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Clogged Filter Option
The unit mounted clogged filter switch monitors the pres-
sure differential across the return air filters. It is mounted in
the filter section and is connected to the RTOM. A diagnostic
SERVICE signal is sent to the remote panel if the pressure
differential across the filters is at least 0.5" w.c.. The contacts
will automatically open when the pressure differential
across the filters decreases to approximately 0.4" w.c. The
clogged filter output is energized when the supply fan is op-
erating and the clogged filter switch has been closed for at
least 2 minutes. The system will continue to operate regard-
less of the status of the filter switch.
Ventilation Override
Applying 24 volts to one of the three Ventilation Override In-
puts 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 Pressurize 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, the IGV to fully
open, 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, the IGV to fully open, 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, the IGV to close, 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 re-
quired to turn off, the Emergency Stop input is used. The ICS
can also initiate any ventilation override mode.Table 15 lists
the sequence of events within the system for each ventila-
tion mode. Refer to the unit wiring diagram for contact
switching and wiring.
Table 15
Ventilation Override Sequence
A ffe c te d F u n c tio n
P re ssu ri z e
1
H e a t /C o o l
o ff
IG V /V F D
o p e n / fu ll
s p e e d
S u p p ly F a n
o n
E x h a u s t F a n
o ff
E c o n o m iz e r
o p e n
V A V B o x e s
fo rc e d o p e n
Emergency Stop
When this binary input is opened, all outputs are immedi-
ately turned off and the system will not be allowed to restart
until the binary input is closed for approximately 5 seconds
minimum. The shut down is communicated to Tracer® if ap-
plicable and the Heat and Cool LED outputs (RTRM J6-7
and J6-8) will blink at a nominal rate of 1 blink per second.
Low Pressure Control
This input incorporates the low pressure cutout of each re-
frigeration circuit and can be activated by opening a field
supplied contact.
If this circuit is open before a compressor(s) is started, nei-
ther compressor in that circuit will be allowed to operate.
Anytime this circuit is opened for 5 continuous seconds, the
compressor(s) in that circuit are turned off immediately. The
M o d e a n d P rio rity
P u rg e
E x h a u st
2
3
o ff
o ff
o p e n /fu ll
o p e n / fu ll
s p e e d
s p e e d
o n
o ff
o n
o n
o p e n
c lo s e d
n o rm a l
fo rc e d o p e n
o p e ra t io n
System Operation (Continued)
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
The high pressure controls are wired in series between the
compressor outputs on the RTRM and the compressor con-
tactors. On 27.5, 30, and 35 Ton units, if the high pressure
safety switch opens, the RTRM senses a lack of current
while calling for cooling and locks both compressors out. On
40 and 50 Ton units, if the high pressure safety opens, the
compressor(s) on the affected circuit is locked out. A manual
reset for the affected circuit is required.
Power Exhaust Control
The power exhaust fan is started whenever the position of
the economizer dampers meets or exceed the power ex-
haust setpoint when the supply fan is on.
The setpoint potentiometer is on the RTOM and is factory
set at 25%.
Compressor Winding Protection
The Compressor Winding Thermostat(s) are wired in series
between the compressor outputs on the RTRM and the
compressor contactors. If in the event that a winding thermo-
stat opens, the RTRM senses a lack of current while calling
for cooling and shuts the compressor(s) off for that circuit.
The compressor(s) on that circuit are locked out and a
manual reset is required.
Lead/Lag Control
Lead/Lag is a selectable input located on the RTRM. The
RTRM is configured from the factory with the Lead/Lag con-
trol disabled. To activate the Lead/Lag function, simply re-
move the jumper connection J3-8 at the RTRM Lead/Lag in-
put. When it is activated, each time the designated lead
compressor(s) is shut off due to the load being satisfied, the
lead compressor or refrigeration circuit switches. When the
RTRM is powered up, i.e. after a power failure, the control
will default to the number one compressor.
Capacity Steps with Lead/Lag Enabled
Unit Size
Step 1
40%
TC*330
LEAD
LAG
60%
TC*360
LEAD
50%
50%
LAG
TC*420
LEAD
50%
50%
LAG
TC*480
LEAD
40%
LAG
60%
33%
TC*600
LEAD
LAG
67%
Coil Frost Protection
The Frostat™ control monitors the suction line temperature
to prevent the evaporator from freezing due to low operating
temperatures when ever there is a demand for cooling.
When an open circuit has occurred for 5 seconds minimum,
the RTRM turns off all of the cooling outputs providing the 3
minute minimum "On" time for the compressor(s) has
elapsed. The Supply Fan will be held "On" until the Frostat
has been closed for 5 continuous seconds or for 60 sec-
onds after the last compressor was shut "Off", which ever is
the longest.
VFD Programming Parameters
See System Troubleshooting section.
35
Step
Step 3
100%
100%
100%
100%
100%
100%
60%
100%
100%
67%
100%
100%
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Table of Contents
Troubleshooting
