6
MHGRV-X Field Technical Guide
WIRING
Installation and Wiring
Installation and Mounting
The MHGRV-X is housed in a plastic enclosure. It is designed to
be mounted by using the three mounting holes in the enclosure
base. It is important to mount the module 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 module.
NOTE:
The MHGRV-X contains no user-serviceable
parts. Contact qualified technical personnel if your
Controller or Module is not operating correctly.
Wiring
The modules must be connected to an 18-30 VAC power source
of the proper size for the calculated VA load requirements. All
transformer sizing should be based on the VA ratings listed in
Table 1, this page
.
NOTE:
If the temperature at the controller is below -22ºF
(-30ºC),the display refresh rate could be less
responsive.
WARNING:
When using a single transformer to power
more than one controller or expansion
module, the correct polarity must always be
maintained between the boards. Failure to
observe correct polarity will result in damage
to the Unit Controller, MHGRV-X, and any
associated modules.
Please carefully read and apply the following information when
wiring the Unit Controller, MHGRV-X and any associated
module.
1. All wiring is to be in accordance with local and
national electrical codes and specifications.
2. 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.
3. Minimum wire size for 24 VAC wiring should be
18-gauge.
4. Minimum wire size for all sensors should be 24-gauge.
Some sensors require two-conductor wire and some
require 3-or 4-conductor wire.
5. Minimum wire size for 24 VAC thermostat wiring
should be 22-gauge.
6. 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.
7. When communication wiring is to be used to
interconnect HVAC unit controllers together or to
connect to other communication devices, all wiring
must be plenum-rated, minimum 18-gauge, two-
conductor, twisted pair with shield. AAON can supply
communication wire that meets this specification and
is color coded for the network or local loop. Please
consult your AAON distributor for information. If
desired, Belden #82760 or equivalent wire may also
be used.
8. Before applying power to the HVAC unit controller,
MHGRV-X, and any associated modules, be sure
to recheck all wiring connections and terminations
thoroughly.
Powering Up
When the Controller and Modules are first powered up, the
POWER LED should light up and stay on continuously. If it does
not light up, check to be sure that you have 24 VAC connected
to the controller, that the wiring connections are tight, and that
they are wired for the correct polarity. The 24 VAC power must
be connected so that all ground wires remain common. If after
making all these checks, the POWER LED does not light up,
please contact AAON Controls Support for assistance.
Contr
ol
De
vice
V
olta
ge
V
A Load
Oper
ating
Temper
atur
e
Humidity
(Non-
Condensing)
MHGRV-X
18-30VAC
18
-22°F to 158°F*
-30ºC to 70ºC*
0-95% RH
Inputs
Resistive Inputs require 10KΩ
Type 3 Thermistor
24VAC Inputs provide 4.7KΩ
Load
Outputs
Relay Outputs: 1 Amp
maximum per output.
Table 1: MHGRV-X Electrical and Environmental
Requirements
