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Operation
RT-SVX20A-E458
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 Table
below lists the selectable dry
bulb values by potentiometer
setting.
2. Reference Enthalpy - controlling
the economizer cycle by sensing
the outdoor air humidity. The
Table below 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 - By
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 52 - Potentiometer Setting
*Factory Setting
ReliaTel™ Control Heating
Operation
When the system switch is set to
the "Heat" position and the zone
temperature falls below the heating
setpoint controlband, a heat cycle is
initiated when the RTRM
communicates ignition information
to the Ignition module (IGN).
Potentiometer
Setting
Dry BuIb Enthalpy
(°C) (KJ/kg)
A 23* 63
B 21 58
C 19 53
D 17 51
Ignition Module
Two Stage (IGN) runs self-check
(including verification that the gas
valve is de-energized). (IGN) checks
the high-limit switches (TC01 &
TC02) for normally closed contacts.
With 115 VAC power supplied to the
ignition module (IGN), the hot
surface ignition probe (IP) is
preheated for approximately
45 seconds. The gas valve (GV) is
energized for approximately
7 seconds for trial for ignition, to
ignite the burner.
Once the burner is ignited, the hot
surface ignition probe (IP) is de-
energized by the ignition module
(IGN) and functions as the flame
sensing device.
If the burner fails to ignite, the
ignition module will make two more
attempts before locking out. The
green LED will indicate a lock out by
two fast flashes. An ignition lockout
can be reset by:
1. Opening for 3 seconds and
closing the main power
disconnect switch
2. By switching the "Mode" switch
on the zone sensor to "OFF" and
then to the desired position
3. Allowing the ignition control
module to reset automatically
after one hour.