Carrier 17EX specifications Ecw, Entering Chilled Water

LEGEND

DP = (Condenser psi) − (Cooler psi)

DT = (ECW) − (LCW)

ECW	Ð Entering Chilled Water
HGBP	Ð Hot Gas Bypass
LCW	Ð Leaving Chilled Water

Fig. 18 Ð 17EX Hot Gas Bypass/Surge Prevention With Default Settings (English)

LEGEND

DP = (Condenser kPa) − (Cooler kPa)

DT = (ECW) − (LCW)

ECW	Ð Entering Chilled Water
HGBP	Ð Hot Gas Bypass
LCW	Ð Leaving Chilled Water

Fig. 19 Ð 17EX Hot Gas Bypass/Surge Prevention

With Default Settings (SI)

Surge Protection Ð Compressor surge can be de- tected by the PIC based on operator con®gured settings. Surge causes amperage ¯uctuations of the compressor motor. The PIC monitors these amperage swings, and if the swing is greater than the con®gured setting (SURGE DELTA PERCENT AMPS) in one second, then one surge event has occurred. The setting is displayed and con®gured on the SERVICE1 screen. Its default setting is 25% amps.

A surge protection chiller shutdown occurs when the surge protection counter reaches 12 within an operator speci®ed time period, known as the surge time period. The surge protection count (SURGE PROTECTION COUNTS

parameter, Table 2, Example 13) can be monitored on the MAINT03 screen. The SURGE TIME PERIOD parameter is displayed and con®gured on the SERVICE1 screen. See Table 2, Example 8. It has a default of 2 minutes.

Lead/Lag Control Ð Lead/lag is a control system pro- cess that automatically starts and stops a lag or second chiller in a 2-chiller system. Refer to Fig. 15 and 16 for menu, table, and screen selection information. On chillers that have PSIO software with lead/lag capability, it is possible to use the PIC controls to perform the lead/lag function on 2 chillers. A third chiller can be added to the lead/lag system as a standby chiller to start up if the lead or lag chiller in the system has shut down during an alarm condition and additional cooling is required.

NOTE: Lead/lag parameters can be viewed and modi®ed on the LEAD/LAG CONFIGURATION screen, accessed from the EQUIPMENT CONFIGURATION table. See Table 2, Example 7. Lead/lag status during chiller operation is viewed on the MAINT04 screen, accessed from the CONTROL ALGORITHM STATUS table. See Table 2, Example 14.

Lead/Lag System Requirements:

·all chillers must have PSIO software capable of perform- ing the lead/lag function

·water pumps MUST be energized from the PIC controls

·water ¯ows should be constant

·CCN Time Schedules for all chillers must be identical

Operation Features:

·2 chiller lead/lag

·addition of a third chiller for backup

·manual rotation of lead chiller

·load balancing if con®gured

·staggered restart of the chillers after a power failure

·chillers may be piped in parallel or in series chilled water ¯ow

COMMON POINT SENSOR INSTALLATION Ð Lead/ lag operation does not require a common chilled water point sensor. Common point sensors can be added to the 8-input option module, if desired. Refer to the certi®ed drawings for termination of sensor leads.

NOTE: If the common point sensor option is chosen on a chilled water system, each chiller should have its own 8-input option module and common point sensor installed. A chiller uses its own common point sensor for control when that chiller is designated as the lead chiller. The PIC cannot read the value of common point sensors installed on other chillers in the chilled water system.

When installing chillers in series, use a common point sen- sor. If a common point sensor is not used, the leaving chilled water sensor of the upstream chiller must be moved into the leaving chilled water pipe of the downstream chiller.

If return chilled water control is required on chillers piped in series, the common point return chilled water sensor should be installed. If this sensor is not installed, the return chilled water sensor of the downstream chiller must be relocated to the return chilled water pipe of the upstream chiller.

To properly control the common supply point temperature sensor when chillers are piped in parallel, the water ¯ow through the shutdown chiller(s) must be isolated so there is no water bypass around the operating chiller. The common point sen- sor option must not be used if water bypass around the op- erating chiller is occurring.

CHILLER COMMUNICATION WIRING Ð Refer to the chiller Installation Instructions and the Carrier Comfort Net- work Interface section on page 53 of this manual for infor- mation on chiller communication wiring.

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