Txv Selection; Other Inputs To The Control Board; Customer Supplied Control (Thermostat); Other Outputs From The Control Board - Emerson Copeland Scroll Installation And Reference Manual

thermistors reading and do a four second averaging.
The EXV opening will be changed every 20 seconds
and the variation is calculated by different ways based
on different purposes.

TXV selection

For EVI, Emerson recommends a balanced port TXV
because it offers a wider operating range for fl oating
liquid temperatures.
See Table 7 (page 14) for specifi cs regarding balanced
port sizing recommendations. Applied with the low temp
units it is recommended that a balanced port expansion
valve be used along with a complete review of the the
distributor & nozzle (orifi ce) that is supplied with the
Evaporator coil being matched with the applicable
condensing unit. Typically nozzles are selected for
standard TXV sizing using 100°F liquid, with the XJAL
those typical selections could be grossly oversized. See
Table 7 for the liquid correction safety factors when
selecting those components.

Other Inputs to the Control Board

Customer Supplied Control (Thermostat)

The control board will accept a normal 220 volt AC
input ON/OFF signal such as the switching action of a
normal commercial thermostat and relay. If the system
is controlled by low pressure control for a multiple
evaporator system and/or pump down system, the
control board will accept the signal directly from the
control. See Wiring Diagrams, pages 21-24, for proper
installation.

Other Outputs from the Control Board

Defrost Control Board

The defrost control board is a basic time initiated module
which is standard on the low temperature units and is
an add on feature for the medium temperature units.
The defrost control board can control either off-cycle or
electric defrost.
The defrost control board will control the liquid line
solenoid valve. When defrost is initiated the liquid line
solenoid valve will close and the unit will go into a
pumpdown cycle. When the suction pressure equals the
setting of the low pressure control, the compressor will
cycle off. After the defrost time has expired, the liquid line
solenoid valve opens and then the low pressure control
will allow the compressor to restart.
Due to heater amperage loads, electric defrost requires
an additional relay or contactor to energize the defrost
heater.
© 2011 Emerson Climate Technologies
Printed in the U.S.A.
Application Engineering
B U L L E T
The defrost cycle can be executed either automatically
or manually. There are two rotary dip switches by which
the user can set up the defrost cycle, see Figure 4. One
rotary dipswitch sets the defrost duration (SW1) and the
second rotary dipswitch sets the time interval between
defrost cycles (SW2). For automatic defrost set SW1
and SW2 as desired. See Table 4 (page 11) for time
settings. The defrost control board also incorporates
a manual defrost button that enables a manual defrost
as an override to the rotary switch setting the defrost
interval. Upon the completion of a manual defrost, the
system will reset to the refrigeration cycle with the same
procedures as automatic defrost and then the automatic
defrost timer will reset.
For setting manual defrost only set SW1 as desired and
set SW2 to "0". Whenever the manual defrost button
is pressed, one defrost cycle will be executed and the
duration of defrost will be determined by the setting of
the rotary dipswitch SW1.
Note: There is no method to terminate a defrost cycle
without resetting the control board.
Table 4 lists rotary dip switch settings for the Defrost
Control Board.
An ON/OFF output connection is provided on the
control board (JP10) for direct connection of a customer
supplied contactor coil/relay when the defrost option is
used. Terminals are male spade type. Coil voltage rating
should be 220VAC and current ratings, 30VA (hold) and
330VA (inrush). See Figure 6 (page 9).
For customers using their existing defrost timer,
remove the defrost cable connecting the defrost control
board to the unit control board. Also on the unit control
board change the mode setting dip-switch bit 2 to ON
and proceed to standard defrost wiring. See Table 5
(page 12)

Evaporator Fan Control

An ON/OFF output connection is also provided on the
control board (JP9) for direct connection of a customer
supplied contactor coil controlling the evaporator fans.
Terminals are the male spade type. Coil voltage rating
is to be 220VAC and a maximum power rating of 30VA
(hold) and 330VA (inrush). See Figure 6.

Diagnostic Display Board

Each condensing unit is supplied with a diagnostic
display board, see Figure 5 (page 13). A two character
display will make up the diagnostic/error code. The fi rst
character will display the unit status as shown in Table
6. The second character will display the error/warning
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