25
Econo Max
Position
(DAMPMAX)
Damper Position
Indoor Fan Speed
Maximum Speed
(SPEEDMAX)
10%
MINP_
MAX
(MP_SPD3,
MP_POS3)
(MP_SPD2,
MP_POS2)
(MP_SPD1,
MP_POS1)
Key
:
Minimum Position Curve
IAQPMAX
(AQP_SPD3,
AQP_POS3)
(AQP_SPD2,
AQP_POS2)
(AQP_SPD1,
AQP-POS1)
IAQ Purge Position Curve
IAQMINP
(AQ_SPD3,
AQ_POS3)
(AQ_SPD2,
AQ_POS2)
(AQ_SPD1,
AQ_POS1)
IAQ Minimum Position Curve
C14326
Fig. 19 -- Minimum Damper Position Curves
Whe n the econom i zer is available for free cooling (OK TO FREE
COOL? = Yes) and the compr ess i on is not on, the dam per will st art
opening from the damper’ s minimum Position in Effect
(EFFECTI VE MIN POS) based on the suppl y ai r temperature
(SUPPL Y AIR TEMP) to provide free cool i ng. A low cooling
dem and (DEMAND = LOW COOL) will utilize the Low Free
Cooli ng SAT Setpoint (LOW COOL SA T SP) as the Free Cooling
Setpoint (FREECOOL SAT SP) to control the ec onom izer. A
me dium or high c ool ing demand (DEMAND = MED COOL or
HIGH COOL) will utilize the High Free Cooling SAT Setpoint
(HI GH COOL SAT SP) as the Fre e Cooli ng Setpoint (FREECOOL
SAT SP) to contr ol the economiz er.
During free cooling the fan will start at the dedicated free cooling
speed (FREE COOL IDF SPD). After the economizer (ECON
CMD POSITION) reaches 100% (or Max) for 5 minutes, the fan
will be changed to the High Cool Speed (HIGH COOL IDF
SPD). When a high cooling demand (DEMAND = HIGH COOL)
is active the control will use the High Cool Speed (HIGH COOL
IDF SPD). The compressor will be allowed for use after the fan
and economizer are 100% (or Max) for 5 minutes. Once
compression is turned on the economizer and fan will remain at
100% until the call for cooling is removed or until the unit is no
longer allowed to free cool (OK TO FREE COOL = No).
Dry Bulb Lockout
Dry Bulb Lockout (DRY BULB LOCKOUT) occurs when any of
the following are true:
S The Out door Air Te m per ature (OUTDOOR AIR TEMP) is invalid.
S When Differential Dry Bulb Control is disabled (DIFF DRY
BULB CTL = Disable) and the Outdoor Air Temperature
(OUTDOOR AIR TEMP) is greater than the configured Free
Cooling Maximum Temperature (FREE COOL MAX OAT) or
less than the configured Free Cooling Minimum Temperature
(FREE COOL MIN OAT).
S When Differential Dry Bulb Control is enabled (DIFF DRY
BULB CTL = Enable) and the return air temperature (RETURN
AIR TEMP) plus the Differential Dry Bulb deadband (DIFF
DB DEADBAND) is lower than the outdoor air temperature
(OUTDOOR AIR TEMP).
Enthalpy Lockout
The control uses the Outdoor Air Temperature (OUTDOOR AIR
TEMP), Outdoor Relative Humidity (OARH LEVEL),and
Barometric Pressure (BAROMETRIC PRESS) to calculate the
Outdoor Enthalpy (OUTDOOR ENTHALPY). The control uses
the Return Air Temperature (RETURN AIR TEMP),Return
Relative Humidity (RARH LEVEL), and Barometric Pressure
(BAROMETRIC PRESS) to calculate the Return Enthalpy
(RETURN ENTHALPY). Enthalpy Lockout (ENTHALPY
LOCKOUT) occurs when any of the following are true:
S When Differential Enthalpy Control is disabled (DIFF
ENTHALPY CTL = Disable) and the outdoor enthalpy
(OUTDOOR ENTHALPY) is greater than the Maximum
Outdoor Enthalpy limit (ENTHALPY HI LIMIT).
S When Differential Dry Bulb Control is enabled (DIFF DRY
BULB CTL = Enable) and the outdoor enthalpy (OUTDOOR
ENTHALPY) is greater than the return enthalpy (RETURN
ENTHALPY). The Differential Enthalpy deadband
(ENTHALPY DEADBAND) is use in the case of unlocking the
Enthalpy lockout (ENTHALPY LOCKOUT).
S The Enthalpy switch input (ENTHALPY SWITCH) is reading
high.
Unoccupied Free Cooling Lockout
Unoc c upied Free Cooling lockout (UFC LOCKOUT?) occurs when
the unit is in the unoccupied per iod (OCCUPIED NOW? = No) and
the Outdoor Air Te m perat ure (OUTDOOR AIR TEMP) is less than
the Unoccupied Free Cooling low tempera t ure (UFC LOW TEMP) .
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