120
RT-SVD03L-EN
Sequence of Operation, 3 to 10
Tons Only
1-Stage Units
Ignition control (IGN) runs a self check (including
verification that the gas valve is de-energized). IGN
checks the high limit switch (TCO1) for closed contacts,
the pressure switch (PS) for open contacts, flame
rollout (FR) for closed contacts.
IGN energizes inducer blower. When PS closes, 20
second pre-purge begins. After 20 seconds, the IGN
energizes the spark and gas valve at the same time.
The spark will stay energized for at least 2 seconds
attempting to establish flame. If a flame is not
established, the spark will continue up to 7 seconds.
Once a flame is established, spark is de-energized and
indoor blower motor (IBM) timing begins. 45 seconds
later, the RTRM energizes the IBM. When the zone
sensor or thermostat is satisfied, the gas valve is de-
energized, the inducer runs for 5 seconds then stops
(post-purge), and the IBM runs for 60 seconds then
stops unless being requested to run continuously.
2-Stage Units
Ignition control (IGN) runs a self check (including
verification that the gas valve is de-energized). IGN
checks the high limit switches (TCO1 & TCO2) for
closed contacts, the pressure switch (PS) for open
contacts, flame rollout (FR) for closed contacts.
IGN energizes inducer blower on high speed. When PS
closes, 20 second (15 seconds on high, 5 seconds on
low) pre-purge begins. After 20 seconds, the IGN
energizes the spark and gas valve at the same time.
The spark will stay energized for at least 2 seconds
attempting to establish flame. If a flame is not
established, the spark will continue up to 7 seconds.
Once a flame is established, spark is de-energized and
indoor blower motor (IBM) timing begins. 45 seconds
later, the RTRM energizes the IBM. If deviation from
setpoint is great enough, there is no minimum delay
before 2
nd
stage is energized. When the zone sensor or
thermostat is satisfied, the gas valve is de-energized,
the inducer runs for 5 seconds then stops (post-purge),
and the IBM runs for 60 seconds then stops unless
being requested to run continuously.
If the burner fails to ignite, the ignition module will
attempt two more ignition cycles before locking out.
The green LED will indicate a lockout by two fast
flashes. An ignition lockout can be reset by:
•
Opening for 3 seconds and closing the main power
disconnect switch.
•
By switching the ’Mode’ switch on the zone sensor
to ’OFF’ and then to the desired position, or
•
Allowing the ignition control module to reset
automatically after one hour.
If the burner trips due to a high temperature limit, the
unit will shut down and initiate a four flash diagnostic.
After the limit cools down and closes, the burner will
again restart. There is no limit to the number of high
limit trips that can occur.
Figure 72.
Direct spark ignition control sequence of operation
1st stage
call for heat
Start trial
for ignition
1st stg on
2nd stg on
End call for heat
5 sec CBM
post-purge
CBM off
No
Minimum
Delay
7 sec trial for ignition
IDM off
IDM on for 60
or 90 sec
IDM on
Start 45 second
delay for IDM
Additional 5 sec
if needed
2 sec minimum
CBM 20 sec pre-purge
Precedent
™
™
6 to 10 Tons
Modulating Gas Heat Units
When there is a call for heat, ReliaTel
™
will send a
command to the ignition module to fire and open the
modulating valve to 100% (10.0Vdc) while also
commanding the gas inducer motor to High speed
(Valve 2 binary output on the ignition module) and
controlling the fan speed to normal algorithm control.
After operating at this condition for the 60 second start-
up period, the modulating heat control will be released
to normal algorithm control and the valve will begin
modulating in the Modulating Gas Heat Output
Operating Range between the unit preferred Min-Fire
Summary of Contents for ReliaTel
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