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16.1 OVERHEAT PROTECTION
Motor overheat protection (if fitted) can be enabled on all single-phase and three-phase motors and can be achieved by using
either thermostats or thermistors. Protection device connected options are listed below:
- Where single-phase or three-phase motors have a full load current of up to and including 6.3 Amps: thermostats can be
wired in series. Where the unexpected re-closure of self-resetting of a thermal cut-out can cause a hazard, or is prohibited
by regulation, it must be connected into a control circuit that will not allow the fan to restart until the circuit has been
manually reset.
- Where single-phase or three-phase motors have a full load current above 6.3 Amps: thermostats must be wired to
separate terminals (K – K) within the terminal box; they operate by opening and closing, depending on the temperature
and must be wired to directly control the motor start contactor. Where thermistors are used these must be wired to
separate terminals (S –S) within the terminal box; they operate by changing their resistive value with temperature and must
be wired to control the motor start contactor via a suitable relay.
NOTE!
When the fan is intended to be used for emergency high temperature operation, overheat protection must be by
passed in the event of an emergency (see Section 16.5).
NOTE!
When a motor cools down, an over-heat protection thermostat will reset. However, to maintain safe operation,
the motor must not be allowed to start until the motor start contactor is manually reset.
16.2 BEARING TEMPERATURE AND VIBRATION MONITORING SENSORS
If monitoring sensors are fitted into the fan control system, then they must be wired to automatically switch the fan off if a fault
occurs, or to provide a fault indication. If the fan is automatically switched off by a monitoring sensor the control system (via a
PLC for example), then the fan is must be fully isolated from the electrical supply, so that it will not automatically reset and re-
start. If the fan is designed for emergency use, then the control system must ensure that all monitoring devices are overridden
so that the fan is immediately switched on during an emergency situation (see Section 16.4).
16.3 SPACE HEATER / ANTI-CONDENSATION HEATER
If monitoring sensors are fitted into the fan control system, then they must be wired to automatically switch the fan off if a fault
occurs, or to provide a fault indication. If the fan is automatically switched off by a monitoring sensor the control system must
ensure that the fan is fully isolated from the electrical supply, so that it will not automatically reset and re-start. If the fan is
designed for emergency use, then the control system must ensure that all monitoring devices are overridden so that the fan is
immediately switched on during an emergency situation (see Section 16.4).
16.4 EMERGENCY-USE FANS
Where the fan assembly is designed for emergency-use (smoke-extraction) at high temperature, the temperature / time capability
of the product will be shown on a special label adjacent to the main nameplate. We recommend that an automatic control system,
or a clearly marked remotely sited emergency-use switch, is fitted to override all other switches and controls, so that the fan is
immediately switched on when an emergency situation occurs. The only exception is where a matched and approved Frequency
Converter drive is fitted, as this can remain "in-circuit" if appropriately selected. If you require further information or advice, please
contact Woods Air Movement USA directly. Also, please refer to sections 1 to 11 of this document for more detailed guidance
related to our HT Series fans.
Appropriately rated high temperature cable must be used to supply power to the fan, while the electrical supply must be from a
guaranteed or separately maintained source to enable that the fan continues to run during the emergency condition. After such an
emergency the fan must be removed, refurbished or safely disposed of (see Paragraph 20), and replaced as necessary.
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