Surge Protectors. Good or Bad?

quote:

Originally posted by Adam Meredith:

quote:

Originally posted by Dr. Exotica:
30 or 45 amps is nuts.

How wonderful to have an expert here - what would you estimate the maximum instantaneous switch-on demand of, say, an Armageddon to be?

Quite a few of our units will occasionally draw well in excess of 45 amps once in a while on switch on.

I do love experts Adam.

Lets see ... in the US, we are limited by law to 15A household circuits as has been discussed previously. I am running all of my gear on a single 15A line. I have an Armageddon (please consult my profile), among many other various Naim boxes. Seems to work, even if I do follow the dogma of keeping everything switched on at all times. Are you implying that it won't work effectively, or that Armageddons are incapable of performing up to spec in the US as we do not have 45A circuits.

Which exactly are the other Naim boxes that will occasionally draw in excess of 45A? Which ones that do not have a power supply? Again, the presumption is that a well/competently engineered power supply will be able to handle small transient loads of this sort without significant voltage sag.

I look forward to this list Adam. I also look forward to a bit of experimentation this weekend with some fast blow fuses of various amperage ratings.

And no, I am not going to be playing with fuses inside my boxes. That is of course a bad thing, as outlined in the handy forum posting guidelines.

Again rereading your posting, are you implying that they only have large loads during switch on (when they are initially filling the reservior caps, etc.)? If this is the case, why would anyone care, given that it is a singular event (i.e., briefly during power-on - it must certainly be brief if it will not trip my 15A circuit breaker), and we are all told to keep our stuff turned on at all times, save for the occasional electric storm.


Finally, Ed, good for you getting the dedicated circuit. You'll enjoy it.

quote:

Originally posted by Dr. Exotica:
Again rereading your posting, are you implying that they only have large loads during switch on (when they are initially filling the reservior caps, etc.)?

No - I am stating it and it is not related to the capacitors (consider Armageddon).
I believe it arises from the immediate current flow across the transformer primary and depends on the point in the power cycle at which this energization occurs.

3 notes from the internet:

"Inrush: The initial current that occurs when a motor or electronic equipment is first turned on. The inrush current is usually several times higher than the normal operating current. In the case of electronic equipment the initial inrush current occurs while the power supply charges up. Equipment with a large current draw can have an inrush current large enough to blow a circuit breaker or damage switches and relays."

"A transformer steel core's remanence means that it retains a static magnetic field when power is removed. When power is then reapplied, the residual field will cause a high inrush current until the effect of the remanent magnetism is reduced, usually after a few cycles of the applied alternating current. Overcurrent protection devices such as fuses must be selected to allow this harmless inrush to pass.

When a transformer is livened, the magnetizing inrush currents are estimated as multiples of the transformer's nameplate kVA.

Time Current
(sec) - (amps)
0.01 -- 25x
0.10 -- 12x"

"When a transformer is switched on to line, at times the circuit breaker trips or their fuse blows. This happens even if the transformer is on no load with its secondary open. This is due to the heavy magnetizing current drawn by the transformer. This current may reach a level exceeding the full load current. However, this heavy inrush current magnitude depends on the instant on the a.c wave at which the transformer is switched on.
If the instant happens to be such that the a.c voltage wave is going through its peak value, then there will be no inrush current drawn by
the transformer. The magnitude of the current in this case will be at normal no load value. If the instant happens to be such that the a.c wave is going through its zero value, then the current drawn will be very high leading to breaker tripping."

I was genuinely shocked at the quality of mains wiring I saw when I lived in the US, but then we have a tendency to seriously over engineer where mains voltages are concerned. The cable 10mm2 cable that one uses with a 45Amp breaker could probably comfortably carry at least 70Amps. The wiring that I sorted out in my apartment over there looked like 16 gauge bell wire, and none of the sockets were earthed. Fair enough, occasionally one will go into an old building over here and find paper insulated wiring, and earthing that consists of some wire wrapped around a lead pipe, but this was a newish building!

Thanks to all who helped. Naim Wiremold now installed and system is back to sounding good. Next on the menu is the electrician to install the dedicated hifi line.

Cheers
Ed