- ページ 16

ヒートポンプ Allied 4SHP16のPDF 取付説明書をオンラインで閲覧またはダウンロードできます。Allied 4SHP16 19 ページ。 Single stage heat pump

ページを印刷する

Operational Description

The defrost control board has three basic operational

modes: normal, calibration, and defrost.

Normal Mode—The demand defrost board monitors the O

line, to determine the system operating mode (heat/cool),

outdoor ambient temperature, coil temperature (outdoor

coil) and compressor run time to determine when a defrost

cycle is required.

Calibration Mode—The board is considered uncalibrated

when power is applied to the board, after cool mode

operation, or if the coil temperature exceeds the termination

temperature when it is in heat mode.

Calibration of the board occurs after a defrost cycle to

ensure that there is no ice on the coil. During calibration,

the temperature of both the coil and the ambient sensor

are measured to establish the temperature differential

which is required to allow a defrost cycle.

Defrost Mode—The following paragraphs provide a

detailed description of the defrost system operation.

Detailed Defrost System Operation

Defrost Cycles—The demand defrost control board

initiates a defrost cycle based on either frost detection or

time.

•

Frost Detection—If the compressor runs longer than

30 minutes and the actual difference between the

clear coil and frosted coil temperatures exceeds the

maximum difference allowed by the control, a defrost

cycle will be initiated.

IMPORTANT - The demand defrost control board will

allow a greater accumulation of frost and will initiate

fewer defrost cycles than a time/ temperature defrost

system.

•

Time—If 6 hours of heating mode compressor run time

has elapsed since the last defrost cycle while the coil

temperature remains below 35°F (2°C), the demand

defrost control will initiate a defrost cycle.

Actuation—When the reversing valve is de-energized, the

Y1 circuit is energized, and the coil temperature is below

35°F (2°C), the board logs the compressor run time. If the

board is not calibrated, a defrost cycle will be initiated after

30 minutes of heating mode compressor run time. The

control will attempt to self-calibrate after this (and all other)

defrost cycle(s).

Page 16 of 19

Calibration

success

temperatures during the 20-minute calibration period. If

the board fails to calibrate, another defrost cycle will be

initiated after 45 minutes of heating mode compressor

run time. Once the defrost board is calibrated, it initiates

a demand defrost cycle when the difference between

the clear coil and frosted coil temperatures exceeds the

maximum difference allowed by the control OR after 6

hours of heating mode compressor run time has been

logged since the last defrost cycle.

NOTE: If ambient or coil fault is detected, the board will not

execute the "TEST" mode.

Termination—The defrost cycle ends when the coil

temperature exceeds the termination temperature or after

14 minutes of defrost operation. If the defrost is terminated

by the 14-minute timer, another defrost cycle will be

initiated after 30 minutes of run time.

Test Mode—When Y1 is energized and 24V power is being

applied to the board, a test cycle can be initiated by placing

the termination temperature jumper across the "Test" pins

for 2 to 5 seconds. If the jumper remains across the "Test"

pins longer than 5 seconds, the control will ignore the test

pins and revert to normal operation. The jumper will initiate

one cycle per test.

Enter the "TEST" mode by placing a shunt (jumper) across

the "TEST" pins on the board after power-up. (The "TEST"

pins are ignored and the test function is locked out if the

shunt is applied on the "TEST" pins before power-up). Board

timings are reduced, the low pressure switch is ignored

and the board will clear any active lockout condition.

Each test pin shorting will result in one test event.

For each "TEST" the shunt (jumper) must be removed for

at least 1 second and reapplied. Refer to flow chart for

"TEST" operation.

NOTE: The Y1 input must be active (ON) and the "O" room

thermostat terminal into board must be inactive.

Issue 1846

depends

stable

507919-01F

system