between 25 &
100 percent. The ramp rate A setpoint specifies
the maximum amount that can be added to
the target at each compressor control interval.
Thus a ramp rate of 0.1 produces the longest
ramp rate. Table 1 gives sample ramp times for
various ramp rate setpoints and start points for a
two-compressor machine.
TABLE 1
Sample Ramp Times (Minutes) For a TwoCompressor Unit with a 2 Second Compressor
Control Interval
Ramp 25% 50% 75%
Rate Start Pt. Start Pt. Start Pt.
Setpoint Setpoint Setpoint Setpoint
.1 38 50 42
.2 29 25 21
.3 19 17 14
.4 15 12 10
A formula for calculating ramp time in minutes is
T = [(# compressors x 100) - start pt.] x Compressor
Control Interval/(Ramp rate x 60)]
The compressor control interval can be determined by
timing the frequency of load/unload pulses given to a
compressor. It is typically 2 seconds.
4.5.
Manual Lead/Lag Selection
The lead compressor can be selected by the lead
B setpoint. The number stored in this setpoint
should be one less than the desired compressor
number. So a 0.0 in the setpoint specifies compressor 1 as the lead, a 1.0 puts compressor 2 as
lead, etc. It is preferable to have compressor 1 as
the lead. If a compressor is locked off, the next
compressor will automatically take its place in the
lead/lag sequence.
Compressor Start Delay
4.6.
A compressor start delay of one or two minutes is
incorporated into the computer to prevent two
compressors from starting at the same time and
insure that the system load requires another compressor. The compressor control point will display
COFF (“clock off”) during this timing.
4.7
Power Loss Reset
This function allows the customer the option of
automatic or manual reset of the computer after
a power loss to the computer. The power loss
could be from the UVR or control switch. For automatic reset, a 0.0 is stored in the power in the
power loss B setpoint. For manual reset after
power failure, a 1.0 is stored in the set- point. A
power loss alarm is also recorded by the computer.
Anti-Recycle Timing
4.8.
At the start of a compressor, a 15 minute timer is
initiated during which the compressor cannot start.
If cooling is called for during this time, a COFF is
displayed in the compressor control point.
CAUTION: This timer is bypassed by manual
control of compressors. DO NOT manually start
a compressor more than once every 15 minutes.
4.9. Low
Pressure Safety
When the evaporator pressure of a given refrigeration circuit drops below the low pressure B
setpoint, a time delay is initiated. If the pressure
stays below the setpoint during the time period,
all compressors on the circuit will be locked off
and the low pressure alarm will be recorded by
the computer.
For an air-cooled unit, the time delay is two minutes when ambient temperature is above 40°F. If
ambient temperature drops below 40°F, the delay
on compressor start up is extended to 4 minutes.
After start-up, the low pressure delay is 2 minutes.
4.10
High Pressure Safety
If the condensing pressure of a refrigeration circuit
exceeds the high pressure A setpoint, all compres-
15
sors on the circuit are locked off. The high pressure
alarm will be recorded by the computer. Typical
setpoint value is 360 psig.
Freeze Safety
4.11
If the leaving water temperature of a chiller drops
below the freeze B setpoint, all of the compressors
will be locked off. The freeze alarm will be recorded
by the computer. Press RESET to clear the lockout.
4.12
High Oil Temp Safety
If the oil temperature switch of a compressor opens,
the oil temperature digital input turns ON. If the
compressor is operating, the compressor will be
locked off. The high oil temperature alarm will be
recorded by the computer and RESET must be pressed
after the problem is resolved.
4.13
Alarm Output
The alarm control point closes the digital output
relay on all safety alarms. This relay is used to turn
an alarm light on. After the problem is resolved,
press RESET to reset the system and turn the alarm
output off.
4.14
Fan Control
The fans are controlled by the microcomputer out
put relays. The computer switches fans on or off
basel on the discharge pressure and the fan
pressure setpoints. The high (A) setpoints are
where the fans turn on and the low (B) setpoints
are where the fans turn off.
Chilled Water Reset (Optional) and Customer Con-
4.15
trol Interlock
If an analog input is available, the chilled water tem-
perature setpoint can be raised automatically by a
0-5 VDC signal provided by an external controller.
The reset signal must be between 0VDC and 5VDC,
with 0VDC being no reset and 5VDC being maximum reset. The maximum temperature reset (increase) desired must be stored in CWR max B
setpoint. For example, to raise the chilled water
setpoint from 44°F to 50°F (6.0°F) with a 5VDC input, a 6.0 is stored in CWR max setpoint.
CAUTION: The voltage input must never exceed
5.0VDC.
Control contacts from an external controller are
used to enable or disable operation of compressors. The wiring diagram specifies the terminals to
which the contacts must be wired. To enable the
compressors, the contacts must be closed. To
place the unit in stand-by mode, open the control
contact.
Note: This control must be used for automatic
control of the package. Do not use the flow
switch to control the package.
4.16 Hot Gas Bypass Control (option)
When hot gas bypass has been supplied with
the package, an output from the computer
controls the solenoid. The solenoid is turned on
if only one compressor is operating and the
target percent capacity of the compressor
drops below the hot gas bypass B setpoint. If
the target percent capacity then climbs above
the hot gas bypass A setpoint, the solenoid is
turned off. Typical setpoints are 45% for the B
setpoint and 80% for the A setpoint.
4.17
Compressor Power Control (No-Stop Alarm) and
Unit Schedule
The control power/schedule feeds power to the
compressor safety and control circuit and closes
the chilled water pump contacts. (See Field
Control Wiring). After power-up, the relay is
held open for 15 seconds to allow for reset of
the high temperature safety switch. The relay is
then closed to allow normal compressor control
if the unit schedule is calling for unit operation.
The computer will open this relay if it detects
that a compressor auxiliary contact digital input
stays ON for 15 seconds when the computer is
commanding the compressor to be off. A NoStop alarm would then be stored in the alarm
history. This would indicate that either a hardware problem is forcing the compressor to run
when it should not or that the digital input is
staying on when the compressor is actually off.
When the problem is resolved, press the RESET
button to allow the machine to start.
During normal operation, this output turns ON/
OFF based on the unit schedule of operation
(see Section 3.9).
Sensor Alarm Shutdown
4.18
If the computer measures an analog sensor
value that is outside of a given boundary, the
associated compressors are shutdown. The
computer then stores the alarm code corresponding to the sensor alarm. The boundary
values are as follows:
Low High
1. Water temp sensor - 190°F
2. Air temp. sensor 25°F 180°F
3. Suction pressure -20 psig See below
4. Discharge pressure 5 psig -
The high setpoint for the suction pressure sensor will
be triggered if the leaving water temperature is less
than 60°F and suction pressure is greater than 150
psig.
not operating if the associated digital input
from the compressor contactor does not
indicate that the contactor is pulled in (digital
input stays OFF), or if the amps of the compressor are less than about 12 amps. If a
faulty No-run alarm occurs, monitor the digital
input and amps to see which is producing the
fault.
4.20
Fast Unload Solenoid Control
When a compressor starts, it’s fast unload
solenoid is energized for 30 seconds to ensure
that the compressor unloads fully. The load
and unload, solenoids are de-energized during
this time delay. After the time delay, normal
control of the load/unload solenoids is restored.
4.21
Low Suction/Discharge Differential Alarm
If the difference between suction and dis
charge pressure is less than minimum differential pressure for 3 minutes while a compressor
is operating, all the compressors on the
affected refrigerant circuit are locked off. A
low differential pressure alarm will be recorded
by the computer and the alarm output will be
turned on. Press RESET to clear the lockout.
4.22
High Motor Temperature Safety
If the high motor temperature switch of a
compressor opens, the motor temperature
digital input turns ON. If the compressor is
operating, the ‘compressor will be locked off.
The high motor temperature alarm will be
recorded by the computer and RESET must be
pressed after the problem is resolved.
Low Chiller Flow Alarm
4.23
A low flow alarm will be generated if a compressor control point is ON and the flow
switch digital input is OFF. All compressors will
be locked off and the alarm light turned on.
After resolving the problem, press RESET.
High Discharge Pressure Unload
4.24
This function unloads the compressor if
discharge pressure is approaching the high
pressure limit. If discharge pressure of an
operating compressor reaches the high
pressure setpoint minus 10 psi, the compressor
will be prevented from loading (HOLD state). If
the discharge pressure reaches the high
pressure setpoint minus 5 psi, the compressor
will begin unloading.
If one of these sensor alarms occurs, it usually indicates a loose wire, blown fuse, defective sensor, or
faulty analog board.
External Shutdown Indication (No-Run Alarm)
4.19
A No-Run control point error is generated if the
computer tries to start (or run) a compressor but the
compressor is held off by an external control. The
computer determines that the compressor is
16
60 Hz HRSC ELECTRICAL DATA (50 - 150)
COMPRESSORS
Model
HRSC
50 208/230 Y-D 179 - 347 - 224 400
60 208/230 XL 205 - 409 - 257 450
75 208/230 XL 209 - 472 - 262 450
100 208/230 XL 179 179 347 347 403 500
110 208/230 Y-D 205 179 409 347 436 600
120 208/230 Y-D 205 205 409 409 462 600
135 208/230 XL 209 205 472 409 467 600
150 208/230 XL 209 209 472 472 471 600
Volts
60 Hz
3 Ph.
208/230 XL 179 - 1040 - 224 400
460 XL 74 422 93 150
460 Y-D 74 - 141 - 93 150
208/230 XL 205 - 1228 - 257 450
460 Y-D 91 - 485 - 114 200
460 XL 91 - 162 - 114 200
208/230 Y-D 209 - 1415 - 262 450
460 Y-D 98 - 539 - 123 200
460 XL 98 180 - 123 200
208/230 Y-D 179 1040 1040 403 500
460 XL 74 74 422 422 167 200
460 Y-D 74 74 141 141 167 200
208/230 XL 205 179 1228 1040 436 600
460 XL 91 74 485 422 188 250
460 Y-D 91 74 162 141 188 250
208/230 XL 205 205 1228 1228 462 600
460 XL 91 91 485 485 205 250
460 XL 91 91 162 162 205 250
208/230 Y-D 209 205 1415 1228 467 600
460 Y-D 98 91 539 485 213 300
460 XL 98 91 180 162 213 300
208/230 Y-D 209 209 1415 1415 471 600
460 Y-D 98 98 539 539 221 300
460 XL 98 98 180 180 221 300
Type
of
Start
RATED LOAD AMPS
MOTOR NO.
1
LOCKED ROTOR AMPS
MOTOR NO.
2
12
Minimum
Circuit
Ampacity
Max Fuse
Size
17
60 Hz HRSC ELECTRICAL DATA (50 - 150)
Model
HRSC
180
210
225
240
255
270
300
Volts
60 Hz.
3 PH.
COMPRESSORS
Type
of
1 2 3 4 1 2 3 4 Cir. 1 Cir. 2 Cir. 1 Cir. 2
Unit
RATED LOAD AMPS
MOTOR NO.
LOCKED ROTOR AMPS
MOTOR NO.
Minimum
Circuit
Ampacity
Maximum
Fuse
Size
208/230 XL 205 205 205 - 1228 1228 1228 - 667 - 800 208/230 XL 205 205 205 - 409 409 409 - 667 - 800 -
460 Y-D 91 91 91 - 485 485 485 - 296 - 350 -
460 XL 91 91 91 - 162 162 162 - 296 - 350 208/230 Y-D 209 209 209 - 1415 1415 1415 - 471 262 600 450
208/230 XL 209 209 209 - 472 472 472 - 471 262 600 450
460 Y-D 98 98 98 - 539 539 539 - 312 - 400 -
460 XL 98 98 98 - 180 180 180 - 312 - 400 208/230 Y-D 209 209 209 - 1415 1415 1415 - 471 262 600 450
208/230 XL 209 209 209 179 472 472 472 - 471 262 600 450
460 XL 98 98 98 74 539 539 539 - 319 - 400 -
460 Y-D 98 98 98 74 180 180 180 - 319 - 400 208/230 XL 205 205 205 205 1228 1228 1228 1228 462 462 600 600
208/230 Y-D 205 205 205 205 409 409 409 409 462 462 600 600
460 XL 91 91 91 91 485 485 485 485 387 - 450 -
460 Y-D 91 91 91 91 162 162 162 162 387 - 450 208/230 XL 209 209 209 209 1415 1415 1415 1415 467 462 600 600
208/230 Y-D 209 209 209 209 472 472 472 472 467 462 600 600
460 XL 98 98 98 98 539 539 539 539 396 - 450 -
460 XL 98 98 98 98 180 180 180 180 396 - 450 208/230 Y-D 209 209 209 209 1415 1415 1415 1415 471 462 600 600
208/230 XL 209 209 209 209 472 472 472 472 471 462 600 600
460 Y-D 98 98 98 98 539 539 539 539 403 - 500 -
460 XL 98 98 98 98 180 180 180 180 403 - 500 208/230 Y-D 209 209 209 209 1415 1415 1415 1415 471 471 600 600
208/230 XL 209 209 209 209 472 472 472 472 471 471 600 600
460 Y-D 98 98 98 98 539 539 539 539 417 - 500 -
460 XL 98 98 98 98 180 180 180 180 417 - 500 -
NOTES:
1. XL: Across the line; Y-D: Star-Delta
2. RLA (Rated Load Amps) rated in accordance with ARI Standard 590.
3. Starting current for normal Y-D start is shown. In certain compressor failure modes, Y-D inrush can be as high as XL
inrush.
4. Wire Size Amps (ampacity) equal 125% of the rated load amps for the largest motor in the circuit plus 100% of the
rated load amps for all other motors in the circuit, per N.E.C.
5. Maximum fuse size is based on 225% of the rated load amps for the largest motor in the circuit plus 100% of the rated
load amps for all other motors in the circuit. This is the largest fuse allowed per N.E.C. A smaller fuse is often recommended based on unit application and ambient temperature.
VOLTAGE TOLERANCES:
1) 208 volt: min. 187, max. 229
2) 230 volt: min. 207, max. 253
3) 460 volt: min. 414, max. 506
18
TYPICAL HRSC 150 POWER WIRING (460/3/60)
COMPRESSOR MOTORS 1-2
SEE NOTE 5
19
TYPICAL HRSC 150 CONTROL WIRING
(Electrical Mechanical)
20
TYPICAL HRSC 150 CONTROL WIRING
(Optional Micro-Computer Controller)
21
HRSC 050 TO 300 PIPING SCHEMATIC
Shown Typical for
Each Separate Refrigerant Circuit
1 CIRG - 050. 060, 075
2 CIRC - 100, 110. 120, 135, 150 3 CIRC 180, 210, 225
4 CIRC - 240. 255, 270, 300
CAP
t
~
~
HOT GAS
REGULATO
R
SOLENOID
VALVE
HOT GAS BYPASS OPTION
(CIRC. #1 ONLY)
TACCESS
VALVE
COUPL
ING
ACCESS VALVE CHECK
COUPLING VALVE
DISCHA@RG@E
,RFW Sum
comp
- SCREW
CAP
LIQUID
VALVt
FILTER DRIER
AND CORES
~
'All
THERMAL (STD)
/- COUPLING
SIGHT SOLENOID
GLASS VALVE
ACCESS VALVE
WATER
OUT
WATE
R
IN
23
CAPACITY CONTROL
Each compressor can modulate from 100% to 30% of full
load by slide valve operation. This provides reduction down
to 7.5% on four-compressor units.
Model Number
HRSC 50-75
HRSC 100-150
HRSC 180-225
HRSC 240 300
Circuits
1
2
3
4
Further reduction is possible on all units through use of
the hot gas bypass option which reduces compressor capacity to 10%. Minimum capacities are tabulated below.
Standard Min.
Unloading
30%
15%
10%
7.5%
Optional Hot
Gas Bypass
15%
7.5%
5%
4%
PHYSICAL DATA
MODELS HRSC-50 THRU 150
Model HRSC 50 60 75 100 110 120 135 150
Nominal Capacity - Tons 40 50 60 80 85 95 110 120
SEMI-HERMETIC SCREW TYPE COMPRESSORS
No. of Compressors 1112 2 2 2 2
Nominal Size (HP) 50 60 75 (2)50 50-60 (2)60 60-75 (2)75
Oil Charge (Oz./Compr) 202 236 236 (2)202 (1)202(1)236 (2)236 (2)236 (2)236
Crankcase Heater (Watts) 200 200 200 (2)200 (2)200 (2)200 (2)200 (2)200
COOLER
Storage Capacity (Gal.) 6.25 9.4 11.1 17.6 25.4 25.4 29.4 29.4
Diameter x Length 860 1060 1160 1360 12102 12102 4102 14102
REMOTE CONDENSER
No. of SPD-SD Condensers 1111 1 1 1 1
SPD-SD Condenser Size 70 70 70 140 140 140 140 140
UNIT
Refrigerant Charge - R22 (lbs.)(1) 96 130 156 208 228 247 280 312
HRSC Operating Weight (lbs.)(2) 1700 2100 2325 3240 3555 4590 5415 5910
MODELS HRSC-180 THRU 300
Model HRSC 180 210 225 240 255 270 300
Nominal Capacity - Tons 145 165 175 190 205 210 230
SEMI-HERMETIC SCREW TYPE COMPRESSORS
No. of Compressors 33 3 4 4 4 4
Nominal Size (HP) (3)60 (1)60(2)75 (3)75 (4)60 (3)60(1)75 (2)60(2)75 (4)75
Oil Charge (Oz./Compr) (3)236 (3)236 (3)236 (4)236 (4)236 (4)236 (4)236
Crankcase Heater (Watts) (3)200 (3)200 (3)200 (4)200 (4)200 (4)200 (4)200
COOLER
Storage Capacity (Gal.) 60.5 60.5 60.5 67.7 67.7 67.7 67.7
Diameter x Length 18122 18122 18122 20122 20122 20122 20122
REMOTE CONDENSER
No. of SPD-SD Condensers 1/1 1/1 1/1 2 2 2 2
SPD-SD Condenser Size 70/140 70/140 70/140 140 140 140 140
UNIT
Refrigerant Charge - R22 (lbs.)(1) 390 442 481 546 575 611 663
HRSC Operating Weight (lbs.)(2) 8710 8860 8950 10460 10560 10650 10800
NOTES: 1. Refrigerant charge includes condenser but does not include refrigerant piping.
2. HRSC operating weight does not include remote condenser. See page 12 for condenser weights.
24
EVAPORATOR WATER PRESSURE DROP
MODEL HRSC-D CHILLER MODEL CURVE NO. MIN. GPM MAX. GPM
50 CHS008601B* 1 70 242
60 CHS010601B* 2 78 316
75 CHS011601B* 3 85 316
100 CHD013601B* 4 100 420
1 10, 120 EXD12102J07DVTO 5 160 444
135, 150 EXD14102J07DVTO 6 175 553
180, 220, 225 EXT18122J07DFRO 7 270 1060
240, 255, 270, 300 EXT20122J07DFRO 8 300 11 40
*These chillers have welded heads. All other chillers have removable heads.
NOTE: Constant water flow through the evaporator is required with a minimum of three gallons per
ton of system water loop volume. System volume should increase
up to ten gallons per ton for process loads, low load applications with small
temperature ranges, or systems with widely fluctuating loads.
25
POWER
KNOCKOUT
HRSC 50-150 RIGGING INSTRUCTIONS
SPREADER BAR ASSEMBLY
(SUPPLIED BY OTHERS)
13 3/8
18
2 1/2" DIA. LIFTING HOLES
3/4" DIA MOUNTING HOLES (9)
HRSC 50-150 ISOLATOR INSTRUCTIONS
6
1
3 3
2
1
1
ISOLATOR CROSS RAIL
ISOLATOR ASSEMBLY (FRONT VIEW)
(SHIPPED LOOSE WITH IS OLATOR OPTION ONLY)
*
MIDPOINT
3
2
1
FRONT
(CONTROL BOX)
UNIT FRAME RAIL
UNIT ISOLATOR (OPTIONAL)
*
(9) 3/4 DIA. HOLES SUPPLIED
SPREADER BAR
6
2
1
26
HRSC 180-300 RIGGING INSTRUCTIONS
2 1/2 DIA. LIFTING HOLES (4)
3/4 DIA HOLES
ISOLATOR MOUNTING
HOLES-6 SUPPLIED
SPREADER BAR ASSEMBLY
(SUPPLIED BY OTHERS)
SPREADER BARS
BY OTHERS
HRSC 180-300 ISOLATOR INSTRUCTIONS
CONDENSER BUMPER RAIL
D
N
E
X
O
B
L
O
R
T
N
O
C
1
R
O
S
S
E
R
P
M
O
1
C
2
2
7512 1/2
(6) 3/4 DIA. HOLES SUPPLIED
3
R
O
S
S
E
R
P
M
O
C
R
E
M
I
R
R
O
D
F
R
T
E
A
T
L
L
P
I
F
3
75
3 1/2
27
TROUBLESHOOTING GUIDE
POSSIBLE CAUSE REMEDY
CHILLER UNIT WILL NOT START
1. Power off 1. Check main disconnect switch
2. Main line open 2. Check main fuses
3. Incorrect wiring 3. Check the wiring diagram
4. Loose terminals 4. Tighten all terminals
5. Control circuit open 5. Check phase loss monitor, flow switch, circuit
breakers, temperature control, low ambient
thermostat, low temperature, thermostat,
remote switch, etc.
6. T ime delay 6. Wait
COMPRESSOR HUMS BUT DOES NOT START
1. Low Voltage 1a. Check at service and unit for loss
b. Consult power company
COMPRESSOR CUTS OUT ON LOW PRESSURE SAFETY CONTROL
1. Refrigerant shortage 1. Check for leaks -- add refrigerant
2. Restriction in liquid line 2a. Plugged strainer -- clean or replace
b. Liquid line valve partially closed — open valves fully
c. Expansion valve clogged or inoperative — clean or
replace as required
d. Solenoid valve partially open — clean or replace as
required
3. Low water flow thru cooler 3. Check water flow thru cooler and correct as required
COMPRESSOR CYCLES ON HIGH PRESSURE CONTROL
1. Compressor discharge valve partially closed 1. Open valve fully
2. Non-condensible gases in system 2. Operate condenser fans with compressors off.
If condenser pressure exceeds saturated
pressure corresponding to condenser entering air
temperature, then reclaim air from the top of hot
gas vertical header coil.
3. Overcharge of R-22 3. Reclaim refrigerant from system while in oper-
ation until head pressure reaches a normal level.
4. Clean the condenser
5. Replace if necessary
6. Check pressure control setting
CAUSES AND PREVENTION OF FREEZE-UP
CAUSES PREVENTION
1. Improper charging 1. Charge per manufacturer’s recommendation
2. Improperly set safety time delay 2. Check the safety time delay low pressure control for
proper setting at the beginning of each season.
3. Improper chilled water circulation 3. Use an ample sized cleanable strainer in the chilled
water circuit. Make certain the strainer is clean to
insure full flow and velocity of chilled water. It may
sometimes be necessary to treat the water to prevent
formation of deposits.
30
ST ART-UP CHECK LIST Date ______________
YES NO
Unit Model No. _________________________
Setting Unit:a. Vibration isolator used _________ _________
b. Spring isolator adjusted for equal heiqht _________ _________
c. If rubber-in-shear isolators are used, is unit leveled by shimming _________ _________
Wiring: a. Power wiring complete _________ _________
b. Control wiring complete _________ _________
c. Electric service adequate for load _________ _________
d. Power source voltage correct for motor(s) used _________ _________
e. Motor circuit has proper size fusetrons _________ _________
f. System wired per diagram _________ _________
g. All wire connections tight _________ _________
h. Wiring complies with local codes _________ _________
i. Flow switch operation _________ _________
j. Microcomputer (if supplied) components dry _________ _________
Piping: a. Piping complies with applicable codes _________ _________
b. External piping independently supported _________ _________
c. Chilled water lines insulated _________ _________
d. All systems refrigerant and water piping leak tested and corrected as _________ _________
necessary
Before Start-Up:
a. Open compressor discharge service valve (if supplied) _________ _________
b.
Open liquid valve(s) _________ _________
c. Open suction, and discharge valves to pressure gauges (if supplied) _________ _________
d. Check rotation of all fan motors _________ _________
e. Start auxiliary equipment (pump s, fans, etc.) _________ _________
f. Is crankcase heater operating? Operate 24 hours prior to
unit start-up. _________ _________
g. Check the compressor oil level through the crankcase sight glass. _________ _________
The oil level should be 1/2 of the glass. If the level is low , add _________ _________
oil in accordance with the directions in the maintenance instructions _________ _________
h. Check all control settings as specified on unit wiring diagram _________ _________
i. Air purged from chilled water system _________ _________
After St art-up:
a. Check high pressure control _________ _________
b. Check oil temperature safety switch _________ _________
c. Check and adjust low temperature freeze control _________ _________
d. Check and adjust unit controller _________ _________
e. Check and adjust low pressure control _________ _________
f. Check and adjust expansion valve superheat _________ _________
31
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