Automatic Restart; Checking The Refrigeration Piping Pressure Drops; Chilled Water Valve Chilled Water (C) Units - Emerson Liebert CRV User Manual

7.2

Automatic restart

If desired, the unit will automatically restart on the return of power after a supply interruption
(see Control manual). If the power interruption is expected to be of several hours, to avoid an auto-
matic cold restart of the compressor stop the unit before the black-out and, on the return of power,
allow the compressor to preheat before restarting the unit.
7.3

Checking the refrigeration piping pressure drops

Liebert CRV is equipped with connections to check the refrigeration piping pressure drops:
room unit → condenser → room unit
To carry out this operation it is necessary to use 2 calibrated manometers and connect them as
follows:
M1, connected to the compressor delivery valve;
M2, connected to theSchrader valve (2) of Fig. p.
When the compressoris ruuning, check M1 and M2.
NOTE:
Refrigeration pipeline Pressure drops (Δp bar), at 45_C
S At the same geodetic level: Δp (bar) = M1-M2
S When condenser is above the room unit:
Δp (bar) = M1-M2+geodetic difference (m x 1,1:10,2)
S When condenser is below the room unit:
Δp (bar) = M1-M2-geodetic difference (m x 1,1:10,2)
Fig. p - Refrigerant line components
1
7.4

Chilled water valve Chilled water (C) units

The 3-way valve controls the chilled water flow and operates as follows (Fig. g):
S When the valve is fully open (i.e. max. chilled water flow) the actuator slot is set to '1'.
S When the valve is closed (i.e. no chilled water flow) the actuator slot is set to '0'.
The valve running time is set to the value specified in the Control Manual.
For more details see also technical bulletin of chilled water valves and related actuators. Technical
bulletins are enclosed with documentation on board of the unit.
Note 1: In the unlikely event of control system failure, the valve can be manually controlled by
means of the rotary knob. It can be used to drive the actuator into any position between 0 and 1.
Note 2: When actuator stem is completely down, the valve is open and chilled water coil is sup-
plied.
Fig. q - Position of the chilled water valve actuator (for 2 or 3-way valve)
0
1
1
Repeat this test , inverting the manometers : tocalculate the correct Δp consider
the average value of the two readings.
2
(3--- way valve: by--- pass open)
0
4
6
5
Position indicator on
0 = CLOSED valve
35
Start-up
1 Liquid receiver valve
Filter dryer inlet Schrader
2
valve
3 Filter dryer
4 Sight glass
3
5 Solenoid valve
Thermostatic expansion
6
valve
Position indicator on
1 = OPEN valve
(3--- way valve: by--- pass closed)