Remak VCS Installation And Operating Instructions Manual page 115

Other Ways of Control, Checks, Failures
Checks
Temperature Difference Monitoring
This enables the difference between the required and
actual supply air or room temperature to be monitored.
The monitored temperature is compared with the pre-
set tolerance ±°C while simultaneously monitoring the
temperature drop below the minimum limit. If the monitored
temperature is below the minimum limit or outside the
permissible tolerance for more than 1 hour, an informative
error will be activated. The optional temperature difference
monitoring can be enabled using the HMI controller, refer to
the chapter Additional Operating Modes and Function Setting
Options. Temperature minimum limit or tolerance can be set
using the HMI controller in the List of Data Points in the section
Monitored temperature Check Settings, System and Network
Setting – Difference Monitoring.
Failures
The VCS unit monitors, evaluates and informs about various
types of system failures. Possible failures are indicated, see
the chapter of appropriate HMI controller (SG, TM, DM or
Web) or Remote Indication. Failure messages identify failed
objects/components which need to be inspected, respectively
to find and remove the cause of the failure (or confirm
absence of any problem) before acknowledging the failure.
For failure reset, refer to the chapters of HMI controllers.
Failure Inputs (digital)
All important air-handling unit components (fan motors,
electric heaters, etc.) are equipped with failure inputs
(contacts) which after being connected to the devoted
inputs (terminals) are evaluated by the VCS unit, respectively
by the controller. If a failure (incorrect state of the contact)
occurs, the VCS control unit will automatically put out an
alarm in accordance with an internal algorithm – indicating
the faulty object and in case of severe failures stopping the
air-handling unit.
Note: In the Stop mode (at the beginning of start-up) the
state of the air-flow sensors is indicated as correct. However,
it is actually a failure state (contacts open) which, in these
situations, is not evaluated by the system as a failure (this
evaluation is performed once a pre-set time has elapsed).
Similarly, the filter fouling sensor in the Stop mode – without
air flow rate – is put into standby mode (contacts closed)
which does not correspond with a failure state even though
a failure occurred and was indicated during the previous
operation (this state will change once the devise has been
started up – if the filter has not been changed).
Temperature Sensor Failures
Information about temperature sensors are specific failure
messages evaluating their state outside the standard
working range of measured temperatures. The controller will
automatically report a disconnected, open or short-circuited
temperature sensor, respectively abnormal value. If the
main control sensors (e.g. supply air temperature sensor) or
protection sensors (antifreeze protection) fail, the controller
will shut down the system.
Control units VCS
Outdoor and indoor temperature sensor failures will not
shut down the entire system, only the functions related
to the required input variable from the sensor. To operate
properly, the VCS system requires all sensors according the
specification to be operative.
Water Heater Antifreeze Protection Failures
The water heater protection system to prevent a breakdown
caused by water freezing during a heating water delivery
failure will report a failure if the heating water or air tempera-
tures drop below the pre-set limits. For details about water
heater antifreeze protection, refer to the chapter Description
of Control and Protection Features.
Possible Causes of Indicated Failures
Antifreeze Protection Alarm
n Low water temperature in the water heat exchanger
n Check water temperature in the water heat exchanger
n Check the heating water source.
n Inspect or clean the SUMX mixing set filter.
n Inspect the heat exchanger's fins for fouling.
n Verify the circulation pump activation and operation.
n Verify functionality of the three-way valve
n
Check the NS 130 temperature sensor in the duct.
Electric Heater Failure
n Inspect the electric heater thermo-contacts.
n Check the electric heater switching.
n
Check the circuit breaker and EOS(X) electric
heater condition.
n
Inspect or clean the filter insert.
n
Inspect the dampers for opening.
n
Verify smooth air flow
Electric Heater Specialities
The EOS series electric heater design provides safe, reliable
and long service life. As semiconductor relays (SSR) are used
to switch the electric heaters, it is necessary to pay close
attention to operating conditions, especially to over-voltage
in the wiring and permissible increases in the temperature
of the SSR relays.
SSR relays are advanced semiconductor components ensur-
ing electric heater output switching with minimum noise. Due
to the SSR relay design technology, the voltage at its poles
must not exceed 1200V. As standard, SSR relays are equipped
with over-voltage protection. If over-voltage exceeds the val-
ues specified by ČSN 330420 for wiring category III, there is a
risk of service life shortening or even SSR relay destruction. In
these cases, it is necessary to provide the control unit supply
line with multistage over-voltage protection. An increased risk
of over-voltage exists in the vicinity of 22kV/400V distribution
transformers, highly loaded power lines routed in parallel,
frequency inverters, etc.
Another danger comes from unacceptable overheating of
the SSR relay internal structure above the permissible limit,
leading to its destruction. Sufficient cooling of the SSR relay
is ensured by placing the SSR cooler in the air duct, where it
is cooled by the air flow.
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