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24
Dehumidification of Fresh Air with DCV Control — Infor-
mation from AHSRAE indicates that the largest humidity load
on any zone is the fresh air introduced. For some applications,
a device such as a 62AQ energy recovery unit is added to re-
duce the moisture content of the fresh air being brought into the
building when the enthalpy is high. In most cases, the normal
heating and cooling processes are more than adequate to re-
move the humidity loads for most commercial applications.
This makes the control of the of the dehumidification device
simple when using the enthalpy or differential enthalpy sensor.
The enthalpy sensor or differential enthalpy sensor is installed
on the equipment to determine economizer operation. The high
enthalpy signal from the enthalpy sensor or differential en-
thalpy sensor can be used to turn on the outdoor air moisture
removal device any time fresh air is required for the space.
The energy recovery device should be sized for maximum
latent and sensible conditioning at maximum ventilation on a
design day. A calculation for leaving-air temperature on a low
ambient, low ventilation day should also be done to determine
the mixed-air temperature of the return and pre-conditioned
outside air. The design should produce air temperature some-
what near room conditions to prevent reheat of the air mixture.
The energy recovery device should be interlocked with the heat
to turn off the device when in the heat mode.
Fig. 33 — Remote Damper Position
Potentiometer Wiring
+
+
+
+
-
-
2-10V
OUT
RED
BLACK
WHITE
24 VAC HOT
TR
BLACK
BROWN
BROWN
BLACK
BLACK
GRAY
BLUE
YELLOW
VIOLET
VIOLET
VIOLET
PINK
PINK
RED
WHITE
WHITE
BROWN
ORANGE
620 OHM
RESISTOR
820 OHM
RESISTOR
SO
5
1
3
1K
1S
1S1
2K
2
4
T
P
P1
Q
Q1
AQ
SD1
SHUTDOWN
FIRE AND SMOKE CONTROL
AIR CHANGE
PURGE
SD
AC
AC1
PG
PG1
ECONOMISER2
DRY BULB
SENSOR
Compressor Lockout N.C.
YELLOW
GRAY
BLUE
TAN
INDOOR
FAN
EXHAUST
FAN
UNIT
CONTROL
FREE
COOL
MAXIMUM
POSITION
ADJUSTMENT
HARNESS
AND PLUG
MINIMUM
POSITION
ADJUSTMENT
AQ1
T1
SR
TR1
24 VAC COM
ECONOMISER2 CONTROLLER
ACTUATOR
4
3
5
2
8
6
7
1
10
11
9
12
}
ECONOMISER2
Fig. 34 — Fire and Smoke Control Wiring
Summary of Contents for 48TF004-007
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