Johnson Controls MR4PMUHV User Manual

MR4PMUHV Electronic Temperature/Defrost Control with Relay Pack Product/Technical Bulletin 9
Defrost Cycle Management Functions
dF Defrost Mode allows the user to select electric
heater defrost or hot gas defrost. See Table 2.
Table 2: Defrost Mode Options
Defrost Mode
Electric
Heater
Hot Gas
Compressor
Relay Contacts
open
closed
Defrost Control
Relay Contacts
closed
closed
Defrost Device
Controlled
electric defrost
heater
electric solenoid
on hot gas bypass
valve
dE Defrost Termination Mode allows selection of
time-based or temperature-based defrost termination.
Maximum Defrost Duration controls time-based defrost
termination. Defrost Termination Temperature controls
temperature-based defrost termination.
dt Defrost Termination Temperature establishes the
temperature setpoint (F° or C°) that ends the defrost
cycle, if temperature-based defrost termination is
selected.
di Defrost Interval establishes the time (hours)
between defrost cycles. When the Defrost Interval is
1 hour, the Maximum Defrost Duration can not exceed
40 minutes.
dd Maximum Defrost Duration establishes the
maximum time (minutes) of the defrost cycle, if
time-based defrost termination is selected. A setting of
0 disables the defrost cycle.
dC Dripping Time establishes the delay time
(minutes) after defrost termination (and before the
compressor starts for the next freeze cycle) to allow
water to drain away from the evaporator coil.
dU First Defrost Delay establishes the time delay
(hours) until the first defrost cycle after starting or
restarting the refrigeration system.
This setting can allow the system to reach operating
temperature before the defrost cycle is initiated.
Setting First Defrost Delay to OFF causes the first
defrost after power-on to occur after the Defrost
Interval has elapsed.
dP Display During Defrost establishes the
temperature value displayed during the defrost cycle.
The user may select either the Setpoint value or the
temperature sensed just prior to starting the defrost
cycle.
dr Display Delay After Defrost establishes the time
delay (minutes) after defrost termination, before the
control displays the sensed temperature.
Evaporator Fan Management Functions
FF Fan Operating Mode establishes when the
evaporator fan operates: continuously or only when
the compressor is running. Fan operation during
defrost cycle depends on application wiring.
Fd Fan Start-Up Delay establishes the maximum time
delay (minutes) after the end of the defrost cycle, before
the evaporator fan restarts. The evaporator fan restarts
after this time delay, even if Fan Start Temperature has
not been reached.
Fr Fan Start Temperature establishes the
temperature setpoint (F° or C°) at which the
evaporator fan restarts after defrost termination.
Binary Input Functions
iF Binary Input Mode establishes how the
compressor, defrost, and evaporator fan relays
respond when the Binary Input Circuit is closed. See
Table 3.
Table 3: System Response to Binary Input Signal
System
Component
Binary Input Function Option
Selected
0
1
2
3
Compressor
--
Off
On
On
Defrost
--
Off
No
Change
No
Change
Evaporator
Fan
--
Off
On
Off
id Binary Input Time Delay establishes the time
delay (minutes) between when the binary input circuit
closes and the response of selected relays
(compressor, defrost, and evaporator fan) initiates.

Johnson Controls MR4PMUHV Specifications