AAON MHGRVX-A2 Technical Guide

33MHGRVX-A2 Module Technical Guide
Frequently Asked Questions
The following are common questions and their answers:
Q: Can the MHGRVX-A2 be used as a replacement for an
existing MHGRV-X?
A: This module is designed to only work correctly with an EBV05H
valve. It is not intended to be used as a drop-in replacement for
any MHGRV-X or MHGRV II modules.
A: It can replace and be replaced by an MHGRVX-B2 which is
also designed to work with an EBV05H valve.
Q: Which controllers and modules can be used with the
MHGRVX-A2
A: VCCX2 or VCB-X Controller, VCCX2 or VCB-X Expansion
Module, and Reheat Expansion Module.
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 conrmed 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 on the Reheat Expansion Board 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 MHGRVX-A2 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 MHGRVX-A2.
Q: The STATUS LED is on solid. What does this mean?
A: The expansion module is performing its own ush cycle. Each
expansion module tracks its own ush cycles. The ush time
setpoints are always the same as the MHGRVX-A2 setpoints.
Q: I have no communications. Can my valve still drive?
A: If communication is lost, the valve will drive closed.
Q: How can I test if the expansion module will drive the
valve?
A: From the MHGRVX-A2, you can go to the Force Menu and
manually drive the expansion module valves open and closed.
Q: Are my valves wired correctly?
A: Both valves per circuit should be wired to the same terminal
block.
A: The Condenser Valve should be wired (from top to bottom)
BLACK, WHITE, RED, GREEN.
A: The Reheat Valve should be wired (from top to bottom) BLACK,
WHITE, GREEN, RED.
Q: How do I conrm the expansion module is operating in
Reheat (Dehumidication) mode?
A: Make sure the enable signal is activated by conrming that the
ENABLE LED is on.
A: Make sure the COMM LED is blinking.
A: Compare the Valve Position displayed on the MHGRVX-A2
screen with the number of STATUS LED blinks.
A: If all three things above are true, then the valve is operating
correctly in Reheat mode.
APPENDIX D: FREQUENTLY ASKED QUESTIONS
Troubleshooting

AAON MHGRVX-A2 Specifications

General

Brand	AAON
Model	MHGRVX-A2
Category	Control Unit
Language	English