Heater Interlock Relays - Novatech 1732 Technical Manual

equipment. It is recommended that a separate isolation switch be used for each transmitter so that a
transmitter can be serviced individually.

The power supply cables must be supplied and installed according to local regulations

The earth connection must comply with the local regulations must have a current carrying capability
equal or greater than the supply fuse current rating

The earth connection must be connected to the primary earth stud inside the transmitter on the right-
hand side

All other bonded earth connections from the external wiring must be connected to the primary earth stud
All operations relating the electrical wiring and installation must be carried out by qualified persons in
accordance with the safety regulations and the wiring rules.
NOTE: The power switch in the transmitter can be used to turn off the transmitter. There must be an
approved isolation device installed to provide complete isolation of the mains power to the transmitter. The
mains wiring terminal must not be used as a disconnect device.

4.7 Heater Interlock Relays

Explosion protection for heated probes is achieved by switching the power to the probe heater off whenever
the main fuel valve is closed.
The principle of safety is that if the main fuel valve is open then main flame has been established. With this
primary source of ignition on, the probe heater can be safely switched on. The most dangerous situation is if
fuel leaks into the combustion appliance when the fuel valve is closed. When power is removed from the
main fuel valve the heater should also be switched off.
To achieve this protection, connect a main fuel valve voltage free contact to the 'BURNER INPUT' terminals
10 & 11. When the main fuel valve is open, the voltage free contact should be closed. For installations
where there is no risk of explosion, connect a link between terminals number 10 & 11.
For safety, contacts must be open
if the main fuel valve is closed
If a safety interlock is not required, a wire must be connected between terminals 10 &11 to enable –

The heaters on heated probes

Process alarms

Auto-purge and auto-cal checking

Run time timer
August 2018
1732 Oxygen Transmitter
CAUTION
Heater Supply Interlock Connection for Heated Probes
10
BURNER INPUT
11
Technical Manual
21