RT-SVF69C-EN
13
Sequence of Operation
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
controlband, the RTRM energizes the first stage of electric
heat. If the first stage of electric heat cannot satisfy the
heating requirement, the RTRM energizes the second
stage electric heat 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
controlband, a heat cycle is initiated when the RTRM
communicates ignition information to the Ignition
module.
Modulating Gas Heat 2.5:1 Turndown
In a modulating heat unit, when a call for heat is received,
the burner will light at full fire (100%). After the burner is
lit, the unit controls will monitor the discharge air
temperature and modulate the input rate down to match
the load.
Ignition Control 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. With power supplied to the ignition module, the
hot surface ignition probe is Preheated. The gas valve is
energized for a few seconds for trial for ignition, to ignite
the burner. Once the burner is ignited, the hot surface
ignition probe is de-energized by the ignition module and
functions as the flame sensing device. If the burner fails to
ignite, the ignition module will attempt two retries before
locking out. The green LED will indicate a lockout 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. Refer to
for the
LED diagnostic definitions.
When the fan selection switch is set to the "Auto" position,
the RTRM energizes the indoor fan relay coil
approximately 30 seconds after initiating the heating cycle
to start the indoor fan motor. The automatic reset high
limit, located in the bottom right corner of the burner
compartment, protects against abnormally high leaving
air temperatures. The automatic reset fan fail limit, located
in the upper middle section of the indoor fan board,
protects against abnormally high heat buildup which
could occur because of extended cycling of the high limit
or if the indoor fan motor fails to operate. Should TCO2
open, the RTRM will energize the indoor fan relay in an
attempt to start the fan motor. The RTRM signals that a
heat failure has occurred by flashing the "Heat" LED on the
zone sensor. There is a green LED located in the Ignition
Control Module.
lists the diagnostics and the
status of the LED during the various operating states.
Ignition Control Module Diagnostics
At any time the control is powered, a green LED indicator
light shall be lit using the following signal:
Enhanced Dehumidification
Note:
Enhanced Dehumidification is not be supported on
Multiple Zone VAV.
Enhanced Dehumidification is available on all units
equipped with a Space Humidity sensor. Once the Space
Humidity value exceeds the Dehumidification Setpoint
and dehumidification is enabled the unit will transition to
the Enhanced Dehumidification mode. If the unit is
actively cooling, the ReliaTel control will latch the current
compressor operation and reduce the current indoor
airflow. If the unit is not actively cooling when the
Enhanced Dehumidification mode is activated, the unit
will energize a single fixed speed compressor and the
modulating eFlex compressor will ramp to a fixed speed
while engaging the IDM and both ODM at the appropriate
airflow for that condition. If during active enhanced
dehumidification the Space Humidity falls below the
Dehumidification Setpoint – 2%, Dehumidification will be
terminated and the unit will transition back to normal
Cooling or Heating control.
Table 12. Ignition module diagnostics
Steady OFF:
No Power/Failure/Internal Failure
Steady ON:
Normal
Slow Flash Rate:
Normal, call for heat (¾ second on, ¼ second
off).
Fast Flash Rate:
Used for error indication only (¼ second off, ¾
second on).
Error Code Fast Flash Rate:
1 Flash
Communication Issue between Refrigeration
Module and 3SH control.
2 Flashes
System Lockout: Failed to detect or sustain
flame.
3 Flashes
Not implemented.
4 Flashes
High Limit switch protection device open.
5 Flashes
Flame sensed and gas valve not energized or
flame sensed and no call for heat.
6 Flashes
Not implemented.
Note:
The pause between groups of fast flashes is approximately two
seconds. Additionally, the LED indicator light shall flash for one
second at power-up.