I have a Memera 2000AD consumer unit with a 100A main switch and I'm thinking of swapping the switch for an RCD (at the moment it has an external RCD which is pretty old and trips out whenever there's a current surge).
Can I use a spare Wylex or MK RCD or do I need a MEM one to fit?
Thanks Roger
I don't think Wylex or MK will fit, but as a suggestion why don't you fit Mem RCBOs to the circuits you wish to be protected, e.g ring mains and lights, and leave the main switch as it is. In this way, if you trip one circuit, the other ones will not be affected. The RCBO replaces the current circuit breaker installed and takes the same space.
John
RCDs should trip to current imbalance i.e. leakage to earth. A simple overcurrent will pass through both L and N connections and this remain in balance so should not trip. If you are getting frequent tripping you have a circuit leakage problem. Blaming current surges simply suggests you haven't any idea what is actually wrong. You would be far better testing the system using suitable test equipment, identifying the real fault and carrying out a proper repair.
Many of the current generation of RCDs are made to DIN standard and can often be used in other manufacturers equipment however you may find it much more satisfactory to retain the separate RCD simply because some manufacturers do have slight differences to ensure you stay with them for spares. there is also the question of complying with BS7671 or the wiring regulations if you prefer that term. A head end single RCD is discouraged nowadays as if it trips it takes everything out, including the lights while you are trying to negotiate the stairs etc. If you are feling particularly flush with money you could replace the whole consumer unit with a 17th edition one but this automatically attracts a requirement to comply with the ridiculous Part P legislation ie pay lots of money to your local Building Control department etc etc
Not seen the Memera ones so can't say for sure, however if they are anything like the memshield II ones then you may have difficulty interchanging.
In this circumstance there may be no real fault. It sounds as if there is a "whole house" RCD in place - i.e. protecting all circuits in the CU. This (deprecated) practice often leads to this problem. If the cumulative leakage is high enough to use most of the trip budget, then surges can push it over the edge (remember that a spike will have high frequency content that will tend to be filtered by appliance inlet filters - this will momentarily increase the leakage to earth as they dissipate the spike).
A more general solution here would be to segregate the circuits such that they are served by more than one RCD. RCBOs are probably the best way to go for a non split load CU.
There is a formative list of interchangeable components here:
or follow the route taken by most people DIYing a CU change...
When I switch off the socket powering 2 PCs, printer, router etc (via surge protected extension lead) it often trips the RCD - and always when turned back on. Interestingly, turning it back on via the ring main MCB does not trip it - perhaps it makes contact more slowly?
The garage fluorescent lights also used to trip it unless turned on slowly - I've now replaced the switch which has fixed the problem.
I want to keep a whole house RCD in the folorn hope of avoiding fires if the 1958 vintage wiring (plastic, fortunately, but with no earth on the lighting circuits) develops too much leakage to earth. With a flat roof there is no access to a loft space to replace it all - will have to wait until I take the whole roof off, which may be years away.
It's a bungalow.
Seems a pity - the CU itself isn't that old.
Thanks Roger
Its sounds like part and parcel of the same issue - quite possibly too much total leakage for one RCD.
A 100mA trip main RCD with time delay (i.e. type S) will offer the same level of protection from fire risk. That if combined with RCBOs for the socket circuits would quite likely cure your problem without too much upheaval.
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