16
RT-SVF69C-EN
Sequence of Operation
zone sensor or remote panel when the clogged filter switch
has been closed for at least 2 minutes during supply fan
operation. The system will continue to operate regardless
of the status of the clogged filter switch.
Ventilation Override
Note:
Applying 24 volts to one of the three Ventilation
Override inputs manually activates ventilation
override. One input is provided to request the
Pressurize Mode, the second input the Purge Mode,
and the third input the Exhaust Mode.
When the Pressurize Mode is selected, activating
Ventilation Override will cause the supply fan to run, the
economizer to open to 100%, the exhaust fan to turn
(remain) off, or the VFD to run at full speed, and the VAV
boxes to fully open.
When Purge is selected, activating Ventilation Override
will cause the supply fan to run, the economizer to open to
100%, the exhaust fan to run, or the VFD to run at full
speed, and the VAV boxes to fully open.
When Exhaust is selected, activating Ventilation Override
will cause the supply fan to turn off, the economizer to
close to 0%, the exhaust fan to run (exhaust damper at
100% if configured for Statitrac), or the VFD to stop, and
the VAV boxes to operate normally.
If more than one mode is requested at the same time, the
Pressurize request will have priority followed by Purge.
When any Ventilation Override Mode is active, all heating
and cooling is turned off. For the case where the unit is
required to turn off, the Emergency Stop input is used. The
ICS can also initiate any ventilation override mode.
lists the sequence of events within the system for
each ventilation mode. Refer to the unit wiring diagram for
contact switching and wiring.
Note:
Fresh air tracking will not work with VOM.
Emergency Stop
When this binary input is opened, all outputs are
immediately turned off and the system will not be allowed
to restart until the binary input is closed for approximately
5 seconds minimum. The shutdown is communicated to
Tracer™ if applicable and the Heat and Cool LED outputs
(RTRM J6-7 and J6-8) will blink at a nominal rate of 1 blink
per second.
Phase Monitor
The Phase Monitor is a 3 phase line monitor module that
protects against phase loss, phase reversal and phase
unbalance. It is intended to protect compressors from
reverse rotation. It has an operating input voltage range of
190-600 VAC, and LED indicators for ON and FAULT. There
are no field adjustments and the module will automatically
reset from a fault condition.
Low Pressure Control
This input incorporates the low pressure cutout of each
refrigeration circuit and can be activated by opening a field
supplied contact.
If this circuit is open before a compressor(s) is started, the
compressor(s) in that circuit will not be allowed to operate.
Anytime this circuit is opened for 5 continuous seconds,
the compressor(s) in that circuit are turned off
immediately. The compressor(s) will not be allowed to
restart for a minimum of 3 minutes.
If four consecutive open conditions occur during the first
three minutes of operation, the compressor(s) in that
circuit will be locked out, a diagnostic communicated to
Tracer, and a manual reset will be required to restart the
compressor(s).
High Pressure Cutout and Temperature
Discharge Limit
The high pressure controls and temperature discharge
limit are wired in series between the compressor outputs
on the RTRM and the compressor contactors. If the high
pressure safety or temperature discharge limit opens, the
compressor(s) on the affected circuit is locked out. If the
compressor output circuit is opened four consecutive
times during compressor operation, the RTRM will
generate a manual reset lockout.
Coil Frost Protection
The Frostat™ control monitors the evaporator coil
temperature to prevent the evaporator from freezing due
to low operating temperatures whenever there is a
demand for cooling. When a closed circuit has occurred for
5 seconds minimum, the RTRM turns off all of the cooling
outputs. The Supply Fan will be held “On” until the Frostat
has been opened for 5 continuous seconds or for 60
seconds after the last compressor was shut “Off”,
whichever is the longest. The compressor shutdown is
communicated to Tracer, if applicable. There is no local
diagnostic for this condition.
Table 13. Ventilation override sequence
Mode and Priority
Affected Function
Pressurize
Purge
Exhaust
(a)
(a) Exhaust mode 3 is not available with the tracking power exhaust option.
1
2
3
Heat/Cool
off
off
off
VFD
full speed
full speed
full speed
Supply Fan
on
on
off
Exhaust Fan
off
on
(b)
(b) For units configured with the Statitrac option, the Exhaust Damper will
open during Ventilation Override modes that request the exhaust fan to
operate.
on
Economizer
open
open
closed
VAV Boxes
forced open
forced open
normal
operation