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In Reply to: Wry smile. Thanks, briggs. Much appreciated. [nt] posted by Zero on December 23, 2006 at 16:27:13:
In contrast, Zero ...20 years ago, when I built my house, I installed a dedicated 20amp circuit for all my source components (it feeds a row of 10 single oulets mounted on a long, hollow wooden wall plate). The wire is about 20' from distribution box to the start of the wall plate.
From corresponding with various people in the intervening time who have made serious mains-power upgrades, as I am now undertaking major renovations to my house, I have taken the opportunity to replace this 1 x 20amp circuit with 2 x 32amp circuits. One will be for analogue comonents such as phono stage and preamp, the other for digital components such as CDP and TT power supply (and spares).
Power amps are on their own 32amp circuit ... AFAIAC, the current draw from power amps compromises the mains supply to source components, so they ideally should not be combined (remember, conventional power amp PSes recharge their PS filter caps in pulses, so that even though the amp might only be putting out a couple of watts, it IS drawing higher mains current than the simple maths would indicate for milliseconds, 100/120 times per second).
So I would suggest you can do better than briggs' suggestion of a single 20amp circuit for everything.
Regards,
Andy
Follow Ups:
From corresponding with various people in the intervening time who have made serious mains-power upgrades, as I am now undertaking major renovations to my house, I have taken the opportunity to replace this 1 x 20amp circuit with 2 x 32amp circuits. One will be for analogue comonents such as phono stage and preamp, the other for digital components such as CDP and TT power supply (and spares).
> > > > > > > > > > > > > > > > > > > > > > > > > > > > > >Here in the US the largest overcurrent device, breaker or fuse, that can be installed on a 120Vac branch circuit supplying power to two or more 15 amp receptacles (NEMA 5-15R)(a duplex is two), or a 20 amp receptacle (NEMA 5-20R) is 20 amps..... The minimum wire size for a 20 branch circuit is #12 awg copper.
That's a pity! :-))All this means is that you need many more circuits - say, one per device (certainly one per power amp!) - to compensate. :-))
Here in Oz, a "normal" circuit for wall power points is 20amp ... 32amp is used for electric ovens, pool pumps etc. Do you have to use a 20amp circuit for these?
Regards,
Andy
Here in Oz, a "normal" circuit for wall power points is 20amp ... 32amp is used for electric ovens, pool pumps etc. Do you have to use a 20amp circuit for these?
The NEMA rating of the receptacle determines the branch circuit size feeding the receptacle here in the US. The NEMA number dictates the voltage and ampere rating of the receptacle. It is a safety thing. You must have standards that are idiot proof. In other words a NEMA 5-15R receptacle shall only be connected to a 120Vac system with an equipment grounding conductor. If it is a single receptacle the overcurrent device, breaker, shall be 15 amp. If two or more 15 amp receptacles are installed on the same branch circuit then the branch circuit can be a 20 amp. Only a NEMA 5-15P plug will plug into the receptacle. If a manufacture builds a piece of equipment with a cord and plug he must meet certain requirements for the FLA, or VA rating of the equipment for the cord and the NEMA plug he uses.
Electric Clothes dryers are typically 30 amp 240Vac
Ranges can vary. 50 amp, 60 amp, 240Vac.
The receptacles and plugs will only plug into their mated others.
A NEMA 5-15R (15 amp recept) or a NEMA 5-20R (20 amp recept), at least here in the US shall not be connected to an over current device larger than 20 amps. That does not mean I can not install a bigger gauge of wire. Many here in the US will use #10 awg wire. The wire is rated for 30 amp. The breaker must still be 20 amp. The branch circuit is thus, a 20 amp branch circuit. Speaking for Square D QO breakers the current carrying contacts in side the 15, 20, and 30 amps breakers are the same. Only the magnetic trip mechanism is different. Cheaper to mass produce the product.
20amp circuits are certainly not the 'norm' in Australia, IME most domestic power 'rings' use 16A. 32A for an electric oven? Thats a lot of power (equates to over 7.5KW on a 240V supply), my electric oven is on a 20A circuit.Current requirements on Australia's 240V will be half that of the US 120V system for equivalent power. My system is on a 20A dedicated line, though this is overkill since it exceeds the systems total (max) power draw by a factor of 5.
I guess if you owned some huge, high powered (300W+), class A/tube amps you might want more than this - though if you're truly utilising multiple 32A circuits, the heat output would drive you from the room!
Based on my recent experience, the quality/integrity of power connections and isolation from noise sources is far more critical than lines with over-spec current rating.
System Details
Paul,In Oz we don't have "rings" ... that's solely a UK thing IME. We have "spurs" - ie. power circuits snaking around the house from a central fuse/MCB in the distribution box (aka CU or "Commercial Unit").
My CU currently has 2 x 32amp and 6 x 20amp circuits for power, and 4 x 10amp circuits for lights. Shortly, it will have 4 x 32amp and 5 x 20amp power circuits, as well as the lighting circuits.
The reason 32amp is used for an oven (or used to be, 20 years ago when my house was built) is to allow for worst-case scenarios.
In terms of a 20amp circuit being "overkill since it exceeds the systems total (max) power draw by a factor of 5" ... you forget that the current draw to a power amp is not the simple steady-state current which your maths implies.
The amp actually draws its output current from the PS's filter caps; this reservoir get recharged 50 (or 100) times a second. Thus, high mains currents flow for milliseconds into the PS.
I also draw your attention to experiments which I've conducted on power transformers (which I know at least some hifi mfrs - like Naim - agree with, as they do the same thing) ... which is that, for a low-draw component like a phono stage, preamp or active XO, if you use a vastly over-specced power transformer in terms of VA rating, you get more bass. (IE. whereas a 100 milliamp current draw would surely indicate a 30VA transformer - ie. specced at 1 amp with 2x15v secondaries - is perfectly adequate, using a 160VA trannie gives a much fuller sound.)
So simple maths does not always deliver the best result.
I think this mains thing is very much something you need to try before you'll believe! :-)) I guess, all I can say is ... I had a single 20 amp circuit feeding all my source components for 20 years. I now think it's worth having two - so I can keep analogue and digital components separated.
And, yes, I agree the quality/integrity of power connections and isolation from noise sources is critical ... in this respect, it's worth reorganising your CU so that the hi-fi circuit(s) is/are the first ones off the main ON/OFF switch (or RCD) and the "noisy" circuits which have fridges, aircons etc. are furthest away.
Regards,
Andy
Andy, perhaps I haven't done the experimentation you have.
I can see the potential value of separate circuits - for keeping digital noise away from analogue components etc - but the super sized fuses I'm not too sure about. I wouldn't be too comfortable using such large fuses.
A fuse is there for protection - to limit damage or fire risk in fault situations. If the component doesn't require a large value - ie no risk of ever tripping a 20A fuse even on high power transients - what's the point of using 32A? (this would be equivalent to using a 64A fuse on a 120Vac US line). The larger fuse is highly unlikely to alter the impedance characteristics of the AC line, but it will certainly afford you less protection.This is a different issue to providing a decently low impedance cable feed (or shielding etc). I'm using 6mm˛ cable (~9AWG) over a 12m run from the fuse panel. What gauge/cable type are you using with those 32A spurs?
BTW, I thought the local sparkys did use rings, since it allows you to use lower gauge cable? Wouldn't know for sure. Most modern houses I've checked use 16A fuses for common power circuits.
System Details
Hi Paul,You said: "This is a different issue to providing a decently low impedance cable feed (or shielding etc). I'm using 6mm˛ cable (~9AWG) over a 12m run from the fuse panel."
Yes, I agree - and that's what I'm using ... "normal" white 6mm2 electrican's stuff which has active/neutral/earth (about 6m runs to my sources and a 12m run to my power amps).
This (as I understand it) is the normal cable for 32amp circuits - yes, you can certainly use it with 20amp MCBs (but you cannot use 32amp MCBs with 20amp cable! :-)) ) but my source for AC mains advice says the sturdier construction of the 32amp MCBs - instead of 20amp - of one particular brand of MCBs, makes them sound better. And, yes, he did actually test them out over an extended period of time - 6 different brands run in for 6 weeks each! :-))
So it's only for this "better sound" reason that I'm using 32amp MCBs ... I agree it's over-the-top in terms of current flow. But because they're MCBs (and not old-fashioned 'fuses'), I don't think I'm taking much of an additional risk in terms of fire risk.
Regards,
Andy
If the 32amp CBs are more ruggedly built (better quality switch, cable clamps etc), that could make a difference.
What brand are you using?Not sure CBs are necessarily 'safer' than fuse type breakers of the same rating. I suspect the construction and contact properties may result in better sound than a fuse type breaker. They sure are a lot more convenient to reset!
Cheers, Paul
System Details
Hi Paul,The make I intend to use is Memera - made by Eaton. They're not (readily) available in Oz ... I imported them via my UK contact. Other people have used them in Oz (so I don't believe they contravene our standards) but my electrician hasn't done the MCB upgrade yet - that's an "after the Christmas break" job!! :-))
So I'll find out in a few weeks.
Regards,
Andy
Just so you know, just because you are changing out a 20 amp breaker to a 32 amp breaker that does not mean more current, amps, will flow. It only means the breaker will withstand a continuous current flow up to 32 amps before it trips open. The amount of current flow within the circuit is solely dependent on the load connected to the circuit. The wire size and the length of the branch circuit from the electrical panel to the receptacle/s is very important.
jim
yes I'm aware of that.To summarise again ... the logical flow for my change in mains circuits is as follows:
1. 6mm2 cable is better than 2.5mm2 cable (less resistance)
2. one circuit for analogue sources and one for digital is better than just one for both
3. yes, 20amp MCBs on each circuit would be entirely adequate (which I could certainly put onto the 32amp wiring) but the 32amp MCBs are built more sturdily and I am told sound better.Regards,
Andy
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