Carrier PC211 Spécifications télécharger pdf (Page 67)

water temperature to save on compressor kilowatt

requirements but, not be below 55 F (12.8 C).

6. Cooler pressure and temperature also will vary with

the design conditions. Typical pressure range will be

between 60 and 80 psig (410 and 550 kPa) [30 to

40 psig (204 to 260 kPa)] with temperature ranging

between 34 and 45 F (1 and 8 C).

7. The compressor may operate at full capacity for a short

time after the pulldown ramping has ended, even

though the building load is small. The active electrical

demand setting can be overridden to limit the compres-

sor IkW, or the pulldown rate can be decreased to

avoid a high demand charge for the short period of

high demand operation. Pulldown rate can be based on

load rate or temperature rate. It is accessed on the

Equipment SERVICE screen, RAMP_DEM table

(Table 3, Example 20).

To Stop the Chiller

1. The occupancy schedule starts and stops the chiller

automatically once the time schedule is configured.

2. By pressing the STOP button for one second, the alarm

light blinks once to confirm the button has been

pressed. The compressor will then follow the normal

shutdown sequence as described in the Controls sec-

tion. The chiller will not restart until the or

softkey is pressed. The chiller is now in the

OFF control mode.

If the chiller fails to stop, in addition to action that the

PIC will initiate, the operator should open the slide

valve to reduce chiller load by overriding the slide

valve count to –20. Then, the operator should open the

main disconnect.

Do not restart the chiller

until the problem is diagnosed and

corrected.

After Limited Shutdown —

No special preparations

should be necessary. Follow the regular preliminary checks and

starting procedures.

Preparation for Extended Shutdown —

The

refrigerant should be transferred into the pumpout storage tank

(if supplied; see Pumpout and Refrigerant Transfer Procedures)

to reduce chiller pressure and the possibility of leaks. Maintain

a holding charge of 5 to 10 lbs (2.27 to 4.5 kg) of refrigerant or

nitrogen to prevent air from leaking into the chiller.

If freezing temperatures are likely to occur in the chiller

area, drain the chilled water, condenser water, and the pumpout

condenser water circuits to avoid freeze-up. Keep the waterbox

drains open.

Leave the oil charge in the chiller with the oil heater and

controls energized to maintain the minimum oil reservoir

temperature.

After Extended Shutdown —

Ensure the water sys-

tem drains are closed. It may be advisable to flush the water

circuits to remove any soft rust which may have formed. This

is a good time to brush the tubes and inspect the Schrader fit-

tings on the waterside flow devices for fouling, if necessary.

Check the cooler pressure on the CVC default screen and

compare it to the original holding charge that was left in the

chiller. If (after adjusting for ambient temperature changes) any

loss in pressure is indicated, check for refrigerant leaks. See

Check Chiller Tightness section, page 49.

Recharge the chiller by transferring refrigerant from the

pumpout storage tank (if supplied). Follow the Pumpout and

Refrigerant Transfer Procedures section, this page. Observe

freeze-up precautions.

Carefully make all regular preliminary and running system

checks. Perform a Control Test before start-up. If the oil level

appears abnormally high, the oil may have absorbed refriger-

ant. TD frame 4 chillers are able to start with an abnormally

high oil level. Ensure that the oil temperature is above refriger-

ant temperature plus 35º F (19º C) (TC frame 1 and 2 chillers

only).

NOTE: TD frame 4 chillers do not have an oil heater.

Cold Weather Operation —

When the entering con-

denser water drops very low (55 F [13 C] minimum), the oper-

ator should automatically cycle the cooling tower fans off to

keep the temperature up. Piping may also be arranged to by-

pass the cooling tower. The PIC II controls have a low limit

tower fan output that can be used to assist in this control (termi-

nal 11 and 12 on ISM).

Slide Valve Operation —

Manual operation of the

slide valve to check control operation, or to control the valve in

an emergency operation, is possible by overriding the manual

slide valve count. Access the Status COMPRESS table on the

CVC and highlight

MANUAL SLIDE VALVE

. To control slide

valve movement, enter a desired count value. The

MANUAL

SLIDE VALVE LOAD/UNLOAD

has an allowable input range

of plus or minus 10 to provide up to 10 seconds of slide valve

movement in the selected direction. If the counts are positive

then the slide valve position will increase to load the compres-

sor and vice versa. To release the valve to PIC II control press

the softkey.

NOTE: The valve can be increased with manual control to

override the pulldown rate during start-up. However, motor

current above the electrical demand setting, capacity overrides,

and chilled water below control point will override the manual

count and decrease the slide valve position. For descriptions of

capacity overrides and set points, see the Controls section.

Entering a 0 count value will cause the slide valve to main-

tain a HOLD state. In this condition, the slide valve will re-

spond to maintain the chilled water (

∆

T) temperature when the

override occurs.

Refrigeration Log —

A refrigeration log, such as the

one shown in Fig. 37, provides a convenient checklist for rou-

tine inspection and maintenance, and provides a continuous

record of chiller performance. It is an aid in scheduling routine

maintenance and in diagnosing chiller problems.

Keep a record of the chiller pressures, temperatures, and liq-

uid levels on a sheet similar to that shown. Automatic record-

ing of PIC II data is possible through the use of CCN devices

such as the Data Collection module and a Building Supervisor.

Contact your Carrier representative for more information.

IMPORTANT: Do not attempt to stop the chiller by

opening an isolating knife switch. High intensity arcing

may occur.

CCN

LOCAL

RELEASE

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