NAP 250DR causing power to trip at switch on

I have a new 250DR (used with 272 and 555PSDR) and usually leave everything switched on.  However I’m currently trying out a SL din/xlr interconnect resulting in having to power down several times.  Every time I turn the 250 back on, it trips the safety switch on my dedicated spur.

I have found only one post back in 2016 referring to a similar issue, with the suggested problem being with the dedicated spurs circuit breaker. I assume if it was a problem with the 250, its internal fuse would blow (which isn’t happening). I also need to try plugging it directly into a normal wall socket to see if the problem is resolved (I’m just putting off turning it off and on again!).  I will check this out with my electrician but just wanted to check with forum members of any similar experiences or anything else I should be aware of?

Original Post

An important question: by safety switch do you mean an RCD (residual current device) if there is one, or just the miniature circuit breaker (MCB)? Former will say something on it like 30mA and to test regularly by pressing a button. Modern circuits commonly have both, though a hifi dedicated spur is permissible without an RCD as long as the sockets are marked to that effect. And it can be confusing because the RCD and MCB are sometimes combined into a single device known as an RCBO (residual current circuit breaker with overcurrent protection).

if it is the RCD being tripped, that is not the inrush current of the power supply, but indicates a fault creating an leakage current which potentially could be a serious safety hazard. The fault would be whatever is being switched on, if only happening at the time of switching it is often the switch itself that is faulty, but it could be anywhere the mains goes after that. It is that that would need to be looked at, rather than the breaker that is tripping.

But if it is indeed the MCB tripping then one more suited to the inrush current would be appropriate, as suggested in another response, subject to the wiring being adequate fir the potential maximum overload current, which most likely it is but your electrician can advise if you are unsure.

When I had a 'Geddon power supply for my LP12 it too would frequently trip the MCB when powering up. I eventually tracked this down to a very poor connection within the wall plug. Only a few strands of wire were in contact with one of the pins. Must have slipped past Naim QA somehow. Anyway, I remade the connection and problems solved. Not saying this is the cause of the fault in your case but it might be worthwhile to check the plug to see that all is OK. 

pixies posted:

Thanks CHRISSU. That is reassuring to know. My electrician has been informed so just trying to arrange a date to get him in.

You will need your electrician to agree that an MCB is acceptable rather than insisting that you must have RCD protection. Some have a rather rigid interpretation of the regulations, and may tell you that (a) an RCD is required and (b) you are a nut case for thinking that your hifi needs any such special treatment. 

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