Super Systems 3L Series - Manual (Page 10)

Operations Manual Series 3L
10
Voltage rating
The maximum continuous voltage applied between any
of the following terminals must not exceed 230Vac:
•
relay output to logic, dc or sensor connections;
•
any connection to ground.
The indicator must not be wired to a three phase
supply with an unearthed star connection. Under fault
conditions, such a supply could rise above 240Vac
with respect to ground, and the product would not be
safe.
Conductive pollution
Electrically conductive pollution must be excluded from
the cabinet in which the indicator is mounted. For
example, carbon dust is a form of electrically
conductive pollution. To secure a suitable atmosphere
in conditions of conductive pollution, fit an air filter to
the air intake of the cabinet. Where condensation is
likely—for example, at low temperatures—include a
thermostatically controlled heater in the cabinet.
This product has been designed to conform to
BSEN61010 installation category II, pollution degree 2.
These are defined as follows:
Installation Category II (CAT II)
For equipment on nominal 230V supply, the maximum
rated impulse voltage is 2500V.
Pollution Degree 2
Normally only non-conductive pollution occurs.
Occasionally, however, a temporary conductivity caused
by condensation shall be expected.
Grounding of the temperature sensor shield
In some installations, it is common practice to replace
the temperature sensor while the indicator is still
powered up. Under these conditions, as additional
protection against electric shock, we recommend that
the shield of the temperature sensor be grounded. Do
not rely on grounding through the framework of the
machine.
Over-temperature protection
When designing any control system, it is essential to
consider what will happen if any part of the system
should fail. In temperature control applications, the
primary danger is that the heating will remain
constantly on. Apart from spoiling the product, this
could damage any process machinery being
controlled, or even cause a fire.
Reasons why the heating might remain constantly on
include:
• the temperature sensor becoming detached from
the process
• thermocouple wiring becoming short circuit
• the controller failing with its heating output
constantly on
• an external valve or contactor sticking in the
heating condition
• the controller setpoint being set too high.
Where damage or injury is possible, we recommend
fitting a separate over-temperature protection unit, with
an independent temperature sensor, which will isolate
the heating circuit.
This indicator can be used in addition to a controller as
an over-temperature device. It is recommended that
the relay used to indicate the alarm condition should
be set to high alarm configured with sensor break and
inverse ‘
Inv’ operation so that it relaxes to the alarm
condition when power is removed.
Installation requirements for EMC
To ensure compliance with the European EMC
directive certain installation precautions are necessary
as follows:
• When using relay outputs it may be necessary to
fit a filter suitable for suppressing the emissions.
The filter requirements will depend on the type of
load.
• If the unit is used in table top equipment which is
plugged into a standard power socket, then it is
likely that compliance to the commercial and light
industrial emissions standard is required. In this
case to meet the conducted emissions
requirement, a suitable mains filter should be
installed.
Routing of wires
To minimize the pick-up of electrical noise, the low
voltage DC connections and the sensor input wiring
should be routed away from high-current power cables.
Where it is impractical to do this, use shielded cables
with the shield grounded at both ends. In general,
keep cable lengths to a minimum.