Wiring for 240 volt properly

[thekraken]

What it is is absolutely unnecessary expense that carries no value what so ever

My understanding is it's code
http://electriciantesting.blogspot.com/2009/12/wire-ampacity-and-conduit-fill.html

I could be wrong

 

[Kh2o]

you really only need 50 amp if you are looking to use large elements or back-to-back batches. assuming you want the full 50 amps with a three-wire circuit (two hots and a neutral), you would be looking at minimum #6 awg ungrounded and grounded conductors (hots and neutral) and a minimum #10 awg equipment grounding conductor (egc, assumes you are running thhn). you would need a 3/4" conduit for those four conductors but that is the bare minimum. 1" conduit would make for easier pulls. these conduit sizes apply to both emt or pvc.

for the receptacle ciruit, that could be a dedicated 1/2" conduit, whether you use #12 or #10. as mentioned above, #10 is overkill and depending on the size of the single-gang boxes the receptacles would be mounted in, you could very will exceed the allowable fill of the box (the volume taken up by the conductors, wire nuts, receptacles, etc. in the box). #10 is harder to bend than #12 and if the box is filled to capacity, it makes for an ugly installation. no real reason to do this and could result in a code violation.

if you want to have a portion of conduit with both the 50 amp and 20 amp circuits, you would need to run minimum 1" conduit, whether emt or pvc (again, with thhn conductors). it would be 1" even if you ran #10 for the 20 amp circuit. it would be 1" conduit from the spa panel to the first receptacle box. from there, the circuits would split into separate conduit runs. note that the first box would need to be two-gang, to accommodate all the conductors. also note that both the 50 amp and 20 amp circuits can share a single #10 egc to that first box. from there, #10 would need to continue with the 50 amp circuit and #12 could run off to the 20 amp circuit (would need to be #10 if the hot/neutral are #10). you could run a full-size #6 egc for the 50 amp circuit and you would still only need 1" conduit.

regarding ampacity derate, the egc does not count as a current carrying conductor (but does count toward conduit fill). the neutral counts if carrying more than unbalanced current. so it would count for two-wire single phase circuit. assuming you have 120 volt loads at your brew panel, that neutral would count as well. so looking at a maximum of five current carrying conductors in a single raceway, resulting in an 80% amapacity derate. however, we are allowed to take advantage of the 90 degree c ampacity column for derating purposes. for these size conductors, the 80% derate ampacity at the 90 degree c values is greater than the 60 degree c column ampacity values with no derate. in other words, no need to increase your conductor sizes to account for derate.

I am very impressed to see an electrician that understands derating. I'm even more impressed the you mention you can use the 90 c column for derating even though i'm sure every lug in the circuit is 75 c. This I was not aware of. But makes complete sense and I'm having a why the hell did I not know that moment.

As far as this installation. Just but the damn thing under the panel and run conduit from it. Or run romex through the attic and drop down to your control panel. Just sleeve the romex that is exposed with conduit to protect it from physical damage.

 

[user 163849]

It never takes long for me to remember why I try to avoid posting anything in an electrical thread.

 

[itsnotrequired]

My understanding is it's code
http://electriciantesting.blogspot.com/2009/12/wire-ampacity-and-conduit-fill.html

I could be wrong

see my previous post. you are correct that it needs to be derated but not derated from 20 amps. with thhn, you can derate from the 90 degree c ampacity value, which is 30 amps. 80% of 30 amps is 24 amps so you are good to go with the #12, no need to increase to #10.

 

[odorf]

..................

 

[thekraken]

you really only need 50 amp if you are looking to use large elements or back-to-back batches. assuming you want the full 50 amps with a three-wire circuit (two hots and a neutral), you would be looking at minimum #6 awg ungrounded and grounded conductors (hots and neutral) and a minimum #10 awg equipment grounding conductor (egc, assumes you are running thhn). you would need a 3/4" conduit for those four conductors but that is the bare minimum. 1" conduit would make for easier pulls. these conduit sizes apply to both emt or pvc.

for the receptacle ciruit, that could be a dedicated 1/2" conduit, whether you use #12 or #10. as mentioned above, #10 is overkill and depending on the size of the single-gang boxes the receptacles would be mounted in, you could very will exceed the allowable fill of the box (the volume taken up by the conductors, wire nuts, receptacles, etc. in the box). #10 is harder to bend than #12 and if the box is filled to capacity, it makes for an ugly installation. no real reason to do this and could result in a code violation.

if you want to have a portion of conduit with both the 50 amp and 20 amp circuits, you would need to run minimum 1" conduit, whether emt or pvc (again, with thhn conductors). it would be 1" even if you ran #10 for the 20 amp circuit. it would be 1" conduit from the spa panel to the first receptacle box. from there, the circuits would split into separate conduit runs. note that the first box would need to be two-gang, to accommodate all the conductors. also note that both the 50 amp and 20 amp circuits can share a single #10 egc to that first box. from there, #10 would need to continue with the 50 amp circuit and #12 could run off to the 20 amp circuit (would need to be #10 if the hot/neutral are #10). you could run a full-size #6 egc for the 50 amp circuit and you would still only need 1" conduit.

regarding ampacity derate, the egc does not count as a current carrying conductor (but does count toward conduit fill). the neutral counts if carrying more than unbalanced current. so it would count for two-wire single phase circuit. assuming you have 120 volt loads at your brew panel, that neutral would count as well. so looking at a maximum of five current carrying conductors in a single raceway, resulting in an 80% amapacity derate. however, we are allowed to take advantage of the 90 degree c ampacity column for derating purposes. for these size conductors, the 80% derate ampacity at the 90 degree c values is greater than the 60 degree c column ampacity values with no derate. in other words, no need to increase your conductor sizes to account for derate.

Tons of good info, than you very much.

Okay, so counting the ground toward fill puts me at 29% fill for 1" pvc conduit.

So you were saying that my 50 amp circuit only needs 10awg ground?

Also, I was figuring the ampacity derate to 10awg based on this data. I've actually seen conflicting data so I thought it best to go with the worst case. Does the table your referring to come from the code book? That would obviously trump and make me sleep better...

 

[itsnotrequired]

Tons of good info, than you very much.

Okay, so counting the ground toward fill puts me at 29% fill for 1" pvc conduit.

So you were saying that my 50 amp circuit only needs 10awg ground?

assuming three #6 conductors (two hots and a neutral for the 50 amp circuit), two #12 conductors (hot and neutral for the 20 amp circuit) and a #10 egc, the cross-sectional area of these conductors is 0.2187 in sq. 1" schedule 40 pvc has a 0.832 in sq cross-sectional area or a touch over 26% fill. if you ran 1" emt, you would be a touch over 25% full (emt has a smaller sidewall thickness compared to pvc). since there are more than two wires in the conduit, maximum allowable fill is 40%.

and yes, a #10 egc is allowed on a 50 amp circuit. hell, #6 nm cable is constructed with an integral #10 egc.

 

[itsnotrequired]

I am very impressed to see an electrician that understands derating. I'm even more impressed the you mention you can use the 90 c column for derating even though i'm sure every lug in the circuit is 75 c. This I was not aware of. But makes complete sense and I'm having a why the hell did I not know that moment.

it is the thhn conductor that let's us get away with it. if it was thwn, we would be stuck with the 75 degree c derate but do they even make thwn conductor that doesn't also carry a thhn rating?

note that nm cable also gets to take advantage of the 90 degree c derate values, even though it is limited to 60 degree c ampacity for continuous operation :mindblown:

 

[thekraken]

assuming three #6 conductors (two hots and a neutral for the 50 amp circuit), two #12 conductors (hot and neutral for the 20 amp circuit) and a #10 egc, the cross-sectional area of these conductors is 0.2187 in sq. 1" schedule 40 pvc has a 0.832 in sq cross-sectional area or a touch over 26% fill. if you ran 1" emt, you would be a touch over 25% full (emt has a smaller sidewall thickness compared to pvc). since there are more than two wires in the conduit, maximum allowable fill is 40%.

and yes, a #10 egc is allowed on a 50 amp circuit. hell, #6 nm cable is constructed with an integral #10 egc.

Cool, #10 ground it is.
And just because it appears you replied to me previous comment before I edited it I'll copy and paste: "I was figuring the ampacity derate to 10awg based on this data (and was indeed looking for 90c). I've actually seen conflicting data so I thought it best to go with the worst case. Does the table your referring to come from the code book?"

 

[thekraken]

It never takes long for me to remember why I try to avoid posting anything in an electrical thread.

Everyones input is genuinely appreciated over here.

 

[itsnotrequired]

Cool, #10 ground it is.
And just because it appears you replied to me previous comment before I edited it: "I was figuring the ampacity derate to 10awg based on this data (and was indeed looking for 90c). I've actually seen conflicting data so I thought it best to go with the worst case. Does the table your referring to come from the code book?"

the table in your link is based on the 2005 version of the nec, i used 2011 but the values are the same for the conductor sizes we are talking about. always be cautious when using ampacity values published by cable manufacturers, they don't always reflect the various nuances of the code. for example, it is showing a #12 as having a 20 amp maximum allowable ampacity at 60, 75 and 90 degree temperature values. they are basing those values off of the requirements of 240.4(D) of the nec, which states #12 awg conductors cannot have overcurrent protection rated greater than 20 amps, regardless of the conductor type or temperature ratings of the terminals where the conductor is temrinated. but looking at the nec ampacity charts, a #12 conductor has ampacity maximums of 20, 25 and 30 amps at 60, 75 and 90 degree c ratings., respectively. the manufacturer is using 20 amps across the board, more than likely so the layperson doesn't see a 25 amp value and think they can put a #12 conductor on a 25 amp circuit breaker. from a practical standpoint, #12 conductors running 25 amps on a 20 amp breaker will be totally safe (assuming 75 degree c ratings at the breaker terminals, which most breakers have). the only reason we can do it is because code says we cant.

 

[thekraken]

@itsnotrequired, while I got your ear, how do the pros feel about these newfangled little guys:

 

[thekraken]

..................

Lol, you're always laughing at me, odorf. I can't figure out why...Is it because after 40+ posts I'll be doing what you said from post #2?

 

[Kh2o]

@itsnotrequired, while I got your ear, how do the pros feel about these newfangled little guys:

I'll way in. We hate them.

 

[thekraken]

I'll way in. We hate them.

Got it. Unsafe or just a p.i.t.a?

 

[Kh2o]

it is the thhn conductor that let's us get away with it. if it was thwn, we would be stuck with the 75 degree c derate but do they even make thwn conductor that doesn't also carry a thhn rating?



note that nm cable also gets to take advantage of the 90 degree c derate values, even though it is limited to 60 degree c ampacity for continuous operation :mindblown:

I have not seen thwn that doesn't carry thhn rating. As far as the NM goes I did not know that. Now the only application I could think of to derate nm would be ambient temp. Unless I guess you bundled a bunch together but that ain't happening. So, you're telling me if I run NM in an attic and derate based on ambient temp I can use 90 c column? Do you have the code article for that? It's not that I don't believe you. I am, and always will be a student of the trade and need to read it for myself.

 

[itsnotrequired]

I have not seen thwn that doesn't carry thhn rating. As far as the NM goes I did not know that. Now the only application I could think of to derate nm would be ambient temp. Unless I guess you bundled a bunch together but that ain't happening. So, you're telling me if I run NM in an attic and derate based on ambient temp I can use 90 c column? Do you have the code article for that? It's not that I don't believe you. I am, and always will be a student of the trade and need to read it for myself.

check out 334.80.

 

[Kh2o]

check out 334.80.

Ha! There it is plain as day. The same damn article that says it shall have an ampacity not more than 60 c. Which pretty much means you do not need to derate romex in an attic. There are a lot of inspectors that can kiss my ass right now!

Thanks dude. You just educated me.

 

[Kh2o]

Got it. Unsafe or just a p.i.t.a?

Well they are UL listed so they are fine. We don't like them because user error when installing can result in failure, which means call backs and losing money.

 

[user 163849]

the table in your link is based on the 2005 version of the nec, i used 2011 but the values are the same for the conductor sizes we are talking about. always be cautious when using ampacity values published by cable manufacturers, they don't always reflect the various nuances of the code. for example, it is showing a #12 as having a 20 amp maximum allowable ampacity at 60, 75 and 90 degree temperature values. they are basing those values off of the requirements of 240.4(D) of the nec, which states #12 awg conductors cannot have overcurrent protection rated greater than 20 amps, regardless of the conductor type or temperature ratings of the terminals where the conductor is temrinated. but looking at the nec ampacity charts, a #12 conductor has ampacity maximums of 20, 25 and 30 amps at 60, 75 and 90 degree c ratings., respectively. the manufacturer is using 20 amps across the board, more than likely so the layperson doesn't see a 25 amp value and think they can put a #12 conductor on a 25 amp circuit breaker. from a practical standpoint, #12 conductors running 25 amps on a 20 amp breaker will be totally safe (assuming 75 degree c ratings at the breaker terminals, which most breakers have). the only reason we can do it is because code says we cant.

And that type of nonsense within the code is one reason I have no real appreciation for it. That and the fact that there are so many electricians who are trained on the job and they innocently confuse code rules with the physical properties of electricity, while they are simply based on fact. It is in fact what they need to know to do their job but electrons never read a code book. This is just my rant and not in reference to anyone involved in this thread.

On internet forums it seems code always trumps common sense, knowledge, and experience. Believe me, if code violations actually resulted in the carnage that we are led to believe every electrical sub station control house in the country would burn to the ground (at least the ones that I have seen). And without them the power lines would all fail leaving us with no need for electrical code. I'm not saying they are unsafe only that a code inspector would have a field day writing up trivial crap in them. They are designed by electrical engineers and wired by knowledgeable technicians who are often charged with the task of converting the engineering concept into something that will actually work in real life and keep the lights on for the masses who simply expect the light to come on when they flip a switch.

Oh, one more thing, while I'm on a rant. If completing the circuit between a hot conductor and ground or another hot conductor with your body were as deadly as the internet leads us to believe, there would be an alarming shortage of electrical workers!

 

[thekraken]

Oh, one more thing, while I'm on a rant. If completing the circuit between a hot conductor and ground or another hot conductor with your body were as deadly as the internet leads us to believe, there would be an alarming shortage of electrical workers!

Nothin like a little 240v zap to get your brew day started in the mornin'!

https://youtu.be/pEig1D4sJdI?t=205

 

[thekraken]

you really only need 50 amp if you are looking to use large elements or back-to-back batches. assuming you want the full 50 amps with a three-wire circuit (two hots and a neutral), you would be looking at minimum #6 awg ungrounded and grounded conductors (hots and neutral) and a minimum #10 awg equipment grounding conductor (egc, assumes you are running thhn). you would need a 3/4" conduit for those four conductors but that is the bare minimum. 1" conduit would make for easier pulls. these conduit sizes apply to both emt or pvc.

So for 30 amp service 10awg do the job? 12awg ground for both the 30amp and 20amp? (thhn)

 

[Kh2o]

And that type of nonsense within the code is one reason I have no real appreciation for it. That and the fact that there are so many electricians who are trained on the job and they innocently confuse code rules with the physical properties of electricity, while they are simply based on fact. It is in fact what they need to know to do their job but electrons never read a code book. This is just my rant and not in reference to anyone involved in this thread.

On internet forums it seems code always trumps common sense, knowledge, and experience. Believe me, if code violations actually resulted in the carnage that we are led to believe every electrical sub station control house in the country would burn to the ground (at least the ones that I have seen). And without them the power lines would all fail leaving us with no need for electrical code. I'm not saying they are unsafe only that a code inspector would have a field day writing up trivial crap in them. They are designed by electrical engineers and wired by knowledgeable technicians who are often charged with the task of converting the engineering concept into something that will actually work in real life and keep the lights on for the masses who simply expect the light to come on when they flip a switch.

Oh, one more thing, while I'm on a rant. If completing the circuit between a hot conductor and ground or another hot conductor with your body were as deadly as the internet leads us to believe, there would be an alarming shortage of electrical workers!

First of all the NEC does not apply to utility wiring so why even bring that up? Almost the entire code book refers to 600 volts or less. You are comparing apples to grenades.

If you have no appreciation for the code that's fine. But PLEASE stay out of people's homes. That entire book is written for a reason. We electricians follow it because those are the rules and that makes the installation safe. We keep our opinions of the code to ourselves and just do what we are supposed to do. I hate that just one person could read your ridiculous comments and hurt themselves. Especially that last part. I have been zapped a ton of times in my career arm to arm, leg to head, face, you name it. Yes I'm alive. There are people in my career that I worked along side with that are now dead. Am I lucky? I don't know. Are you trying to come off as some bad ass that doesn't like to follow rules? I mean read that **** back to yourself and ask. How has this helped anybody?

I'm seriously sick to my stomach right now.

 

[Kh2o]

So for 30 amp service 10awg do the job? 12awg ground for both the 30amp and 20amp? (thhn)

I wont get into the details but 10 awg conductors need 10 awg ground. After 10 awg is when the ground starts becoming smaller than the ungrounded conductors (the "hot")

 

[itsnotrequired]

I wont get into the details but 10 awg conductors need 10 awg ground. After 10 awg is when the ground starts becoming smaller than the ungrounded conductors (the "hot")

yep. quick reference for minimums:

15 amp breaker -> #14 ground
20 amp breaker -> #12 ground
25 amp breaker -> #10 ground
30 amp breaker -> #10 ground
35 amp breaker -> #10 ground
40 amp breaker -> #10 ground
45 amp breaker -> #10 ground
50 amp breaker -> #10 ground
60 amp breaker -> #10 ground
70 amp breaker -> #8 ground
80 amp breaker -> #8 ground
90 amp breaker -> #8 ground
100 amp breaker -> #8 ground

beyond that, we're talking about a pretty gnarly brewery.:fro:

it is okay to increase ground conductor sizes larger than what is required without the need to correspondingly increase ungrounded conductor size but the inverse is not necessarily true. in the op example of running #10 conductors for the 20 amp receptacles, that circuit would also need a #10 ground, even though #12 ground is acceptable for a 20 amp breaker. without getting too much into physics, the larger ungrounded conductors result in greater current flow in the event of a ground fault and hence greater current flow in the ground. the ground conductor needs to be increased in size proportionately to safely carry this larger fault current. yet another reason to not oversize non-grounded conductors unless there is a good reason.

 

[Kh2o]

yep. quick reference for minimums:

15 amp breaker -> #14 ground
20 amp breaker -> #12 ground
25 amp breaker -> #10 ground
30 amp breaker -> #10 ground
35 amp breaker -> #10 ground
40 amp breaker -> #10 ground
45 amp breaker -> #10 ground
50 amp breaker -> #10 ground
60 amp breaker -> #10 ground
70 amp breaker -> #8 ground
80 amp breaker -> #8 ground
90 amp breaker -> #8 ground
100 amp breaker -> #8 ground

beyond that, we're talking about a pretty gnarly brewery.:fro:

it is okay to increase ground conductor sizes larger than what is required without the need to correspondingly increase ungrounded conductor size but the inverse is not necessarily true. in the op example of running #10 conductors for the 20 amp receptacles, that circuit would also need a #10 ground, even though #12 ground is acceptable for a 20 amp breaker. without getting too much into physics, the larger ungrounded conductors result in greater current flow in the event of a ground fault and hence greater current flow in the ground. the ground conductor needs to be increased in size proportionately to safely carry this larger fault current. yet another reason to not oversize non-grounded conductors unless there is a good reason.

I'm glad you are here and take the time to write this out for people. The larger the conductor the larger the ground fault current path we need. Spot on. You're a nerd like me and love talking about this don't you?

 

[user 163849]

First of all the NEC does not apply to utility wiring so why even bring that up? Almost the entire code book refers to 600 volts or less. You are comparing apples to grenades.

If you have no appreciation for the code that's fine. But PLEASE stay out of people's homes. That entire book is written for a reason. We electricians follow it because those are the rules and that makes the installation safe. We keep our opinions of the code to ourselves and just do what we are supposed to do. I hate that just one person could read your ridiculous comments and hurt themselves. Especially that last part. I have been zapped a ton of times in my career arm to arm, leg to head, face, you name it. Yes I'm alive. There are people in my career that I worked along side with that are now dead. Am I lucky? I don't know. Are you trying to come off as some bad ass that doesn't like to follow rules? I mean read that **** back to yourself and ask. How has this helped anybody?

I'm seriously sick to my stomach right now.

I worked at the monitoring, control and metering level not on the high voltage lines. When I worked sub station construction we did the house wiring including lights, receptacles, HVAC, and control equipment wiring. With the exception of some 125 volt DC circuits, the voltage levels were exactly the same as you have in your home. The last 20 years of my career I was responsible for 23 substations which controlled many miles of 345,000 volt transmission lines, but I never actually worked on the high voltage lines. I am not sure whether that was apples or oranges though.

First of all I have been retired for almost 10 years, I have never done wiring in anyone's home. I even hired an electrician to upgrade the service to my home. He did nothing that I couldn't have done other than apply his knowledge of the NEC to pass inspection. I never suggested that anyone not follow code. I do not know where you get the idea that I should stay out of people's homes. I bring homebrew and they welcome me.

I agree that electricians follow the rules of the NEC for good reason. I only question the fact that those rules are the ONLY safe way the job could be done. I never suggested that anyone not follow the rules of the "King James version" of the NEC.

Well we are both proof that the urban legend that any contact with electricity will result in instant death is false. I choose to inform people that is not necessarily the case. I have worked around electricity since the Air Force "made me" back in 1968. I lost a few people I knew back then but electricity had nothing to do with that. In fact I have never known anyone who was killed by electricity. I am not suggesting that anyone go stick their keys in an outlet to test the theory, but removing some of the fear might just make them less nervous and therefore more safe when working around electricity.

No, I am not some bad ass but I have survived a heart attack and throat cancer since retiring. I guess that makes me tougher than even John Wayne.

Sorry you took offense to my rant. It was not an attack on you or your's.

Oh, and in my experience a bit of fiber can do wonders for the stomach problem you mentioned.

 

[thekraken]

I'm price checking, it seems 50 amp gfci is easy to come by with the spa panel.

But what's the best way to get gfi on a 30 amp circuit?

 

[itsnotrequired]

I'm price checking, it seems 50 amp gfci is easy to come by with the spa panel.

But what's the best way to get gfi on a 30 amp circuit?

couple options here. one is to buy a 30 amp gfci breaker. this is not commonly stocked by your home depots, lowes, etc. so you will likely need to order it. get ready for sticker shock...

the other option is to get a 'regular' 30 amp breaker and use that to serve the 50 amp spa panel, eventually on to the brew panel. this approach is often cheaper than purchasing just a 30 amp gfci breaker.

both installations would use #10 conductors.

 

[thekraken]

couple options here. one is to buy a 30 amp gfci breaker. this is not commonly stocked by your home depots, lowes, etc. so you will likely need to order it. get ready for sticker shock...

the other option is to get a 'regular' 30 amp breaker and use that to serve the 50 amp spa panel, eventually on to the brew panel. this approach is often cheaper than purchasing just a 30 amp gfci breaker.

both installations would use #10 conductors.

Found my gfi breaker on amazon, coincidentally nearly the same cost as putting together a breaker+spa panel from home depot.
http://www.amazon.com/dp/B00ECKLKBM/?tag=skimlinks_replacement-20