Stage Reciprocating Chiller - T775L - Honeywell T775 Series Application Manual And Cross Reference

T775 SERIES 2000 ELECTRONIC STAND-ALONE CONTROLLERS
3 Stage Reciprocating Chiller – T775L
Application Description
The T775L is controlling the return water in a reciprocating
chiller with fast-dump freeze protection, low temperature
cutoff, and optional low pressure cutoff.
Sensor Designation
This device application requires two sensors.
• Sensor A is sensing return water and controlling three
stages of cooling.
• Sensor B is sensing discharge water and is controlling
relay 4 for freeze protection.
Operation
Return water is one indication of the cooling load in the water
loop. For example, the higher the return water temperature
the higher the apparent load and more stages of refrigeration
or cooling would be required. If a large load is quickly dropped
from the loop, or for some reason water flow through the
chiller is reduced, discharge water temperature may drop
rapidly to freezing conditions. In this example, Sensor B in the
discharge water will prevent damage to the system by fast-
dumping all cooling stages upon close-to-freezing conditions.
Programming Example
Program in Setup:
Press and hold the MENU button for 5 seconds to enter
Setup mode. Select the Outputs menu, and then select:
— # Relays = 3
— # Loops = 1
→
— Options DI Options = Disable
(acts as low pressure cutoff)
→
— Loop 1 # Relays = 3
→
— Loop 1 Reset = NO
Loop 1: Chiller cooling
Program for:
— Setpoint = 62° F (17° C)
— Throttling Range = 12° F (-11° C)
— Sensor A
— Cool
Relay 4: Low temperature cutoff for freeze protection
Program for:
— Setpoint = 40° F (4° C)
— Differential = 4° F (-16° C)
— Sensor B
— Heat
IMPORTANT
After the desired value is selected, be sure to press
the # or $ or HOME button in order to save that
value in the controller's memory.
Wiring
All output relays should have a common power wiring source,
which may or may not be the same as the T775 power wiring.
63-7147—3
SENSOR A
(RETURN WATER)
SENSOR B
(DISCHARGE
WATER)
DIGITAL INPUT
(LOW PRESSURE
CUTOFF)
L1 (HOT)
L2
COOL #1
COOL #2
COOL #3
1 POWER WITH 24 VAC OR 120/240 VAC AT THE APPROPRIATE TERMINAL BLOCK.
2 24 VAC POWER TERMINAL BLOCK.
Fig. 29. T775L Wiring - Reciprocating Chiller.
STAGE 3 ON
STAGE 2 ON
STAGE 1 ON
-33%
58°F
1
STAGE ENERGIZES
CHILLER DISCHARGE WATER TEMPERATURE
1
Fig. 30. Chiller Control Staging Behavior (when the
effective setpoint = 62° F (17° C)).
24
T
T
T775L
T
T
2
C
RELAY RELAY
4 3
NC NC
C C
NO NO
NO NO
C C
NC NC
RELAY RELAY
1 2
STAGES
HYST.
STAGE 3
STAGE 2
STAGE 1
0% 33% 67%
62°F 66°F 70°F
THROTTLING RANGE (12°F)
STAGE DE-ENERGIZES
1
120 VAC
COM
M25514
M13895