My question is if you’ve got a lighting circuit and you ad addition loads to the circuit will this always trip the breaker if you add too much load on a circuit?
If the total possible load on a circuit is insufficient to cause overload then you need not provide any overload protection.
You must still provide both Short Circuit protection and Earth Fault protection.
Both of these (and overload protection) may be provided by a fuse or MCB .
An RCD may be used for Earth Fault protection, usually as a supplementary protection along with such fuse or MCB or on its own on a TT system (a system whose earthing relies on a rod/plate etc in the ground).
i think the answer to your question is yes , you can overload any circuit and cause the breaker to trip , you need to calculate the design current for what you have plus your additions .
