Table 7: Configuring the superheat control
Minimum Stable Superheat (MSS):
The controller will be searching for the minimum stable superheat between an
upper and lower boundary specified by the user. Then if the superheat is stable at
a certain value, the controller decreases the superheat reference, if the SH gets
unstable, the SH reference is raised again. The goal of this method is to search for
the lowest possible superheat that can be obtained while still maintaining a sta-
ble system.
EIM
365
Applicable
✔
Danf
os
s
84B1487.10
100 %
10 %
40 %
Superheat
Q
o
Uns
table
region
(wet
)
Stable
regi
on (
dry)
Min. SH
Max. SH
Danfoss MSS
LoadAP:
In LoadAp application, SH reference follows a defined curve as shown in the dia-
gram. This two-point curve is defined by SH max and SH min. These two values
must be selected in such a way that the curve is situated between the MSS curve
and the curve for average temperature difference ΔTm (temperature difference
between media temperature and evaporating temperature). This makes the regu-
lation more stable compared to MSS because it does not seek a usability.
EIM
365
Applicable
✔
Danf
os
s
84B1489.10
100 %
Superheat
Q
o
Uns
table
regio
n
(wet
)
Min. SH
Max. SH
10 %
90 %
Stable
reg
ion
(dr
y)
NOTE:
A fixed superheat reference can be achieved by setting the “n10 Min SH” and “n09 Max SH” can both be set to the
desired reference value. This will disable the minimum stable superheat search algorithm and the controller will
instead regulate the superheat according to this reference.
Figure 7: Superheat reference tracking
Table 8: Superheat control configuration
Symbolic name
PNU
Description
n21 SH mode
3026
1: MSS; 2: LoadAp
n09Max. SH
3015
Maximum superheat reference setting.
n10Min. SH
3021
Minimum superheat reference setting.
n20Kp T0
3025
Pressure feedback gain.
n22SH close
3027
Superheat close level. If the superheat goes below
this value, the valve will close faster.
---Tn SH
3103
Integration time for superheat control
---Alpha
3111
Design time constant. A large alpha means a slow re-
sponse, a small alpha mean a fast response.
© Danfoss | Climate Solutions | 2022.09
BC415322248492en-000101 | 13
Superheat controller, type EIM 365 (PV01)