S-24 Testing Defrost Timer Board - Amana VCA Service Instructions Manual

SERVICING
OUT SEN
When the control is powered on, or after a power interruption
(longer than 30 seconds), the first frost build interval is 30
minutes.
Amana part number 10865001 defrost controls, used through
9412 production. After the initial 30 minute frost build interval
the second and subsequent frost build intervals will be
adaptive to a target 7 minute defrost time.
Amana part number 10865002 defrost controls, used after
9412. After the initial 30 minute frost build interval, the
second and third frost build intervals will be 90 minutes.
Subsequent frost build intervals will be adaptive to a target
5.5 minute defrost.
For either version of the control, the adaptive logic will
essentially add or subtract 26 minutes to the previous frost
build interval, for every minute under or over the target
defrost time. The maximum increase in the frost build
interval is 37.5% of the last frost build interval. The maxi-
mum frost build interval is 360 minutes for the -01 through
-03 controls.
To reduce the possible perception of improper operation
due to heavy frost, two additional software changes have
been made in the -04 & -05 controls. These changes include
a maximum defrost interval of 3 hours (180 minutes) rather
than the 6 hour (360 minutes) defrost interval used on
previous controls. Also, if the defrost sensor remains open
for 6 hours or longer, the control resets itself to a 90 minutes
defrost interval. This means that after the defrost sensor
closes the next defrost will be in 90 minutes, subsequent
defrosts will be adaptive.
A defrost termination of 10.5 minutes will occur if the sensor
does not open. If a time termination occurs, the next frost
build interval will be 30 minutes and will be adaptive there-
after.
24VAC HLD TST COM

S-24 TESTING DEFROST TIMER BOARD

To check the defrost timer board for proper sequencing,
proceed as follows: With power ON; unit running.
WARNING
TIME TEMPERATURE DEFROST CONTROL
(RHA-A mdls)
1. Jumper defrost control (30/60) by placing jumper wire
from (R) wire of low voltage terminal board, to (24VAC)
terminal of defrost timer board.
2. Using a VOM, measure voltage between (24VAC) termi-
nal and (COM) terminal of defrost timer board - should
read 24 VAC.
3. Connect VOM between (24VAC) terminal and (OUT)
terminal - should read 0 VAC. If it reads 24 VAC, board
may be in defrost mode.
4. With VOM still connected, and the unit in operation, short
or jumper two TST terminals on board. (Test Terminals
Jumpered - Count time speeds up - 90 minutes =
approximately 21 seconds).
5. Watch VOM - should read 24 VAC at end of frost build
interval, - then read 0 VAC at end of defrost interval (about
2 to 3 seconds after first reading).
Amana P/N C6431001
HSCI P/N 621-509
TRI
3
1
DFR
30/60
1. 24VAC - power is connected through the 30/60 sensor.
2. HOLD - accumulation of compressor run time.
3. OUT - connect common to defrost relay.
4. TEST - accelerate time, does not change sequence.
Timing:
Timer T1 = 30 min
T2 = 60 min
T3 = 90 min
10 min max def
T3 T2 T1
TST
2
4
Short Cycle
Protector
or Contactor
Y2
R Terminal
C/X Terminal
33 Rev 1