Relay Contact Protection And Interference Suppression - ABB Nitrate 8236 Instruction Manual

...2 INSTALLATION
2.8 Relay Contact Protection and Interference
Suppression – Fig. 2.5
If the relays are used to switch loads on or off the relay contacts
can become eroded due to arcing. Arcing also produces radio
frequency interference (r.f.i.) which can cause instrument
malfunctions and incorrect readings. To minimize the effects of
r.f.i., arc suppression components are required; these are
resistor/capacitor networks for a.c. applications, or diodes for d.c.
applications. These components can be connected either across
the load or directly across the relay contacts.
For a.c. applications the value of the resistor/capacitor network
depends on the load current and inductance that is switched.
Initially fit a 100 R/0.022 µF RC suppressor unit (part no. B9303)
115V Position
110V min. to 120V max. AC
50/60Hz
Mains
Transformer
F3 0.5A 250V AC (T)
Relay
Board
F2 5A 250V AC (F)
Solenoid Valves
and Heater
Indicators
Caution. The protective
earth be connected
must
to terminal 16.
Internal
Interconnection
Cable Terminals
6
Mains Voltage Selector
110V to120V 220V to 240V
L
MAINS
N
INPUT
N/C
RELAY
C
1
N/O
N/C
RELAY
C
2
N/O
N/C
C CAL
N/O
N/C
OUT
OF
C
SERVICE
N/O
N/C
OUT
OF
C
SAMPLE
HEATER N/O
+
O/P 1
-
+
O/P 2
-
Interconnection Cable from/to
Microprocessor Unit and Instrument
Components (wet section)
Fig. 2.3 Location of User Junction Box Components
Fig. 2.4 Selecting The Current Output Range
as shown in Fig. 2.5A. If the instrument malfunctions the value of
the RC network is too low for suppression and an alternative
value must be used. If the correct RC suppressor unit cannot be
obtained, contact the manufacturer of the switched device for
details of the RC unit required.
For d.c. applications fit a diode as shown in Fig. 2.5B. For
general applications use an alternative IN5406 type (600 V peak
inverse voltage at 3 A – part no. B7363).
Note. For reliable switching the minimum voltage must be
greater than 12 V and the minimum current greater than
100 mA.
230V Position
220V min. to 240V max. AC
50/60Hz
MAINS
OFF
ON
F1 250V
OFF
ON
User
Cable
Entry
Glands
Note. The mains and pump ON/OFF
switches are situated on the right
hand side of the junction box.
Caution. The AC power supply
External
ground cable
User
Connection
the earth (ground) stud
Terminals
Mains 'ON'
Indicator
Mains
ON / OFF
Switch
MAINS
Mains Fuse –
1A, 250V AC (T)
1A (T)
Pump
PUMP
ON / OFF
Switch
Cable Gland
be connected to
must
.