Economizer Set-Up; Reliatel™ Control Heating Operation (For Cooling Only Units); Reliatel™ Control Heating Operation; Units) - Trane YSC036G Installation, Operation And Maintenance Manual

Sequence of Operation
relay (F) is energized and allows mechanical cooling
operation.
When the unit is equipped with the optional fan failure
switch, wired between terminals J7-5 and J7-6 on the
RTOM, the RTRM will stop all cooling functions and
produce an analog output if the fan failure switch (FFS)
does not open within 40 seconds after a request for fan
operation. When the system is connected to a remote
panel, the "SERVICE" LED will flash when this failure
occurs.
Note: For units equipped with the dehumidification
option, if the unit is economizing, the damper
resets to minimum position while in
dehumidification mode.

Economizer Set-Up

Adjusting the minimum position potentiometer located on
the unit economizer actuator (ECA) sets the required
amount of ventilation air.
Two of the three methods for determining the suitability of
the outside air can be selected utilizing the enthalpy
potentiometer on the ECA, as described below:
1. Ambient temperature - controlling the economizing
cycle by sensing the outside air dry bulb temperature.
The following table lists the selectable dry bulb values
by potentiometer setting.
2. Reference enthalpy - controlling the economizer cycle
by sensing the outdoor air humidity. The following
table lists the selectable enthalpy values by
potentiometer setting. If the outside air enthalpy value
is less than the selected value, the economizer is
allowed to operate.
3. Comparative enthalpy - utilizing a humidity sensor and
a temperature sensor in both the return air stream and
the outdoor air stream, the unit control processor
(RTRM) will be able to establish which conditions are
best suited for maintaining the zone temperature, i.e.
indoor conditions or outdoor conditions. The
potentiometer located on the ECA is non-functional
when both the temperature and humidity sensors are
installed.
Table 18. Potentiometer settings
Potentiometer
Setting Dry Bulb
A 73°F (22.8ºC)
B 70°F (21.1ºC)
(a)
C 67°F
D 63°F (17.2ºC)
E 55ºF (12.8ºC)
(a) Factory settings
58
Reference Enthalpy
27 Btu/lb (63 kJ/kg)
25 Btu/lb (58 kJ/kg)
(19.4ºC) 23 Btu/lb (53 kJ/kg)
22 Btu/lb (51 kJ/kg)
19 Btu/lb (44 kJ/kg)
ReliaTel™ Control Heating Operation (for
Cooling Only Units)
When the system switch is set to the "Heat" position and
the zone temperature falls below the heating setpoint
control band, the RTRM energizes (K1) relay coil. When the
(K1) relay contacts close, located on the RTRM, the first
stage electric heat contactor (AH or AH and CH) is
energized.
If the first stage of electric heat can not satisfy the heating
requirement, the RTRM energizes (K2) relay coil. When the
(K2) relay contacts close, located on the RTRM, the second
stage electric heat contactor (BH) is energized, if
applicable. The RTRM cycles both the first and second
stages of heat "On" and "Off" as required to maintain the
zone temperature setpoint.
ReliaTel™ Control Heating Operation (for
Gas Units)
When the system switch is set to the "Heat" position and
the zone temperature falls below the heating setpoint
control band, a heat cycle is initiated when the RTRM
communicates ignition information to the Ignition module
(IGN).

Ignition Module

Two-stage (IGN) runs self-check (including verification
that the gas valve is de-energized). (IGN) checks the high-
limit switches (TC01 and TC02) for normally closed
contacts, the pressure switch (PS) for normally open
contacts, and the flame rollout (FR) switch for continuity.
(IGN) energizes inducer blower on high speed to check
pressure switch closure. If the pressure switch is closed,
the inducer blower starts a 20-second pre-purge (15
seconds on high speed followed by 5 seconds on low
speed). If the pressure switch (PS) is still open, the inducer
blower will continue to be energized on high speed until
pressure switch closure. After pre-purge completes, the
(IGN) energizes the first stage of the gas valve, initiates
spark for 2 seconds minimum, 7 seconds maximum
(ignition trial) and detects flame and de-energizes spark.
From this point, a fixed 45 second indoor blower delay on
timing starts. After the indoor blower delay on is
completed, the (IGN) energizes the indoor blower. The
(IGN) enters a normal operating loop where all inputs are
continuously monitored. If the first stage of gas heat can
not satisfy the heating requirement, the thermostat closes
W2. The (IGN) energizes the second stage of the gas valve
and the second stage of inducer blower. When the zone
thermostat is satisfied, the (IGN) de-energizes the gas
valve. The (IGN) senses loss of flame. The (IGN) initiates a
5 second inducer blower post purge. The (RTRM) initiates
a second indoor blower delay off.
For Ultra Low NOX gas furnace units, the vestibule
temperature limit switch must also be in closed state in
order for the gas valve and the premix blower to be
energized. In absence of gas valve and premix blower not
being energized, the burner will fail to ignite.
RT-SVX21AC-EN