8
This can be done in two different ways:
1. Local detection freezing rain warning
If the device is set to LOCAL DETECTION, i.e. local detection of risk of freezing rain, the
device will heat the surface as soon as it notices a sharp rise in temperature after a lengthy
period of cold weather.
The rise in air temperature is performed by an air temperature sensor which is delivered
together with the device.
The device can recognise a lengthy period of cold weather by means of a ground
temperature sensor, if the ground temperature has been below a set value for 18 hours.
See also the sections on the rise in temperature and the low ground temperature for an
18 hour period in the paragraphs relating to the following parameters.
2. Freezing rain warning via the weather service
With this function, the device waits for a logic signal sent from an additional device to
the terminals of the air temperature sensor. The additional device, which is not part of the
standard package, evaluates information from the weather service and converts these into
the relevant logic status.
The control device expects the following logic status:
Logic status Input in control device Reaction of the control device
0 open Heating OFF (no risk of freezing rain)
1 short circuit Heating ON (risk of freezing rain)
Instructions for early recognition of freezing rain
• If it has recognised the possibility of a fall of freezing rain, the device switches on for 5
hours. If the warning has come via the weather service, the five-hour period begins from
the moment the logic status signal changed from 0 to 1. The heating is switched off
as soon as the ground temperature reaches the threshold value or the five hours have
elapsed. If however, after five hours, the ground temperature and moist conditions are
present for heating to continue, the heating is not turned off, i.e. following the five-hour
period the device continues to operate under normal operating conditions.
• If the device is set for the local detection freezing rain warning, you should ensure
that the base temperature is lower than the 18-hour ground temperature value, since
otherwise the temperature will never fall below the 18-hour value and the freezing rain
warning will not function.
• The reliability of the early recognition function heavily depends on the correct setting
of the parameters. It is possible that ice may build up on the surface or the device may
come on unnecessarily.
Range of settings: 0.5K/h ... 4.0 K/h
Interval: 0.5 K/h
Default setting: 2.0 K/h
This parameter* is used for setting the minimum rise in the air temperature in order to
recognise the potential risk of freezing rain after a lengthy period of cold weather.
Range of settings: –15°C ... –1.0°C
Interval: 1.0 K
Default setting: – 1.0°C
* This parameter temperature is indicated only when “local detection” is selected.
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