6.8.3 7-7* Pressure to Temperature Conversion
The conversion of a feedback signal P in units of a pressure to a temperature T is accomplished via the formula:
T = A2/(log(P+1)-A1) – A3
where A1, A2 and A3 are refrigerant dependent constants.
Figure 6.11 Converting Pressure to Temperature
The parameters in this group allow selection of a refrigerant, which implicitly determines the constants A1, A2 and A3.
Alternatively, user dened constants can be programmed explicitly.
7-70 Refrigerant
Option: Function:
[0] R22
[1] R134a
[2] * R404A
[3] R407C
[4] R410A
[5] R502
[6] R744
[7] User dened
7-71 User Dened Refrigerant A1
Range: Function:
[8.0000 –
12.0000]
Selects the value used for the constant A1 in
the pressure to temperature conversion
formula (see parameter group 7-7* Pressure
to Temperature Conversion).
7-72 User Dened Refrigerant A2
Range: Function:
[-3000.00 –
-1500.00]
Selects the value used for the constant A2
in the pressure to temperature conversion
formula (see parameter group 7-7* Pressure
to Temperature Conversion).
7-73 User Dened Refrigerant A3
Range: Function:
[200.000 –
300.000]
Selects the value used for the constant A3 in
the pressure to temperature conversion
formula (see parameter group 7-7* Pressure
to Temperature Conversion).
6.8.4 7-8* Thermostat/Pressostat Function
The Thermostat-Pressostat Function (TPF) can be used to
stop and start the compressor when running in closed
loop. The TPF monitors and compares the resulting
feedback with the Cut-out value in parameter 7-81 Cut-out
Value. When the resulting feedback gets below
parameter 7-81 Cut-out Value a stop signal is generated and
the compressor stops. When the resulting feedback gets
above the Cut-in value in parameter 7-82 Cut-in Value the
stop signal is removed and the compressor starts again.
The Set-point should be set to a value in between Cut-in
and Cut-out.
Parameter Descriptions Operating Instructions
MG34M422 Danfoss A/S © Rev. 2013-07-03 All rights reserved. 79
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