Thermoking defrost logic

[bessershmit]

I need help troubleshotning defrost on SL 200 TG-VI

Startning At setp -20 C and pulling down,
after ca 90 min starts first defrost "demand".
When defrost exited the unit runin in high speed cool
aprx 20 min then defrost start again.... a

What`s trigger the defrost mode beside the 2 timers

dFI and dFn

Help me with the logic on this

Best regards Bessershmit

[DaButcher]

A demand defrost cycle will occur if the
differences between the return air temperature,
discharge air temperature, and coil temperature
are greater than predetermined values.

Two defrost timers are used. When the unit is
In-Range (within a few degrees of setpoint),
defrost intervals are controlled by the Defrost
Interval In-Range timer (dFI). This timer can be
set for 4, 6, 8 or 12 hours. The standard setting is 6
hours. When the unit is not In-Range, defrost
intervals are determined by the Defrost Interval
Not In-Range timer (dFn). This timer can be set
for 2, 4, 6, 8 or 12 hours. The standard setting is 4
hours. This feature allows a shorter defrost
interval to be used when the unit is out of range
during a pull-down and more frequent defrost
cycles may be beneficial.
Normally, longer defrost timer intervals are used
for colder loads. The defrost interval may need to
be changed if the unit will not hold the
compartment temperature at setpoint.
• Use a longer defrost interval if defrost is not
being initiated on demand.
• Use a shorter defrost interval if defrost is
frequently being initiated on demand.

[bellg]

What Revision has it? Some of the earlier ones had this problem.
By upgrading to Revision 1083 will cure the problem

[tspgr]

check the air swich that is at the left side uper door round with 2 wires (11a and 12) and 2 pipes take the wires of and test again .....

Mixalis GR

[MRW]

does this problem ocour when the return air temp gets to -18c,had problems with these units on 1080 software,sometimes it was an expansion valve issue and on some that couldnt be cured by adjustment a sl400 expansion valve was fitted,1083 software should address this problem,its down to the parameters that are set for demand defrost in the 1080,the difference between the sensor readings change at -18c with 1080,