Industrial Climate Engineering ECUA90 Installation & Operation Manual page 18

Low Voltage Wiring
IMPORTANT. The following instructions are generic wiring instructions and may not be applicable
for air conditioners with various options. Always refer to the wiring diagram in the air conditioner for
the proper method to wire your unit.
1. On single units, pull the low voltage wiring (e.g., 18 gauge 4-conductor Class 2 thermostat wire)
from the air conditioners into the thermostat / subbase assembly. See Figure 4a for connections to
various thermostats.
2. Mount the thermostat on the wall of the shelter. The thermostat should be located so that the supply
air from the unit does NOT blow directly on to the thermostat. Connect the thermostat to the terminal
block in the air conditioner as shown in Figure 6a.
3. On dual units, refer to either the Marvair CommStat 3 or CommStat 4 Controller Specification sheet.
Wire the two air conditioners to the Lead/Lag Controller, according to the wiring diagram on the
specification sheet.
Remote Signalling: Terminals 5 & 7(N.O.) and 6 & 7 (N.C.) on the air conditioners terminal board are dry
contacts which can be used for remote signalling in the event of a/c cutoff on low or high pressure limit.
Continuous fan operation: For continuous indoor fan operation on single units, install a jumper between
terminals 8 and 3.
CommStat 3 Controller (See Figure 4b)
The CommStat 3 Controller by Marvair
fully or partially redundant air conditioning system for a telecommunication cabinet or shelter. The
CommStat 3 Controller is factory programmed with standard industry set points to facilitate installation.
If desired, each of the set points can be quickly and easily changed in the field by the installer. See
CommStat 3 Product Data Sheet for installation and programming instructions.
CommStat 4 Lead /Lag Controller
Please refer to the Product Data sheet for the CommStat 4 controller for complete instructions
on installing and programming this controller.
is a solid state control package designed to operate a
®
18 ECU 12/2014 NEW