Orion System MHGRV III - Manual (Page 5)

Operator Interface
MHGRV III Controller Technical Guide
5
Installation & Wiring
Controller Mounting
It is important to mount the controller in a location that is free from
extreme high or low temperatures, moisture, dust, and dirt.
Be careful not to damage the electronic components when mounting
the controller. Remove the controller from its snap track mount. Mark
the control enclosure base using the snap track as a template. Drill pilot
holes in the enclosure base and secure the snap track to it using sheet
metal screws. Do not allow metal shavings to fall onto the circuit board.
Reattach the controller to the snap track.
General Wiring Information
Please carefully read and apply the following information when wiring
the MHGRV III controller.
1. All 24 VAC wiring must be connected so that all ground
wires remain common. Failure to follow this procedure
can result in damage to the controller and connected
devices.
2. All wiring is to be in accordance with local and national
electrical codes and specifi cations.
3. Minimum wire size for 24 VAC wiring should be 18 gauge.
4. Minimum wire size for all sensors should be 24 gauge.
5. Be sure that all wiring connections are properly inserted and
tightened into the terminal blocks. Do not allow wire
strands to stick out and touch adjoining terminals which
could potentially cause a short circuit.
Important Wiring Considerations
Depending on if the MHGRV III controller is to be connected to the
HVAC controller or is to be used as a stand-alone controller determines
how the MHGRV III should be wired. For the wiring diagram to use
when the MHGRV III controller is connected to a VCM controller, see
Figure 2. For the wiring diagram to use when the MHGRV III controller
is connected to a VCM-X controller, see Figure 3. For the stand-alone
wiring diagram, see Figure 4. Please carefully read and apply the fol-
lowing information when wiring the MHGRV III controller.
Additional Modulating Hot Gas Valve
Control
HGR Valve Slave Board
This board is connected to the MHGRV III board with a cable that plugs
into the connector labeled Valve Exp. This board provides control to an
additional set of modulating valves. The position of the valves will be
the same as the board they are plugged into.
MHGRV III Slave Board Confi guration
Whenever the MHGRV III has both its setpoint switches set to 1, it will
work as a slave board. The board is active when it has a 24 VAC signal
on the RHT EN input. When the board is active, it looks for a 0-10
VDC on the AUX IN input and moves the HGR valves accordingly.
For example, if the input is at 10 VDC, then the reheat valve would be
100% open. If the voltage is at 5 VDC, the reheat valve would be 50%
open. See Figures 3 and 4.