User Guide

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Appendix 4: External Relays
The relays on the αlpha pH 190 series controller are rated for 6 amps at 110 VAC
and can be wired directly to your final control element (provided its power
requirements does not exceed this). However, to preserve the life of your
controller, or if higher power is needed, it is recommended that you use the
controller relay to drive an external relay.
Diagram below shows a typical installation. Wiring should be changed
appropriately if normally closed (N.C.) operation is desired.
+
4 - 20 mA
12
19
3
11
18
2
10
17
19
16
8
15
7
14
6
13
54
NC NC NC NC
-
4 - 20 mA
RELAY 1 - NO
RELAY 1 - POLE
RELAY 1 - NC
Pt 100 - GND
RELAY 2 - NO
Pt 100 - IN
RELAY 2 - POLE
Pt 100 - SENSE
GROUND RELAY 2 - NC
N
LIQUID GND
L
pH/ORP
WARNING
10 9