Table of Contents
Advertisement
Control and Protection Functions
n
when T
> T
flue gas
flue gas required
(closed = 0 V)
n
when T
< T
flue gas
flue gas required
(open = 10 V)
Protective and Safety Functions
The control unit ensures fan run-down to cool down
the gas sections (the pre-set run-out time is 180 s).
The gas section (chamber) temperature for protection and
safety functions outside the VCS control system is picked up
by the ESD3J triple electronic safety thermostat (located on
the chamber) while the temperature before the heater cham-
ber is picked up by the TH167 stem thermostat (it is necessary
to install this thermostat when connecting the control system
and set it to 50 °C). The system of safety thermostats along
with the control unit provides the following functions:
n
If a temperature of 50 °C (T3) is exceeded, even in the
STOP mode, forced switching of fans (and opening of damp-
ers) is activated in order to cool down the heater chamber.
n
If a temperature of 80 °C (T2) is exceeded in the Operating
mode, the heater output control signal is switched off. When
the temperature falls, this signal is switched on again. This is
an operation safety function with no signalling of the failure.
n
If a temperature of 110 °C (T1) is exceeded, forced discon-
nection of the burner from the supply voltage is performed
and this state is maintained until the thermostat is reset by
the button located on its body. The reset cannot be performed
until the chamber has cooled down to below the tempera-
ture evaluating threshold. Before the burner can be reset or
restarted, it is necessary to evaluate and remove the reason
for overheating (by-pass cannot be closed, insufficient air flow
though the heat exchanger, exhaust gas temperature setting,
etc.). The T1 stage of the triple thermostat is detected by the
control unit (including/in series with the burner failure when
it is not disconnected form the power supply) which initialises
the Burner (heater) failure message and switching off of the
unit (STOP) with run-out of fans to cool down the chamber.
n
If the air back draught (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 heater will be cooled down.
n
Fan failure – the unit is immediately switched to the STOP
mode without fan run-out (evaluated also during the STOP
mode).
n
The control unit monitors the states of the control sensors
and evaluates exhaust gas overheating as well as failures of
sensors.
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. The 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
The first digital contact is used to define the air temperature
adjustment type – cooling/heating. The second digital contact
is used to define the process activation – off/on. The analogue
the bypass damper closes
the bypass damper opens
Control units VCS
output 0..10 V represents the proportion of the request for
heating or cooling.
Option B
The first digital contact is used to define the heating process
– heating off/heating on. The 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.
The heat pump control is equipped with an outdoor tempera-
ture-dependent blocking. The blocking alert is only informative
and is not a failure state. The heat pump will be shut down if
the outdoor temperature is equal to or lower than the refer-
ence temperature (see the Data Points). The 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. The 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%). The 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). The unit can be equipped
with a function blocking the air-handling unit operation when
defrosting the heat pump. The shut-off state of the air-handling
unit is indicated on controllers. After 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).
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. The 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 after 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.
The 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. The 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.
13
Advertisement
Table of Contents
