Electric Heater Interlock By Supply Air Controller (Lte Mode Only) - Siemens RDG400KN Basic Documentation
Room thermostat with knx communications
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Notes
Caution
Caution
Siemens
Building Technologies
3.10.9 Electric heater interlock by supply air controller
(LTE mode only)
To avoid overheating of an electric heater, sufficient flow of supply air must be
guaranteed. The thermostat features the function "Interlock of el. heater via supply
air controller", which is active when a supply air controller (e.g. Synco RMU7xx) is
used in the system. The supply fan controller sends the fan status (StatusSATC) to
the thermostat when the supply fan is running, after which the el heater is allowed
to turn on if there is a call for heat.
When the supply fan is not running, then the el. heater keeps turned off, even
though there is a demand for heat.
The fan symbol
is displayed, when the supply fan is on.
Electric heater enable via local input X1 / D1 or via KNX will override any release
by this interlock function and vise versa (last intervention wins).
After power-up of the thermostat the electric heater is completely disabled for at
least 5 minutes or until a supply air controller is detected. If no supply fan
controller is in the system, the el. heater is allowed to turn on if there is a
demand for heat.
The fan information is broadcast every 15 minutes or on change of value. If no
value is received any more, the thermostat will disable the interlock function after
a timeout of 31 minutes.
General rule: In case of insufficient air flow, the thermostat cannot protect the
electrical heater against overtemperature. Therefore the electric heater MUST
feature a separate safety device (thermal cutout).
3.10.10 Primary fan overrun after switching off the electric
heater
To avoid overheating of an electric heater after it has been switched off, the air flow
must be maintained for a while.
In conjunction with a supply air controller (e.g. Synco RMU7xx) this will be
automatically assured by exchanging the necessary information. The supply fan
controller will only switch off the supply fan once all el. heaters are cooled off.
Note: The cool off time of the el. heater can be adjusted for each el. heater via
parameter "fan overrun time" (P54, factory setting 60sec).
General rule: In case of insufficient air flow, the thermostat cannot protect the
electrical heater against overtemperature. Therefore the electric heater MUST
feature a separate safety device (thermal cutout).
RDG400KN Basic documentation
Functions
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CE1P3192en
20 Jul 2010
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