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MODGAS-XWR2 Technical Guide
SEQUENCE OF OPERATION
Valve Failure, Force Mode and Master vs. Normal
Valve Failure
If a valve failure occurs, the board fails that stage and then
continues to the next available stage. This is to make sure that
if there is a call for heat, heat is being supplied. A valve failure
consists of either a Valve No Detect or a Proof of Flame Fail.
Here is what valve failures look like for each configuration:
1V1IGN1S/2V1IGN1S:
If the modulating valve fails, Heat 1
(RLY3) is turned off and the board then moves to the fixed
stages (if available). If the valve fails when there is first a call
for heat, then the first fixed stage will come on immediately.
Every ignition retry period (set in the hidden configurations
menu), the board will re-attempt to detect the valve(s) and retry
the ignition process.
2V2IGN2S:
If the first stage (the first modulating valve) fails
when there is first a call for heat, Heat 1 (RLY3) is turned off and
the board immediately moves to the second stage (the second
modulating valve). If the first stage fails when the board is in
MODULATE_MODE, then normal board operation continues.
If the second stage fails, Heat 2 (RLY4) is turned off and the board
continues normal operation and moves to the next fixed stages.
Every ignition retry period (set in the hidden configurations
menu), the board will re-attempt to detect the valve(s) and retry
the ignition process.
Force Mode
This mode is used to test that the valve firing sequence is
functioning. This mode is NOT meant to replace heating mode
by any means. There is no staging in this mode, and there is no
PID Loop running in this mode. Once a stage is forced on through
the Force Screen, the board will enter Force Mode and will not
leave this mode until all the stages that were forced on have been
turned off or 10 minutes pass with no user input to the board.
The following options are the Force Mode configurations.
1V1IGN1S:
Forcing Stage 1 on forces Heat 1 (RLY3) on, and
then the next screen allows the option to decide the modulation
percentage for the valve. Forcing stages 2-4 on forces Heat 2-4
(RLY4-RLY6) on, respectively.
2V2IGN2S:
Forcing Stage 1 and 2 on forces Heat 1 (RLY3)
and Heat 2 (RLY4) on, respectively, and the screens following
each force screen allow you to select the percent modulation
for each valve.
NOTE:
Configuring one stage below the low speed cutoff
and the other above it will cause low speed relay
difficulties.
Forcing stages 2-4 on forces Heat 2-4 (RLY4-RLY6) on.
2V1IGN1S:
Forcing Stage 1 on forces Heat 1 (RLY3) on, and
the next screen allows the option to select the modulation
percentage (since both valves are one stage, they both modulate
at the same percentage). Forcing Stages 2-4 on forces Heat 2-4
(RLY4-RLY6) on.
2V2IGN1S:
Forcing Stage 1 on forces Heat 1 (RLY3) and Heat
2 (RLY4) on, and the screens following allow you to select the
modulation percentage for the respective valve. Even though both
valves are considered one stage, since they operate on separate
relays, the option to modulate them at different percentages is
available.
NOTE:
Configuring one stage below the low speed cutoff
and the other above it will cause low speed relay
difficulties.
Forcing stages 3 and 4 on force on Heat 3 (RLY5) and Heat 4
(RLY6), respectively.
Master vs. Normal
In order to help clarify operating modes, master and normal
are used to denote two MODGAS-XWR2 boards that are
communicating with one another. With one MODGAS-XWR2,
the maximum number of modulating valves is two, but with two
boards the maximum is four (two for each board). In a master/
normal operation, the secondary board is slaved to the master
board.
•
To configure a master board, put the “S/A MODE” for
the board to “FORCED” and put “OPERATION” to
“MASTER” (both configurations found in the hidden
screens).
•
To configure a secondary board, put “OPERATION” to
“NORMAL” (found in the hidden screens).
The following options are the Master/Normal configurations.
2V2IGN2S:
In this configuration, both boards utilize both heat
relays for a modulating gas valve. Stage 1 is the valve attached to
Heat 1 (RLY3) for both boards, and Stage 2 is the valve attached
to Heat 2 (RLY4) for both boards. The valves on both boards are
always modulated to the same position, and both boards stage
up (i.e. turn on Heat 2 (RLY3)) at the same time.
2V1IGN1S:
In this configuration, both boards utilize Heat 1
(RLY3) to turn on two modulating gas valves (a total of four for
the two boards). This means that each board has an open relay
(Heat 2 (RLY4)) for an additional on board fixed stage. The two
valves on both boards (i.e. all of the four valves) are always at
the same modulation position. The first stage up (i.e. Stage 2)
will energize Heat 2 (RLY4) on the master board, and the second
stage up (i.e. Stage 3) will energize the Heat 2 (RLY4) on the
secondary board.
