Wire Size and Current Capacity

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thargrav

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A while ago I started a thread about installing a electric water heater element into a stainless steel brew pot. I got chastised about using a 14 gauge power cord to carry what could easily be 17 amps and several quoted that 14 gauge should carry a maximum of 15 amps.

I finally took the time today to chase down the answer about #14 wire and current carrying capacity. And I am correct - #14 wire is perfectly safe for up to 20 amps! But don't believe me, do your own research starting with table 310.16 in the NEC code book.

It is true that #14 wire is used to carry up to 15 amps in house & commercial wiring and #12 wire is used to carry up to 20 amps, and some believe that this means you can only use #14 wire for up to 15 amps. And everywhere you look on the net you see "experts" claiming that #14 wire is only good for up to 15 amps. But it turns out that all of these "experts" are only quoting partial facts, or maybe they are quoting the local "expert" at LOWE'S? Is this is another example of "if it's on the net it must be true"? I don't know but it sure seems so.

But here is the real deal. The same NEC code that specifies that #14 wire can carry no more than 15 amps states that #14 in a branch circuit is good for up to 20 amps (table 310.16 in NEC clearly states the max of 20 amps)! A branch circuit is a circuit run to a single device and this sure reads like a power cord to me, but not a extension cord. In other words, #14 gauge is perfectly safe for 20 amps, they just don't want you to run a string of 20 Amp outlets across your house with #14 wire. And they are correct with this - they are concened about voltage drop across distances.

I dug further into my Engineering books and discovered that #14 wire is actually good for up to 32 amps in chassis wiring.

Also, don't use this info as an excuse to run sub-standard or under size wiring in any of your projects. You still need to brew safe!
 
I'm no 'expert' but as a licensed electrictian, I'll say you have to read the WHOLE chart. The footnote at the bottom clearly says your wrong.


1 The load current rating and the overcurrent protection for conductor types shall not exceed 15 amperes for 14 AWG, 20 amperes for 12 AWG, and 30 amperes for 10 AWG aluminum and copper-clad aluminum after any correction factors for ambient temperature and number of conductors have been applied.

http://lugsdirect.com/WireCurrentAmpacitiesNEC-Table-301-16.htm
 
This does not change the current carrying capacity of the wire.

The resistance of #14 copper wire is 0.002525 Ohms per foot and at 20 Amps the voltage drop across a 8 foot power cord (16' total) is only 0.8 Volts. This works out to 16 Watts of power dissipated across the entire length of the cord at 20 Amps - not enough to even get warm. And my brew pot draws 16 Amps (25% less).

Also, do you know how much current needs to pass through #14 wire before it becomes dangerous? I'll give you a clue - the fusing current (the point where the wire goes "poof") of #14 copper wire is 166 Amps.

And 20 Amps is no-where near 166 Amps.
 
The wire doesn't have to go 'poof' to ruin your day. I've been in situations where someone was running a AC unit with 14 wire and it was so hot it was melting the insulation. 166 amps you say? It doesn't matter to me what you do at your own home. I'm just saying that no electrical inspector in any state in this country will allow you to use 14awg wire for 20 Amps. Besides, you have to fuse wires (as well as derate for protection the wire itself ) at 80% of capacity. So actually (per code) you can only put a load of 12amps on 14awg wire and use a 15 amp breaker. Your logic about voltage drop may be valid. But for the cost of a few bucks to use 14 wire, it isn't worth it to me or my home. Just because the wire can physically handle more amperage doesn't make it a smart move. My car speedometer goes to 120mph. Even if it will go that fast (which I doubt), I'm not going to try. I may survive the first time and maybe even the next 10 times. But eventually it'll bite me in the arse. Most safety regulations over do it. But there is a reason for that.
 
You need to understand that I 100% agree with you when it comes to house wiring. And that's what the NEC is for - building wiring, not product wiring. I also understand the derating formula as it applies to house wiring. I also understand that there is a additional derating formula for wires run in a conduit that's based on the conduit size and number of conductors in the conduit that you did not bring up.

But none of this applies to the point I'm trying to make! Matter of fact, we are discussing two different subjects! You are applying building wiring standards to product wiring which includes power cords.

Engineers make decisions about wire & amp carrying capacity in products without referencing NEC every day because building codes do not apply to product safety. They are two different animals with different sets of requirements. Product design uses the same reference materials I use - I've been a Engineer for over 30 years.

I've read most of the electric brewery threads on this site and it's good to know that most are defaulting to the safe side when it comes to wire sizing - you'll note that I never mentioned that a wire can be too large. At least their wire selection will not burn the building down. My purpose of this thread was to point out that a #14 gauge power cord is safe for my 16 Amp electric brew pot and I backed that opinion up with data.

But if you want a real discussion about safety lets discuss the crimp on terminals I see everyone use. From what I see on the outside I suspect that most of the terminal crimps are suspect. But there is a simple test to tell - after you crimp a terminal grab the terminal in one hand and move the wire from side to side with the other. If the wire moves any at all inside the crimp then it's a connection that will get hot and possibly fail.
 
Hammy71 said:
The wire doesn't have to go 'poof' to ruin your day. I've been in situations where someone was running a AC unit with 14 wire and it was so hot it was melting the insulation.
Click to expand...

And BTW, that electrician who ran a AC unit on #14 wire should be shot for putting a 40 Amp circuit on 14 gauge wire!
 
Hammy71 said:
Besides, you have to fuse wires (as well as derate for protection the wire itself ) at 80% of capacity.
Click to expand...
Done by installing a 15A breaker
So actually (per code) you can only put a load of 12amps on 14awg wire and use a 15 amp breaker.
Click to expand...
You are saying we homeowners have to know our load current to make sure we don't exceed the 12 A limitation?
As long there is a 15 A breaker in my box I should be able to run up to the 15A limit all day long as long the breaker can handle it.
What does NEC recommend how we homeowners should handle the monitoring?

I'm just saying that no electrical inspector in any state in this country will allow you to use 14awg wire for 20 Amps.
Click to expand...
Just some info.
The NEC 2011 code was first adopted 09/01/2011 in Texas as the minimum standard for all electrical work.
Inside the corporate limits of a municipality, electricians followed the city codes, outside maybe wild wiring went on in some homes.


Cheers,
ClaudiusB
 
ClaudiusB said:
Done by installing a 15A breaker

You are saying we homeowners have to know our load current to make sure we don't exceed the 12 A limitation?
As long there is a 15 A breaker in my box I should be able to run up to the 15A limit all day long as long the breaker can handle it.
What does NEC recommend how we homeowners should handle the monitoring?


Just some info.
The NEC 2011 code was first adopted 09/01/2011 in Texas as the minimum standard for all electrical work.
Inside the corporate limits of a municipality, electricians followed the city codes, outside maybe wild wiring went on in some homes.


Cheers,
ClaudiusB
Click to expand...

When an electrician wires a house (or anything, be it commercial or whatever), he/she must use calculations in the NEC to basically guesstimate the load that will be used on a circuit. Basically each receptacle is one volt/amp, so at most maybe 12 receptacles on a 15 amp circuit. That's the simplistic answer. So yes, the homeowner should be aware of what they have plugged in. Especially in older homes. Who among us has not at least heard of a neighbor with two teenage daughters using their hair dryers and stereos/tvs blasting in their bedrooms at the same time and the breaker tripping? It happens all the time, especially in older homes. That's why our parents and grandparents used coins to bypass the ole fuse boxes. A 15 amp breaker will eventually stop being able to hold a load and start tripping with an amperage that is 'close' to 15 amps. Hence the lower rating capacity of 12 amps. The NEC is used by most municipalities as a guide line. Whether they choose to follow every recommendation by the NEC is up to their discretion. But I'd be really surprised if 310-16 wasn't one of them.

As far as power cords, every cord in my home that I see (from the microwave to the dryer) is of an appropriate rating for the appliance per 310-16.

Look, I don't really care about 17 amps on a piece of 14 wire. I just felt a need to address the original post that the OP felt he was getting "internet wisdom" when it came to wire size and amperage. I still think it is sound advice not to exceed 12 amps on a piece of 14 wire, whatever the application. At the end of the day we all do what we want, and I guess I'm unaware of any chastising that might have occurred to the OP. But I really think that people mean well and want to help. It's not some kind of d$%K measurement that my wire is bigger than yours, but I think genuine concern.

And since I saw Forrest Gump on TV the other night for the godzillionth time.

That's all I have to say about that.

:mug:
 
Hammy71 said:
When an electrician wires a house (or anything, be it commercial or whatever), he/she must use calculations in the NEC to basically guesstimate the load that will be used on a circuit. Basically each receptacle is one volt/amp, so at most maybe 12 receptacles on a 15 amp circuit. That's the simplistic answer. So yes, the homeowner should be aware of what they have plugged in. Especially in older homes. Who among us has not at least heard of a neighbor with two teenage daughters using their hair dryers and stereos/tvs blasting in their bedrooms at the same time and the breaker tripping? It happens all the time, especially in older homes. That's why our parents and grandparents used coins to bypass the ole fuse boxes. A 15 amp breaker will eventually stop being able to hold a load and start tripping with an amperage that is 'close' to 15 amps. Hence the lower rating capacity of 12 amps. The NEC is used by most municipalities as a guide line. Whether they choose to follow every recommendation by the NEC is up to their discretion. But I'd be really surprised if 310-16 wasn't one of them.

As far as power cords, every cord in my home that I see (from the microwave to the dryer) is of an appropriate rating for the appliance per 310-16.

Look, I don't really care about 17 amps on a piece of 14 wire. I just felt a need to address the original post that the OP felt he was getting "internet wisdom" when it came to wire size and amperage. I still think it is sound advice not to exceed 12 amps on a piece of 14 wire, whatever the application. At the end of the day we all do what we want, and I guess I'm unaware of any chastising that might have occurred to the OP. But I really think that people mean well and want to help. It's not some kind of d$%K measurement that my wire is bigger than yours, but I think genuine concern.

And since I saw Forrest Gump on TV the other night for the godzillionth time.

That's all I have to say about that.

:mug:
Click to expand...

Thanks for replying, :mug:
ClaudiusB
 
A question popped into my head recently while thinking about power ratings and the like. When a current is specified with regard to a element or whatever in An AC circuit, is this rating rms or peak value.just thought it would be important for selecting write guages and resistor values.
 
Just some interesting findings in regards to breakers ...

http://inspectapedia.com/fpe/CPSCsummary.htm

"The failures relate to hazardous conditions in at least two ways. First, a fault in the wiring or utilization equipment which causes excessive- current-can result in fire if the circuit is not opened by the breaker -- this is its principal functional requirement.

Secondly, it was determined in these tests that some of the breakers overheat to hazardous levels when subjected to overcurrent conditions (due to their own failure to trip) for sustained periods of time.

The overheating can result in incapacitation of the breaker (i.e.: it will no longer open under any condition), and the temperature can be high enough to ignite fire in the vicinity of the breaker, as evidenced by charring of the case on some samples"
 
Brewer Gerard said:
A question popped into my head recently while thinking about power ratings and the like. When a current is specified with regard to a element or whatever in An AC circuit, is this rating rms or peak value.just thought it would be important for selecting write guages and resistor values.
Click to expand...

Whatever the source is specified in. I'm pretty sure it's RMS. Unless you're worrying about stuff like power factors, 3-phase systems, etc, worrying about peak vs. RMS is splitting hairs.
 
Just a comment regarding all the code stuff being slung around. Basically, designing something in brewing to meet NEC standards means that it's over engineered to the point that you have to deliberately try to shock yourself or start an electrical fire. The code should be written such that the most extreme example you can come up with that falls within code constraints should be still safe.

That's not to say that you can callously disregard it either. 17 amps on a 14 AWG conductor might be safe in certain applications. When you run regular NM cable, you need 8 AWG for 40 amps, yet 10AWG THWN is ok too. It's all a question of risk. Every mile I drive, there's a non-zero probability of getting killed in a wreck. If you follow NEC perfectly in your brewery design, there's still a non-zero risk of frying yourself. Deviating from the NEC just increases the risk. How much additional risk depends on the deviation, and requires sufficient experience and knowledge to assess that risk.

I'd go as far as to argue that while a licensed electrician might be qualified to assess whether something is compliant with the NEC, they may not be qualified to objectively state that a non-compliant design is inherently safe or unsafe. If you know enough that you're on the committee that writes the NEC, then you are. Or, maybe you have some other certification in the field of electrical design safety. Otherwise, we're all spitballing.
 
bdjohns1 said:
Basically, designing something in brewing to meet NEC standards means that it's over engineered to the point that you have to deliberately try to shock yourself or start an electrical fire.
Click to expand...
May be so, but if you burn down your house, you'd probably have a better chance of collecting insurance money if everything was done to code.
 
thargrav said:
You need to understand that I 100% agree with you when it comes to house wiring. And that's what the NEC is for - building wiring, not product wiring. I also understand the derating formula as it applies to house wiring. I also understand that there is a additional derating formula for wires run in a conduit that's based on the conduit size and number of conductors in the conduit that you did not bring up.

But none of this applies to the point I'm trying to make! Matter of fact, we are discussing two different subjects! You are applying building wiring standards to product wiring which includes power cords.

Engineers make decisions about wire & amp carrying capacity in products without referencing NEC every day because building codes do not apply to product safety. They are two different animals with different sets of requirements. Product design uses the same reference materials I use - I've been a Engineer for over 30 years.
Click to expand...

Manufactured products will have a little label like this that allows them to use a different set of rules.
th


All said, we are wiring our breweries in our houses so the NEC applies. 17A on #14...you'll probably be ok. If you are worried, print out that label and stick it on the control panel:D
 
I work for a pump OEM and I can tell you that the codes designed to protect the equipment/property/operator do exist and are nearly as stringent as an NEC code. As an example, for submersible pumps, it is against code to draw more than 12 amps through any pump with a NEMA 6-15 plug cap. That applies to the NEMA 6-15 receptacles that we find in our homes. It doesn't always apply to all other products but it is a valid example. Whether or not it is safe is another question but it doesn't make any sense to use an undersized conductor on a project when the correctly sized conductor can be sourced for a minor increase in price. Telling people with very little electrical experience that all the safety stuff they read is bogus is not a good plan. I don't know about you but I would feel pretty crappy if someones house burnt down because of mis-information I provided them on the web.

I see this kind of thing all too often on forums anymore. People think that because they tried it one time and it worked for them that is must be safe and appropriate for everyone. I've been burned by following peoples advice from forums in the past and my feelings are that if it sounds too easy/good to be true/downright fishy, then just walk away and focus on things that are well documented and make logical sense. Its one thing to cut corners for yourself but to recommend to others that they do the same without understanding the risks is just negligent in my book.
 
In my opinion, why would you risk it? Yeah I get that it will hold whatever you say(166amps). I also know that when they test let's say a rigging strap, if a nylon rigging strap is rated at 10,000 pounds, I know that that strap was actually tested and certified at 1-1/2 times it's capacity, does that mean I would rig up a 12,000 pound piece with that strap, no. We all know that wire acts like a garden hose, if I'm putting 100 pounds of pressure through a hose, I'm not going to use 1/4" hose. Let's not loose out common sense here, if this whole thread is a I told you so, I was right and now I'm taking my ball and going home, well then congrats on digging through endless books, codes, or whatever it may be. I don't think someone saying, uh, I don't think you should run 20 amps through a 14 ga wire is a chastise, but who am I, I guess you have to be an engineer to understand all the ins and outs. What if I said, am am an engineer too, but I don't have to get every piece of literature in the world to prove to you that some times our computers and literature and codes and books to know that sometimes their are "bad ideas". That's where the common sense and the book smarts hit head on.
 
I built my electric system 4 years ago. It isn't built to any code and i don't really care either. I haven't shocked myself, burned down any buildings, caused a nuclear holocaust or changed the tide.
I didn't tell people on the web what I used or why I did it the way I did it to avoid threads like this.
Thargrav, just build it, I am positive you won't change the tide either.
 
cjp4627 said:
I work for a pump OEM and I can tell you that the codes designed to protect the equipment/property/operator do exist and are nearly as stringent as an NEC code. As an example, for submersible pumps, it is against code to draw more than 12 amps through any pump with a NEMA 6-15 plug cap. That applies to the NEMA 6-15 receptacles that we find in our homes. It doesn't always apply to all other products but it is a valid example. Whether or not it is safe is another question but it doesn't make any sense to use an undersized conductor on a project when the correctly sized conductor can be sourced for a minor increase in price. Telling people with very little electrical experience that all the safety stuff they read is bogus is not a good plan. I don't know about you but I would feel pretty crappy if someones house burnt down because of mis-information I provided them on the web.

I see this kind of thing all too often on forums anymore. People think that because they tried it one time and it worked for them that is must be safe and appropriate for everyone. I've been burned by following peoples advice from forums in the past and my feelings are that if it sounds too easy/good to be true/downright fishy, then just walk away and focus on things that are well documented and make logical sense. Its one thing to cut corners for yourself but to recommend to others that they do the same without understanding the risks is just negligent in my book.
Click to expand...

I totally agree with this. The potential reward of saving, at most, a couple bucks, isn't worth the real risk of someone using this shoddy design advice and putting their house or themselves or their families life in danger. The codes are there for a reason.
 

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