65
Fig. 98 — SCR Control Electric Heat
ENERGY RECOVERY VENTILATOR CONTROL
The 62XC,XD units can be equipped with an optional enthalpy
type Energy Recovery Ventilator (ERV). ERV operation is en
-
abled whenever the unit is in occupied mode. See the Operation
section of this manual for ERV operating sequence.
VFD Defrost
The ERV may be equipped with a VFD for frost control. The VFD
will slow the rotating speed (45 RPM) to the configured minimum
speed (10 RPM) when the temperature of the return air coming off
the wheel (WExAT) is equal to or less than 25°F (configurable in
the VFD controller). Slowing the wheel with inhibit the formation
of frost. Refer to the VFD section for additional information on
the VFD.
NOTE: The variable speed defrost control slows down the speed
of the wheel to reduce its effectiveness and keeping the return air
from getting fully saturated which can lead in condensation of the
wheel and possible frosting.
The 25°F default setpoint does not cover the whole range of appli
-
cations where frosting may occur. Under certain conditions (high
R.H. % from the return air and very low OA DB temperatures)
frosting may occur even below the default setpoint.
This setpoint MUST be adjusted to ensure that the return air when
cooled down by the ERV does not reach its dew point temperature.
The Heat source must be sized accordingly to account for reduc
-
tion in capacity for applications where the unit will enter in defrost
mode.
ERV Maintenance
BEARINGS
All units will be equipped with permanently lubricated inboard
bearings. These bearings should require no maintenance for the life
of the equipment. If the ERV is equipped with external flanged
bearings, lubricate annually with a petroleum based lubricant.
ERV MOTOR
Verify motor alignment and electrical connections.
BELT
Check motor alignment, belt tension and wear. Replace belt as re
-
quired.
VFD
Check electrical connections, tighten as required.
BYPASS
Check operation for binding, lubricate as required. Check actuator
electrical connections.
FILTERS
Replace as required.
W
C
TO UNIT
CONTROL
CIRCUIT
TERMINAL
BLOCK
24V CIRCUIT
TERMINAL
BLOCK
HEATER
RELAY
MAIN
TERMINAL
BLOCK
GROUND
GROUND
L1
L2
L3
3 PHASE
60 CPS
SUPPLY
TRANSFORMER
YELLOW
SCR CONTROLLER
POWER TO
FAN MOTOR
BLUE
MANUAL
RESET
LIMIT
AIR PRESSURE
SWITCH
LIMIT
SWITCH
HEA
TER
ELEMENTS
SEE MANUAL FOR
INPUT SIGNAL
WIRING
YELLOW
YELLOW
YELLOW
BLUE
BLUE
PURPLE
3 2 1
TERMINAL
BLOCK
0-10
VDC
INPUT
SIGNAL
+
–
