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Sequence of Operation
approximately 30 seconds after initiating the heating cycle
to start the indoor fan motor (IDM). The automatic reset
high limit (TCO1), located in the bottom right corner of the
burner compartment, protects against abnormally high
leaving air temperatures. The automatic reset fan fail limit
(TCO2), 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 (TCO1) or if the indoor fan motor (IDM) fails to
operate. Should TCO2 open, the RTRM will energize the
indoor fan relay (F) 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.
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:
Table 18. Ignition module diagnostics
Steady
No Power/Failure/Internal Failure
OFF:
Steady ON:
Normal
Slow Flash
Normal, call for heat (¾ second on, ¼ second off).
Rate:
Fast Flash
Used for error indication only (¼ second off, ¾ second
Rate:
on).
Error Code Fast Flash Rate:
Communication Issue between Refrigeration Module
1 Flash
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.
Flame sensed and gas valve not energized or flame
5 Flashes
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.
Dehumidification
The dehumidification cycle is only permitted above 40 ºF
and is not permitted during a heating cycle or during a
nd
demand for 2
stage cooling. Otherwise, when an
installed zone humidity sensor indicates a relative
humidity equal to or greater than the RH set point as
adjusted on the ReliaTel Options Module (RTOM), a
dehumidification cycle is initiated.
Notes:
•
Dehumidification takes priority over a call for one
stage cooling.
•
Heating or 2 stage cooling takes priority over
dehumidification, and a relative humidity sensor takes
priority over a humidistat.
44
Dehumidification Coil Purge Cycle (for units
with the Dehumidification option)
On multiple circuit units with Dehumidification/Reheat
configured, a purge cycle will be active for compressor
reliability. The purpose of this function is to properly
distribute refrigerant and lubricant throughout the system
by temporarily switching to the unused section of the coil
for 3 minutes (purge cycle). The function operates as
follows:
1. A purge cycle will be initiated after 90 minutes of
Table 18, p. 44
lists
2. A purge cycle will consist of transitioning to the mode
3. The 90-minute cycle count will be reset anytime there
4. If the purge cycle is a cooling cycle, only the first circuit
5. The purge cycle will ignore the Low Ambient
6. A purge cycle takes priority over normal cooling or
Two-Speed Indoor Fan (Title 24)
Control
For units equipped with two-speed indoor fan control,
standard unit operation for cooling, heating, and
dehumidification will continue and all unit functions will
operate normally, except for the control of the indoor fan
speed. All units configured with any type of heating or
reheat/dehumidification will heat and reheat/dehumidify
the supply air and space as normal utilizing full speed
indoor fan by energizing the appropriate outputs. The two-
speed indoor fan unit will only utilize two speeds during
the cooling operation modes described below.
Cooling Operation
For cooling operation, the unit will operate at Low Fan
Speed during Fan Only, Economizer Only, and the first
stage of compressor unit modes by Default. When the unit
receives a call for cooling, if the economizer is enabled, the
unit will energize the associated Low Speed output and
begin to modulate the OA Damper open above minimum
position up to 100% as necessary. By default, the supply
fan will remain at low speed for the duration of
Economizer-Only cooling. If the OA damper reaches 100%
accumulated compressor run time in only one mode:
cooling or dehumidification, without transitioning to
the other mode.
that hasn't run in 90 minutes of total compressor
operation. The cycle will last for a period of 3 minutes.
is a normal transition between cooling and
dehumidification. Transitioning from one of these
modes to any other mode (off or heat) will not reset the
counter.
will be activated. If it is a dehumidification cycle then
the normal 2-compressor dehumidification mode
cycle will be used.
Dehumidification lockout feature.
dehumidification requests, but will discontinue for all
high priority lockouts and alarms.
RT-SVX26R-EN
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