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SAFETY STRING DESCRIPTION
The Safety String is a SERIES based circuit where any open switch will cause the
controller to be inoperative. Wire the Traveler and Safety String to the
appropriate terminals using the provided drawings. The Safety String is
designed to:
1. Operate on 120vac.
2. Pass through a customer installed Stop Switch
and a series of safety switches (buffer, pit,
hatch, finals, machine room stop switch, etc.),
the SF2 relay on the Cartop and through the
Machine Room SF1 relay when commanded.
3. Stops the car immediately if any switch is opened during operation.
4. For Emergency Situations: The Safety String is bypassed by jumping SF1 to
120, allowing the car to run as if the safety circuitry is intact.
5. Hydros – Provides power to the Valve Interface Board (COM) and Fault
contactor.
6. Tractions – Provides power to the M, B1 & B2 contactors.
SAFETY STRING TROUBLESHOOTING
The first step in troubleshooting the Safety String is to determine:
1. Do you have 120vAC at terminal SF2 on the machine room DIN rail?
2. Are there any active faults?
3. Are the proper relays or contactors functioning?
Safety String open:
1. Start by measuring the safety string at the TSF terminal on the machine
room DIN rail.
a. If it measures 120vAC then the open is either in the hoistway or
machine room. Check the PIT, Buffer, Bottom or Top Final switch.
b. If it measures less than 70vAC then the open is on the cartop. Check
the cartop stop switch, car safeties, escape hatch or fire stop -
second pole switch.
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