Electrical Help?

[BeanAnimal]

<a href=showthread.php?s=&postid=8405946#post8405946 target=_blank>Originally posted</a> by revance
You should NEVER run a 20A receptacle on a 40A breaker because then there is nothing protecting that receptacle from being overloaded and catching fire.

Receptacles do NOT limit the current... if it is rated at 20A and you have it on a 40A breaker, it is possible for you to run 40A through that receptacle and have it catch fire.

As opposed to what i said above.... the NEC DOES NOT ALLOW 20A breakers on a 40A branch!!!


However, the NEC does allow a 15A breaker to be used on a 20A branch circuit!!!

Again the plug configuration is the limiting factor. YOU CAN NOT HOWEVER run a 20A receptacle on a 15A breaker.


In any case, the wire lugs on the receptacle would not handle the #8 wire.... you will find the 30A and 40A receps have larger wire lugs...

Bean

 

[oldsaltman]

Bean, I have added the 2 X 20a std breaders in a sub box. 40a double breaker in the main panel, 8/3 wire, 4 X 20a GFCI outlets. Is there a problem with this setup? I have all the stuff except an empty 20a sub box.

 

[BeanAnimal]

<a href=showthread.php?s=&postid=8406210#post8406210 target=_blank>Originally posted</a> by Paul B
All of these answers are correct. Of course it would work fine but it is also a code violation. As was said a 20 amp GFCI recepticle is not rated for 40 amps. Even though you are not plugging in 40 amps to it, it is a violation. A 20 amp receptacle has internal copper bars rated for 20 amps and they would melt if for instance your powerhead shorted and drew 30 or 40 amps which it could do with a 40 amp breaker. Two panel circuit breakers are very common. Go to an electrical supplier not Home Depot.
Use a 40 amp sub panel and connect two 20 amp breakers but even that is overkill. Just use two 20 amp seperate circuits with #12 wire.
I myself have a 100 gallon reef on a 20 amp line for over 30 years and it is not even a dedicated circuit. I have never tripped that circuit and there is no reason it should ever trip unless I drop a light in the water.
Paul

Edited...to remove poor information I gave

 

[Paul B]

The NEC does not restrict you from hooking up two 20 amp receptacles on a 40 amp breaker but it does restrict you from installing two convenience outlets on a 40 amp circuit. I really don't want to go through that book now but it is in there somewhere. I have been out of school for three decades and it would take me forever to find it. First I would have to find the book and since I am retiring soon I am trying to forget all of my electrical knowlege :lol:

 

[BeanAnimal]

<a href=showthread.php?s=&postid=8406620#post8406620 target=_blank>Originally posted</a> by SA057
Bean, I have added the 2 X 20a std breaders in a sub box. 40a double breaker in the main panel, 8/3 wire, 4 X 20a GFCI outlets. Is there a problem with this setup? I have all the stuff except an empty 20a sub box.

NO a subpanel is by far the best way to go.

The SUB panel must NOT HAVE NEUTRAL BONDED TO GROUND!!!!!

So the feeder wire needs to be 8/3 with ground! That means 2 hot legs, 1 neutral and 1 ground. The hots will tie to the bus lugs the neutral to a SEPERTE NON BONDED bus bar and the ground will tie to the ground bus bar.

IF ANY OF THIS SOUNDS AT ALL FOREIGN.... CALL A QUALIFIED HELPER OR ELECTRICIAN, YOUR LIFE WILL DEPEND ON IT!

You don't need a main breaker in the sub panel... but it is nice if you can afford a box with one. I would not use GFCI breakers... but instead use GFCI outlets (1) for each device. In other words I would use a seperate GFCI for each critical device.

Bean

 

[BeanAnimal]

<a href=showthread.php?s=&postid=8406650#post8406650 target=_blank>Originally posted</a> by Paul B
The NEC does not restrict you from hooking up two 20 amp receptacles on a 40 amp breaker but it does restrict you from installing two convenience outlets on a 40 amp circuit. I really don't want to go through that book now but it is in there somewhere. I have been out of school for three decades and it would take me forever to find it. First I would have to find the book and since I am retiring soon I am trying to forget all of my electrical knowlege :lol:

Yeah I just thumbed through and couldn't find it. I was pretty sure there was no limitation on the receptacle and breaker size but thought there may be a cord and plug or other similar gotcha that reigned it in anyway.... the convenience receptacle limitation does sound reasonable. I am also to lazy to go look for it again!

I guess the NEC left this mostly to common sense

 

[Paul B]

Bean, whoever wrote that book had no common sense

 

[BeanAnimal]

You really want a laugh, read the meeting notes on the NFPA website where the actual discussions on each code decision are made... it will curl your hair! Some of the arguements and positions these boneheads take will illustrate why the NEC is so hard to read and follow...

When you done with that take a gander at 30 CFR (MSHA coal mining codes) It makes the NEC look and read like a beginers book. It is truley a travel through absurdity.
Bean

 

[oldsaltman]

Thanks...Thanks that is what I wanted to know..

 

[revance]

BeanAnimal:

While it is poor practice, there is nothing unsafe about putting a 20A receptacle on a 15A breaker. The ultimate goal is to be protected. The only thing that will happen with putting a 20A receptacle on a 15A breaker is someone might try to put >15A on it and will keep on tripping the breaker. It will be annoying, but not dangerous.

On the other hand, it is very dangerous to put a 15A receptacle on a >15A breaker. While I don't have my NEC book with me, I am pretty sure there are restrictions on this. Few people look at an outlet and think "hmm... that is a 15A receptacle, I better be careful not to overload it". Instead, they plug stuff in until the breaker trips. If you have it hooked up to a 30A breaker, you could possibly start a fire. Also, as mentioned before, the person might have less than 15A on the receptacle and something shorts out. This poses ANOTHER fire hazard. If it shorts out, it will allow more current to flow through the receptacle than it is rated for.

Edited: meant to say receptacle up there rather than breaker.

 

[Paul B]

Revance, I think you have a few confusing errors on there. Re read it.

 

[revance]

I don't think so (unless I am reading my own post wrong)...

what I am saying is having a larger breaker than receptacle is really dangerous. Having a larger receptacle than breaker isn't.

All a larger receptical will do is give people the idea they can pull more current through it than they really can. If it is a 20A receptacle on a 15A breaker and they try to put 18A of stuff on it, they will just trip the breaker.

A larger breaker than receptical will ALLOW them to pull 20A through a 15A receptical and thus possibly melt/burn the outlet.

Example:

15A outlet on 30A breaker = Dangerous!
20A outlet on 15A breaker = Possibly annoying but not a fire hazard.

 

[BeanAnimal]

Revance... with all due respect, you are incorrect.

Code allows a 15A receptacle on a 20A breaker
Code prohibits a 20A recepacle on a 15A breaker

I can quote the relevant sections... but the 1999 NEC Table 210-21(b)(3) "Receptacle Ratings for Various Size Circuits"

Circuit Rating -*- Receptacle Rating
15 -*- not over 15
20 -*- 15 or 20
30 -*- 30
40 -*- 40 or 50
50 -*- 50

SO as you can see (I was wrong about the specifics of the 40A) but not the 15A and 20A branches and receptacles.

Tab le 210-24 is a summary of the receptacle sizes, wires sizes and amapacities of each circuit with max load ratings and a reference to the permsisible loads.

Let me make this clear. WHAT I SAID ABOUT 40A breakers was wrong... and I have corrected it. BUT WHAT YOU have said is WRONG also and we need to correct it!

So lets take exactly what you said again and look at it. You said

While it is poor practice, there is nothing unsafe about putting a 20A receptacle on a 15A breaker.

This is wrong and against NEC code. We can get into the reasons why... but suffice to say the point is moot... it is prohibited. (please see section 210-21 of the NEC)

Next you said

On the other hand, it is very dangerous to put a 15A receptacle on a >15A breaker. While I don't have my NEC book with me, I am pretty sure there are restrictions on this..

Again if you look at section 210-21 the 20A receptacle is allowed on the 20A branch circuit. Why? Both the 15A and 20A receptacle are the same, other than the blade configuration.

With regards to the 30A receptacle... yes it needs to be on a 30A branch circuit. Thre are some exceptions to the above rules (arc welders and some specialized cord and plug equipment).

In any case don't want to fight over something that is clearly stated in the NEC.

Bean

 

[BeanAnimal]

I have edited my previous posts to remove the poor info I gave about the 40A breaker and receptacle limitation... it is as clear as a bell in 210! I was unable to edit my first post on the subject... Maybe a mod can (I don't want anybody to read such bad info).

Bean

 

[revance]

Whether it is prohibited or not, I would NEVER put a 15A receptacle on a 20A breaker.

The ONLY thing limiting current is your breaker.

By putting a 15A outlet on a 20A breaker, it is perfectly possible for someone to pull 18A through that outlet that is only rated for 15A. While that probably won't catch fire, try that with a larger breaker and it might.

If this is not true, please explain to me how pulling 20, 30 or more amperes through a 15A outlet is "ok".

Again, the only reason it is prohibited to put a 20A outlet on a 15A breaker is because it will lead people to think they can pull more current than the breaker allows. While it is always a bad idea to overload the breaker, more than likely the breaker will trip and all will be good. Everyone who doesn't realize it is only a 15A breaker will be really confused and it will be a big hastle. It is more a labeling issue than a safety issue. Most homeowners have no idea how much current their appliances pull and try to pull more than 15A on a 15A circuit all the time.

If this is not true, please explain to me how using a larger sized receptacle can be dangerous (other than what I already mentioned).

 

[revance]

Wait, I see your comment about a 20&15A receptacle being the same.


I did not know that

 

[46bfinGA]

wow this went way too far from what it needs to be.

1. 15 amp outlets can be installed on 20 amp breakers,the logic behind that 99.9%of the time you are not going to be installing something on that outlet, that is going to draw 15 amps so its not a concern.the idea is that you can install multiple outlets around your house on the same circuit to where if you add them all up they will not exceed 20 amps of electrical draw.

2.same thing with a 20 amp receptacle on a 15 amp breaker.its perfectly fine because the breaker will trip long before the outlet is damaged by overcurrent.waste of money is all that you accomplish with this.if you look at any store the 20 amp receptacles are quite costly compared to the 15 amps.

3.dont waste your money on a subpanel for two circuits.unless you just like to do projects for the hell of it.pull a 12/3 over to your tank or wherever ,and install one gfi on each circuit,then you can branch as many receptacles as you need off the gfi's and they will be well protected.problem solved and they will last as long as your tank will with minimum cost to you

 

[Paul B]

Ravance I was talking about this quote.

On the other hand, it is very dangerous to put a 15A receptacle on a >15A breaker.

And this one.

The only thing that will happen with putting a 20A receptacle on a 15A breaker is someone might try to put >15A on it and will keep on tripping the breaker. It will be annoying, but not dangerous

I know they are just typos though, I do it all the time.

I don't want to get into the dialog between you guys. I don't read the code anymore and don't want to.
Paul

 

[revance]

BeanAnimal: Thanks

Knowing that, it does just come down to a labeling issue. The different blade configuration identifies the circuit as being 20A. They don't want you encouraging people to overload the circuit by misidentifying it (even though it should be protected by the breaker). The other way around... since the outlets can really handle 20A they don't really care if people THINK its a 15A circuit and accidentally put 20 on it (its pretty hard for normal people to get 20A on one plug anyway).

Thanks for your patience (I am at work and my nec book is at home). I don't do enough stuff to have that memorized. I also didn't realize the 15A and 20A outlets were the same other than the blade configuration. The 20A ones definitely FEEL more substantial.

 

[BeanAnimal]

<a href=showthread.php?s=&postid=8407160#post8407160 target=_blank>Originally posted</a> by 46bfinGA
wow this went way too far from what it needs to be.

1. 15 amp outlets can be installed on 20 amp breakers,the logic behind that 99.9%of the time you are not going to be installing something on that outlet, that is going to draw 15 amps so its not a concern.the idea is that you can install multiple outlets around your house on the same circuit to where if you add them all up they will not exceed 20 amps of electrical draw.

2.same thing with a 20 amp receptacle on a 15 amp breaker.its perfectly fine because the breaker will trip long before the outlet is damaged by overcurrent.waste of money is all that you accomplish with this.if you look at any store the 20 amp receptacles are quite costly compared to the 15 amps.

3.dont waste your money on a subpanel for two circuits.unless you just like to do projects for the hell of it.pull a 12/3 over to your tank or wherever ,and install one gfi on each circuit,then you can branch as many receptacles as you need off the gfi's and they will be well protected.problem solved and they will last as long as your tank will with minimum cost to you

Well I hate to disagree... but only point 1 is correct!!!

Point 2 is prohibited by the NEC. YOU CAN NOT PUT A 20A receptacle on a 20A branch circuit!!!!! Again this is 210(b) Your an electrician, you know this

Point 3 What can I say.. but I disagree. You can run 12/3 and use (2) non handle tied breakers. If you use a double pole breaker, then a faulting device on one leg will bring the entire tank down!!!!

I opted not to tell the OP to use non tied breakers because we would then have to get into the discussion of ensuring that both breakers were not on the same leg. If he puts them on the same leg, then he overloads the neutral.

Lastly, DO NOT USE GFCI breakers. If a device faults it will bring everything on that GFCI down. YOU DON'T WANT THIS!!!!

The best thing to do is use multiple GFCIs on each branch. That way each device is isolted from the next. A faulint device will only trip its own GFCI outlet and leave the rest of the tank running.

Remember a lot of our loads (ballasts and large pumps) tend to cause nuisance GFCI tripping.

Bean