RT-SVF25C-EN
15
Sequence of Operation
These units are offered with two control options,
electromechanical and ReliaTel™.
Note:
Refer to the unit nameplate: If the 9th digit of the
model number = R, proceed with the following
Sequence of Operation. If the 9th digit of the model
number = E, proceed with
.
Note:
The Condensate Overflow Switch (COF) (optional)
will shut the unit down if the float is raised and the
switch is closed.
ReliaTel Controls
ReliaTel Control is a microelectronic control feature, which
provides operating functions that are significantly
different than conventional electromechanical units. The
master module is the ReliaTel Refrigeration Module
(RTRM).
The RTRM provides compressor anti-short cycle timing
functions through minimum “Off” and “On” timing to
increase reliability, performance and to maximize unit
efficiency.
Upon power initialization, the RTRM performs self-
diagnostic checks to insure that all internal controls are
functioning. It checks the configuration parameters
against the components connected to the system.
The LED located on the RTRM module is turned “On”
within one second after power-up if all internal operations
are okay.
ReliaTel Control Cooling without an
Economizer
When the system switch is set to the “Cool” position and
the zone temperature rises above the cooling setpoint
control band, the RTRM energizes the (K9) relay coil
located on the RTRM. When the K9 relay contacts close,
the compressor contactor (CC1) coil is energized provided
the low pressure control (LPC1), high pressure control
(HPC1) and discharge line thermostat (TDL 1) are closed.
When the CC1 contacts close, compressor (CPR1) and the
outdoor fan motor (ODM) start to maintain the zone
temperature to within ± 2ºF of the sensor setpoint at the
sensed location.
If the first stage of cooling can not satisfy the cooling
requirement, the RTRM energizes the (K10) relay coil
located on the RTRM. When the (K10) relay contacts close,
the compressor contactor (CC2) coil is energized provided
the low pressure control (LPC2), high pressure control
(HPC2) and discharge line thermostat (TDL 2) are closed.
When the CC2 contacts close, compressor (CPR2) starts to
maintain the zone temperature to within ± 2ºF of the sensor
setpoint at the sensed location.
Three-Stages of Cooling
1
When the unit is configured for three-stage cooling, and
the system switch is set to the cool position and the zone
temperature rises above the cooling setpoint control band,
the RTRM energizes the (K10) relay coil located on the
RTRM. When the (K10) relay contacts close, compressor
contactor (CC2) is energized.This is the smaller of the two
compressors (CPR2). This staging order is opposite
standard staging order.
If the first stage of cooling can not satisfy the cooling
requirement, the RTRM energizes the (K9) relay coil and
de-energizes the (K10) relay coil on the RTRM. Compressor
contactor (CC1) is energized, bringing on the larger of the
two compressors (CPR1). Compressor contactor (CC2) is
de-energized, turning off the smaller compressor.
If the second stage of cooling can not satisfy the cooling
requirement, the RTRM keeps the (K9) relay coil energized
and energizes the (K10) relay coil. Compressor contactors
(CC1) and (CC2) are energized, and both compressors
(CPR1 and CPR2).
Lead/Lag is disabled with three-stage cooling. A unit
configured for three-stage cooling and controlled with a
thermostat will operate as a two-stage unit.
ReliaTel Control Evaporator Fan Operation
(for Gas Units)
When the fan selection switch is set to the “Auto” position,
the RTRM energizes the (K6) relay coil approximately 1
second after energizing the compressor contactor coil
(CC1) in the cooling mode. In the heating mode, the RTRM
energizes the (K6) relay coil approximately 45 second after
gas ignition. Closing the (K6) contacts on the RTRM
energizes the indoor fan relay (F) coil to start the indoor fan
motor (IDM).
The RTRM de-energizes the fan relay (F) approximately 60
seconds after the cooling requirement has be satisfied to
enhance unit efficiency. When the heating cycle is
terminated, the indoor fan relay (F) coil is de-energized
approximately 90 seconds after the heating requirement.
When the fan selection switch is set to the “On” position,
the RTRM keeps the indoor fan relay coil (F) energized for
continuous fan motor operation.
When the unit is equipped with the optional clogged filter
switch, wired between terminals J7-3 and J7-4 on the
ReliaTel Options Module (RTOM), the RTRM produces an
analog output if the clogged filter switch (CFS) closes for
two minutes after a request for fan operation. When the
1
High efficiency units only.
