www.ventilation-system.com
16
UNIT CONTROL
Control unit of VUT R 400-2000 WH EC
pGD1 control panel connector
Controller
Electromagnetic relay
Transformer
230 VAC / 24 VAC
Safety bolt-down terminal
Ground terminal
Terminal block
AUTOMATIC CONTROL SYSTEM DESIGN AND OPERATION
The automatic control system comprises a Carel controller (PCO5 compakt), an outdoor air temperature sensor, a supply air temperature
sensor, a sensor for the air temperature in the exhaust duct, a room temperature sensor, relays, a return heat medium temperature sensor,
circuit breakers, a supply transformer and a water heater overheat protection thermostat.
The unit is controlled via th-Tune or PGD1 control panel.
The automatic control system enables safe automatic operation of the unit in the Auto or Ventilation mode. The Ventilation mode can be
enabled only from the pGD1 control panel.
In the Auto mode the unit maintains the indoor temperature at the pre-set level by sending a signal to the actuators of the water heater
damper and the rotary heat exchanger. While in the Ventilation mode the unit adjusts the supply and exhaust fan speed. The Ventilation mode
is appropriate for energy saving if the difference between the outdoor and indoor temperatures is insignificant.
The supply and exhaust fan speed is set for each speed stage as a percentage from the maximum rotation speed.
The temperature is set up by changing the “Setpoint” parameter value.
The fans can be operated according to a daily schedule (up to 4 time ranges).
The Automatic Speed Drop mode is enabled when the air temperature is low. In this mode the fan speed is adjusted according to the supply
air temperature. The speed is reduced at temperature dropping and is restored to the initial setting provided a sufficient temperature reserve.
The unit switches between Heating and Cooling modes according to the outdoor temperature (factory s18 °C).
The unit incorporates a number of protective measures against water heater freezing:
If the temperature drops below +14 °C (factory setting) in the Heating mode and +8 °C in the Cooling mode the unit turns off.
If the outdoor air temperature drops below +10 °C the “Winter start” mode is activated. When activating the unit the water heater is warmed
up first: the heat medium pump switches on, the heat medium regulating valve is opened to the maximum to warm up before starting the fans.
When the return heat medium temperature r55 °C the air dampers are opened and the fans are switched on.
In winter the controller maintains a return heat medium temperature of not less than +25 °C for preventing a water heater failure.
To prevent a water heater freezing in the Heating mode the Water Heater Warm-Up mode is activated when the heat medium temperature
drops below +10 °C. The automatic control system generates an alarm signal to warn of low heat medium temperature. The warning alarm is
switched off automatically when the heat medium temperature e55 °C.
A freeze protection thermostat of a water heater is active in any mode.
WARNING! Changing the thermostat settings will void the Warranty.
In case of a freezing danger the fans are turned off, the supply air damper is closed, the heat medium regulating valve is fully opened to
provide 100 % air capacity of a heat medium and the circulating pump is switched on.
The unit is equipped with a built-in automatic control system and a control panel.
The automatic control system has the following functions:
1. Turning the unit on/off
2. Unit operation mode selection: Automatic mode, Ventilation
mode (can be enabled only from the pGD1 control panel).
3. Maintaining a pre-set room temperature by activating/
deactivating the rotary heat exchanger as well as setting
a required water heater heating capacity and its smooth
controlling.
4. Automatic reduction of the supply and exhaust ventilation
flow rate to obtain the user-defined heating temperature.
5. Supply and exhaust fan control.
6. Unit operation according to a pre-programmed schedule.
7. Controlling the electric actuators of the supply and exhaust
air dampers.
8. System shutdown on signal from fire fighting system.
9. When connecting external electrical heating elements
and/or CCU to the unit the activation signal controls their
operation if cooling/heating is required.
10. Filter contamination control by the number of operating
hours.
11. Water heater freeze protection in the winter period.
