Merlin CT1250 Gas Interlock System Product Data Sheet
Vent Direct Ltd 3
1 General information
The Merlin CT1250 is a ventilation interlock panel with two built in current monitors.
The Merlin CT1250 can receive connections from either remote air pressure differential
switches or the internal current monitor & remote emergency shut-off buttons. It can also be
integrated with a BMS and fire alarm.
It is recommended that the user reads this guide before using the system. Please do NOT
attempt to operate the unit until the contents of this document have been read and are
thoroughly understood.
2 Installation
2.1 Panel Mounting. The control panel is designed for surface mounting using 4 mounting screws.
Removing the cover on the panel gives access to the circuit board.
2.2 Mains Supply. A 230-volt electrical supply should be supplied to the panel. This should be
externally fused at 3 Amps using a fused spur and should be connected to the terminals
marked ”LNE Power IN”
2.3 Gas solenoid valve. The gas solenoid valve should be powered using the terminals on the
Merlin CT1250 marked “LNE to VALVE”.
2.4 Air Pressure differential Switches. These terminals are linked out as a factory setting. Wiring
to the air pd switches should be made using two-core volt free connections. The wiring
connections should be made from the terminals marked “FAN PD SWITCHES”. If supply and
extract air pd switches are being used terminals marked “SUPP FAN” and “EXTR FAN” should
be used. If only one fan is being used the terminals not in use should be left linked out.
2.5 Current Monitor. On the base of the circuit board there are two sets of terminals, one marked
“SUPP FAN LIVE” the other marked “EXTR FAN LIVE”. If you are monitoring the fan by
measuring electrical current going to the fan these terminals should be used. The live feed
from the fan controller should be taken to the Merlin CT1250 and connected to either the
supply or extract side depending on which fan or fans are being monitored. On the circuit
board just above the “Live feed” there is a potentiometer marked “sens 1” on the supply fan
side and marked “sens 2” on the extract side. The fan should be run at minimum speed and
the potentiometer turned clockwise until the green LED on the PCB, located below the
potentiometer, lights up.This indicates the panel has seen the electrical current going to the
fan. If a second fan is connected this procedure should then be repeated on the other
potentiometer. The panels are sent from the factory with links in the terminal connections
marked “Fan PD Switches supp fan & Extr fan” These terminals are low voltage, mains supply
must NOT be introduced to these terminals. If both supply fans and extract fans are being
monitored both theses links should be removed. If only one fan is being monitored the relevant
link should be taken out of the terminal connection.
2.6 BMS Connections. Terminal connections are available on the circuit board for connections to
Building Management systems etc. Detailed on the circuit board as “TO BMS N/C, Com and
N/O” these are volt free connections.
2.7 Remote emergency shut off buttons. The terminal for remote emergency shut-off buttons is
detailed on the circuit board as “EM Rem”. These connections are linked out as a factory
setting. Remote emergency shut-off buttons should be volt free and wired to the Merlin
CT1250 using two-core cable.
2.8 Internal Buzzer. Operates at 65dB measured 30cm from closed panel.
