Yes, there is. If your wire is too fat, the short-circuit current won't be enough to trip your breaker. The breaker will pass overrated current, which can heat up the northbound side of your wire. It's not rocket science. And no need to shout misinformation.
breaker/wire size for heating element
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Yes, there is. If your wire is too fat, the short-circuit current won't be enough to trip your breaker. The breaker will pass overrated current, which can heat up the northbound side of your wire. It's not rocket science. And no need to shout misinformation.
Perhaps we can invoke @Ischiavo.
Bowtiebrewery
Well-Known Member
I would ask a buddy of mine to chime in, but unfortunately being an electrician he is never online. Meh...
Honestly, how do you know?
I was "licensed" at one time in Oklahoma. Written test only and was good for one year during which you had to do you practical training and 9 hours of approved continuing education. Regardless, it said "Licensed Residential Electrician" and I was allowed to pull permits for a whole year. I managed less than a 1/3 rd of the "practical" hours when I realized I did not want to do that for a living.
Practicing professional electrician...not so much
Bowtiebrewery
Well-Known Member
To my knowledge there are several tests and certification levels associated with being an Electrician. Several states have electrical contractor licenses which you can test for. Primary purposes are to pull permits.
My bad for assuming none had chimed in, but also I should have been more clear. My comment should have been
"I'm surprised no E-1 Licensed Electicians have not chimed in here" My friend happens to be E-1 Certified.
In CT there are 2 licenses... E1 AND E2, Master and Apprentice. You can't practice or wire as an E2 unless employed by an E1.
So that being said, I would look for input from someone on the level of an E1 if I was concerned
Valid response. To muddy the waters even more, for almost two years I was an electrical inspector for US military installations overseas on a code (I think 2000 IET but it might have been earlier) I knew only from the books I read on the flight over to Kuwait. My job was to ensure the grounding and bonding upgrades that three electrical contractors were retrofitting throughout our "contigency operations locations".
Electrical work is a little bit of knowledge, a lot of tables and a lot of common sense. Oh, and acronyms out the wazooo.
Owly055
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This is NOT true..... not at all. The current passing through your circuit breaker is what heats the internal thermal sensor. That current is completely unrelated to the wire sizing external to the breaker........ I don't know where you came up with that bit of misinformation, but it is absolute bunk!! External wiring size has no bearing at all on the operation of a circuit breaker...... that's beyond absurd!! It's utter hogwash.
H.W.
RufusBrewer
Well-Known Member
I hope you can understand my confusion on this one.
A circuit breaker is rated for let's use 20 amp as an example. The breaker will hold nominally 20 amps. As you draw more than the nominal 20 amps, the breaker will trip. The more above 20 amps you go, the quicker the breaker will trip. Example: 135% above the rating might be a couple minutes, 200% might be a couple seconds, 1000% trips close to instantly.
Your position is that it is possible to draw so much current that the circuit will not trip fast enough to avoid damage on the north (source?) side of the breaker. And this level of of damge indcuing current is the result wiring capable of drawing too much current. Due to it's large size and low resistence.
The question I have: In our example of a 20 amp breaker, (120 VAC) how big of a wire is too big?
Now I am going to do some calcualtions:
Looking a a wire gauge chart
12 gauge wire is ~1.6 ohms/1,000 feet
6 gauge is ~ 0.40 ohms/1,00 feet.
100 foot run of 12 gauge, 120 volts shorted = 375 amps @ 45 K watts
100 foot run of 6 gauge, 120 volts shorted = 1,500 amps @ 180 K watts
The second value, the higher power, is enough to damage the north side of the breaker when the first one would not.
This is where I get my puzzlements. If you have a 25 foot run of 12 gauge shorted out, you would get 1,500 amp @ 180 K watts. Seems to me it is more complicated than "Do not use that wire gauge, it is too big,"
I stayed at a Holiday Inn once.
I am Groot
ingchr1
Well-Known Member
Calculating the available short circuit current is more complicated than that. You would need information all the way back to the transformer on the pole outside your house. This includes transformer data, cable sizes and cable lengths. Basics of short circuit current: http://ecmweb.com/content/short-circuit-current
In any case, you're not going to cause your breaker to not trip under a short circuit by using upsized wire.
Yes, but was it Holiday Inn Express?
"Kal's setup advice" ?? Who is kal and where is this advice?
augiedoggy
Well-Known Member
it got out of hnd because many poster including myself (and you btw since the op is using a 4500w element which draws 4 amps less than a 5500w you mentioned) that means he has an 18-19amp load at the very most
Most here agree that the correct rated type and size cable here is 25a SJ or SO cable... 10 or 12 gauge will be perfectly safe and meet code... I have been using 25a rated 12 gauge for two years and nothing gets hot because 18 amps through a cable designed for up to 25 is FINE regardless of the silly comments that keep insisting 10 gauge 30 amp wire is needed I'm guessing some just dont do the math and repeat what they read without question.
The thread is just going on because people here are bored and like to argue over silly petty things.. (including myself apparently since I just felt the need to correct you.)
and using 14 guage (rated for 15 amps) wire for pids power which draws less than 1/2 an amp is completely unecessary..especially when you look at the plastic devices they are wired too. As long as the circuit is protected with the correct size fuse or breaker there is no logical reason for it that I know of... I believe anything under 16 gauge does not meet code for ac use but im not sure if that is stand alone or if it still applied inside an electrical device such as a control panel. I used 18 and even 20 for certain indicator lights and such... I have no plans to have my panel UL listed and I know its just as safe so theres no point.
kal does a lot of other things that are not commonly done like his element enclosures which were nice as the time but there are safer methods out there now in my opinion.... he also charged over 2 grand for less functionality than the one I built for $300.... He would make a good engineer working for the government.. I get that he wanted it as safe as possible since non electrical people would be assembling them and it also means less chance of any type of maintenance or failure but it doesnt mean anything else is unsfe or wrong.
augiedoggy
Well-Known Member
I should put this quote in my signature...lol he is the grand poobah of sorts.... The guy who basically took electric brewing mainstream...
his site,
Theelectricbrewery.com
lots of great info and top quality but top dollar options.
RufusBrewer
Well-Known Member
I did some research and figured out what the "Prospective short circuit current" is all about. You are correct. They are measuring the output impedance of the source power coming into the building. Calculating if the source provide a current in excess of what the breaker will operate properly.
I was trying to sort out the statement "Too big of wire is dangerous!" in the context of making an electric brew system. What ever calculations and testing to be done with regards "Prospective Short Circuit Current" would have been addressed when the breaker was installed.
Putting "too big" of a conductor down stream and after the testing & calculations does not change anything. In fact the testing and calculations assumes you are going to put a zero ohm cable on the system and everything will work properly.
azazel1024
Well-Known Member
That's...um, the opposite of what would happen. The larger the diameter of the wiring, the lower the resistance of the wire, the HIGHER the short circuit current. So "too heavy" AWG wire would actually trip the breaker sooner.
The two issues with too large wiring is that it won't fit properly on underrated terminals, which can be hazardous. The second is it is wasteful. 10/2 costs more than 12/2 costs more than 14/2. Also harder to work with, but that is generally a pretty tertiary concern.
Generally a step above what you need isn't going to be a big deal. The only super hazardous thing is to have oversized breakers vs the wiring employeed. As this can result in too much heat generated by the wiring. Generally you aren't looking at that wiring starting a fire (as even a good double load on the wire isn't likely to produce temperatures in excess of 60C in the wire even over time, which is what most/all romex is rated for, if it isn't 80 or 100C romex)...but it CAN cause the wiring to expand too much, which is a termination issue and can result in shorts. Yes, there are instances where it is possible for wire to be installed in such a way that double the rated load can eventually melt the wiring, but that is REALLY hard to accomplish (in a reasonably insulated location combined with a high temperature location).
It is the expansion of the wire that is the primary concern, melting the sheathing is very secondary. As that generally takes a 3-4x over rated load to eventually generate that much heat. Breakers are designed to carry loads between 125-150% of the rated capacity for a few minutes before tripping from thermal load. They are designed to trip immediately with loads roughly 2x rated capacity, through magnetic tripping. There are some breakers which are magnetic only and some which are thermal only. Most/all residential breakers are the combined type. It is to allow temporary overloads, such as motors starting or lugging, to be carried by the circuit as short duration overloads are not dangerous to the wiring, outlets, etc. However, things like a short circuit or massive overload (like say a 2kw motor trying to be carried on a 15A 120v circuit, which is likely to have a 3-4kw starting surge) should trip the breaker immediately.
If the breaker AND the wiring AND the recepticals are all oversized for your planned load, the only real issue is you are spending more and having more hassle on installation than you need. So long as you don't mind that, no big deal at all. Of course you need to ensure that your end devices have their own breakers or fuses if appropriate and they need protection.
azazel1024
Well-Known Member
Keep in mind, that is with a DIRECT connection. Shorts are rarely full connection, you typically get a brush between the wires causing a short circuit, which will pop the breaker immediately.
It is certainly possible to damage a breaker from a short and the higher the short circuit current is, the more likely it is. However, I've never once seen a breaker fail from a short in the closed position. I suppose this is completely possible. That said too, your main breaker will trip if the breaker fails in the closed position if you have a true short circuit sufficient to damage a branch circuit breaker. Unless you are running some 00 AWG wire or something as a branch circuit, you are not going to generate sufficient current to damage the main breaker.
Owly055
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Note the statement used to justify the claim that too large a conductor was dangerous:
"If your wire is too fat, the short-circuit current won't be enough to trip your breaker. The breaker will pass overrated current, which can heat up the northbound side of your wire."
Everything about it is absurd. A larger conductor will have a HIGHER short-circuit current, not a lower short-circuit, current due to it's lower resistance.
I must confess that I found absolutely nothing on the Wikipedia page that could be construed to support the contention it was intended to support.....(not that Wikipedia is the ultimate authority).... I'd be interested in knowing what sort of convoluted reasoning was used to arrive at this conclusion. In the real world it is completely wrong.
H.W.
azazel1024
Well-Known Member
And to flesh it out, I don't think I've actually seen anyone other than an electrician or two recommend it, but ideally every couple of years you'd test every single breaker to make sure it is working. Both test manual open, but also test the breaker by tripping it (good circuit testers have a breaker test option, which shorts the circuit at an outlet).
I HAVE seen the occasional breaker that was non-operation in the closed position. Not a good thing to have. Generally older breakers and I think over the years (10+) I think I've only ever seen 2 or 3 "failed" breakers of hundreds and hundreds I've tested.
I HAVE seen the occasional breaker that was non-operation in the closed position. Not a good thing to have. Generally older breakers and I think over the years (10+) I think I've only ever seen 2 or 3 "failed" breakers of hundreds and hundreds I've tested.
ingchr1
Well-Known Member
And as others have mentioned, increasing wire size will increase the short circuit current.
RufusBrewer
Well-Known Member
Looking at the videos on youtube, the test point is at the breaker panel. The test and calculations assumes a zero ohm load beyond the breaker. This would be the prudent worse case scenario procedure.
In this case, you would not pass or fail the design based on wire gauge between the panel and the outlet. In this test, the gauge of the wire out of the breaker panel is irrelevant.
ingchr1
Well-Known Member
Correct, a short circuit in your panel will give you the worst case scenario. And the breakers in the panel need to be rated to interrupt that fault current, since the fault could be at the load side terminals of the breaker.
If the short occurs down the line at the load then the fault current will be less and it could be significantly less then what a fault in the panel would be. If the wire size to the load is increased, then you would increase the available fault current on that branch circuit. That's all I was saying.
I thought it might be nice to go back to the original question.
Running 10g wire off a 30 amp breaker in the main panel is what I'd expect to see for 4500 or 5500 watt elements. You MAY be able to get away with 12 gauge and 20 amp breaker for 4500w but frankly you might as well commit to 5500 watts as the price differences between said breakers, wire and panel components is negligible but the performance of the extra 1000 watts is noticeable.
If you do run 10g wire, then you should not use a 50 amp breaker in the main panel because you CAN overheat the wire without tripping the breaker. If you DO plan to put a 50 amp breaker in, for purposes of future growth and use of two 5500w elements at the same time, then you should use 6 gauge wire.
Other things... Whatever amperage you plan to use, look for a used or surplus GFCI breaker for your main panel and if it's more than $100, consider using a spa disconnect panel inline with your wire run.
If you use wire that has two hots and a ground, you will not be able to derive 120 volts in your control panel for pumps or other 120v accessories unless you run a separate 120v input. Running 240v and 120v items on the same entry cable requires 4 wires, hot, hot, neutral and ground.
It sounds a bit like you want to direct wire an element right to the panel breaker but I really don't recommend it. You should have a fast and convenient way to regulate both on/off functions and power output.
I think that's it, and should provide ample fodder for the garage mechanics and intellectuals alike.
There has certainly been a lot of rambling about various issues many of which have been responded to with information of various degrees of accuracy. It might be worthwhile to set forth a few fundamentals here.
1) The breaker in the panel is there to protect the wiring between the breaker and the load. That is all. It insures that if a load is connected which draws so much current that the wire can get too hot the current flow will be interrupted. The heat that is developed in a wire PER UNIT LENGTH is I^2*R where R is the resistance of the wire PER UNIT LENGTH. The temperature rise in the wire is the product of the heat developed depends on the thermal conductivity between the copper and the ambient, the thermal mass of the conductor and the heat developed all PER UNIT LENGTH. Thus it doesn't matter if you have 1 foot of wire carrying current I or 1000' carrying current I. The temperature rise will be the same. A breaker should be chosen for the size of the conductor, its insulation, how it is bundled with other conductors (single wire in open air, Romex, BX, wires in a conduit, etc.) and the ambient at which it is expected to operate. The tables in the NEC consider all of these in specifying ampacities for different types of wire.
2)You cannot have a wire too big. The bigger the wire, the less the temperature rise and the 'safer' you are ceteris paribus not to mention the fact that there will be less voltage drop along its length. But you can get silly pretty quickly and copper is darned expensive these days.
3)The fact that the breaker is not there to protect the load means that if you want protection for the load it should be furnished at the load (not a bad idea). If something happens to a 5 kW load such that it draws 8 kw on a 10 kw circuit the panel breaker would not (and should not) open though the temperature of the load may go high enough to start a fire. A protective device on the load should detect that and interrupt the current.
4)It is not the least bit uncommon to plug loads much smaller into the current ratings of a circuits wiring and panel breaker. Consider a 100 W reading lamp plugged into a 15 amp 120V circuit in your house.
5)Fault impedances refer to the impedance of the fault path. If a 20 amp 240 V circuit 'shorts' to ground through a 120 Ω path the fault current is only half an amp and a 20 amp breaker will not trip. It is therefore important to insure that the installed fault path, i.e. the grounding conductor plus hot wire impedances summed are low enough that a phase to grounding conductor fault will trip the breaker. Here is where wire resistance can come into play. The NEC seems to be happy with a grounding conductor size 1 or 2 AWG smaller than the phases.
As for the utility side of the panel: Let's suppose you have a ground fault on a 20 amp circuit with properly wired grounding conductor (low Z) but the 20 amp breaker fails and does not clear the fault. If the impedance of the grounding conductor is high enough that the main breaker does not trip the fault will continue to draw enough current to start a fire but that's what happens when a protective device fails. The codes are not based on the presumption of panel breaker failure else we'd have to run 4/0 grounding wires throughout our chateaus.
1) The breaker in the panel is there to protect the wiring between the breaker and the load. That is all. It insures that if a load is connected which draws so much current that the wire can get too hot the current flow will be interrupted. The heat that is developed in a wire PER UNIT LENGTH is I^2*R where R is the resistance of the wire PER UNIT LENGTH. The temperature rise in the wire is the product of the heat developed depends on the thermal conductivity between the copper and the ambient, the thermal mass of the conductor and the heat developed all PER UNIT LENGTH. Thus it doesn't matter if you have 1 foot of wire carrying current I or 1000' carrying current I. The temperature rise will be the same. A breaker should be chosen for the size of the conductor, its insulation, how it is bundled with other conductors (single wire in open air, Romex, BX, wires in a conduit, etc.) and the ambient at which it is expected to operate. The tables in the NEC consider all of these in specifying ampacities for different types of wire.
2)You cannot have a wire too big. The bigger the wire, the less the temperature rise and the 'safer' you are ceteris paribus not to mention the fact that there will be less voltage drop along its length. But you can get silly pretty quickly and copper is darned expensive these days.
3)The fact that the breaker is not there to protect the load means that if you want protection for the load it should be furnished at the load (not a bad idea). If something happens to a 5 kW load such that it draws 8 kw on a 10 kw circuit the panel breaker would not (and should not) open though the temperature of the load may go high enough to start a fire. A protective device on the load should detect that and interrupt the current.
4)It is not the least bit uncommon to plug loads much smaller into the current ratings of a circuits wiring and panel breaker. Consider a 100 W reading lamp plugged into a 15 amp 120V circuit in your house.
5)Fault impedances refer to the impedance of the fault path. If a 20 amp 240 V circuit 'shorts' to ground through a 120 Ω path the fault current is only half an amp and a 20 amp breaker will not trip. It is therefore important to insure that the installed fault path, i.e. the grounding conductor plus hot wire impedances summed are low enough that a phase to grounding conductor fault will trip the breaker. Here is where wire resistance can come into play. The NEC seems to be happy with a grounding conductor size 1 or 2 AWG smaller than the phases.
As for the utility side of the panel: Let's suppose you have a ground fault on a 20 amp circuit with properly wired grounding conductor (low Z) but the 20 amp breaker fails and does not clear the fault. If the impedance of the grounding conductor is high enough that the main breaker does not trip the fault will continue to draw enough current to start a fire but that's what happens when a protective device fails. The codes are not based on the presumption of panel breaker failure else we'd have to run 4/0 grounding wires throughout our chateaus.
Agreed, but in such a dedicated use circuit like this, there's no harm in having the panel breaker as close to the intended load as possible to avoid doubling up on protection.
if you reread the original post, the poster doesn't have a dedicated breaker for brewing, it is some times shared with the rest of the house, so his question was do I step up the breaker as recommended from a friend to account for the added use
if thats the case than just get a dedicated 30 amp for brewing only
if I red that wrong sorry, my glasses broke lol
if thats the case than just get a dedicated 30 amp for brewing only
if I red that wrong sorry, my glasses broke lol
RufusBrewer
Well-Known Member
The OP is a bit confusing.
If he is installing a new socket, the breaker and wiring from the breaker to the socket should be per local code for that voltage and socket. A GFI socket is strongly recommended.
For the wiring from the socket to the heating element, that should be sized as appropriate for the element's voltage and current. There is no reason to wire it to accommodate 220 VAC, 50 amps - unless that is the element's rating.
There are some different opinions about what gauge the element wiring should be. Most say 12 gauge is adequate.
12 is good for 25 amps in wire rated for 60 and 75°C service. 12 AWG rated for 90 °C service is good for 30 amps (not more than 3 current carrying conductors in the cable). It is, of course, a simple thing to hook up the element with the cable to be used, run the element and measure the temperature of the cable (tape a thermocouple to it or shove the thermocouple down into the jacket at one end. If it gets hotter than you are comfortable with, go to the next larger wire size and try again.
Ajdelange:
Most sensible advice I have seen!
A portable heater or a kitchen kettle will have thinner wire, but they are not made to be on 24h a day. The wire on these will get warm but not hot.
For a heating element we will have it on for 2 hours max and it will be in the free air. In my mind, if you do. It feel a bit of heat on the cable after that time you have bought too much copper.
(But then again I like to live on the edge)
Tom
Most sensible advice I have seen!
A portable heater or a kitchen kettle will have thinner wire, but they are not made to be on 24h a day. The wire on these will get warm but not hot.
For a heating element we will have it on for 2 hours max and it will be in the free air. In my mind, if you do. It feel a bit of heat on the cable after that time you have bought too much copper.
(But then again I like to live on the edge)
Tom
augiedoggy
Well-Known Member
yeah thats still pretty confusing to me
SSA? do you mean ssr? that should be in the box with whatever is controlling it (pid or potentiometer) and you should have a flexable stranded wire cord such as SO or SJ cable running from your control panel to the element... ideally with a plug at one or both ends for removal and cleaning..... from your description you have things all broken up along the way ... in separate boxes I hope? or am I not understanding this either?
the 50a breaker would be for the main service going to your brweing area... the GFCI portion would still work and trip correctly regardless of amps but you would want to add smaller correctly rated breakers or fuses for your element and control panel devices ... These are normally located inside of your control panel. people looking to be fancy or that learn everything here usually go with DIN breakers ... although if your on a budget, correctly sized fuses work just as well and once the cover is on know one will know anyway..
yeah thats still pretty confusing to me
SSA? do you mean ssr? that should be in the box with whatever is controlling it (pid or potentiometer) and you should have a flexable stranded wire cord such as SO or SJ cable running from your control panel to the element... ideally with a plug at one or both ends for removal and cleaning..... from your description you have things all broken up along the way ... in separate boxes I hope? or am I not understanding this either?
the 50a breaker would be for the main service going to your brweing area... the GFCI portion would still work and trip correctly regardless of amps but you would want to add smaller correctly rated breakers or fuses for your element and control panel devices ... These are normally located inside of your control panel. people looking to be fancy or that learn everything here usually go with DIN breakers ... although if your on a budget, correctly sized fuses work just as well and once the cover is on know one will know anyway..
Sorry, yes, I meant SSR
Typed that after a very long weekend. Nothing broken up along the way, at least I don't think there is. Only "break up" is the junction box I have on the wall instead of going directly from the house breaker panel right to the control panel. Other then that, it's my control panel to my ssr to my heating element. Really, the only thing confusing, to me anyway, are the mixture of answers I got in this post
augiedoggy
Well-Known Member
Sorry, yes, I meant SSR
The ssr is normally a component found INSIDE of a control panel mounted to a heatsink with control wires running from the control knob or pid..... Thats what mainly has me confused? are you confusing the pid with a control panel?
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