13
AE5-1412 R1
© 2016 Emerson Climate Technologies, Inc.
6.20. Defrost Controls.
6.20.1. Holiday Defrosts
If you are using real time clock mode (
rtc
), holiday
defrosts can be set in the advanced options menu. To
set a holiday, change
Hd1
from
nU
to whatever day
of the week you would like to have a different defrost
schedule. (An example would be if a store is closed
on Sundays and needs less defrosts). You can set a
second holiday by changing
Hd2
. The defrosts for the
set holidays are controlled by parameters
5d1
through
5d6
.
6.20.2. Defrost Functionality
During a defrost the controller will display
dEF
.
To manually initiate a defrost, press and hold the defrost
button for 3 seconds.
The controller will terminate defrost after 45 minutes
MDF
(Pr1 parameter) or after the defrost termination
input (Terminal 'X') is closed.
6.20.3. Liquid Line Solenoid Control
By default, the unit assumes that a liquid line solenoid
is used to pump down the system during a defrost.
When the unit enters a defrost, the evaporator power
(Connection 3 on the terminal strip) will turned off,
turning off the liquid line solenoid as well. The unit will
then run until the suction pressure drops below the
cut out value, then turn off the compressor. When the
defrost is complete, the unit will apply power to the
evaporator, opening the solenoid and the compressor
will start running once the suction pressure is above
the cut in.
If a pump down solenoid is not present or the unit should
not pump down when entering a defrost, parameter
tLS
should be set to
no
. TLS is set to
YES
by default.
6.21. Enhanced Vapor Injection (EVI)
For Low Temperature Units
The injection valve is a key part of the EVI system.
It regulates vapor injection flow to optimize the
performance of system and cool the scroll set. When
the compressor first calls for power, the injection valve
opens a preset amount before the compressor turns
on. After startup, the EVI injection valve is controlled
using a proportional-integral (PI) algorithm to control
the differential between the vapor inlet temperature
and the vapor outlet temperature. The differential is
9°F for R404A, R507, R134a, and R22. It is 18°F for
other approved refrigerants. The PI algorithm for the
EVI injection valve control is auto-adaptive, so it does
not need to be adjusted.
6.21.1. Low Temp EVI Discharge Line
Temperature Protection Mode
If during normal operation the DLT temperature reaches
225°F the control changes to act as a liquid injection
valve to control the DLT temperature. Once the DLT
temperature falls below 200°F, normal vapor injection
control resumes.
If the discharge temperature goes above 250°F, the
compressor trips off and the control displays an
E44
error. The compressor cannot turn back on until the
temperature drops below 170°F and has been off for
3 minutes.
