TM_i-BX(-N)_NC05_00_06_20_EN
MEHITS S.p.A.
●
TECHNICAL MANUAL
Version NC05 - Translation of the Original Instructions
52
The
“
PRESSURE 2
”
type defrost follows the logic below:
Max or less
Revolution
[rps]
Time
30 sec
2 sec or more
30 sec
2 sec or more
Defrost
(Max. 10 min)
134G
134H
134I
Max. 10rps/sec
Synchronous drive
Asynchronous drive
Asynchronous drive
Synchronous drive
Changing a reversing valve
Note: In case of “PRESSURE 2” type defrost, the compressor deceleration before the time given by parameter
134G
is defined by parameter
138L
.
For the default values of the various parameters, see the parameters table
Using parameter
0802
it is possible to enable the defrost condition as a function of the external temperature, with a corresponding setpoint (
0810
),
below which defrost may take place.
If for any reason the defrost end setpoint (
0801
) is not reached, the cycle ends due to the maximum set time being exceeded (
0804
) (counting of the
maximum time takes place in conjunction with the restarting of the compressor). If the conditions persist after the defrost procedure, another one will
start after the delay between two defrost operations (
0805
).
When the unit is switched OFF, the interval between one defrost procedure and the next (
0805
) is reset. Therefore, in this case two defrost operations
at close intervals would also be possible, if switching on took place immediately and the pressure were below the defrost start threshold.
In i-BX(-N) units dynamic defrost (
0815
) is enabled. Therefore, the defrost start threshold will change dynamically depending on the external air
temperature: when the air temperature read by the external probe (B4) falls below the threshold set by parameter
0816
“Differential activation T
threshold”, the defrost start pressure defined by parameter
0808
is reduced by the value set in parameter
0817
“Defrost input differential”, according
to the proportional band set in parameter
0818
“Defrost input proportional band”.
Differential activation
T threshold (0816)
Defrost input
prop. band (0818)
Defrost start
[bar]
0808
External T [°C]
Defrost input
differential (0817)
Moreover, it is also possible to enable the forcing of the defrost cycle time (parameter
0821
). The enabling of this function will trigger a count after
the first defrost cycle. After the elapse of a time equal to parameter
0822
(found in Mnu08), if no defrost cycles following the already set logics have
been initiated, a forced defrost cycle will be initiated.
The activation of a “natural” defrost cycle will stop the count, which will be reset and reinstated as soon as the “natural” cycle is completed.
Depending on the operating mode set, the defrost cycle will if necessary be performed in accordance with the rules below
Set operating mode
(
active one in red
)
Defrost mode
Only
DHW
Without stopping the compressor, towards the DHW storage tank
Only
HOT
Without stopping the compressor, towards the SYSTEM storage
tank
Only
COLD
No defrost cycle
HOT
+ DHW
Without stopping the compressor, towards the SYSTEM storage
tank
HOT +
DHW
towards the SYSTEM storage tank with compressor STOP (also
the return towards DHW will take place after the compressor stop)
COLD
+ DHW
No defrost cycle
COLD +
DHW
Without stopping the compressor, towards the DHW storage tank
For the default values of the various parameters, see the parameters table.
