Armstrong Air Conditioning 4HP14 Instruções de instalação e arranque - Página 9

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DEFROST BOARD PRESSURE SWITCH

CONNECTIONS

The unit's automatic reset pressure switches (LO PS -

S87 and HI PS - S4) are factory-wired into the defrost board

on the LO-PS and HI-PS terminals, respectively.

(OPTIONAL) Low Pressure Switch (LO-PS) — When the

low pressure switch trips, the defrost board will cycle off the

compressor, and the strike counter in the board will count

one strike. The low pressure switch is ignored under the

following conditions:

! during the defrost cycle and 90 seconds after the

termination of defrost

! when the average ambient sensor temperature is below

15° F (-9°C)

! for 90 seconds following the start up of the compressor

! during "test" mode

High Pressure Switch (HI-PS) — When the high pressure

switch trips, the defrost board will cycle off the compressor,

and the strike counter in the board will count one strike.

DEFROST BOARD PRESSURE SWITCH SETTINGS

High Pressure (auto reset) - trip at 590 psig; reset at 418.

Low Pressure (auto reset) - trip at 25 psig; reset at 40.

5-STRIKE LOCKOUT FEATURE

The internal control logic of the board counts the pressure

switch trips only while the Y1 (Input) line is active. If a

pressure switch opens and closes four times during a Y1

(Input), the control logic will reset the pressure switch trip

counter to zero at the end of the Y1 (Input). If the pressure

switch opens for a fifth time during the current Y1 (Input),

the control will enter a lockout condition.

The 5-strike pressure switch lockout condition can be

reset by cycling OFF the 24-volt power to the control board

or by shorting the TEST pins between 1 and 2 seconds. All

timer functions (run times) will also be reset.

If a pressure switch opens while the Y1 Out line is

engaged, a 5-minute short cycle will occur after the switch

closes.

DEFROST SYSTEM SENSORS

Sensors connect to the defrost board through a field–

replaceable harness assembly that plugs into the board.

Through the sensors, the board detects outdoor ambient,

coil, and discharge temperature fault conditions. As the

detected temperature changes, the resistance across the

sensor changes. Sensor resistance values can be checked

by ohming across pins .

506318-01

Sensor Temp. / Resistance Range

Temperature

Sensor

Range °F (°C)

Outdoor

-35 (-37 to 120

(Ambient)

(48)

-35 (-37) to 120

Coil

(48)

Discharge (If

24 (-4) to 350

applicable)

(176)

Note: Sensor resistance decreases as sensed temperature increases.

NOTE - When checking the ohms across a sensor, be

aware that a sensor showing a resistance value that is

not within the range shown, may be performing as

designed. However, if a shorted or open circuit is

detected, then the sensor may be faulty and the sensor

harness will needs to be replaced.

Coil Sensor—The coil temperature sensor considers

outdoor temperatures below -35°F (-37°C) or above 120°F

(48°C) as a fault. If the coil temperature sensor is detected

as being open, shorted or out of the temperature range of

the sensor, the board will not perform demand or time/

temperature defrost operation and will display the

appropriate fault code. Heating and cooling operation will

be allowed in this fault condition.

Issue 0946

Pins/Wire

Red Led (DS1)

Color

3 & 4

280,000 to 3750

(Black)

5 & 6

280,000 to 3750

(Brown)

1 & 2

41,000 to 103

(Yellow)

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