Originally Posted by Patrick Collins
...So picture cooking dinner on an electrical cooktop. If you started with boiling a pot of water on high, you're going to see that burner go to full current draw until the thermostat kicks in. Then picture cooking four different items on burner 1-4. They're going to have different start times and different temperature settings. Then their thermostats are going to be peaking at different times. Say burners 1&2 are capable of 2 1/2 amps and 3&4 are 5 amps. Unless you're boiling 4 pots of water started at the same time, you're chance of drawing 15 amps is less than hitting the lottery. You're electronics looks like that to the circuit breaker.
Strange analogy, but I hope you get the point. Theory has it's place, but sometimes you need real world testing to come to a conclusion.
About that 15 amp breaker, today's receptacle circuits are typically 20 amps with 15 usually saved for lighting. If you know wire sizes, check to see if it's really 14 gauge. If it is 12 gauge plop a 20 amp breaker in there for a start. Also if that's a standard convenience outlet sharing other loads on a 15 amp circuit, it might be time to consider pulling a new dedicated 20 amp circuit.
Good analogy, just like the other day when I did a current reading on my AC unit to see if I could run it off my generator during a power outage. Nope, the AC is fed with 20 amp breaker, when the compressor starts inrush is 60 amps for a fraction of a second, the only draws 7 amps while running. The generator would run the AC, but not start it. Also with the cook top analogy, this would be duty cycle, time on vs. time off. Music is dynamic always changing frequency, amplitude, etc. There will never be a constant current draw, well unless you are playing a constant test tone and high volume.
True in a newer house usually the practice out there is to use 15 amp circuits for lighting. Some areas like a kitchen have to have 20 amp receptacle circuits by NEC. Most of the time a 15 amp duplex ( what you normally see in your house) receptacle is installed on a 20 amp circuit, which is code compliant. Each spot to plug in is considered a receptacle, so there is technically (2) 15 amp receptacles on the circuit. What I'm getting at is that the one of the two you plug into is only rated for 15 amps, another bottle neck. Upgrade it to a 20 amp unit.
Originally Posted by FOH
Yes a breaker will pass extra-ordinary amounts of current for surprisingly long periods of time. I just shared this in another thread 3 days ago;"Another pertinent aspect, oversizing branch circuit wiring. I've recommended it for years around here, but amplifier circuits for subwoofers,...upsize the wiring significantly if you want to remove the wiring as a potential choke-point impeding current delivery.
A 20 amp circuit can pass 7-8 times the rated 20amp trip amount, .. for up to a second or more. It will allow up to 3x the rated amount for up to 10sec or so. And most importantly, the same 20amp circuit, can allow up to 1.5-2times the rated amount for a period extending as long as 30 seconds.
* That's over 100amps for around 1-2 seconds, about 60amps for around 10 seconds, and the circuit will allow 30-40amps for as long as 30 seconds! From a 20a breaker."
As stated, assure connections are tight from the breaker lug/screw, all the way to the device. Moderately high (yet within normal range) currents will find a slightly loose connection point, and this will exacerbate the situation even more. Expansion and contraction from thermal effects can easily further loosen connections, so always be mindful of such.
Upsizing a branch circuit (or as many circuits as it takes) primarily to accommodate subwoofer amplification, and to a lesser extent other high wattage amplification, can be a significant performance upgrade if the situation warrants it. It all depends on the distance between the panel and the load, but upsizing at least one trade size can offer benefits eliminating the wiring as a potential limiting factor in low impedance current delivery. So just be mindful of all aspects when examining both the safety and the performance situation.
Up sizing wire in your average home for voltage drop isn't really needed, but if you are looking for every edge then go for it. The cost to amount of return is minimal. If you have the extra time and money to do it, go for it. Otherwise save if for something else.
There's that reoccurring theme of making sure you have properly made tight connections. Good point on the thermal effects.
Originally Posted by Patrick Collins
Practically speaking, a marginal circuit is better served with another 20 amp circuit, essentially doubling the wattage available. While a one gauge increase has it's place, mostly for long runs and not likely in residential, you're incrementally increasing headroom unless you also up the breaker size to 10 gauge, but then everything else will be rated for 20 amps. Then you've only increased ampacity by a factor of 1/2. Everything 12 gauge or less is so common it makes anything larger seem disproportionately expensive.
If any work is done it might be a good time to tighten all connections in the breaker panel although the line side of the main should be done by an electrician. If you have stab-in breakers, likely for residential, you might want to have someone turning on and off devices in the house, especially your HT, while it's dark, with the panel's dead front off and look for any arcing. There shouldn't be any. You could clean the bus bar links. You can clean the breaker tabs or replace them. With the main turned off the only danger point is the line side of the main breaker.
Be careful working in your panel, it can be done. Electricity has always been potentially dangerous, but you should see how nuts the industry is lately with arc flash and wearing the proper gear. True just the top of the main is "hot" if you shut the main off. Do yourself a favor and work arms length away, keep your body back. Wear some leather gloves if you can work in them. For sure where all cotton and a long sleeve shirt and pants. This betters your odds of not getting burned if something happens.
Another thing to keep in mind with an older home. Say you take the cover off your panel and see a #12 gauge wire, which is good for 20 amps on a 15 amp breaker, this doesn't mean you can put it on a 20 amp breaker. You really need to know what gauge every inch of the wire is on the circuit. All it take is for someone who was handy and added something down stream and used #14 gauge wire between two junction points (boxes). Now anything down stream of this can draw "20" amps and is going through the #14 wire only rated at 15 amps. Before you consider upping the breaker size it is wire to open up every "box" and check the gauge of the wire.
Easier than this and it has been said before, at this point just fish in a dedicated 20 amp circuit with #12 gauge wire (yellow jacketed) and be done with it.