Carrier 23XRV manual Guide specifications cont, F. Refrigerant Flow Control

Guide specifications (cont)

liquid refrigerant to a reduced temperature, thereby increasing the refrigeration cycle efficiency.

F.Refrigerant Flow Control:

To improve part load efficiency, liquid refrigerant shall be metered from the condenser to the cooler using a float-type metering valve to maintain the proper liquid level of refrigerant in the heat exchangers under both full and part load operating conditions. By maintaining a liquid seal at the float valve, bypassed hot gas from the condenser to the cooler is eliminated.

G.Controls, Safeties, and Diagnostics:

1.Controls:

a.The chiller shall be provided with a factory- installed and factory-wired microprocessor control center. The control center shall include a 16-line by 40-character liquid crystal display, 4 function keys, stop button, and alarm light. Other languages are available using the inter- national language translator software.

b.All chiller and motor control monitoring shall be displayed at the chiller control panel.

c.The controls shall make use of non-volatile memory.

d.The chiller control system shall have the ability to interface and communicate directly to the building control system.

e.The default standard display screen shall simul- taneously indicate the following minimum information:

1)Date and time of day

2)24-character primary system status message

3)24-character secondary status message

4)Chiller operating hours

5)Entering chilled water temperature

6)Leaving chilled water temperature

7)Evaporator refrigerant temperature

8)Entering condenser water temperature

9)Leaving condenser water temperature

10)Condenser refrigerant temperature

11)Oil supply pressure

12)Oil sump temperature

13)Percent motor rated load amps (RLA)

f.In addition to the default screen, status screens shall be accessible to view the status of every point monitored by the control center including:

1)Evaporator pressure

2)Condenser pressure

3)Compressor speed

4)Bearing oil supply temperature

5)Compressor discharge temperature

6)Motor winding temperature

7)Number of compressor starts

8)Control point settings

9)Discrete output status of various devices

10)Variable frequency drive status

11)Optional spare input channels

12)Line current and voltage for each phase

13)Frequency, kW, kWhr, demand kW

g.Schedule Function:

The chiller controls shall be configurable for manual or automatic start-up and shutdown. In automatic operation mode, the controls shall be capable of automatically starting and stopping the chiller according to a stored user programmable occupancy schedule. The controls shall include built-in provisions for accepting:

1)A minimum of two 365-day occupancy schedules.

2)Minimum of 8 separate occupied/unoc- cupied periods per day

3)Daylight savings start/end

4)18 user-defined holidays

5)Means of configuring an occupancy timed override

6)Chiller start-up and shutdown via remote contact closure

h.Service Function:

The controls shall provide a password protected service function which allows authorized individuals to view an alarm history file which shall contain the last 25 alarm/alert messages with time and date stamp. These messages shall be displayed in text form, not codes.

i.Network Window Function:

Each chiller control panel shall be capable of viewing multiple point values and statuses from other like controls connected on a common network, including controller main- tenance data. The operator shall be able to alter the remote controller’s set points or time schedule and to force point values or statuses for those points that are operator forcible. The control panel shall also have access to the alarm history file of all like con- trollers connected on the network.

j.Pump Control:

Upon request to start the compressor, the control system shall start the chilled and condenser water pumps and shall verify that flows have been established.

k.Ramp Loading:

A user-configurable ramp loading rate, effec- tive during the chilled water temperature pulldown period, shall prevent a rapid increase in compressor power consumption. The controls shall allow configuration of the ramp loading rate in either degrees per min- ute of chilled water temperature pulldown or percent motor amps per minute. During the ramp loading period, a message shall be

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