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MHGRV-X Field Technical Guide
Q and A
The following are common questions and their answers:
Q: Is there power to the expansion module?
A:
The POWER LED should be lit at all times. If not, check the
24 VAC input voltage. If the input voltage is confirmed and
the POWER LED is not lit, the board is physically damaged.
Q: Is the expansion module communicating?
A:
You should always see the COMM LED(s) blinking
simultaneously on all modules. The communication chain
is physically connected from board to board; however, the
communications circuit is a parallel connection so it is
possible one module could be inoperable while others down
the chain are operating.
A:
If you see the COMM LED on solid, then the module has
not detected communications for over 60 seconds.
Q: Is the valve position correct?
A:
The STATUS LED will blink the valve position every 10
seconds if the valve is not closed. It will blink the position
divided by 10. So, for example, if the position is 68%, the
STATUS LED will blink six times.
A:
The valve position displayed on the MHGRV-X Status Screen
should match the expansion module’s valve position. The
expansion module must have the enable signal activated for
the valve position to mirror the MHGRV-X.
Q: The STATUS LED is on solid. What does this
mean?
A:
The expansion module is performing its own flush cycle.
Each expansion module tracks its own flush cycles. The
flush time setpoints are always the same as the MHGRV-X
setpoints.
Q: I have no Communications. Can my valve still
drive?
A:
If communication is lost, the valve will drive closed.
A:
If the expansion board is configured (from MHGRV-X) for
independent flush cycles: If the cooling enable binary input
is activated, the cooling flush timer will run and when the
cooling flush time is met, the valve will perform a flush cycle.
A:
If the expansion board is configured (from MHGRV-X) for
synchronous flush cycles: No flush cycles will occur.
Q: How can I test if the expansion module will
drive the valve?
A:
From the MHGRV-X, you can go to the Force Menu and
manually drive the expansion module valves open and
closed.
APPENDIX C: REHEAT EXPANSION MODULE
Troubleshooting
