WaterFurnace Envision (XL) - Manual (Page 28)

ENVISION 7-25 TONS INSTALLATION MANUAL
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operation until the controller is reset. If the control faults
due to the low pressure input (BI-3) being open during
the pre-compressor startup check, the control will go into
lockout mode immediately, disabling the compressor from
starting and enabling the alarm output (BO-6). The lockout
condition can be reset by powering down the controller, by
a command from the BAS, or by the holding the ESC and
Return keys on the MUI for 5 seconds.
Freeze Detection (AI-5)
The freeze detection sensor will monitor the liquid
refrigerant temperature entering the water coil in the
heating mode. If the temperature drops below the freeze
detection trip point for the recognition delay period,
the condition will be recognized as a fault. The freeze
detectopm 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 fault condition will be bypassed
2 minutes at normal compressor startup, to allow the
refrigeration circuit to stabilize. If the freeze detection
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.
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 degrees 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.
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.
Optional FX10 Microprocessor Control cont.