Sterling 30RA010-055 manual Major System Components, Control Module Communication, Unit Sizes

	Table 1 — Unit Sizes
UNIT		NOMINAL CAPACITY
		(TONS) 50/60 Hz
30RA010		10/10
30RA015		14/13
30RA018		16/16
30RA022		22/20
30RA025		24/23
30RA030*		27
30RA032†		30
30RA035		35/34
30RA040*		38
30RA042†		40
30RA045		43/45
30RA050*		47
30RA055*		54

*60 Hz only. †50 Hz only.

MAJOR SYSTEM COMPONENTS

General — The 30RA air-cooled reciprocating chillers contain the ComfortLink™ electronic control system that controls and monitors all operations of the chiller.

The control system is composed of several components as listed in the sections below. See Fig. 1 and 2 for typical control box drawing. See Fig. 3-6 for control schematics.

Main Base Board (MBB) — See Fig. 7. The MBB is the heart of the ComfortLink control system. It contains the major portion of operating software and controls the operation of the machine. The MBB continuously monitors input/output channel information received from its inputs and from all other modules. The MBB receives inputs from the discharge and suction pressure transducers and thermistors. See Table 2. The MBB also receives the feedback inputs from each compressor contactor, auxiliary contacts, and other status switches. See Table 3. The MBB also controls several outputs. Relay outputs controlled by the MBB are shown in Table 4. Information is transmitted between modules via a 3-wire communication bus or LEN (Local Equipment Network). The SCN (Sterlco Comfort Network) bus is also supported. Connections to both LEN and SCN buses are made at TB3. See Fig. 8.

Scrolling Marquee Display — This standard device is the keypad interface used for accessing chiller information, reading sensor values, and testing the chiller. The marquee display is a 4-key,4-character,16-segment LED (light-emitting diode) display. Eleven mode LEDs are located on the display as well as an Alarm Status LED. See Marquee Display Usage section on page 23 for further details.

Energy Management Module (EMM) — The EMM module is available as a factory-installed option or as a field- installed accessory. The EMM module receives 4 to 20 mA inputs for the leaving fluid temperature reset, cooling set point and demand limit functions. The EMM module also receives the switch inputs for the field-installed2-stage demand limit and ice done functions. The EMM module communicates the status of all inputs with the MBB, and the MBB adjusts the control point, capacity limit, and other functions according to the inputs received.

Enable/Off/Remote Contact Switch — The Enable/ Off/Remote Contact switch is a 3-position switch used to control the chiller. When switched to the Enable position the chiller is under its own control. Move the switch to the Off position to shut the chiller down. Move the switch to the Remote Contact position and a field-installed dry contact can be used to start the chiller. The contacts must be capable of handling a 24 vac, 50-mA load. In the Enable and Remote

Contact (dry contacts closed) positions, the chiller is allowed to operate and respond to the scheduling configuration, SCN configuration and set point data. See Fig. 8.

Emergency On/Off Switch — The Emergency On/Off switch should only be used when it is required to shut the chiller off immediately. Power to the MBB, EMM, and marquee display is interrupted when this switch is off and all outputs from these modules will be turned off.

Board Addresses — The Main Base Board (MBB) has a 3-position Instance jumper that must be set to ‘1.’ All other boards have 4-position DIP switches. All switches are set to ‘On’ for all boards.

Control Module Communication

RED LED — Proper operation of the control boards can be visually checked by looking at the red status LEDs (light-emitting diodes). When operating correctly, the red status LEDs should be blinking in unison at a rate of once every 2 seconds. If the red LEDs are not blinking in unison, verify that correct power is being supplied to all modules. Be sure that the Main Base Board (MBB) is supplied with the current software. If necessary, reload current software. If the problem still persists, replace the MBB. A red LED that is lit continu- ously or blinking at a rate of once per second or faster indicates that the board should be replaced.

GREEN LED — The MBB has one green LED. The Local Equipment Network (LEN) LED should always be blinking whenever power is on. All other boards have a LEN LED which should be blinking whenever power is on. Check LEN connections for potential communication errors at the board J3 and/or J4 connectors. Communication between modules is accomplished by a 3-wire sensor bus. These 3 wires run in parallel from module to module. The J4 connector on the MBB provides both power and communication directly to the marquee display only.

YELLOW LED — The MBB has one yellow LED. The Sterlco Comfort Network (SCN) LED will blink during times of network communication.

Sterlco Comfort Network (SCN) Interface —

The 30RA chiller units can be connected to the SCN if desired. The communication bus wiring is a shielded, 3-conductor cable with drain wire and is supplied and installed in the field. See Table 5. The system elements are connected to the communication bus in a daisy chain arrangement. The positive pin of each system element communication connector must be wired to the positive pins of the system elements on either side of it. This is also required for the negative and signal ground pins of each system element. Wiring connections for SCN should be made at TB3. Consult the SCN Contrac- tor’s Manual for further information.

NOTE: Conductors and drain wire must be 20 AWG (Ameri- can Wire Gage) minimum stranded, tinned copper. Individual conductors must be insulated with PVC, PVC/nylon, vinyl, Teflon, or polyethylene. An aluminum/polyester 100% foil shield and an outer jacket of PVC, PVC/nylon, chrome vinyl, or Teflon with a minimum operating temperature range of –20 C to 60 C is required. Wire manufactured by Alpha (2413 or 5463), American (A22503), Belden (8772), or Columbia (02525) meets the above mentioned requirements.

It is important when connecting to a SCN communication bus that a color coding scheme be used for the entire network to simplify the installation. It is recommended that red be used for the signal positive, black for the signal negative, and white for the signal ground. Use a similar scheme for cables contain- ing different colored wires.

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