Unit installation

Electrical Connections
44
9.3 Protective Features of Electrical Heaters
Figure 41 Electrical heating with temperature sensor protection
When the temperature sensor detects overtemperature of electrical heating, the thermal protection
turns Off the current. To reset the thermal protection, push the button on the front of the unit (see
Figure 41).
9.4 Temperature Probes Placed on Racks
The 2T rack temperature sensors provide feedback to the cooling unit about the condition of the air
entering the server racks. This information allows the Liebert CRV to ensure it is providing just
enough cold air to each rack, virtually eliminating hot spots. Overcooling and excessive airflow are
avoided, greatly reducing unnecessary energy consumption.
Each Liebert CRV includes three 2T rack temperature sensors to monitor three racks. A total of ten
2T temperature sensors can be connected to each cooling unit to monitor every rack a Liebert CRV is
protecting. When multiple cooling units are connected in a Unit-to-Unit iCOM control network, all
sensor data is shared to optimize their performance as a system.
While 2T rack sensor installation is not required, it is HIGHLY recommended. Each 2T sensor con-
sists of two temperature probes for redundancy to be attached to the front door of the server racks.
The sensor probes should be located at the highest part of the rack door while still in the supply air-
flow path of the servers.
A sensor network can be extended at any time by connecting additional 2T sensors to the last 2T sen-
sor on the network. Sensors connect in a daisy chain fashion back to the cooling unit; individual wires
from each sensor to the cooling unit are avoided.
2T rack sensors can also be initially installed on empty racks reserved for future growth with the con-
trol set to ignore these sensor readings. The extra 2T temperature sensor readings can also be dis-
played on the local display and reported remotely for monitoring purposes only; not impacting unit
operation. This function provides users with a built-in mini-monitoring system.
2T Sensor Placement Guidelines
The 2T rack sensors come with the Liebert CRV unit to help prevent any problem spots in the row.
Rack sensors help combat cooling problems related to recirculation air, uneven rack loading, and air
distribution. The 2T rack sensors are intended for cold aisle use only.