Trane RRU150F N Series Installation, Operation And Maintenance Manual page 19

Y1 – O/Air Cooling Enable Set Point (CSP) is operator
adjustable between 68°F and 90°F.
Y1 - O/AIR COOLING ENABLE SET POINT (CSP):
COOL 1 is activated through RTRM Y1 by the RRUCM
through the COOL 1 R3 Relay when the OAT rises above
the CSP and the Outdoor Air Enthalpy (OE) is below the Y1
– O/Air Dehumid Enable Set Point (OES1). The
Refrigeration Capacity Control (RCC) is enabled when
COOL 1 is active. COOL 2 is disabled during cooling mode.
RCC Operation
The Refrigeration Capacity Control (RCC) monitors
COOL 1 evaporator suction pressure and meters
compressor discharge gas into a de-superheating
chamber where it is mixed with refrigerant introduced
through an integral TXV providing cooling of the hot gas.
Cooled gas is then bypassed to the suction line between
the evaporator and compressor. An integral pressure
controller modulates the quantity of hot gas bypassed to
maintain desired suction pressure-temperature and
prevent frosting indoor coil. The RCC is factory set and
field adjustment is typically not required.
RCC PRE-SET SUCTION PRESSURE SETTING:
38°F SATURATED SUCTION TEMPERATURE (APX.)
The RCC effectively reduces compressor nominal capacity
and energy consumption when active.
"Occupied" Dehumidification Mode
Call for dehumidification is based on the Outdoor Air
Enthalpy (OE) relative to Y1 – O/Air Dehumid Enable Set
Point (OES1) and Y2 – O/Air Dehumid Enable Set Point
(OES2). Y1 – DEHUMID is activated when the OE is above
OES1.
Y2 – DEHUMID is activated when the OE rises above OES2.
OES1 and OES2 set points are operator adjustable within
a preset range at the ROD. The RCC will operate anytime
the suction pressure drops below the RCC pressure set
point.
DEHUMIDIFICATION SET POINTS (OES1 & OES2): 23–30 BTU
28 BTU (OES1) & 34 BTU (OES2) DEFAULT
Y2 – DEHUMID is deactivated after OE drops 1 Btu below
OES2 set point.
Y1 – DEHUMID is deactivated after OE drops 1 Btu below
OES1 set point.
Hot Gas Reheat (Optional)
Use of this option requires the optional hot gas reheat coil
and requires the operator to INSTALL the HGRH Option at
the ROD.
Call for reheat is controlled by the Supply Air Temperature
(SAT) sensed at the factory mounted Supply Air
RRU-SVX02F-EN
Temperature Sensor (STS) located in the supply air
discharge plenum. Reheat is controlled by the operator
adjustable HGRH (Hot Gas Reheat) Control Dead Band
68°F–90°F
(HGRHD) set point at the RRUCM. On call for reheat, the
78°F DEFAULT
RRUCM energizes the Reheat Valve (RHV) through the R5
Relay when the SAT falls below Occupied S/Air Heating
Set Point (HSP) minus HGRHD and is de-energized when
the SAT rises above HSP plus HGRHD.
HGRH HEATING DEAD BAND (HGRHD):
HGRH SUPPLY AIR TEMPERATURE SETPOINT:
"Occupied" Heating Mode
Call for heat is based on Outdoor Air Temperature (OAT)
sensed by the Outdoor Air Temperature Sensor (OTS).
When the Supply Air Temperature (SAT) sensed by the
Supply Air Temperature Sensor (STS) drops below the
O/Air Heating Enable Set Point (HESP) a call for HEAT is
initiated by the RRUCM through the R6 HEAT Relay.
Burner initiation sequence energizes the Combustion Fan
Motor (CFM) through the R7 CFM Relay. The Combustion
Damper Actuator (CDA) and the Modulating Gas Valve
Actuator (MGA) are controlled through RRUCM Analog
Output A01 (AO1).
114 LB
Burner Lighting Sequence: The opens the Combustion
Damper Actuator (CDA) opens while the Combustion Fan
Motor (CFM) begins a 30-second heat exchange pre-
purge. Following the pre-purge, the RRUCM, through R6,
energizes the burner safety circuit—Ignition Control
Module (IGN), Ignition Transformer (TNS5), Burner Air
Proving Switch (APS), High Temperature Cutout (TCO1),
Fan Failure Limit (TCO2), S/Air Low Cutoff (SLT), and
S/Air High Cutoff (SHT). During the IGN 30-second pre-
ignition routine, the RRUCM modulates the CDA to the
CLOSED ignition position.
Following the IGN 30-second pre-ignition routine, the IGN
begins a 6-second "single-try" ignition trial. Upon
successful ignition, the RRUCM holds the CDA in the
ignition position for 60 seconds. At the end of the 60-
second hold in ignition position, the CDA initiates full
modulation as controlled by the RRUCM. The RRUCM
monitors SAT at the Supply Air Temperature Sensor (STS)
(OES1)
and varies the output signal from AO1 to the MGA
32–40 BTU
modulating gas flow to the burner to maintain Occupied
(OES2)
S/Air Heating Set Point (HSP); refer to
output signal range. Approximately 90 seconds from a call
for heat, the RRUCM will begin full modulating control.
Failure to prove flame at the burner flame sensing rod
within the 6-second ignition trial, or failure to maintain
flame signal following successful ignition LOCKS-OUT the
ignition process. In the event that proof of flame is lost
following successful ignition a single ignition retry will be
initiated. To retry ignition following ignition or single retry
failure, power must be turned off for 10 seconds and then
powered up. The ignition process and timing sequences
begin upon re-establishment of power.
Sequence of Operation
±4–20°F
±5°F DEFAULT
68°F DEFAULT
Table 5, p. 35, for
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