4 WAY MAINS EXTENSION OVERLOAD?

[GURU]

Hi, first ever post so hopefully I won't come across as too stupid or naive.

I have just moved into a new flat and due to a lack of wall sockets I need to use a 4 way mains extension (Bowthorpe 4 way Professional grade surge protector - description/specifications graph on page 5 under 4/6 way surge and RFI protector - http://www.keison.co.uk/products/bowthorpe/SurgeProtectors.pdf ), and was intending to plug four (4) power amplifiers into it, however given my complete lack of elctrical knowledge I was wondering if someone could tell me (given the supplied information) if the following is safe or dangerous (won't/shouldn't trip, etc), and in turn, will my amplifiers function/perform somewhere near their maximum under such conditions?

As I mentioned above I have four (4) power amplifiers with the following specs - (I run all four in Bridged Mono mode)

Power Output - Stereo/Mono 200W per channel 8 Ohms 350W per channel 4 Ohms

Power Output - Bridged Mono 500W 8 Ohms 800W 4 Ohms

Power consumption - Maximum 2400W, Active (no signal) < 180, Standby < 5W

Hopefully I have supplied enough information

Many thanks in advance

 

[cheyworth]

Using the simple Ohm's law of...

-given a maximum wattage of 4*2400W =9600W

-Voltage = 240V

Wattage=Voltage*Current

Current=Wattage/Voltage

Current=9600/240

Current=40A

This will be a maximum draw of 40A and will overload the fuse on the extention (you will unlikely get anyware near this)

when active the draw will be a minimum of 3A, I guess you will be ok as a draw of 16A will give close to 4000W and I doubt you will get that loud.

Chris

 

[RobinKidderminster]

Suggest, if worried, try 10A or even 6A fuse. If thwy dont blow thwn u u know all is well in limits

 

[GURU]

Thanks for the replies

Cheyworth/RobinK - I understand how you reach the figures but could you elaborate slightly as I'm still alittle uncertain.

Am I right in understanding that if all four amplifiers were pushed/worked to their specified maximum 40 amps (2400 watts - 9600 watts total divided by 240V) then it would definitely "blow" (the mains strip), given that the strips maximum current rating is only 13 amps, however, are you saying given that the amplifiers may/would never actually reach this figure combined that it would be safe to use?

Also, under the strips specification it states - Maximum Surge Current Handling (8/20us) = 19,500 Amps (or 6500 per element), what exactly does this mean?

(Sorry if I come across as thick).

 

[visionary]

Why do you need that much amplification in a flat?

Glad I'm not your neighbour

 

[Covenanter]

A standard domestic ring main is limited to 30 amps (the circuit breaker will pop) so you aren't going to draw 40 amps out of any type of connection! Also any one socket on a ring main is designed to bear a load of only 13 amps.

Chris

 

[GURU]

Visionary

Yes you are correct, it does seem like/is overkill, however I have only just moved into the flat due to having to downsize (made redundant plus other unfortunate issues) so where there used to be no issues re noise/plugs, etc, there now is/maybe - trust me you would love me as your neighbour, I don't play my music that loud, honest.

Call me selfish or indulgent but the system simply purrs with the four amps in use (at any volume) so that is the way I use it, yes of course I could simply use two or one amp (set to stereo), and depending on how quickly or not I can find re-employment I might be forced to sell some (or God forbid all), of the amps, however until such time I still want to listen to the system as I know and love it - irrespective, of how many amps I use I will/would still need to employ the mains strip given the lack of wall sockets.

 

[cheyworth]

what amps are they anyway?

And what speakers?

 

[GURU]

Cheyworth

Cambridge Audio 840W's and ATC SCM35's (with modifications). Prior to the "unforseen and unfortunate" circumstances striking I was planning/in the process of going the active crossover route hence the number of amps - but alas the project for now is on the back burner.

Referring back to the initial and secondary question(below), and again I apologise if I sound or come across as "thick", in short will I be able (and will it be safe) to use the strip with all four amps connected?

"Am I right in understanding that if all four amplifiers were pushed/worked to their specified maximum 40 amps (2400 watts - 9600 watts total divided by 240V) then it would definitely "blow" (the mains strip), given that the strips maximum current rating is only 13 amps*, however, are you saying given that the amplifiers may/would never actually reach this figure combined that it would be safe to use?

Also, under the strips specification it states - Maximum Surge Current Handling (8/20us) = 19,500 Amps (or 6500 per element), what exactly does this mean?"

*is the entire strip rated at 13amps in total, or is each of the four sockets rated at 13 amps?

 

[cheyworth]

I would suggest that you will be fine, as your speakers will take a maximum of 300W (even if you push that to say 500W each) then you will not blow the strip.

You could as said before put a 10A fuse in the strip plug and test with that, or even a 5A fuse.

I am 99% sure you will not have a problem.

 

[pauln]

*is the entire strip rated at 13amps in total, or is each of the four sockets rated at 13 amps?

The strip is rated at 13 amps because that is the rating of the plug on the other end of it. If it has a 13 amp fuse the worst that you can do is blow the fuse in the plug - so why not go with until (if) that happens. An electric kettle is generally 3kw and that's roughly the maximum load for a 13 amp socket.

 

[Overdose]

Why not plug it all in and see what happens?

The worst that you can expect is to have to replace a fuse. In this case, use two extensions and split the load.

 

[Covenanter]

Looking up the 840Ws on the Cambridge site it says their maximum power consumption is 1200 Watts, which is 5 amps. As you have 4 of them that comes to 20 amps. I can't imagine you would get anywhere near the maximum but I would certainly split them over two sockets.

Chris

 

[GURU]

Thanks very much guys your input/replies/suggestions are thoroughly appreciated!

Chris (Covenanter) - I noticed on Cambridge Audio's Tech Spec webpage - http://www.cambridgeaudio.com/media/azur-840w-technical-specifications-1357822470.pdf it does state 1200Watts, however in the 840W user manual it clearly states - 2400Watts??? (I don't actually know which is the correct figure).

 

[Covenanter]

Thanks very much guys your input/replies/suggestions are thoroughly appreciated!

Chris (Covenanter) - I noticed on Cambridge Audio's Tech Spec webpage - http://www.cambridgeaudio.com/media/azur-840w-technical-specifications-1357822470.pdf it does state 1200Watts, however in the 840W user manual it clearly states - 2400Watts??? (I don't actually know which is the correct figure).

I don't know either but 2400 watts for that output sounds too much, the amp would have to lose heat like an electric fire!

Chris

 

[GURU]

Chris

Like I said I don't know which figure is actually correct, but the amps can and do run very hot indeed.

Prior to purchasing the amps I was made well aware of their "heat", in my old place I had no real worries as I simply placed a box fan behind them and tried to keep the temperature at a constant, and whilst they did run warm they never got too hot, unfortunately in the flat the area constraints will restrict me to placing the fan in front (not ideal) so I will have to see how the amps "behave" (especially if summer ever appears).

Given their design, I'm sure Cambridge Audio assessed the temperature levels as they incorporated protection circuitry (CAP5) that will (or is supposed to) shut the amps down if they get too hot (overheat), as of yet I haven't seen this circuitry in action (and fingers crossed I won't), but I'm sure if the amps were driving reasonably inefficient speakers, long and hard, then the operator may well find out if the amps CAP5 circuitry actually works .

The amps are mighty fine for what they are and for what they cost, don't get me wrong they are no Bryston's, Jeff Rowland's, etc, but then they don't claim to be, yes if I could afford the aforementioned then I probably wouldn't have thought twice about the Cambridge's, however I couldn't, so I decided I would give them a whirl and in truth I was pleasantly surprised, they are very decent amps indeed even taking the heat into the equation.

Once again thanks for your input/replies

 

[cheyworth]

You could always start with 2 amps and run for a while, the go to three, then four.

Then see if you can tell the difference between them?

I am sure you will be fine I very much doubt you will draw more than 8A nevermind the 13A to blow the fuse.

I imagine your electric bill is quite big!

Chris

 

[GURU]

Chris (Cheyworth) (and others)

Once again thanks for the replIies.

Well today I connected everything up with all four amps plugged into the Bowthorpe strip and not wanting to tempt fate but everything seems to be running smoothly (well over 2 hours listening/operating) and seemingly stress free. I suppose I was being slightly over cautious and worrying needlessly, but as I said I my original post - I know absolutely nothing when it comes down to electricity, amps, etc, and whilst I do have common sense, it is something I do not MESS WITH!

As for the electricity bill I will have to wait and see. In my old place, and prior to the redundancy, I will admit that I never really stopped to think about whether or not it was excessive or not, but when it occasionally came up in conversation my electricity bill always seemed much lower then my mates (similar usages), and whilst music/hi fi is definitely one of my major "vices", now that monetary/financial circumstances are much tighter I will definitely have to monitor the situation alot closer then I have done so in the past.

 

[formbypc]

Surely calculations should be based on their power consumption (what they draw from the mains) rather than their rated audio output (as somebody above determined from the spec sheets)?