FELV on the other hand permits only simple separation - e.g. the equivalent of just single insulation between primary and secondary windings - so a single fault could impose mains voltage on the ELV circuit.
Not even that , a FELV may be designed to not any isolation at all between the LV and ELV, in normal operation. The example of the ELV signal relative to neutral that between the linked kidde smoke alarms, is also an example of FELV. So the cable of the ELV link needs the same insulation and respect as the L and N.
FELV on the other hand permits only simple separation - e.g. the equivalent of just single insulation between primary and secondary windings - so a single fault could impose mains voltage on the ELV circuit.
Not even that , a FELV may be designed to not any isolation at all between the LV and ELV, in normal operation. The example of the ELV signal relative to neutral that between the linked kidde smoke alarms, is also an example of FELV. So the cable of the ELV link needs the same insulation and respect as the L and N.
