Carrier 16JB Manuel d'utilisateur télécharger pdf (Page 21)

Control sequence

To start: Local start-up(manual start-up)is initiatedby press-

ing the LOCAL menu softkey which is indicated on the de-

fault local interface device (LID) screen. All pre-start safeties

are checked to verify that all pre-start alerts and safeties are

within limits. If one is not, an indication of the fault will be

displayed and the start is aborted. The signal is sent to start

the chilled water pump. Five seconds later, the condenser

water pump is energized. Thirty seconds later, the controls

check to see if ﬂow has been conﬁrmed by the closure of

the chilled water and condenser water ﬂow switches. If ﬂow

is not conﬁrmed, the controls continue to monitor ﬂows for

a maximum of 5 minutes. If ﬂow is conﬁrmed, the controls

checkthe chilledwater temperatureagainst thecontrol point.

If the temperature is less than or equal to the chilled water

control point, the condenser water pump turns off and the

controls go into a recycle mode.

If the water/brine temperature is high enough, the start-

up sequence continues and starts the solution pump. Once

the pump starts, the controls look for and verify that the

solution pump pressure is greater than 10 psig (67 kPa). If

the pump pressure is not veriﬁed in 2 minutes, the start-up

procedure is terminated and a solution pump pressure fault

is displayed. After solution pump pressure is veriﬁed, the

controls go into the warm-up period.

The refrigerant pump is energized and the steam control

valve slowly opens to 50%. The initial steam control valve

position for warm-up can be adjusted. The controls moni-

torthe strongsolution temperaturefromthe generator.When

this temperature reaches 158 F (70 C) and there is a tem-

perature difference across the evaporator, the controls go

into ramp loading. If both conditions are not met in

20 minutes, the unit will shut down on a solution warm-up

fault.

Once started: The controls enter the ramp loading mode

to slowly open the steam control valve to prevent a rapid

increase in boiler demand. Once ramp loading is com-

pleted, the controls enter the capacity control mode. Any

failure that results in a safety shutdown immediately acti-

vates the dilution cycle, closes the steam control valve at its

maximum rate of travel, activates the alarm light and relay,

displays the fault that occurred, and updates the alarm his-

tory log.

Shutdown sequence: Chiller shutdown can occur if any

of the following events happen:

• The Stop button is pressed for at least one second

• A recycle shutdown is initiated

• Time schedule has gone into Unoccupied mode

• Machine protective limit has been reached and chiller is

in alarm

• The start/stop status is overridden to stop from the CCN

network or the LID

Once thecontrols are placedin shutdown mode,the shut-

down sequence closes the steam control valve. The soft-

ware then initiates a 15-minute dilution cycle to lower the

concentration of the solution and equalize chiller tempera-

tures. Solution pump ontime and service ontime stops. The

condenser and chilled water pumps stop.

Restart: Restart is permitted after the dilutioncycleis com-

pleted and there is a need for chilled water. If the shutdown

was due to a safety shutdown, the reset button must be de-

pressed before restarting the chiller.

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Carrier 16JB Manuel d'utilisateur Page 21

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