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attempt two retries and then lock out if flame is not
proven. The unit will attempt to ignite at 60 minute
intervals until the heating call is removed.
An IGN lockout due to flame loss can be reset by:
•
Open and close the main power disconnect switch.
•
Switch the MODE switch on the zone sensor to
“Off” and then to the desired position (VAV units –
remove and reapply the mode input).
•
Allow the IGN to reset automatically after one hour.
When ignition takes place, the hot surface igniter (IP) is
de-energized and functions as the flame sensor.
Two Stage—If, after 60 seconds, the unit requires 1st
stage heating only, the IGN will change the combustion
blower from high speed to low speed. If additional
heating is required and first stage heat has been
operating for a minimum of 10 seconds, the IGN
inducer relay will change the combustion blower motor
(CBM) to high speed, delivering second stage heat
capacity.
Modulating—Units with modulating heat will fire the
modulating bank first at high fire for 60 seconds. The
unit will then modulate the heater to the necessary
rate. If the modulating heat bank cannot satisfy the
zone needs alone, the second bank will come on and
the modulating will find the appropriate operating
point.
Constant Volume (CV) Unit Fan
Operation
If the fan selection switch is in the “AUTO” position for
constant volume units, the RTRM will delay starting the
supply fan for 60 seconds to allow the heat exchanger
to warm up. When the zone temperature rises above
the heating setpoint, the IGN control module will
terminate the heat cycle. The supply fan remains
energized for an additional 90 seconds.
Variable Air Volume (VAV) Unit Fan
Operation (2 Stage and Modulating Gas
Heat)
During Unoccupied heating, Morning Warm up, and
Daytime Warm up mode, the VFD must be at 100%.
Therefore, before the unit can heat, the VHR relay must
have been energized for at least 6 minutes to ensure
that the VAV boxes have driven to maximum. For
example, 6 minutes after a Daytime Warm up mode is
initiated, the VFD output will go to 100% and then the
heat cycle will begin. The VHR relay is energized during
Unoccupied mode, Morning Warm up mode, and
Daytime Warm up mode.
Variable Air Volume (VAV) Unit Fan
Operation (Modulating Gas Heat Only)
During Changeover Heat (LTB5-1 shorted to LTB5-2),
the unit will heat to the Supply Air Heating Se/-
7ºF. The VFD will modulate to maintain the Static
Pressure Setpoint.
Ignition Control Module
There is a green LED located on the ignition module.
Any time the Ignition module is powered, the LED will
be on to provide status of the ignition system.
•
Steady OFF - no power/ internal failure
•
Steady ON - no diagnostic, no call for heat
•
Slow flash rate ¾ second on, ¼ second off - normal
call for heat
Error Code Flashes
•
One flash - Communication loss between RTRM
and IGN
•
Two flashes - System lockout; failed to detect or
sustain flame (3 tries, lockout after 3
rd
try)
•
Three flashes - Not used
•
Four flashes - High limit switch TCO1, TCO2, or
TCO3 open (auto reset)
•
Five flashes - Flame sensed and gas valve not
energized; or flame sensed and no call for heat
(auto reset)
The pause between groups of flashes is approximately
two seconds.
High Temperature Limit Operation and
Location
All of the heater limit controls are automatic reset. The
high limit cutouts (TCO1) and/or (TCO3) protect against
abnormally high supply air temperature. The fan failure
limit (TCO2) protects against abnormally high heat
build up due to excessive high limit (TCO1) (TCO3)
cycling if the indoor fan motor (IDM) fails. If TCO1,
TCO2, or TCO3 open during a heating call, the heat will
shut down and the supply fan will be forced to run. The
heat will automatically restart should the TCO circuit
re-close during an active heating call. While the TCO
circuit is open, a heat fail diagnostic will be sent from
the IGN to the RTRM.
The TCO1 and TCO3 is located in the bottom right
corner of the burner assemblies on both downflow and
horizontal units. TCO2 is located on the IDM partition
panel; below and to the right of the blower housing on
downflow units. On horizontal units, TCO2 is located
on the IDM partition panel above the blower housing.
Electric Heat Sequence Of
Operation
Constant Volume (CV)
When heat is required and the Fan selection switch is in
the “AUTO” position for constant volume applications,
the RTRM energizes the Supply Fan approximately one
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