Johnson Controls RC Series Engineering Manual page 14

RC SERIES ENGINEERING GUIDE
Controls - FX10 cont.
temperature drops below the freeze detection limit trip point for the
recognition delay period, the condition will be recognized as a fault.
The freeze detection limit trip point will be factory set for 30°F and
will be field selectable for 15°F by removing a jumper wire on BI-5.
The freeze detection limit fault condition will be bypassed 2 minutes
at normal compressor startup, to allow the refrigeration circuit to
stabilize. If the freeze detection limit sensor becomes unreliable
at any time compressor operation will immediately be suspended
until the problem is corrected. This should be displayed as an alarm
on the BAS and the MUI. This alarm will be reported a "Water Low
Temp Limit" fault.
High Pressure (BI-11)
The high-pressure switch shall be a normally closed (NC) switch
that monitors the systems refrigerant pressure. If the input senses
the high-pressure switch is open it must disable the compressor
output immediately and count the fault. The compressor minimum
on time does not apply if the high-pressure switch opens. The
compressor will not restart until the compressor short cycle time
delay has been satisfied.
Low Pressure (BI-3)
The low-pressure switch shall be a normally closed (NC) switch
that monitors the systems refrigerant pressure. The input shall be
checked 15 seconds before compressor start up to be sure the
pressure switch is closed and then ignored for the first 2 minutes
after the compressor output (BO-2) is enabled. If the switch is open
continuously for (30) seconds during compressor operation the
compressor output (BO-2) will be disabled. The compressor will not
restart until the compressor short cycle time delay has been satisfied.
Condensate Overflow
The condensate overflow sensing circuit will monitor the
condensate level as a resistance input to AI-3. If the condensate
water level rises resulting in the input resistance rising above the
set point for the recognition delay period, the condition will be
recognized as a fault. The condensate will be subjected to a (30)
second lockout delay which requires that the fault be sensed for a
continuous (30) seconds before suspending unit operation.
Alarm Output (BO-6)
The alarm output will be enabled when the control is in the lockout
mode and will be disabled when the lockout is reset.
Test Mode
Raising the zone temperature input (AI-1) reading to 180–220°F or
by holding the ESC and down arrow keys on the MUI for 5 seconds
will put the control into test mode. In test mode the random start
delay and the compressor fixed on delay time will both be shortened
to 5 seconds and the reversing valve will be allowed to cycle with
out shutting down the compressor. If an MUI is connected to the
control LED 8 will flash and the words "Test Mode Enabled" will be
shown on the LCD display when the control is in test mode. Test
mode will be disabled after a power cycle, 30 minute timeout, or by
holding the ESC and Up arrow keys on the MUI.
Sequence of Operation
Power Fail Restart
When the controller is first powered up, the outputs will be
disabled for a random start delay. The delay is provided to prevent
simultaneous starting of multiple heat pumps. Once the timer
expires, the controller will operate normally.
Random Start Delay
This delay will be used after every power failure, as well as
the first time the compressor is started after the control exits
the unoccupied mode or the emergency shutdown mode. The
delay should not be less than 1 second and not longer than 120
seconds. If the control is in test mode the random start delay will be
shortened to 5 seconds.
Compressor Fixed On Delay Time
The Compressor Fixed On Delay Time will ensure that the
compressor output (B02) is not enabled for (90) seconds after
the control receives a call to start the compressor. This delay is
adjustable from 30 – 300 seconds over a BAS or a MUI. If the
control is in test mode the Compressor Fixed On Delay Timer will
be shortened to 5 seconds.
Compressor Minimum On Delay
The compressor minimum on delay will ensure that the
compressor output is enabled for a minimum of (2) minute each
time the compressor output is enabled. This will apply in every
instance except in the event the high pressure switch is tripped
or emergency shutdown then the compressor output will be
disable immediately.
Compressor Short Cycle Delay Time
The compressor short cycle time delay will ensure that the
compressor output will not be enabled for a minimum of (5) minutes
after it is disabled. This allows for the system refrigerant pressures
to equalize after the compressor is disabled.
Heating Cycle
On a call for heating, the blower enable output and accessory
output 2 will turn on immediately after the random start delay timer
has been satisfied. If the compressor short cycle time delay has
been satisfied, the compressor will turn on after the blower enable
and accessory output 2 are on and the fixed compressor start delay
timers have been satisfied.
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