Dedicated circuits

@jea48  , thank you for clarifying that for us. 

where to buy a magnetic breaker?

You won’t buy em for your electrical panel... Only T-M, Thermal-Magnetic, breakers are available. The Thermal protection unit of the breaker is for overload protection of the branch circuit wiring. The magnetic unit provides short circuit protection. It usually trips the breaker open in a matter of milliseconds. An electrical short circuit can cause a dangerous electrical explosion if not cleared quickly...

The only place I can think of where a Magnetic circuit breaker is used is on a piece of equipment. It is never used to protect branch circuit or feeder wiring...

Per NEC, UL, NEMA, only the manufacture’s breaker type/stye can be used in an electrical panel. A label on the back side of the electrical panel’s breaker cover door lists the manufacture’s type/style(s) for the breaker(s) that can be used in the panel. Using the wrong breaker will void the UL Listing.

Here is a video of the inside of a circuit breaker and how it works. Note the circuit breaker that is used for the demonstration is a EATON type/style BR breaker, not a Square D QO circuit breaker. A Square D QO breaker works on the same principal but in my opinion is of a better build quality.

The guy making the video does a pretty good job except, imo, when it comes to his personal electrical safety.

where to buy a magnetic breaker?

@gp4jesus  , what I was getting at is I think that the problem is going to be, if for legal reasons you feel constrained to have the brand of your CB  match your box, that magnetic CBs may not be available in the brand that you want.  

I’m very sorry for my lousy proof-reading of two replies before.

OTOH how spell check got “bracket” from “breaker” is beyond me.

regardless the take-away is KNOW your panel’s brand or, like me, bring a picture w/you and ask a CSA for confirmation before checkout.

That behind us, about that Sunfire subwoofer’s power demands?

&

where to buy a magnetic breaker?

In my limited experience in my previous & current domiciles, I think the wrong brand bracket won’t fit/work.

@gp4jesus  you might be right,  I don’t do much of this, but once upon a time I was warned that (as an example) putting a GE circuit breaker in a box of a different brand was grounds for your homeowners insurance to deny a fire claim. I don’t know all the details, but I just thought I’d pass that along.

@immatthewj 

”make sure that [breaker & box brands match.]”

Yes. In my limited experience in my previous & current domiciles, I think the wrong brand bracket won’t fit/work. I’ve always brought a picture of the box to avoid that mistake. 
 

regardless thanks for that VERY important reminder. 
 

Tony

@gp4jesus   for homeowners insurance purposes, make sure that you use the same brand of breaker that your box is.

@Audiencllc

where to buy magnetic breakers - Lowe’s or Home Depot?

This thread is has a few people that know a thing or two about power demands. Getting ready to swap in a Sunfire True Sub Signature to handle LFE duty and the CC’s heavy lifting.

Would appreciate counsel to power this Carver-designed beast! It seems it minimum, it may need sole use of one of the existing 20As. I reading somewhere it can pull 27 amperes?  Someone in an earlier reply has one these.

Thanks. Tony

Lots of good information on this thread. Regarding breakers, magnetic type are preferred over thermal as thermal act as a resister, working against dynamic flow. Audience, makes some dedicated in-wall AC power wire as well as duplex outlets under the Hidden Treasure line. I am affiliated with the company.

Good call eliminating the stab connections. They're poor.

@mesch and @everyone else who took the time to clarify this concept for me--thank you. I may be a little bit dyslectic when it comes to this stuff--the way I was seeing it was that with a 20A outlet & 12-2 connecting it to the box, I had a 20A circuit protected by a 15A breaker. When actually I had the opposite. But now I understand the error in my thinking & I am rectifying it. I do not want a catastrophic event--period; but if one occurs, I do not want my insurance company finding a way not to pay me.

Anyway, I would have already put those 20A breakers in, but since this is the dedicated circuit thread, something else had been gnawing at me. My circuit needed to move to another room a few years ago, so what I did was put a work-box in my attic for a junction from which I could drop the lines down into my new location. I went to Lowes to load up on the stuff I would need, and the electrician guy who was there sold me on these (for lack of knowing what they are really called I will call them) "stab connectors" instead of wire nuts. (one stab for black from box/one stab for black to new location/one stab for black going to original location X white & copper X three circuits . . . I never really liked the way I felt about the way they grabbed on to the stripped leads from the Romex, and a while back ago I wound up putting wire nuts on all the grounds because I lost a ground on one circuit (must not have been a patent stab) and after I read a reply on this thread about circuits made up of "back stabbed outlets," I decided to get up in the attic today and pig tail and wire nut ALL the splices on ALL three of the circuits. Which is not as much fun as it sounds like, because I had to reroute some of the Romex as I had it stapled down after I finished it the last time, and I needed more Romex in order to work with it inside the work-box. So that’s what I have been doing today & will finish up tomorrow.

So going back to a few years ago, when I was buying stuff at Lowes, the electrician guy who was assisting me asked me to describe the Romex I had used, & when I did, he told me it was only rated for 15A. Since I only do this when I need to, and since I originally did it 25 years ago, I thought it would have been strange that everyone who told me what I needed to do and the electrician who actually hooked my Romex runs up to the upgraded box I bought, would have told me to buy 15A Romex and then hooked it up to the 20A breakers I had for those 3 circuits, but I am not rocket scientist or brain surgeon so I decided to put 15A breakers in for those 3 circuits. As I was working on my new lines, I did note that my existing Romex was clearly marked "12-2 with ground" and I did later show a piece to an electrician who assured me that it was good for 20A. But, a 15A CB just seemed like an error on the side of safety for all the misguided reasons that I was asking about in my last half dozen posts or so to this thread, so I never asked anybody, until now, about the legitimacy or wisdom of that.

However, I am glad I did. Sorry for writing War And Peace.

jea48, my apologies, I left out one important detail. The heat cabling came in pre-configured lengths from the manufacturer, with factory terminations. The heat zone in question was the maximum length offered. The electricians knew their job, but in this case merely read the literature and provided the specified cable in the thermostat box. You can probably guess what the solution was.

My takeaway from the above:

A 20 amp receptical should never terminate a 15 amp line. A very reasonable rule.

A 15 amp breaker will trip earier than a 20 amp breaker when used in a 20 amp line.  Electrically this may be safer however may not be code in many locales.

Insurance companies may care more about what is code than what one might percieve as safer when it comes to claimes.

If one feels the need to overkill the power supply side of your audio system regardless of one's thoughts to the sink requirements do so using an approach that is safe and follows code.

@bigtwin Wrote:

@dpop Wow!! That’s a 30 amp plug alright. I’m confused by your comment. The specs on the crown amp show it’s draws 0.75 amps at idle. My Hegel H30s put out the same power as the Crown.

The Crown Studio Reference I output power:

Stereo mode (with both channels driven):

1,160 watts into 4 ohms.

780 watts into 8 ohms.

Mike

OP:  There may be a little confusion because of 120 V 15A outlets.  It is legally acceptable to put these on 20A circuits, but this is the only place I know of where this is true. As I recall this is more to do with the likelihood of having multiple outlets on the same circuit, so you want a little extra current rating to support multiple appliances.

Anything rated for more usually doesn't share a circuit.

I think I know where the mistake in VA is coming from.  Too little understanding of the math around transformers.

For an ideal transformer (without losses) the VA on the input equals the VA on the output, however!! If the V on the input drops, V*A is less on input, therefore V*A is less on output.

Transformers are often used in voltage regulators, but they do their magic by altering the output taps.  Most linear gear is not this lucky, but most line level gear is well regulated so 20% voltage changes won't matter.  Amps are not so lucky.

. . . you see, my misunderstanding was that I was considering the outlet part of the Romex. In other words, since is legit to run heavier Romex in a circuit than what the breaker is rated for, I was thinking that the same would apply to the outlet. In other words, it would NOT be legit to have a 20A breaker for a circuit ran with 14 gauge Romex, but it would be legit to have 12-2 Romex with a 15A breaker, and therefore, I was thinking that as long as the other components of the circuit (Romex and outlets) were rated for more than the breaker, that would be safe and legit.

Thank you for clarifying for me what was wrong with that logic--safe, but not legit.

@bigtwin 

Wow!! That's a 30 amp plug alright.   I'm confused by your comment. 

I've never seen an audio amplifier with a 30 amp plug on it before. 

Thank you, @jea48 .

FWIW, what you did is electrically safe,... It just doesn’t meet code.

I am putting the 20A breakers back in tomorrow.  In the event of a catastrophe, even an unrelated catastrophe, I'd rather meet code and not be trying to argue with the insurance code about it.

jea48, thanks for all you do here on these threads, it’s appreciated.

As an aside, we had a job 10 years ago with in-floor heat, continuous cable laid under stone tile. The largest zone was apparently a bit too big, on a 20A breaker, and pulling a consistent 17-18 amps. The breaker would hold it for hours, but then finally trip.

@immatthewj

Myth is a breaker will trip when the current passing through the breaker reaches its handle rating.

NEMA requirements says a breaker must trip in less that one hour if overloaded 135%. It also says a breaker must trip within 2 minutes if overloaded 200%.

15A breaker X 135% = 20.25A. Can take up to an hour to trip.

15A breaker X 200% = 30A. Can take up to two minutes to trip.

Both calculations above are for constant, continuous, load current.

In most cases the branch circuit wiring is 14 gauge with an ampacity rating of 15 amps for a 15 amp circuit, breaker. (The breaker amperage rating determines the size of the branch circuit. (Not the branch circuit wiring.)

(Old white paper but still holds true for a regular type breaker.)

https://goodsonengineering.com/wp-content/uploads/2017/08/CircuitBreakerMyths_web.pdf

FWIW, in most cases spec grade or better 5-15R (15A receptacles) use the same internal contacts as a 5-20R (20A receptacle). The only difference is the face plate.

For cord and plug connected appliances and equipment NEMA has requirements that manufacturers must follow. To be able to use a 15A plug the FLA of the appliance or equipment can not exceed a continuous load current of 12A. (Continuous is defined as three hours or more.) For most consumer made products manufactures make sure the FLA is 12 amps or less. Why? Because the majority of wall duplex receptacles outlets in residential dwellings are 15 amp... Even though the kitchen, laundry, dinning room, bathroom, and garage, branch circuits are 20 amp, 15 amp receptacle outlets can be used. NEC, two or more on a 20 amp branch circuit. (A duplex receptacle is two.)

If the FLA is greater than 12A continuous the plug must be a 20A. NEMA Says the FLA can not exceed 16A FLA Continuous for a 20A plug .

The face plate on the 15A outlet makes the outlet idiot proof. A 20 amp plug will not plug into it... It prevents a possible 16 amp load from being connected to 14 gauge copper wiring in the wall. A continuous 16 amp load probably would never trip a 15 amp circuit breaker.

FWIW, what you did is electrically safe,... It just doesn’t meet code.

@immatthewj   Yes.  The 20A outlet may be a bit more sturdy, but the 15A outlet is missing the "t" slot specifically to keep 20A plugs from geing inserted.  

@immatthewj  There is nothing wrong with using the 12G wire between 15A breaker and 15A plugs.  You would use 10G or 8G if you wanted.  The wire has nothing to do with the flow of current.  That is held in check by the breaker.  The amount of "draw" on the circut is determained by the appliance (s) connected to it.  There is an ongoing argument as to any benefit to using the heavier wire.  I can't hurt.   

Thank you, @bigtwin and @builder3 Okay, the 20A breakers are going back in.

I believe that one of the misconceptions I had was that the 20A outlet was actually a heavier duty outlet built to safely carry more current than a 15A outlet . . . that isn’t so, is it? The difference is only in the ’T’ slot, and that difference is to protect a 15A circuit from having a 20A appliance connected to it?

Okay, so bear with me for one more question, and I assure you that this is strictly a hypothetical question. If 12-2 Romex was in between a 15A breaker and a 15A outlet, that would be legit, wouldn’t it? The 12-2  in between the breaker and the outlet would be overkill, but there would be nothing technically wrong with that because the outlet matches the breaker’s rating?

You see, that’s what I thought I was doing with the 15A breaker protecting what I felt was, in all other aspects, a 20A circuit. But I am starting to see the error in my thinking, and I do want my homeowners to cover me in event of catastrophe, so seeing as how changing breakers is easier than changing outlets, the 20A breakers are going back in tomorrow.

immathew, that was my point. Or more properly, that the outlet should be sized correctly at 20A rating, not undersized at 15A.

In your case, with 15A breakers on 12 gauge wire, you haven't done anything unsafe, but you have placed an unnecessary restriction on your circuit.

I think these "dedicated circuit" threads always set the standard for misinformation.  and much of the information that is correct is cited for the wrong reason.  People don't know the difference between physics and code requiremets.  Many people want to just tell others that they are wrong, no matter what the answer is.  the most common error is trying to equate watts to wire size.  If you just use ampacity of the wire, a 250W amplifier is good on 26 awg wire which is good for 2.2 amps on common ampacity charts.   Starting to see that it isn't that simple?  

So if you're a newbie trying to figure it out, this isn't the place.  Good luck.  Jerry

@immatthewj   In therory, there is nothing wrong with your argument.  However, the building code clearly says you can't do it.  There is a reason why a 20A receptacle will accept both a 20A plug and a 15A plug, but the reverse is not true.  My guess would be something like this.  Your 12 gauge wire can handle 20A, but not the 15A breaker.  What happens if the breaker tries to trip but fails to operate properly.  Could it start to arc at the main breaker box?  Installing a breaker that you know can't support the potential current draw is simply unwise.  I have told my story and have nothing more to say. 🤣

You can plug numerous items into a 15A receptacle that exceed 15 amps, portable heaters come to mind. My Skilsaw. The outlet is undersized for the circuit, and the potential load(s).

@builder3 wouldn’t one be better off if the outlet was oversized for the circuit and the potential load(s)?

@immatthewj A 15A receptacle on a 20A breaker is not an issue as any 15A appliance will never exceed the wiring in the circut. The reverse of a 20A outlet on a 15A circut is where the potential of fire comes into play. We assume the breaker will trip and protect us from harm, but what it it doesn’t? That’s why we don’t push our luck. Cheers.

@bigtwin , thank you for bearing with me on this; I know that I have a tendency to be kind of dense on this stuff. What I have is essentially three circuits that consist of 20A outlets connected to the box by 12-2 Romex and I put 15A breakers in those slots as I felt the 15A breaker was actually added protection. I can easily rectify this by putting 20A breakers in it. I just felt that as long as the circuit breaker’s amperage capacity did not exceed the capacity of the rest of the circuit, I was good. I guess I felt that by taking the breaker down to 15A I was being extra good.

You can plug numerous items into a 15A receptacle that exceed 15 amps, portable heaters come to mind. My Skilsaw. The outlet is undersized for the circuit, and the potential load(s).

@immatthewj   A 15A receptacle on a 20A breaker is not an issue as any 15A appliance will never exceed the wiring in the circut.  The reverse of a 20A outlet on a 15A circut is where the potential of fire comes into play.  We assume the breaker will trip and protect us from harm, but what it it doesn't?  That's why we don't push our luck.  Cheers.

That's incorrect. A 15A outlet shouldn't used on a 20A circuit.

@bigtwin  , actually it was me, not @jea48  who was wondering about a 15A circuit breaker on a 20A circuit.  Anyway, I am not trying to be argumentative, I was just thinking that if the circuit breaker is designed be the weakest link in the circuit I thought that making it a little bit weaker could only be further protection for the circuit. 

I did a search and found this

Should a 20 amp circuit have a 20 amp outlet?

The amperage of the outlet must never exceed the amperage of the circuit. According to National Electrical Code, only a 15-amp or 20-amp electrical receptacle can be installed to a 20-amp circuit.

@jea48  It's against building code to install 20A outlets on a 15A breaker.  You may be correct that the 15A breaker would trip, but do you want to risk your home insurance not paying out after your house burns down?  Just follow the code and be protected.  It's there for a resaon.  

The breaker handle rating determines the size of the branch circuit, not the wire.

@jea48 okay, I understand that. But what I was getting at was wouldn’t a circuit with Romex and outlets rated for 20A but protected by a breaker that will trip at 15A actually be safer? I mean the 15A breaker should now trip way before the 20A circuit can get hot enough to be dangerous?

So far I haven't seen anyone question why the dedicated circuit made such a difference. So here is the answer: typical wiring for receptacles is several, often two or more rooms worth, on the same branch circuit. Aside from the smaller consequence of the longer cable run to reach the last receptacle on the branch circuit, the major consequence is the number of splices or receptacles that are in the path. This is a major consequence because the splices are often less than optimal, and where the branch circuit is wired through one receptacle, and on to other(s) it is usually with the backstab connections. A chain of many weak links is what you get, unless you properly pigtail wire each receptacle. 
 

With that myth debunked, let's look at another myth: isolated grounds in dedicated branch circuits. By definition, when you do a dedicated branch circuit run, the ground is isolated. So what do isolated ground receptacles exist for? The answer is in commercial branch circuits, the circuit has a common junction box that each receptacle is wired into, in a hub and spoke topology. This can cause undesirable effects to the shared ground, from eddy currents induced in each spoke. So, where we want a "clean" ground, devoid of such electrical noise, we run a dedicated ground, and use an isolated ground receptacle to keep the noisy branch ground separated separate from the equipment safety ground. 

if a 15A breaker was in front of a circuit that was made of 12-2 Romex and 20A outlets, wouldn’t that be safer? I mean, the 15A breaker would trip way before the 12-2 or the 20A outlet got hot enough to catch fire, right?

No you can not put a 20A duplex receptacle outlet on a 15 amp branch circuit. The breaker handle rating determines the size of the branch circuit, not the wire. The wire could be #10 and if the breaker is a 15A the branch circuit rating is still 15 amp.

You can put two 15 amp receptacles or a combination of 15A and 20A receptacles outlets on a 20 amp circuit, (20 amp breaker). You can install one 15 amp duplex on a 20 amp circuit. (Duplex is two.)

.

Yes, in theory your thinking is correct and as long as the installation is up to code (which it may be) in your area, you should be fine. Remember that local electrical code inspectors can vary in their understanding and interpretation of electrical codes, which can vary a bit by location.

The one issue for the discussion is that a 20-amp receptacle has a physically slightly different plug configuration which implies it is connected to a 20-amp circuit. Someone may be misled when they see a 20-amp receptacle thinking they can use a 20-amp rated device. Of course, the 15-amp breaker would trip if the 20-amp device were to overload it so there should be little to no risk of an overload causing a fire.

**Disclaimer-I am not a licensed electrician**

If you have an electrical fire as a result of your non-NEC code compliant installation, your insurance can deny your claim. In order to make this code compliant, you need to put a 20-amp breaker before a 20-amp receptacle.

I think folks should be careful of offering their non-code-based suggestions regarding how to install electrical circuits in a residential environment.

@nmolnar , if a 15A breaker was in front of a circuit that was made of 12-2 Romex and 20A outlets, wouldn’t that be safer? I mean, the 15A breaker would trip way before the 12-2 or the 20A outlet got hot enough to catch fire, right? I ask this with no intent of sarcasm whatsoever--I would really like to know.

@dpop Wow!! That's a 30 amp plug alright.   I'm confused by your comment.  The specs on the crown amp show it's draws 0.75 amps at idle.  My Hegel H30s put out the same power as the Crown.  As I stated above, the entire system in operation draws about 3 amps.  

Here's an interesting video from PS Audio on Damping factors.

If you have an electrical fire as a result of your non-NEC code compliant installation, your insurance can deny your claim. In order to make this code compliant, you need to put a 20-amp breaker before a 20-amp receptacle.

I think folks should be careful of offering their non-code-based suggestions regarding how to install electrical circuits in a residential environment.

See discussion on this point at the below electrical forum of Mike Holt's electrician code training forum.

Can I put a 20 amp receptacle on a 30 amp circuit? | Mike Holt's Forum

Peter,

receptacles - Oyaide, PS Audio, Furutech, Cardas

Yes @ditusa  I never new such an amp existed.  Thanks!

👍

Mike

Looking at the Crown Studio Reference 1 manual, I’ve never seen an amplifier with a damping factor of over 20,000! Wow!! That's a 30 amp plug alright. Thanks for bringing that to our attention.

@mesch Wrote:

Does anyone know of an amplifier that would require greater than a 15 amp curcuit?  By this I mean one that even for a mil sec would draw 15 amps?

Yes, my Crown Studio Reference 1 Amp requires a 120 Volt, 30 amp dedicated circuit. See power cord below image 2:

Mike