WattMaster MUA II - Manual (Page 7)

Technical Guide
MUA II Controller
7
Controller Installation & Wiring
General
Correct wiring of the MUA II Controller is the most important factor in
the overall success of the controller installation process. In general, most
MUA II Controllers are factory installed and wired. It is also possible to
purchase these controllers directly from WattMaster Controls for instal-
lation in the fi eld. Some of the following information pertains to fi eld
wiring and may not apply to your installation since it was pre-wired at
the factory. However, in the unlikely event that troubleshooting of the
controller is required, it is a good idea to be familiar with the system
wiring, no matter if it was factory or fi eld wired.
Controller Mounting
When the controller is to be fi eld mounted, it is important to mount the
controller in a location that is free from extreme high or low temperatures,
moisture, dust, and dirt. It is recommended that it be installed in the
HVAC unit control panel. If this is not practical, it should be mounted
in a separate control enclosure that is weathertight. Be careful not to
damage the electronic components when mounting the controller. Re-
move the controller from its backplate. Mark the control enclosure base
using the backplate as a template. Drill pilot holes in the enclosure base
and secure the backplate to it using sheet metal screws. Do not allow
metal shavings to fall onto the circuit board. Reattach the controller to
the backplate.
Important Wiring Considerations
Please carefully read and apply the following information when wiring
the MUA II Controller. See Figure 5 for MUA II Controller wiring
diagram.
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.
Some sensors require 2-conductor wire and some require
3-conductor.
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.
6. When communication wiring is to be used to interconnect
controllers together or to connect to other communication
devices, all wiring must be minimum 18-gauge,
2-conductor, twisted pair with shield.
7. Before applying power to the MUA II Controller, be sure
to recheck all wiring connections and terminations
thoroughly.