Current consumption (1 Viewer)

[Yogi]

I was Browsing Tweeter last night. I went into one of the theater rooms which had a B&K ref 30 with 7250 + 2220 amps driving Sonusfabers (grand piano l/r) all around with a REL subwoofer. All the A/V equipment was plugged to the back of a Monster power conditioner (forget the model number but it was the top of the line in the store). The power conditioner was displaying the total current consumed by all the equipment hooked to it. The movie playing was Toy Story 2. I put the first scene of the movie and cranked the ref 30 to the 0 db setting. Man did the opening chapter rock!!! but guess what? At no time during all the explosions and rumbling did the total current consumption go above 12 amps. This was a big room (bigger than most people's living rooms) and the ref 30 was at the 0 db setting and yet I was amazed that the current consumption never went above 12 amps. That makes me feel that most people's homes with 15 amp outlets are just fine for all their audio gear, be it a flagship receiver or a full blown separates setup. Plus if you have two dedicated outlets, one for your high powered gear like the amps and subwoofers and the other for the rest of your system you should be perfectly fine with a 15 amp outlet. Just makes me rest easy.

 

[DanielSmi]

the most I've ever pulled was 9.1 amps, I have the Monster HTS 5100.

Daniel Smith

 

[Saurav]

Does this device store the peak value reached over a period of time, or does it just show the current being drawn at that moment? If it's the latter, I doubt you'd see the real peaks, because the transients would last less than a second. If it's the former, where it can latch and hold on to the last peak value, then the numbers are more meaningful.

 

[Yogi]

It was only showing instantaneous current values. I am sure it was fast enough to show (even momentarily) what the current drawn was at that particular moment. The max numbers that I am talking about did last less than a second. They were changing very rapidly. It must have been going through several changing numbers (after the decimal) in a second. So I am sure it was capturing all or most of the transient current peaks, although I am not sure what its transient response would be i.e., whats its speed of response would be. All I was paying attention to was the number before the decimal (that wasn't changing so rapidly) and that number never went above 12 amps. Also speaking of transient response, what is the transient response of a house breaker, i.e., how fast can the breaker trip in response to a change in current (above its max value)?

 

[Brae]

Yogi, a one-cycle peak is 1/60 of one second. Now, if you think a) the Monster product can show this, and b) you think you can visually discern this event, please let us all know. Personally, I can't discern on flicker of my incandescent lamp from the one coming 10 cycles later.

 

[Yogi]

Personally, I can't discern on flicker of my incandescent lamp from the one coming 10 cycles later.

Hmmm.. I thought the human eye can discern changes in visual frames at a rate of 30 FPS but you are telling me that if I play a movie to you at the rate of 6 FPS you wouldn't see any discontinuity? Hmmm..interesting indeed

 

[Brae]

Yogi, I am trying to find a way to describe to you what is apparent to me.
A frame-rate of 30FPS means that there are 30 distinc events in one second. The decimel value of the amount of time each event lasts is 0.033333 seconds.
AC voltage in the US is 60Hz, or cycling at a rate of 60 times per second. This, in decimel, is 0.016667 seconds for one complete AC cycle event. This is exactly half the amount of time of the 30FPS example.
Now, keep in mind two things that makes it even harder for a Positive or Negative amplitude peak to be seen:
First, each AC cycles has two different sub-events that occur. The first sub-event causes the amplitude from rise from zero (0) volts to maximum amplitude (say, positive 120V) at one-forth (1/4) the 0.016667s time interval, which is 0.004167s, then fall back down to zero volts at one-half (1/2) the 0.016667s time interval, which is 0.008333s.
This sub-event lasts only 0.008333 seconds compared to the duration a 30FPS event lasts, which is 0.033333s. The 30FPS event lasts four times longer! It is also wise to remember that at 60Hz there are 120 peaks being reached in one second!
Now, if you slow your frame rate down so that it is 1/5 (6/30=1/5) then the duration of the individual frames is five times longer! I do not know, but to me it is a LOT easier to see, and discern, 6 unique events occurring in one second's time than it would be to see 120 voltage peaks in the same second of time.
Now, if I were a Hummingbird flying south for the winter which direction would I be flying in?

 

[Bill Kane]

Yogi,

Your observations that began this thread are quite useful to anyone with 15A household circuits who ever wondered about overloading. Electrical Code "suggests" (I dont have the book) maintaining an 80 percent safety factor -- meaning no more than 12 amps or 1440 watts load on a 15A line.

If you had turned the store amp volume down to less than reference level, I'm certain the amperage would've dropped to 9-amp PEAKS and less.

Good report.

bill

 

[MikeRP]

Just for reference:
I had my electrician over the other night to check the current consumption on my system.
Sony 35" TV
Magnovox VCR
Toshiba DVD
RCA CD
Pioneer 45 TX
Definitive Sub
Scientific Atlanta Cable Box
Some lighting on the circuit.
When we checked the system with LOTR playing at volumes I wouldn't listen to (wife mad) - we peaked at 8.1 amps current usage.
I'm adding my Pioneer SX 1080 as a 2 channel amp and I haven't decided but I may add an additional sub or speakers with built in subs.
I'm putting in a dedicated home theater feed with a 20 amp circuit. The breaker will have surge protection built in.
The values on the meter did change rapidly and the meter kept the high value in storage. I didn't look at the type of meter.
I'm not sure this helps but I felt like typing........
Mike

 

[Saurav]

But what I am getting at is that a transient has to last a few tenths of a second to trip the breaker, right?

I don't think so. I'm not sure about this, but a good breaker should react in milliseconds or maybe even less. A few tenths of a second would probably be enough to fry equipment, specially things like conputers. I think a surge protector would react even faster than that.

This is all conjecture though, and if you're interested, you should be able to look up specs on circuit breakers and surge protectors online to get some real data.

 

[Yogi]

Nice math Brae, but I still dont get your point. I am not interested in how fast the AC signal is modulating or how many discreet events are happening in a waveform. All I want to know is if transients can occur at a rate of 120 Hz as you suggest and if they can, will they cause the breakers to trip?
Well I did a search on Saurav's suggestion, to find out a breakers response time and here is a link on 'electronically controlled fault protection' that I found.
http://216.239.53.100/search?q=cache...n&ie=UTF-8
Here is an excerpt from that:

The modified Vista TCC will initiate a trip open operation of the "main" interrupter well in advance of the upstream breaker's 6 kA instantaneous setting, and well before the breaker's 1/10-second response indicated by the horizontal line on the CO-9 TCC at right

Which suggests that the breakers response time is 1/10 second, and thats all I am interested in. If the monster power conditioner is monitoring the current at that speed and if my eye can discern a change in numbers at that rate (which I believe a human eye can), I know what I want to know and I am a happy camper watching the humming bird fly and not worry which direction its going in
You can chop up an AC sine curve in how many ever discreet events as you want. Why stop at zero to max interval? Why not include the average point in between zero and max where the slope of the curve goes from an increasing rate to a decreasing rate, i.e., where the derivative of the curve has a maxima. That way you can further chop up the sine curve and double the number of events in a waveform to 8 instead of 4 and add more zeroes behind the decimal. And why stop at the first derivative....for the love of holy math go beyond that...

 

[Craig_Kg]

Remember that any decent amp (including the one in the REL) will have capacitive storage for transients so the instantaneous peaks are smoothed by this. Power draw will increase a moment later to replenish the caps but power draw is averaged out.

 

[Yogi]

Good point Craig.

 

[Brae]

Yogi, the only thing I am suggesting is that we humans are not capable of discerning with the naked eye a sequence of events occuring at a rate of 120 times per second, and that your comparitive example is a lot easier to see because fewer events are taking place in the same amount of time.
Since I have no idea what your background is, and I would not assume, I chose to reply using a ground-up descriptive explanation of the point I wished to illustrate. I will admit that I cannot see one event out of a series of 120 events in any given second of time.
Of course, I am willing to also admit that I could see one of six events events (a la your 6FPS scenario) occuring in that same one second timelapse.
Now, as to whether the breakers you have in your home, electronics, etc. are capable of reacting to a single event which a peak voltage way out of spec fot then this I could not answer. BTW, I tried the URL but it failed. Sorry.
Craig, this, of course, makes the assumption that the receiver or amplifier in question has sufficient capacitive storage to handle any abusive consumption the system may draw upon. Sure, one would expect this to be the case in a good component, but then again that is why not all components are created equally.

 

[Yogi]

.

Craig, this, of course, makes the assumption that the receiver or amplifier in question has sufficient capacitive storage to handle any abusive consumption the system may draw upon. Sure, one would expect this to be the case in a good component, but then again that is why not all components are created equally.

I would think that even if the abusive consumption of a high impact explosive scene taxed the capacitor bank to its full capacity it wouldn't immediately show up as a draw on house current as it is separated from the house mains via the amp power supply with all the soft start elements and other protective features. All it would do is to make the amp clip. So most of us with 15 amp breakers still can rest easy that they are not going to exceed the 12A mark.

 

[Brae]

True, and I'm trying to resolve a local shop's condition in which a set of main loudspeakers were repeatedly able to shut down the receiver when the volume took off in a movie seen. They've treated it as a problem with the receiver (lemon), but the replacement is doing the same thing.

Now, if what I am being told and that is a given speaker is designed to be amplified in the middle-third of the speaker's amplification range then that poor 45TX will need some help as a 100WPC receiver is not capable of feeding speakers more than willing to suck down the juice at 200WPC.

I still wish to do some experimentations as I bought the speakers that were shutting down the receiver in question (which I also plan on buying). Should be interesting, but hopefully not costly.

 

[John Royster]

So most of us with 15 amp breakers still can rest easy that they are not going to exceed the 12A mark.

which is why you want a 20 amp circuit. 12 amps is cutting it too close for comfort for me.

 

[Saurav]

Thanks for digging that up, Yogi. Those numbers aren't what I expected. You learn something new every day

 

[Yogi]

which is why you want a 20 amp circuit. 12 amps is cutting it too close for comfort for me

Yeah but only if you had 4 ohm speakers all around (are Sonus Fabers 4 ohms?) and if you had a room the size of this Tweeter's theater and if you had 200x7 channels of amplification playing at above reference levels. Thats why I say most of us because most of us dont place that kind of demand on our HT and so would be quite fine with say two dedicated 15 amp outlets, which would be quite common in most households. I am sure there are people that use monster monoblocks from Krell and Mark Levinson all around that wouldn't even power up from a 15 or 20 amp outlet. But they probably are only amongst 1% of the HT crowd. The rest of us should be happy and rest easy with two 15 amp outlets and not worry about getting the electrician to rewire the house.

 

[Saurav]

I thought another advantage to dedicated wiring was that you won't have the fridge and the dishwasher and the computer on the same power circuit?