Carrier 30RAP010-060 specifications

Energy Management Module (Fig. 12) — This factory-installed option (FIOP) or field-installed accessory is used for the following types of temperature reset, demand limit, and/or ice features:

•4 to 20 mA leaving fluid temperature reset (requires field-supplied 4 to 20 mA generator)

•4 to 20 mA cooling set point reset (requires field- supplied 4 to 20 mA generator)

•Discrete inputs for 2-step demand limit (requires field- supplied dry contacts capable of handling a 24 vac, 50 mA load)

•4 to 20 mA demand limit (requires field-supplied 4 to 20 mA generator)

•Discrete input for Ice Done switch (requires field- supplied dry contacts capable of handling a 24 vac, 50 mA load)

See Demand Limit and Temperature Reset sections on pages 41 and 37 for further details.

CAUTION

Care should be taken when interfacing with other manufac- turer’s control systems due to possible power supply differences, full wave bridge versus half wave rectification. The two different power supplies cannot be mixed. ComfortLink™ controls use half wave rectification. A signal isolation device should be utilized if a full wave bridge signal generating device is used.

Loss-of-Cooler Flow Protection — A proof-of- cooler flow device is factory installed in all chillers. It is recom- mended that proper operation of the switch be verified on a reg- ular basis.

Electronic Expansion Valves (EXV) — All units are equipped from the factory with EXVs. Each refrigeration cir- cuit is also supplied with a factory-installed liquid line filter drier and sight glass.

The EXV is set at the factory to maintain 9° F (5.0° C) suc- tion superheat leaving the cooler by metering the proper amount of refrigerant into the cooler. The superheat set point is adjustable, but should not be adjusted unless absolutely necessary.

The EXV is designed to limit the cooler saturated suction temperature to 50 F (12.8 C). This makes it possible for unit to start at high cooler fluid temperatures without overloading the compressor.

Capacity Control — The control system cycles com- pressors, digital scroll modulting solenoid (if equipped), and minimum load valve solenoids (if equipped) to maintain the user-configured leaving chilled fluid temperature set point. En- tering fluid temperature is used by the main base board (MBB) to determine the temperature drop across the cooler and is used in determining the optimum time to add or subtract capacity stages. The chilled fluid temperature set point can be automati- cally reset by the return fluid temperature, space, or outdoor-air temperature reset features. It can also be reset from an external 4 to 20-mA signal (requires energy management module FIOP or accessory).

The standard control has an automatic lead-lag feature built in which determines the wear factor (combination of starts and run hours) for each compressor. If all compressors are off and less than 30 minutes has elapsed since the last compressor was turned off, the wear factor is used to determine which

compressor to start next. If no compressors have been running for more than 30 minutes and the leaving fluid temperature is greater than the saturated condensing temperature, the wear factor is still used to determine which compressor to start next. If the leaving fluid temperature is less than the saturated con- densing temperature, then the control will start either compres- sor A1 or compressor B1 first, depending on the user-configu- rable circuit lead-lag value. For units with the minimum load control valve, the A circuit with the minimum load valve is al- ways the lead circuit. The A circuit is also always the lead for units with the digital compressor option. On units with the dig- ital scroll option, the A1 compressor operates continuously, providing close leaving chilled water control. For this reason, on/off cycling of the unit’s compressors is dramatically re- duced, which in turn reduces wear associated with compressor start/stop cycles.

The EXVs will provide a controlled start-up. During start- up, the low pressure logic will be bypassed for 21/2 minutes to allow for the transient changes during start-up. As additional stages of compression are required, the processor control will add them. See Table 19.

If a circuit is to be stopped, the compressor with the lowest wear factor will be shut off first except when a digital compres- sor is used. The digital compressor is always the last compres- sor to shut off.

The capacity control algorithm runs every 30 seconds. The algorithm attempts to maintain the Control Point at the desired set point. Each time it runs, the control reads the entering and leaving fluid temperatures. The control determines the rate at which conditions are changing and calculates 2 variables based on these conditions. Next, a capacity ratio is calculated using the 2 variables to determine whether or not to make any changes to the current stages of capacity. This ratio value ranges from –100 to +100%. If the next stage of capacity is a compressor, the control starts (stops) a compressor when the ratio reaches +100% (–100%). If installed, the minimum load valve solenoid will be energized with the first stage of capacity. Minimum load valve value is a fixed 30% in the total capacity calculation. The control will also use the minimum load valve solenoid as the last stage of capacity before turning off the last compressor. A delay of 90 seconds occurs after each capacity step change. Refer to Table 19.

MINUTES LEFT FOR START — This value is displayed only in the network display tables (using Service Tool, ComfortVIEW™ or ComfortWORKS® software) and represents the amount of time to elapse before the unit will start its initialization routine. This value can be zero without the machine running in many situations. This can include being unoccupied, ENABLE/OFF/REMOTE CONTACT switch in the OFF position, CCN not allowing unit to start, Demand Limit in effect, no call for cooling due to no load, and alarm or alert conditions present. If the machine should be running and none of the above are true, a minimum off time (DELY, see below) may be in effect. The machine should start normally once the time limit has expired.

MINUTES OFF TIME (Configuration→OPT2→ DELY) — This user-configurable time period is used by the control to determine how long unit operation is delayed after power is applied/restored to the unit. Typically, this time period is configured when multiple machines are located on a single site. For example, this gives the user the ability to prevent all the units from restarting at once after a power failure. A value of zero for this variable does not mean that the unit should be running.

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