SystemAir HHFlex C, Руководство по эксплуатации

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5.9 Electrical reheating Coil
Parameters for this function are available in the menu Actual/setpoint and Settings.
5.9.1 Temperature Control
If heat recovery is not enough to control temperature, the electrical booster heater is basically controlled as shown in the
sketch below.
A PID controller is used. Tuning of the PID controller is possible in the menu Settings (Advanced User).
The modulating control signal to the electric heater creates a fully proportional performance variation of the electric
heater.
For information : The solid state relays use integral cycle control which is a technique to vary the amount of complete AC-
half cycles of load current (switch in the zero current passage); hence a resistive load without creating electrical noise.
Proportional control is achieved with solid state relays, integrated in the terminal box of the electric heater.
Depending on the heating capacity, the rods of the heater are split into one or more groups of rods.
Each group is equipped with 2 solid state relays. All solid state relays simultaneously receive the quasi-modulating pulse
signal generated by the controller. During each voltage pulse period the solid state relays are activated and give power
supply to the heating rods. The pulse signal is basically an on/off voltage signal, but due to its switching frequency, a
proportional performance operation of the electric heater is achieved. The pulse control signal operates on all groups
simultaneously.
5.9.2 Overheating protection (TA04)
To avoid overheating, heating command is limited by actual air flow (QV04). Very low air flow will set heat signal at
zero. As an additional safeguard against overheating, the electric heater is equipped with 2 safety thermostats:
• maximum temperature thermostat (TA04) with fixed temperature setting at 82°C and auto reset.
• fire thermostat with fixed setpoint at 128°C and manual reset on the thermostat in the terminal box of the
heater.
Both thermostats are connected in series as a digital alarm input (normally closed) on the controller.
An activated alarm results in:
• fans running at design speed
• heat signal at zero
5.9.3 Cool down at unit stop
When unit stops and if electrical heaters was active, the fans are running for an adjustable delay (default 180s) and the
dampers (if applicable) remains opened during this delay.
Pulse Width
Measured Value
100%
Setpoint