looks like a crabtree starbreaker, not sure you can still get them and if so likely expensive.
however the fault could be on any of the 5 circuits connected to it
or
the unit is faulty as DS suggested.
A ramp test basically increases the ma testing until it gives the level the unit trips, which should be within the units specification.
if it trips at a fairly lower level then it suggests a possible faulty unit.
To be honest id suspect a fault on one of the 5 circuits or something connected to them.
To trace your fault is not easy and sometimes sorts out Good electricians from basic electricians, its down to ones experience in fault finding and can be time consuming.
however the fault could be on any of the 5 circuits connected to it
or
the unit is faulty as DS suggested.
A ramp test basically increases the ma testing until it gives the level the unit trips, which should be within the units specification.
if it trips at a fairly lower level then it suggests a possible faulty unit.
To be honest id suspect a fault on one of the 5 circuits or something connected to them.
To trace your fault is not easy and sometimes sorts out Good electricians from basic electricians, its down to ones experience in fault finding and can be time consuming.