Fig. 22 - Cv Space Sensor Cooling Al Go Rithm; - Econ O Miz Er Not Suitable; Fig. 23 - Cv Space Sensor Cooling Algorithm - York eco2 050 Installation Operation & Maintenance

Sensor with Unoccupied Override Button – This Sen sor
has a RTD and an Override button that shorts the Sen-
sor when pushed. After the Over ride button has been
pushed for a minimum of one sec ond the unit will go
into the Unoccupied Override mode for the Un oc cu pied
Override Time . The Override mode is cleared if the
unit goes Occupied during this Over ride mode.
Sensor with Space Setpoint Adjust – This Sensor
has a slider potentiometer on it that rep re sents (as a
de fault) ± 3°F adjustment to the Space Setpoint. The
Space Setpoint Offset Setpoint speciÞ es the amount of
± ad just ment, in range from 0°F to 5°F.
Sensor w/ Space Setpoint Adjust and Unoccupied Over-
ride Button – This Sensor has a slider po ten ti om e ter and
an Un oc cu pied Override button. Both func tions operate
as de scribed above.
Cooling Operation with a Space Sensor
For cool ing operation, the space temperature will be
controlled to either the:
• Unoccupied Cooling Setpoint or the
• Occupied Cooling Setpoint based on the Oc cu pied/
Un oc cu pied state of the unit (i.e. Occ/Unocc In put,
or Internal Scheduling).
Control Algorithm For Space Sensor Cooling
– Econ o miz er Not Suitable
The Space Sensor Cooling control algorithm is as il lus -
trat ed in Figure 22.
Compressor
Stays OFF
OFF-Time
OFF-Time
(minutes)
Min.
ON-Time
(6 minutes)
0%
Output of Cooling Zone
Temp. Control (PI)
Low Saturation
FIG. 22 – CV SPACE SENSOR COOLING
AL GO RITHM - ECONOMIZER
NOT SUIT ABLE
YORK INTERNATIONAL
Compressor
Stays ON
ON-Time
On-Time
(minutes)
Min.
OFF-Time
(6 minutes)
100%
High Saturation
LD06553
• A direct acting, proportional – in te gral space tem-
per a ture controller generates a 0 – 100% output
signal that responds to space cooling demand.
• The output of the controller is used to cal cu late on
and off time of the compressor most re cent ly start ed
based on the calculation method in Fig ure 22.
• PI gain values are to be determined by such that
all compressors are on within 28 minutes with a
10°F space temperature error; or 42 minutes for a
6-compressor system with a 10°F space temp. er-
ror.
• When the duty cycle reaches 100% (the PI al go rithm
reaches a "High Saturation state" and a sat u ra tion
time delay expires), the modulated com pres sor stops
cycling and remains on.
• An additional compressor is staged every time the
space control PI al go rithm reach es a High Sat u -
ra tion state and a programmed saturation time delay
expires.
• A compressor is destaged when the PI al go rithm
reach es a Low Saturation state and a pro grammed
sat u ra tion time delay expires.
Control Algorithm For Space Sensor Cooling -
Econ o miz er Suitable
In CV cooling operation with a space sensor and when
free cooling is available ("economizer suitable"), the
SAT is controlled by the economizer control algorithm
(see page 53; Economizer Operation). The con trol
al go rithm is shown in Figure 23 (see section on Econ-
o miz er Op er a tion for a more speciÞ c explanation on
econ o miz er operation).
E conomizer 2nd
S tage S AT
S etpoint
E conomizer
1s t S tage S AT
S etpoint
S pace S atis fied
(Des taging S AT
S etpoint) -1.5°F
S pace T emperature Deviation F rom S etpoint (°F )
FIG. 23 – CV SPACE SENSOR COOLING
ALGORITHM - ECONOMIZER
SUITABLE
FORM 100.50-NOM1 (604)
+0.5°F +2.0°F
S pace T emperature
S etpoint F or C ooling
LD06554A
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