Thermo King 914 724, Руководство пользователя

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Electrical Maintenance (Rev. 1/99)
40
2. Check the operation of the defrost termination switch.
If the unit will not come out of defrost, disconnect the
12 wire from the defrost termination switch. If the unit
shifts back to cool, the defrost termination switch is not
opening and should be replaced. If the unit remains in
defrost, move to step 3.
3. Check the 11 and 12 wires for a ground:
If the unit remains in defrost, use an ohmmeter to check
the 11 and 12 wires for a ground. If the 11 or 12 wire is
grounded, find the grounded portion and repair it.
Defrost Timer
The defrost timer both initiates and terminates the defrost
cycle.
First, the timer will initiate a defrost cycle at 4, 8, or 12 hour
intervals. The jumper between the 7 terminal and the 5, 8 or
9 terminal of the timer socket determines the time interval.
The timing cycle begins when the defrost termination
switch closes. If the defrost termination switch opens during
the timing cycle, the timer will reset at zero when the
defrost termination switch closes.
Second, the defrost timer will terminate the defrost cycle
after 45 minutes if the defrost termination switch has not
opened.
1. Test Terminal
Defrost Timer
1
AEA502
Temporary Defrost Timer Bypass Procedure
If the timer fails and a replacement is not available, bypass-
ing the timer will allow the manual defrost switch to pro-
vide defrost control.
Bypass Procedure
1. Remove the defrost timer from its socket.
2. Remove the defrost jumper from the bottom of the ter-
minal board. Insert the defrost jumper into slots 1, 2,
and 3 in the defrost timer socket.
3. To install a new timer, remove the defrost jumper from
the defrost timer socket and insert the new defrost
timer. Place the defrost jumper back on the bottom of
the terminal board.
Defrost Timer Test
1. With the defrost termination switch open, press the
Manual Defrost switch. The unit should not go into
defrost.
2. Connect the screw terminal on the defrost termination
thermostat (12 circuit) to CH. Press the Manual Defrost
switch. The unit should go into defrost. Disconnect the
CH circuit from the 12 circuit. The defrost relay should
open.
3. Connect the jumper from the timer test terminal to
ground. Reconnect the CH circuit to the 12 circuit, and
then press the manual defrost switch. The unit should
go into defrost for about 10 seconds, and then terminate
defrost even though the 12 circuit is still connected to
CH.
Cycle Interval Test Duration
4 hours 1 minute
8 hours 2 minutes
12 hours 3 minutes