12
NT538 WS EVO
POWER SUPPLY
The NT538 WS EVO can be supplied by 85 to 260 Vac-Vdc, 50/60 Hz irrespectively of polarity in Vdc (terminals 40-42).
This is obtained thanks to the use of a tested power supply unit, newly designed and manufactured, that frees installers from
worrying about the correct Vac and Vdc supply.
The earthing cable must always be connected to terminal 41.
When the control unit is powered directly by the secondary of the transformer to be protected, it can be burnt out by high
intensity overvoltages.
These problems occur if the main switch is closed and the transformer does not have the load (no load test).
The above is much more evident when the 220 Vac voltage is taken directly from the bars of the secondary of the transformer
and there is a fixed capacitor battery for power factor correction of the transformer itself.
To protect the control unit against line overvoltages, the PT-73-220 electronic arrester, designed by TECSYSTEM S.r.l.
for this specific purpose, is recommended. Alternatively, it is advisable to use 110 V AC supply voltages or, even better,
110 VDC.
If an existing control unit must be replaced with a new one, to guarantee its correct and safe operation, the
sensor/relay/supply connecting terminals must be replaced with the new terminals supplied.
ALARMS AND VENTILATION
Carry out the electrical connections on the removable terminal blocks only after disconnecting them from the unit.
When the control unit is in one of the modes indicated below it does not perform any thermal monitoring, moreover the relays
will all be disabled. The fault contact switches and the fault LED flashes.
•
Programming viewing display.
•
PRG programming.
•
Relay test.
The ALARM and TRIP relays only switch when the set temperature thresholds are exceeded.
The FAULT (fault) contact, programmed in active failsafe mode (default YES), opens (11-12) when the appliance is powered,
only if during the access phase the control unit does not detect anomalies, and keeps the switching until when one of the
following events occurs:
•
Data memory fault (Ech message).
•
Pt100 sensor fault (FCC short-circuited sensor, FOC interrupted sensor or Fcd quick temperature increase)
•
CAL damage to the measurement circuit.
•
Insufficient supply voltage.
•
During the power on reset after programming (PRG), displaying the data (VIS) and test relay.
The FAULT failsafe mode can be disabled FAULT failsafe "NO" see programming step 30-31 page 14.
NOTE: in order to avoid unwanted system outages, do not connect the FAULT relay to the transformer tripping circuit.
FAULT AND RESET MESSAGE SEQUENCE
Find below the sequence of fault messages and RESET function condition.
1) ECH
2) CAL
3) FCD
4) ERR PT
The FAN1 and FAN2 contacts can be used to control the cooling fans, or they can be inserted in the conditioning system of the
transformer room, see paragraph cooling fan control on page 17.
NOTE: always disconnect the unit before performing any electrical connections.
11 12
FAULT 11-12 NC: ALARM FAULT OR POWER OFF
FAULT 11-12 NO: POWER ON OR NO FAULT
11 12
FAULT CONTACT OPERATION (failsafe active)
eeprom fault
measurement circuit fault
Temp. increase rapid fault
FCC or FOC sensor fault
erasable message
erasable message
resettable condition
non-resettable condition
