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Defrost Control Components
1– Timing Pins 30, 60, 90
Each of these pins provides a different timed
interval between defrosts. A jumper connects the
pins to circuit board pin W1. Table 4 shows the
timings of each pin. The defrost interval can be field
changed to 30, 60 or 90 minutes. The defrost period
(14 minutes) cannot be changed. To change the
interval between defrosts, simply remove the
jumper from the pin it is connected to and
reconnect the jumper to one of the other available
pins (see figure 8).
TABLE 4
INTERVAL BETWEEN DEFROSTS
WITH JUMPER CONNECTED TO:
30
60
90
NORMAL
OPERATION
“TST” PINS
JUMPER
30 + 3
60 + 6
90 + 9
14 + 1.4
7 + 0.7
14 + 1.4
21 + 2.1
3.3 + 0.3
MIN.
MIN.
MIN.
MIN.
SEC.
SEC.
SEC.
SEC.
TOGETHER
CMC1 DEFROST
CONTROL
TIMINGS
DEFROST
TIME
1– Turn off all power to the unit to avoid circuit board damage.
2– Grasp wire connector firmly with fingers.
3–
Gently pull connector from pin.
4– Select new timing pin. DO NOT SELECT A “TST” PIN.
5– Gently push connector onto desired pin (see Table 4 for timings).
6– Turn on power to unit.
FIGURE 8
WARNING – AVOID CONTACT WITH OTHER CON-
TROL TERMINALS OR CONTROL COMPONENTS.
WARNING – DO NOT
CONNECT TIMING
JUMPER TO EITHER
“TST” PIN.
TO CHANGE CONTROL TIMINGS:
DEFROST CONTROL TIMING CHANGES
2– Timing Jumper
The timing jumper is a factory installed jumper
on the circuit board used to connect pin W1 to
one of the three timing pins. The jumper may be
connected to any one of the timing pins but must
never be connected to either of the “TST” pins.
See Caution below.
CAUTION
3– “COM” Terminal
Terminal “COM” provides 24VAC Common.
4– “HLD” Terminal
Terminal “HLD” holds the internal timer in place
between thermostat demands and allows the unit
to continue timing upon resumption of thermostat
demand. Terminal “HLD” is connected directly to
thermostat demand.
NOTE – Hold function operates between thermostat
demands only when defrost thermostat is closed. This
is the only time that the timer is operating.
5– “TST” Pins
Each board is equipped with a set of test pins for
use in troubleshooting the unit. When jumpered
together, these pins reduce the control timing to
about 1/256 original time (see table 4 and figure 9).
IMPORTANT
Control will begin test mode only if normal load is
applied to control terminals. Do not attempt to
operate or test control out of unit.
FIGURE 9
WARNING – AVOID CONTACT WITH
OTHER CONTROL TERMINALS OR
CONTROL COMPONENTS.
TO PLACE CONTROL
IN TEST MODE:
1– Turn off all power to avoid
damaging the circuit board.
2– Make sure all control terminals are
connected as shown on unit wiring
diagram before attempting to place control in
test mode. See NOTE below.
NOTE – Control will not go into test mode when disconnected
from unit. Unit load must be applied to control terminals before
the control will go into test mode.
3– Connect jumper to “TST” pins as shown.
4– Turn indoor thermostat to heat mode and adjust to highest
temperature setting.
5– Turn on power to unit.
6– See Table 4 for control timings in “TST” mode.
7– Be sure to turn off power and remove jumper when test is com-
plete. Turn on power and re–adjust thermostat.
DEFROST CONTROL TEST MODE
6– “24V” Terminal
Terminal “24V” receives 24VAC from the control
transformer through the defrost thermostat. This
terminal powers the control’s internal timer and
relays. Terminal “24V” is powered only when there is
a call for defrost (defrost thermostat closed). The
timer begins timing at 0 only after terminal “24V”
receives power.
7– “OUT” Terminal
Terminal “OUT” controls defrost when connected
to one side of the defrost relay coil. An internal
relay connected to terminal “OUT” closes to allow
external defrost relay to energize and initiate
defrost. At the end of the defrost period, the
internal relay connected to terminal “OUT” opens
to de-energize the external defrost relay.
