11
NT539
POWER SUPPLY
The NT539 has UNIVERSAL power supply, i.e. it can be supplied by 24 to 240 Vac-Vdc, 50/60Hz 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 ground must always be connected to terminal 41.
When the unit is supplied directly by the secondary of the transformer to protect, it can be burnt out by strong
overvoltages.
This happens if the main switch is closed and the transformer has no load (blank test). The above-mentioned problems
are much more evident when the 220 Vac voltage is taken directly from the transformer secondary bars and there is a
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 mentioned below, it does not monitor the temperature and the relays
are all blocked, the fault contact switches and the fault LED flashes.
•
Vis. programming display
•
PRG programming
•
Relay test
The ALARM and TRIP relays switch only when the set temperature thresholds are exceeded.
The FAULT contact switches when the equipment is powered only if the unit detects no fault on start up, and stays in
this condition until one of the following events occurs:
•
Data storage 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.
NOTE: do not connect the FAULT relay to the transformer tripping circuit to avoid unwanted system interruptions
FAULT CONTACT SWITCHING
The FAN contact can be used to control the cooling fans, or it can be included in the conditioning system of the
transformer room, see paragraph Fan control on page 15.
NOTE: always disconnect the unit before performing any electrical connections.
FAULT 63-64 NC: ALARM FAULT OR POWER
OFF
FAULT 63-64 NO: POWER ON - NO FAULT
To protect the monitoring device from line overvoltages, we suggest you use the PT-73- 220 electronic
discharger, designed by TECSYSTEM S.r.l. for this specific purpose.
As an alternative we suggest using 110
Vac or, even better, 110 Vdc supply voltages.
