Ampcontrol MEC-1 - Power Supply and Optional Inputs; Relay Contacts and Fuses

Ampcontrol CSM Pty Ltd - ABN 35 000 770 141
ECDB006 MEC-1 User Manual
Rev 1 – MARCH/2020
MEC-1 USER MANUAL R0 13/03/2020 13:16 Page 11 of 18
Wherever a screened cable is to be connected to Earth, ensure that the screen is
earthed at ONE END ONLY, as near to the MEC-1 as practicable.
4.2.1 Supply
The appropriate power supply for the MEC-1 relay is 24VAC/DC ±20%.
4.2.2 Pilot Terminal
The pilot terminal provides a connection through which the MEC-1 performs resistance measurements.
Typically the pilot terminal will be connected to the pilot conductor of a trailing or reeling cable. The load end of the pilot
conductor will then be terminated with a diode to earth, creating a return path through the earth conductors of the cable to the
main earth point of the outlet and then to the MEC-1 earth terminals. The primary function of the MEC-1 relay is to verify the
resistance of this pilot earth-loop is below a selectable level.
4.2.3 Earth Terminals
The earth terminals provide the MEC-1 with an earth reference for the pilot resistance measurement. At least one of these
terminals must be connected directly to the outlet’s main earth point.
4.2.4 Reset - Optional
This is an active high input that allows MEC-1 trips to be reset in latching mode, after the fault has been cleared. The reset input
has no affect in non-latching mode.
The Reset input should be connected to the MEC-1’s ‘+’ terminal via a normally open switch with a minimum rating of the
supply voltage.
4.2.5 Relay Contacts
The default position of the relay contacts (Normally Open or Normally Closed) is described on the MEC-1 front label and Figure
2. The relay contacts will change state when the MEC-1 is started (Status LED flashing) and will return to the default state when
the MEC-1 trips.
The relay contacts are rated for 1A @ 110Vac and 1A @ 30Vdc (Resistive).
4.2.6 External Fuse
The MEC-1’s Pilot Terminal is designed such that in the event of a phase to pilot fault the voltage will be clamped at the pilot
terminal to a safe level and protects the relay from damage. However this connection can only withstand 5.25A for 1s. The
MEC-1 relay must, therefore, be installed in a system with earth fault current limitation of 5A or less and an earth fault clearance
time of less than 1s. Alternatively a 3A external fuse rated to system voltage can be installed between the MEC-1’s pilot
terminal and the pilot conductor.
4.2.7 Stop Button - Optional
The stop button should be a normally closed switch installed in the pilot conductor. When opened, the MEC-1 will detect an
open circuit pilot and trip on open circuit.
4.2.8 Start Button and Resistor - Optional
When remote start mode is selected a 100Ω, 1%, 5W resistor must be installed in series with the pilot conductor. The start
button is then installed in parallel to this resistor. The start button should be a normally open switch.