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Control and Protection Functions
The extent of the mixing valve opening depends on the water
heat exchanger's return water temperature value. Antifreeze
protection will be deactivated when temperatures rise above
the limit parameters.
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If the air-handling unit is in the STOP - STAND-BY mode,
then antifreeze protection is activated when the outdoor
temperature drops below 10 °C (factory settings) and the
water heat exchanger's return water temperature drops
below 30 °C (factory settings). The extent of the mixing valve
opening depends on the water heat exchanger's return water
temperature value. Antifreeze protection will be deactivated
when temperatures rise above the limit parameters.
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The control unit continuously monitors the water heat
exchanger's return water temperature. If the temperature is
still falling and drops below 8°C (factory settings), the following
protection actions will be immediately taken regardless of the
outdoor temperature:
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The air-handling unit will be shut down, the dampers will
be closed, the fans will be switched off and the failure alarm
will be activated.
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The mixing valve will be opened depending on the water
temperature, and the circulation pump will be switched on.
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The above-mentioned state will last until the operator
checks the air-handling system or removes the failure cause
and confirms the air-handling system is free of failure and
resets the failure.
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The control unit simultaneously monitors the supply air
temperature in the Run mode. If the supply air temperature
drops below 6 °C (factory settings), the following protection
actions will be immediately taken regardless of the outdoor
temperature:
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The air-handling unit will be shut down, the dampers will
be closed, the fans will be switched off and the failure alarm
will be activated.
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The mixing valve will be opened depending on the water
temperature, and the circulation pump will be switched on.
Pre-Start Unit Pre-Heating Functions
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To avoid false freezing danger assessment in winter or
during transition seasons, especially when the air-handling
unit is being started, the control unit features a heating
circuit pre-heating.
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Pre-heating is dependent on the outdoor temperature
value. If the outdoor temperature is higher than 10 °C, the
value of the valve opening will be 0 %, and pre-heating will
not be activated.
Pre-heating will be activated when the outdoor temperature
drops below 10 °C. The mixing set valve will be forced to open
to the value which is derived from the outdoor temperature
(factory settings: +10 °C = +10 %, -10 °C = 100 %) for 120
seconds. Once this time has elapsed, the valve will be closed,
"ramped down", until the mixing set control signal for heat-
ing is reached.
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If the air-handling unit is restarted within 5 minutes of the
moment the air-handling unit was shut down, pre-heating
will not be activated.
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Antifreeze protection setting parameters can be accessed
through the HMI controller in the List of Data Points menu,
sections Parameters and Control Constants.
12
Electric Heating
Electric heating can be controlled using the following options:
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Switching of the full EO, EOS heater output
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Sequential switching of the EOSX electric heater's indi-
vidual sections
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Sequential switching of the EO heaters
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Control of the EOS electric heaters using a PV valve (up
to 45 kW)
Electric heater protection
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If electric heater overheating (failure) is signalled (the
temperature inside the heater exceeds +80 °C) by opening
the emergency thermostat contacts in the heater, this signal
is interpreted by the control unit.
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Electric heater control in the REMAK unit is doubled – the
heater thermostat failure signal is simultaneously sent to the
controller and auxiliary module.
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The controller will interpret the failure signal and perform
appropriate safety functions; first, the control signal for
electric heating is blocked and then the heater contactor is
disconnected.
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The auxiliary safety module will mechanically disconnect
the EO/S/X circuit breaker (i.e. it will trip the under-voltage
trigger of the circuit breaker).
At the same time, control logic will ensure safe cooling of the
heater when the air-handling unit is being shut down – transi-
tion to the STOP mode. The controller will ensure run-down of
the fans (optional) so that the heating core is cooled.
Gas heating
The gas heater is controlled using a burner output controller
and a bypass damper (if the section is equipped with a BP
damper). The required heating temperature is controlled
depending on the required temperature (selected mode) and
the readings from the inlet temperature, outdoor temperature
and flue gas temperature sensors.
Gas Burner Output Control
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Single-stage ON/OFF control
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Two-stage control (two output stages)
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Modular (three-point), step-less control of the entire burner
output range
Burner lighting is contingent on the fan operation.
At a 5 % request for heating, the 1st burner output stage is
switched on. The minimum pre-set running time of this stage
is 150 seconds. If the required temperature is not reached,
the 2nd stage will be switched on at 70 % of the request for
heating (two-stage output control). The second output stage
is not restricted to the minimum running time, and will be
switched off at 40 % of the request for heating.
Further re-lighting of the burner is possible once the protec-
tion time of 150 seconds has elapsed. Modular control of
the burner is step-less based on the actual requirement (set
point) within the Min to Max output range of the gas burner.
The bypass damper (if included in the section) is controlled by
a 0-10V signal (the operating range is 2–10 V depending on
the required flue gas temperature (160 °C pre-set). The regulat-
ing damper position controls the air flow coming through the
gas section and bypass section so that a constant flue gas
temperature is maintained. Accordingly:
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