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MODGAS-XWR2-B Technical Guide
SEQUENCE OF OPERATION
Heating Mode
Heating Mode
Ignition Sequence for each Valve Configuration
After heat is enabled, the modulating valve(s) will move into the
ignition sequence. As long as there is a call for heat, at least one
stage will be on. Despite the Supply Air Temperature relation to
the Supply Air Temperature Setpoint, the MODGAS-XWR2-B will
continue heating as long as Heat is enabled (through either binary
enable or Modbus enable).
1V1IGN1S/ 2V2IGN2S:
Valve 1 moves to the valve start position (set
in the hidden screen configuration and defaulted to 70% modulation)
and Heat 1 (RLY3) is on. The valve will remain at this position until
the proof of ignition time is satisfied. In order to establish proof of
ignition, the binary input used for the proof of ignition must remain
high for 20 seconds.
2V1IGN1S:
Valve 1 and 2 move to the valve start position (set in the
hidden screen configuration and defaulted to 70% modulation) and
Heat 1 (RLY3) is on. Both valves are connected to the same relay.
The valve will remain at this position until the proof of ignition time
is satisfied. In order to establish proof of ignition, the binary input
used for the proof of ignition must remain high (24 VAC signal)
for 20 seconds.
2V2IGN1S:
Valve 1 and 2 move to the valve start position (set in the
hidden screen configuration and defaulted to 70% modulation) and
Heat 1 (RLY3) and Heat 2 (RLY4) are on. The valve will remain
at this position until the proof of ignition time is satisfied. In order
to establish proof of ignition, the binary input used for the proof of
ignition must remain high (24 VAC signal) for 20 seconds.
Modulating Modes for each Valve Configuration
After a configuration has completed its ignition sequence, then it
moves into a modulating mode.
1V1IGN1S:
The PID loop runs every 10 seconds and determines
the modulation percentage and commands the valve accordingly.
The valve will not close more than the minimum position while the
heating is enabled. During the modulation sequence, if the valve
position is below 55%, the combustion fan low speed relay (RLY2
- LOW SPEED) will energize. Once it goes above 55%, the relay
will de-energize and move the fan back into high speed.
2V2IGN2S:
The PID loop runs every 10 seconds and determines
the modulation percentage and commands the valve accordingly.
The valve will not close more than the minimum position while the
heating is enabled. Only after the stage up delay requirement has
been met will the board stage up and open the second valve. Then
both valves will move to the same position. During the modulation
sequence, if the valve position is below 55%, the combustion fan
low speed relay (RLY2 - LOW SPEED) will energize. Once it goes
above 55%, the relay will de-energize and move the fan back into
high speed.
2V1IGN1S/2V2IGN1S:
The PID loop runs every 10 seconds and
determines the modulation percentage for both valves. During
the modulation sequence, if the valve position is below 55%,
the combustion fan low speed relay (RLY2 - LOW SPEED) will
energize. Once it goes above 55%, the relay will de-energize and
move the fan back into high speed.
Additional Staging Information for each Valve
Configuration
During the heating sequence, if it is determined that there is currently
not enough/too many stages, then a stage up/down will occur,
respectively. For a stage up to occur, the valves that are currently
in modulating mode must be fully open (100% modulation) for the
stage up time, and the current Supply Air Temperature must be at
least 2ºF below the Supply Air Temperature Setpoint. For a stage
down to occur, the valves must be at their minimum position (35%
modulation) and the current Supply Air Temperature must be at least
6ºF above the Supply Air Temperature Setpoint. Additionally, all
stages will stage down in the reverse order they staged up (i.e. the
first one to stage down is the last one to stage up). Below is additional
staging information for each of the configurations:
1V1IGN1S/2V1IGN1S:
Additional stages of fixed heat will be turned
on using Heat 2 (Rly 4) through Heat4 (Rly 6). Stage 3 would
be configured on Heat 3 (RLY5) and Stage 4 on Heat 4 (RLY6).
Additional stages must be off board.
2V2IGN2S:
Both on-board heat relays are used for modulating
valves, so the first stage up (i.e. turning on Stage 2) turns on the
second modulating valve. Stage 3 would be configured on Heat 3
(RLY5) and Stage 4 on Heat 4 (RLY6). Additional stages must be
off board.
2V2IGN1S:
Both on-board heat relays are used for modulating
valves (Stage 1), Stage 2 would be configured on Heat 3 (RLY5)
and Stage 3 on Heat 4 (RLY6). Additional stages must be off board.
