User`s manual

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42
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Tabl e 22 — Durablade Economizer Service Analysis (cont)
LEGEND
PROBLEM CAUSE REMEDY
Damper does not close.
Incorrect wiring of economizer. 1. Verify that SW2 and SW4 are wired and working prop-
erly (see unit label diagram).
2. Check diode D18. If diode is not functioning properly,
replace economizer control board.
Verify economizer control board
is functioning properly.
1. After verifying that the wiring is correct, modulate the
damper to the minimum position. Remove the calls
for G.
2. If the damper does not move, check for 24 vac at PL6-1
(red wire). If 24 vac is not present, check wiring (see
unit label diagram).
3. If damper still does not move, check for 24 vac at blue
terminal of economizer control board (blue wire). If
24 vac is not present, replace the economizer circuit
board.
Check SAT. 1. After verifying that the wiring is correct and the econo-
mizer control board is functioning properly, place the
OAT or EC switch in the closed position. Place a call for
Y1 and open the damper to the fully open position.
Confirm that the 24 vac terminal of the SAT has 24 vac
(white wire). If 24 vac is not present, check wiring (see
unit label diagram).
2. If supply-air temperature is less than 52 F, 24 vac
should be found at terminal T1 on the SAT (violet wire).
If 24 vac not found, replace SAT.
Economizer motor failure. If economizer control board and SAT are functioning prop-
erly, verify that there is a minimum of 18 vdc at the pos-
itive motor terminal. If a minimum of 18 vdc is present and
the motor is still not operating, replace the motor.
Economizer damper does not
close on power loss.
Verify that close-on-power-loss
and economizer control board
are functioning properly.
1. Check voltage potential across batteries. If lower than
14 vdc, replace close-on-power-loss power supply
(9-v alkaline batteries). It is recommended that you
check this emergency power supply on a regular basis
or whenever the filters are changed.
2. If the close-on-power-loss and economizer control
board are functioning properly, check for 14 vdc or
higher at the blue terminal of the economizer control
board (blue wire) when power is disconnected from
unit. If 14 vdc is not present, replace the control
board.
C1 —
Common Power
EC —
Enthalpy Control
IFC —
Indoor (Evaporator) Fan Contactor
IFO —
Indoor (Evaporator) Fan On
OAT —
Outdoor-Air Thermostat
PL —
Plug
SAT —
Supply-Air Thermostat
SW —
Economizer Position Switch