Since replacing my old consumer unit with a new split load one, a small fluorescent lamp trips the RCD. The lamp is similar to the kitchen under-cupboard ones, and its wired into a plug. I've checked the bulb holder and socket for loose and incorrect connections and replaced the plug, lampholder and bulb with an identical arrangement. An inspection lamp with conventional bulb off the same socket works fine. Both lamps work ok on a separate circuit. The problem circuit is the only power ring circuit, and I don't have any other problem. Admittedly this part of the circuit is a bit dodgy - since I extended the original single socket to two doubles either side of the wall without a fused spur. I can run high load appliances off the circuit without tripping, including underfloor heating. Any ideas?
An RCD is designed to trip when there is an imbalance in current on the phase or neutral conductors, depending on the trip rating ie 30mA it should trip when a fault current equal or greater than the trip rating flows to earth. When a fault to earth develops the cpc carries some or all of the return path current (depending on the fault)rather than just the neutral carrying the return current. So in answer to your question the lamp in itself being only 2-wire (no earth) should not trip the RCD,it sounds like there is some other problem - interesting!!
they sometimes do trip rcds, its the initial draw when it is switched on, one of the reasons lights are almost always put on the main switch side of the cu, probrably worth you running a cable from your lighting circuit to run it off BR
Is there any inverter circuitry in the fitting (is the lamp 240v or low voltage?) RCD's don't like inverters!!!