2-Pipe Fan Coil Unit With Electric Heater - Siemens RDG100 Basic Documentation

Heating or cooling with
auxiliary heater
Electric heating, active in
cooling mode
Note
Electric heating in
heating mode
Electric heating and
manual changeover
Digital input "Enable
electric heater"
Caution
On/Off electric heater
on RDG160T.. with
ECM fan
On/Off control
Control sequence
On/Off output
Siemens
Building Technologies
4.7.4

2-pipe fan coil unit with electric heater

On 2-pipe applications with electric heater, the thermostat controls a valve in
heating/cooling mode with changeover, heating only, or cooling only plus an electric
heater.
Cooling only is factory set (P01=1) with enabled electric heater (P13).
In cooling mode, the valve receives an OPEN command if the acquired temperature is
above the setpoint.
The electric heater receives an ON command if the acquired room temperature drops
below "setpoint" minus "dead zone" (= setpoint for electric heater) while the electric
heater is enabled (parameter P13 = on).
"Setpoint for electric heater" is limited by parameter "Maximum setpoint for Comfort
mode" (P10).
In heating mode, the valve receives an OPEN command if the acquired temperature is
below the setpoint. The electric heater is used as an additional heating source when
the heating energy controlled by the valve is insufficient.
The electric heater receives an ON command, if the temperature is below "setpoint"
minus "setpoint differential" (= setpoint for electric heater).
The electric heater is active in heating mode only and the control output for the valve
is permanently disabled when manual changeover is selected (P01=2).
Remote enabling/disabling of the electric heater is possible via input X1, X2 or D1 for
tariff regulations, energy savings, etc.
Input X1, X2, or D1 must be commissioned accordingly (parameters P38, P40, P42).
See section 4.10.
An electric heater must always be protected by a safety thermostat!
With a DC 0...10 V (ECM) fan it is possible to select On/Off control for the electric
heater by setting parameter P47 = 1. The electric heater has to be connected to
output Q2.
The electric heater starts with a delay of 15 s, to make sure the fan delivers
sufficient air flow to dissipate the heat.
To avoid overheating of the electric heater, the thermostat guarantee at least a fan
speed II (middle value between Vmin (P56) – Vmax (P55)) when the electric heater
need to be energized.
Adaptive temperature compensation P45 need to be set accordingly
(Refer to section 4.8).
The diagrams below show the control sequence for 2-position.
Heating mode
(automatic changeover = heating or heating only)
Heating mode with manual changeover (P01=2) ) on RDG100.. and RDG110..
RDG100.., RDG110.., RDG160T.. Basic Documentation
Functions
Cooling mode
(man./auto. changeover = cooling or cooling only)
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CE1P3181en
2015-07-29