Control; High Pressure Cutout And Temperature Discharge Limit; Power Exhaust Control; Statitrac - Trane Voyager Commercial Installation, Operation And Maintenance Manual

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).
The hot gas reheat option has one reheat low pressure
cutout (RLP). The RLP is located on the reheat circuit.
Hot Gas Reheat Low Pressure Control
The RLP has been added to insure proper refrigerant
management during active modulating hot gas reheat
operation.
The RLP will be ignored for the first 10 minutes of
compressor run time during active hot gas reheat
operation. 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 active
hot gas reheat, the compressor(s) in that circuit will be
locked out.
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.
On 27.5, 30, and 35 Ton units, if the high pressure
safety switch or temperature discharge limit opens, the
RTRM senses a lack of current while calling for cooling
and locks both compressors out with an auto reset. On
40 and 50 Ton units, 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.

Power Exhaust Control

The power exhaust fan is started whenever the position
of the economizer dampers meets or exceed the power
exhaust setpoint when the supply fan is on.
The setpoint potentiometer is on the RTOM and is
factory set at 25% for traditional constant volume and
variable air volume units.
For SZ VAV units the default power exhaust enable
setpoint will be 25% as on non-SZ VAV units. However,
for SZ VAV the Exhaust Enable Setpoint will need to be
adjusted for the proper setpoint during the maximum
Fan Speed Command for the unit. Once selected, the
difference between the Exhaust Enable Setpoint and
Design OA Damper Minimum Position at Full Fan
Speed Command will be calculated. The difference
RT-SVX34R-EN
calculated will be used as an offset to be added to the
Active Building Design OA Minimum Position target to
calculate the Dynamic Exhaust Enable Target to be
used throughout the Supply Fan Speed/OA Damper
Position range:
Exhaust Enable Target = Active Bldg Design OA Min
Position Target + (Active Exhaust Enable Setpoint –
Active Bldg Design OA Min Position @ Full Fan Speed
Command)
The Exhaust Enable Target could be above or below
the Active Bldg Design OA Min Position Target
Setpoint based on the Active Exhaust Enable Setpoint
being set above or below the Bldg Design Min Position
at Full Fan Speed Command. Note that an Exhaust
Enable Setpoint of 0% will result in the same effect on
Exhaust Fan control as on non-Single Zone VAV
applications with and without Statitrac; Exhaust Fan
ON. See Figure 46, p. 61
setpoint is modified throughout the OA damper
operating range.
Figure 46. SZ VAV exhaust
OAD
Posi on
Setpoints
Exhaust Enable Target
Exhaust Enable @ Full
Fan Speed
Design @ Full Fan Speed
Minimum Fan Speed Middle Fan Speed
Space Pressure Control - Statitrac
A pressure transducer is used to measure and report
direct space (building) static pressure. The user-defined
control parameters used in this control scheme are
Space Pressure Setpoint and Space Pressure
Deadband. As the Economizer opens, the building
pressure rises and enables the Exhaust Fan. The
Exhaust dampers will be modulated to maintain Space
Pressure within the Space Pressure Deadband.
N N o o t t e e : : The Exhaust Enable setpoint will need to be
selected as on units with standard power
exhaust control.
S S t t a a r r t t u u p p
for how the exhaust enable
Exhaust Enable
Offset
Maximum Fan Speed
61