12
Control and Protection Functions
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.
e 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). e 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:
n when T
flue gas
> T
flue gas required
the bypass damper closes
(closed = 0 V)
n when T
flue gas
< T
flue gas required
the bypass damper opens
(open = 10 V)
Protection and Safety Functions:
e control unit ensures fan run-down to cool down the gas sec-
tions (the pre-set run-out time is 180 s). e gas section tem-
perature is monitored by the ESD3J triple safety thermostat,
which ensures the following protection and safety functions:
n If the temperature exceeds 50 °C, the fans will be switched
on, even if in the STOP mode.
n If the temperature exceeds 80 °C in the Run mode, the
burner will be stopped, the fans switched to the run-down
mode and then the unit STOPPED; if the temperature exceeds
110°C, the burner will be disconnected from the supply volt-
age. If back air draw (chimney effect) occurs during the STOP
mode and the air temperature in front of the gas section rises
above 50 °C, the TH 167 thermostat will close and switch on
the fans, open the inlet and outlet dampers, and thus the gas
section will be cooled down.
n Fan malfunction – the unit is immediately switched to the
STOP mode without fan run-out (evaluated also during the
STOP mode)
Heating and Cooling using Heat Pump
Two general control options are available for heat pumps.
Control is not fixed to a specific heat pump type. e control
option selection depends on the designer’s consideration
and heat pump type. Two control contacts and an analogue
output are used for control.
Option A
e first digital contact is used to define the air temperature
adjustment type – cooling/heating. e second digital contact
is used to define the process activation – off/on. e analogue
output 0..10 V represents the proportion of the request for
heating or cooling.
Option B
e first digital contact is used to define the heating process
– heating off/heating on. e second digital contact is used to
define the cooling process – cooling off/cooling on.
Analogue output 0..10 V represents the proportion of the
request for heating or cooling.
e heat pump control is equipped with an outdoor tempera-
ture-dependent blocking. e blocking alert is only informative
and is not a failure state. e heat pump will be shut down if
the outdoor temperature is equal to or lower than the refer-
Cooling Control
All cooling sources can be disabled depending on the outdoor
temperature. Cooling is not disabled if the outdoor tempera-
ture is higher than the pre-set cooling enable temperature
(pre-set 12 °C).
Water Cooling
It is controlled the same way as water heating. e mixing
set pump is switched depending on the control signal for the
cooling valve. If the air-handling unit is in the Run mode, the
pump will be switched on when the control signal for the cool-
ing valve is higher than 5% and switched off when the control
signal for the cooling valve is lower than 1%.
n Pump turning for 60 seconds is performed aer every 168
hours of pump inactivity..
Direct Cooling
Direct cooling is controlled by switching the condensing unit
output or by step-less control of the inverter condensing unit.
If a single-circuit condensing unit is used, it will be switched on
when 20 % of the control signal is required and switched off at
10 % (10 % hysteresis) of the control signal. If a double-circuit
condensing unit, respectively two single-circuit condensing
units are used, two stages will be switched. e first stage will
be switched on when 20% of the control signal is required and
switched off at 10% (10% hysteresis) of the control signal. e
second stage will be switched on when 70 % of the control
signal is required and switched off at 60 % (10 % hysteresis)
of the control signal. Frequent switching of the single-stage
condensing unit is eliminated by repeated cooling blocking
for a certain time depending on the setting.
To eliminate the simultaneous switching of both stages at
a sudden control signal increase, the timing (duration of the
first stage) is set.
Inverter Cooling Unit
It is controlled using the start enable signal and step-less
compressor output control signal. e minimum operating
time can also be set. e condensing unit will be switched on
when 20 % of the control signal is required and switched off at
10 % (10 % hysteresis) of the control signal. e unit compres-
sor speed is controlled using a 0–10 V control signal.
ence temperature (see the Data Points). e heat pump will be
started if the outdoor temperature is higher than the reference
temperature (with hysteresis of 3 °C). Frequent switching of
the heat pump is eliminated by blocking of the cooling/heating
restart for 120 seconds. e minimum operating time of the
heat pump can also be set. When cooling/heating is required,
the heat pump will be switched on at 20% of the control signal
and switched off at 10% of the control signal (hysteresis of
10%). e low reference signal on the analogue output (0-10V)
can be set in a range from 0% to 50 % of the control signal
(pre-set 30 %, i.e. a 3-10 V control). e unit can be equipped
with a function blocking the air-handling unit operation when
defrosting the heat pump. e shut-off state of the air-handling
unit is indicated on controllers. Aer the heat pump defrosting
process has been completed, the air-handling unit operation
will automatically be resumed.
Furthermore, it is possible changing behaviour of different
control signals, e.g. AO signal inversion (see Data Points).
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