Manual
EKC 315A Industrial Evaporator Controller
© Danfoss USCO (HMR_MKS), 04-2008
USCO.PD.RD0.A1.22 /521U0092
13
If superheat fluctuates excessively
Once the refrigeration system is stable, the controller’s factory set-
tings will usually provide fast reaction to changes in load. If, however,
the superheat fluctuates excessively, there are two possible causes:
Either superheat parameters are set too low, or regulation param-
eters need some adjustment.
Adjustment of superheat parameters:
First, try to solve the problem by increasing the superheat param-
eters as follows:
it is likely that superheat parameters should be adjusted to higher
values. This is accomplished as follows:
If adaptive superheat has been selected:
Adjust: n09, n10 and n18.
If load-defined superheat has been selected:
Adjust: n09, n10 and n22.
Adjustment of regulating parameters:
These adjustments should only be undertaken by specially trained
technicians using data monitoring equipment. If superheat
parameter adjustment does not result in stability, Adjust regulation
parameters using the following procedures:
If the oscillation time (T
p
) is longer than the integration time (T
n
,
parameter n05) time:
(T
p
> T
n
, (T
n
is, say, 240 seconds))
1. Increase T
n
to 1.2 times T
p
2. Wait until the system is in balance again
3. If there is still oscillation, reduce K
p
(initially by about 20%)
4. Wait until the system is in balance
5. If it continues to oscillate, repeat 3 and 4, reducing K
p
by smaller
amounts.
If the oscillation time is shorter than the integration time:
(T
p
< T
n
, (T
n
is, say, 240 seconds))
1. Reduce K
p
by, say, 20% of the scale reading
2. Wait until the system is in balance
3. If hunting continues, repeat steps 1 and 2, decreasing K
p
by a
smaller amount.
If the superheat has excessive underswing during
start-up
If regulation is by valve type ICM with ICAD motor or by AKV/A
pulse-width modulation valve:
Increase n22 slightly, or decrease n04 slightly, or both.
If you regulate with discontinued valve type TQ:
Decrease n26 slightly.
Troubleshooting
Failure to regulate after Setup
If, after setting up according to the Quick Setup Guide on page 6, the
valve will not regulate, the cause may be one of the following:
1. There is no connection (either a closed switch or a jumper wire)
between terminals 1 & 2.
2. The internal start-stop parameter (r12) has been set to OFF.
3. No valve has been selected by parameter o09.
4. The thermostat function is being used and the thermostat is
satisfied.
