nVent RAYCHEM VIA-DU-20 Mode D'emploi page 6

The moisture threshold determines the level of moisture which must be exceeded for the heating to come on,
providing the temperature is low enough. 1 is the most sensitive setting, i.e. very little moisture is enough to reach
this value.
EN
DE
If the moisture threshold is set to 'OFF', the control device will always switch the heating on, as long as the
temperature falls below the threshold value. No moisture is required. The value of moisture is no longer indicated in
FR
the display.
IT
RU
The post-heating period is the time for which the device continues to heat after the threshold conditions which set
the heating on are no longer present.
If the temperature in the ground falls below the base value, the control device will keep on heating (regardless of
the moisture). This functions speeds up the time required to clear the surface from snow and ice. If the ground
temperature rises above the base temperature again, the heating timer will remain switched on for the post-heating
period.
This function addresses the issue of freezing rain, the purpose is to preheat the surface to prevent the associated
problems.
* For the purpose of the use of VIA-DU-20 in the UK, 'sleet' is used to describe the condition and effect of
freezing rain.
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
0
1
Instructions for early recognition of freezing rain
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6 nVent.com/RAYCHEM
Range of settings:
Interval:
Default setting:
Range of settings:
Interval:
Default setting:
Range of settings:
Default setting:
Input in control device
open
short circuit
30 ... 120 min.
10 min.
30 min.
OFF, –15°C, ...–1.0°C
1.0 K
OFF
L OCAL DETECTION,
WEATHER FORECAST, OFF
LOCAL DETECTION
Reaction of the control device
Heating OFF (no risk of freezing rain)
Heating ON (risk of freezing rain)