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79
Fig. 11 —
Custom Changeover Curve Example
UNOCCUPIED ECONOMIZER FREE COOLING
This “Free Cooling” function is used to start the supply fan and
use the economizer to bring in outside air when the outside
temperature is cool enough to pre-cool the space. This is done
to delay the need for mechanical cooling when the system en
-
ters the occupied period. Once the space has been sufficiently
cooled during this cycle, the fan will be stopped.
In basic terms, the economizer will modulate in an unoccupied
period and attempt to maintain space temperature to the “occu
-
pied” cooling set point. This necessitates the presence of a
space temperature sensor.
Configuring the economizer for Unoccupied Economizer Free
Cooling is done in the
UEFC
group, with 3 configuration op
-
tions,
FC.CF
,
FC.TM
, and
FC.LO
.
Unoccupied Economizer Free Cooling Configuration
(FC.CF)
This option is used to configure the “type” of unoccupied econ
-
omizer free cooling control that is desired.
0 = disable unoccupied economizer free cooling
1 = perform unoccupied economizer free cooling as available
during the entire unoccupied period.
2 = perform unoccupied economizer free cooling as available,
FC.TM
minutes before the next occupied period.
Unoccupied Economizer Free Cooling Time Configuration
(FC.TM)
This option is a configurable time period, prior to the “next oc
-
cupied period,” that the control will allow unoccupied econo
-
mizer free cooling to operate. This option is only applicable
when
FC.CF
= 2.
Unoccupied Economizer Free Cooling Lockout Temperature
(FC.LO)
This configuration option allows the user to select an outside
air temperature, below which unoccupied free cooling is disal
-
lowed. This is further explained in the logic section.
Unoccupied Economizer Free Cooling Logic
Unoccupied free cooling can only operate with the qualifications:
• Unit configured for an economizer
• Unit in the unoccupied mode
•
FC.CF
set to 1 or
FC.CF
set to 2 and within
FC.TM
min
-
utes of the next occupied period
• Not in the Temperature Compensated Start Mode
• Not in a cooling mode
• Not in a heating mode
• Not in a tempering mode
• Space temperature sensor enabled and sensor reading healthy
• Outside air temperature sensor healthy
• The economizer would be allowed to cool if the fan were
requested and in a cool mode.
•
OAT
>
FC.LO
(1.0 dF hysteresis applied)
• The rooftop is not in a fire smoke mode
• No fan failure when configured to shut the unit down on a
fan failure
If all of the above conditions are satisfied:
Unoccupied Economizer Free Cooling shall start when both of
the following conditions are true:
{SPT > (OCSP + 2)} AND {SPT > (OAT + 8)}
The Night Time Free Cooling Mode shall stop when either of
the following conditions are true:
{SPT < OCSP} OR {SPT < (OAT + 3)}
…where SPT = Space Temperature and OCSP = Occupied
Cooling Setpoint
When the Unoccupied Economizer Free Cooling mode is ac
-
tive, the supply fan is turned on and the economizer damper
modulated to control to the supply air set point (
Set
-
points
SASP
) plus any supply air reset that may be applied
(
Inputs
RSET
SA.S.R
).
35
40
45
50
55
60
65
35
40
45
50
55
60
65
10
15
70
75
80
85
70
75
80
85
90
95 100
105 110 115
20
25
30
35
40
45
50
10%
20%
30%
40%
50%
60%
70%
80%
90%
ENTHALPY
REL
ATIVE HUMIDITY
DEWPOINT
TEMPERA
TURE
E
R
U
T
A
R
E
P
M
E
T
B
L
U
B
Y
R
D
Содержание WeatherExpert 48N2
Страница 135: ...135 Fig 18 48 50N Typical Power Schematic Nominal 075 Ton Unit Shown ...
Страница 136: ...136 Fig 19 48 50N Typical Power Schematic Nominal Ton 90 150 Units Shown ...
Страница 137: ...137 Fig 20 48 50N Main Base Board Input Output Connections ...
Страница 138: ...138 Fig 21 48 50N RXB EXB CEM Input Output Connections a48 9307 ...
Страница 139: ...139 Fig 22 48 50N EXV SCB Input Output Connections a48 9308 ...
Страница 140: ...140 Fig 23 48N Typical Modulating Gas Heat Unit Control Wiring ...
Страница 141: ...141 Fig 24 50N Typical Electric Heat Unit Control Wiring ...
Страница 144: ...144 Fig 27 48N Typical Gas Heat Section Wiring Nominal Ton 120 to 150 Units ...
Страница 145: ...145 Fig 28 48 50N Typical Power Component Control Wiring 460 v ...
Страница 146: ...146 Fig 29 48 50N Component Control Wiring 575 v Nominal Ton 075 to 150 Units ...
Страница 147: ...147 Fig 30 48 50N Component Arrangement Power Box ...
Страница 148: ...148 Fig 31 48 50N Component Arrangement Control Box ...
Страница 168: ...168 Fig 47 Sensor and Ignition Position Fig 48 Combustion Blower Details SENSOR DETAILS IGNITION DETAILS ...
Страница 240: ...240 APPENDIX D VFD INFORMATION CONT Fig G VFD Bypass Wiring Diagram WHEN USED ...