Flooded type water cooled screw chiller (PCB Control)
63
2) Time Relay
Time relay use Omron H3Y type.
3) Compressor and fan thermal overload relay
Thermal overload relay takes advantage of heating effect to protect the compressor and fans.
Compressor thermal relay value:
The calculation of compressor overload value (transformation ratio of current mutual inductor is A/B) is as
follows:
(Maximum running current of compressor/current mutual inductor A) x B = Thermal relay value of compressor
For example, if the maximum running current of compressor is 250 A, and the transformation ratio of current
mutual inductor is 300/5, Thermal relay value = (250/300) x 5 = 4.17
Note: Use a value that is smaller than the calculated one. For example, in the preceding calculation, the calculated
value is 4.17; in practice, set the value to 4.15.
Unit Type
Maximum Running
Current of Compressor
Transformation Ratio of
Current Transformer
Thermal Relay Value of
Compressor
340
139.6
250/5
2.8
440
174.1
250/5
3.5
540
203.5
300/5
3.4
690
277.5
400/5
3.4
805
342.7
500/5
3.4
890
370.8
500/5
3.7
1080
203.5x2
300/5
3.4
1200
224.6x2
300/5
3.7
1385
277.5x2
400/5
3.4
1620
342.7x2
500/5
3.4
T
：
6S
Power LED
On display red
Time
’
s up LED
Up display green
TEST key: to press to test whether the
overload relay is normal in stop condition
Reset key: to press to reset the overload
relay if there is compressor overload
protection
Current setting panel: to set the
protection current value.
Note
：
Compressor overload relay, only apply to 3UA series of Siemens brand
