Switch-on power requirements NAP250 (EU PSU, Non DR)?

[JochenF]

Is there a document which describes the power requirements of a NAP 250 (non DR with EU PSU) during switch-on?

During normal operation my two 250s behave very benignly, only when I switch them on too quickly one after the other, they occasionally trigger a fuse in my home. The fuse is specified as 16A, so I assume the switch-on current must be somewhere above 8A?

[robert_h]

This has been covered a few times, search for “inrush current”. Here are a few posts that should help.

Why does my breaker trip occasionally when I power up my 250

It’s normally the wrong type of circuit beaker. You need type C as opposed to type B which is standard. The 250 has a large transformer and when turned on you will get a large inrush of current which trips the breaker. I have type B and get the same problem when the Supercap 2 is switched on. The 135s, 555PS and XPS2 are okay when turned on. I will change the MCB at some point. I wouldn’t worry too much about it. Just turn the MCB back on with the 250 still on and you should be okay. I don…

Tripping Electric

First thing I would change is the type B circuit breaker. These are not good for heavy inrush currents at power up such as we have with transformers. Type B trips between 3 and 5 X rated current Type C is 5 to 10 X Type D is 10 to 20 X

Amplification Nap 250 strong enough for?

It happens if you have fast-triggering circuit breakers, like most people. The inrush current can make it trigger. The solution is getting the breaker changed to a slower one by an electrician, or try a few times and leave it on once it runs. (Of course leaving it on is not a solution when trying things)

[JochenF]

So assuming that the fuse 16A is of type B (3x-5x) and that one amp alone does not trigger it but two can, one should conclude that the inrush current for a single amp is between 24A and 40A?

[GadgetMan]

Just get your 16amp swapped for a 16amp type C

[james_n]

As you say it occasionally happens when you switch both on too quickly, just stagger the switch on of the two 250 amps to limit inrush current and the nuisance trip.

[JochenF]

That’s what I’ll probably continue to do, wait a minute or so. With a single amp at a time there never has been a problem.

[ChrisSU]

A Type C breaker will certainly help here. Naim recommend that I put my HiFi on a 32Amp Type C breaker (NDX/282/200 at the time) although if you are outside the UK you should seek local advice on this.

[Mike-B]

Hi JochenF, I assume you are living in mainland Europe, where power circuits are radial & protected with a 16 amp fuse or circuit breaker.
This is different to UK with ring circuits protected with 32 amp circuit breaker. So you need not follow any UK 32 amp suggestions with the various type rated circuit breakers.
Maybe better if you ask an electrician with full knowledge of your countries regulations for help, be sure you know if you do have fuse protection or circuit breaker, and explain the problem is the fuse/circuit breaker in your house does not support “the transformer in-rush current at power up”

[JochenF]

Thanks for all the suggestions. Yes, I live in mainland Europe. For clarification it’s indeed a circuit breaker not a fuse, up until now I didn’t know the difference.

I don’t own the electrical installation here, so I will not be able to change the circuit breaker. I need to be careful when powering on, that’s OK. I just wanted to make sure that a triggered circuit breaker is indeed expectable behaviour and that the NAPs are fine nevertheless.

[Mike-B]

It looks like you are aware of the cause & solution & have done as much as you can in your situation.