Feed wire sizing to my garage

We had our garage professionally rewired about 10 years ago. The electricians ran about 80' of 4 gauge 3 conductor wire to a 100 amp service. There are 2, 50 amp outlets, 2, 30 amp outlets, about a dozen 20 amp outlets around the perimeter and another half a dozen in the ceiling for lighting.
 
Balance panel is no myth.

First home had most all loads on one side and resulted in cooked panel parts.

Was older home with aluminum wire that had old and cruddy grease on connectors.

Meter would get hot to touch.

The theroy is simple and the neutral carries the non balanced loads if and when load is not balanced which is often in shop with lots of 120 volt equipment with large motors.

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Balance panel is no myth.

First home had most all loads on one side and resulted in cooked panel parts.

Was older home with aluminum wire that had old and cruddy grease on connectors.

Meter would get hot to touch.

The theroy is simple and the neutral carries the non balanced loads if and when load is not balanced which is often in shop with lots of 120 volt equipment with large motors.

Sent from my SAMSUNG-SGH-I337Z using Tapatalk

Aluminum wire and the result of using isn't as a good example for an unbalanced. There's a myriad of reasons for the failure or overheating but the first is using aluminum wire. Unfortunately an electrical service using aluminum wire requires maintenance. Aluminum wire manufacturers swear this isn't the case. Unfortunately the home owners doesn't know this. The "cruddy grease" Noalox, which is a nonconductive grease and zinc powder mix, is placed on the connection to prevent oxidation or corrosion caused by dissimilar metal. The expansion and contraction of aluminum wire due to heat causes loose connections, in electrical service panels.

"The theroy is simple and the neutral carries the non balanced loads if and when load is not balanced which is often in shop with lots of 120 volt equipment with large motors."

Yes, this would be/could be true if the service is 3-phase. What standard voltage range uses the common as a conductor?
 
Thank you all for taking the time to comment, whether it was constructive or not. To the handful who read what I am trying to do and, maybe more importantly, why I am not doing more, and provided relevant feedback I appreciate it as that is what I was looking for by starting this thread.

On the note of technical discussion, I do plan to install a sub-panel, off of which I will run one 240V circuit and two 120V circuits. I have no idea how the emt is still there, but I can run a fishing tape through so I think I will be good, and yes it is emt not rigid. Anyone have a suggestion for a GFI breaker that won't fight with my VFD? While I don't intend to tell the township what I am doing (they would lose it if they came in for inspection and saw the knob and tube), I do want to do everything right. I am a mechanical engineer, so the NEC is far from my wheelhouse, but this is not the first time I have used it, I just like to consult with others when I'm outside my comfort zone.

I do not intend to come off as arogant or angry that someone disagrees with what I am doing, but consider this. The large majority of replies (aside from a recent patter of discussion about analysis methods which I don't mind a bit) simply statedin some form: "I used ____ (insert big wire/amp size), you should too" or "that won't be enough, just bite the bullet and install a big service" I would absolutely love to do that, I am not trying to skimp by to be cheap or lazy. I am trying to make what I have work so that I can use what equipment I have now, rather than let it wait for years. When you are responding to these types of threads, keep in mind your audience may not be in the same place in life so, while personal experience and recommendations are great, maybe try not to come off acting as though what you have done is the only way, it can be a bit discouraging. Also, I live in the hills outside of Pittsburgh, if anyone who attests to how quick and easy a trench would be to dig wants to show me, I would love the help. Don't bother bringing a shovel, we will start with matocks and move to digging irons. The trench will come in time, but it won't be a weekend project.

This is the one statement kin the thread which I actually find quite offensive:

Hate to point this out, but.... It's never a good idea to sit and think about how little you are going to do and then subtract from what you think you need for power in a shop. If you are not going to work in the shop, then forget about it. Put up a sky light to get some light in and start building shelves to store crap on. It's typically easier to begin building shelves in the middle of the floor so you can store as many things you will never use again on them. OR you can do it with the idea that you WILL be working out there. And buying equipment that will consume more power and build to accommodate it now.

Perhaps I am in a small majority that folks these days don't understand, but I am trying to take care of my family and my responsibilities. When all that is done, I try and sneak out to the garage and pursue my personal passion. Unfortunately, that meanes digging a trench and installing a large service comes after buying diapers, paying for daycare, sending my wife occasional flowers, doing dishes, updating the house, saving for someone elses college, and sitting on the floor building lego towers for a toddler (who has no appreciation for their architectual beauty) to knock down shortly before running off in a vain effort to catch the infinitely quicker dog. So no, I am not "sitting around thinking about how little I am going to do" I am working damn hard and knowing that my hobby needs to come absolutey last on the priority list.
 
Because that is what residential 120V/240V service is commonly referred to as by many, myself included. Call it whatever you like.


Correct, and code requires that for any more than a single circuit run to an outbuilding. You can't run 2 circuits to an outbuilding without putting in a feeder, panel, and ground rod. It is the only way to do it legally.


Agreed, I wasn't the one raising voltage drop as a concern.


Most likely yes, although depending on the install the neutral could be smaller than the line conductors as long as it is properly calculated and meets requirements. In some cases, the neutral actually has to be bigger.


Correct again, but I think you misunderstood my post. I was saying of 100A on leg A and 20A on leg B then I need to size the feeder for 100A, meaning I would use #3 assuming conductors in pipe. If I rebalance the load by moving single pole breakers to swing 40A of load from leg A to leg B, then I would have 60A for each leg and now I would only have needed a 6AWG feeder. These problems tend to happen a lot more in commercial settings than residential. Again, as I said, things generally balance themselves.

I have run into 120V inverter based solar systems were balancing can be a problem, but that is an edge case nowadays.

In commercial settings with UPSs, balancing the 120V loads is critical. I actually had to do that in January. A UPS was slipping into soft bypass because it was overloaded all because one of the 2 legs was much hotter than the other. I moved some of the loads to the other leg, and the UPS went from over 100% utilization (where it goes into bypass) down to the low 90's.

It may not mean much to some, but this allows my company to defer the UPS upgrade to next year.


Who suggested that and how did you read that into my post? That said, see comment above about neutral. However, my previous post was not advocating using 2 different size conductors for the feeder. Just that if my example 100A/20A load had been properly calculated at the start, and balanced effectively, then the feeder could have been installed as a 6AWG feeder to begin with. Balancing the load properly most efficiently uses both line feeder conductors.

At this point I am done at this discussion. I feel that you are intentionally trying to twist my words and interpret what I am saying differently to try to make me out to look like an idiot. For what reason I do not know, but I am done with it. This forum isn't about that.

I wasn't attempting to twist your words, I was attempting to untwist. Not only for myself but other readers. The original question presented was in regards to residential power so introducing an anecdotal commercial power issue with UPS being the example is a twist. I understand that geographics and demograpics play a large part in how we express ourselves.

As ewkearns stated in his last comment, split-phase was the forerunner of our current single phase supply. It's a 19th century power source that was used in a specific geographical area. Specific geographically because power lines to other parts of the country had not been strung yet. By the time power was supplied the issues with split-phase were out in front and transformers had changed or were in the process of change.

I'm no electrical engineer but I cringe when unproven electrical theory is presented as fact. It's easy to unbalance a 3-phase electrical service, but taking this and applying it to a residential application and telling/selling a home owner on an estimate to upgrade and rebalance their electrical service is ethically wrong. It does happen and it happens often. Yes, I do agree you were presenting voltage drop, but you were also presenting an electrical panel being out of balance based on circuit breaker placement, whereas in a single-phase service, it just isn't going to happen.

Another area with a twist is switching between feeder and branch circuit conductors. A 240v (single phase) branch ciruit requires two hot legs equally sized and a ground. A 240v (single phase) feeder requires three equally sized conductors comprised of two hot legs and a common.
 
Thank you all for taking the time to comment, whether it was constructive or not. To the handful who read what I am trying to do and, maybe more importantly, why I am not doing more, and provided relevant feedback I appreciate it as that is what I was looking for by starting this thread.

On the note of technical discussion, I do plan to install a sub-panel, off of which I will run one 240V circuit and two 120V circuits. I have no idea how the emt is still there, but I can run a fishing tape through so I think I will be good, and yes it is emt not rigid. Anyone have a suggestion for a GFI breaker that won't fight with my VFD? While I don't intend to tell the township what I am doing (they would lose it if they came in for inspection and saw the knob and tube), I do want to do everything right. I am a mechanical engineer, so the NEC is far from my wheelhouse, but this is not the first time I have used it, I just like to consult with others when I'm outside my comfort zone.

I do not intend to come off as arogant or angry that someone disagrees with what I am doing, but consider this. The large majority of replies (aside from a recent patter of discussion about analysis methods which I don't mind a bit) simply statedin some form: "I used ____ (insert big wire/amp size), you should too" or "that won't be enough, just bite the bullet and install a big service" I would absolutely love to do that, I am not trying to skimp by to be cheap or lazy. I am trying to make what I have work so that I can use what equipment I have now, rather than let it wait for years. When you are responding to these types of threads, keep in mind your audience may not be in the same place in life so, while personal experience and recommendations are great, maybe try not to come off acting as though what you have done is the only way, it can be a bit discouraging. Also, I live in the hills outside of Pittsburgh, if anyone who attests to how quick and easy a trench would be to dig wants to show me, I would love the help. Don't bother bringing a shovel, we will start with matocks and move to digging irons. The trench will come in time, but it won't be a weekend project.

This is the one statement kin the thread which I actually find quite offensive:



Perhaps I am in a small majority that folks these days don't understand, but I am trying to take care of my family and my responsibilities. When all that is done, I try and sneak out to the garage and pursue my personal passion. Unfortunately, that meanes digging a trench and installing a large service comes after buying diapers, paying for daycare, sending my wife occasional flowers, doing dishes, updating the house, saving for someone elses college, and sitting on the floor building lego towers for a toddler (who has no appreciation for their architectual beauty) to knock down shortly before running off in a vain effort to catch the infinitely quicker dog. So no, I am not "sitting around thinking about how little I am going to do" I am working damn hard and knowing that my hobby needs to come absolutey last on the priority list.

Thanks for the reply and chuckle regarding the trench...........I grew up in Florida and have visited Pennsylvania...I dig. :)

My comments to you were code and safety related. Code: What you pull conductors through is important and size is important. Let me address what you pull the conductors through. EMT isn't for direct burial and you may have EMT or it could be ridgid? The condition at this point is most important and it's a family matter. If you pull a conductor through damaged conduit you take a chance of skinning the conductor. Current flowing back through the damaged metal conduit (doesn't matter if it's EMT or Rigid) to ground doesn't care who's hand is in the sink full of water when they are electrocuted. Sidebar: This is one reason 110v plugs are polarized. It separated the hot leg from the **common and ground** which is mistaken sometimes by the novice handyman as unimportant, or based on when the common connects in the service panel.

The skinned wire may end up in an air space not touching anything. When the conduit floods with water....what then? The code is written for many reasons and safety is the primary one. -Russ
 
Rustrp: I've worked on farms in Florida, I'll take digging in rocks over fire ants and mosquitoes any day.

I have an appreciation for code concerns so long as logic rules, and absolutely for safety. Gone are my days of working with live wires instead of walking to the breaker.

I can't say for sure what the conduit is under ground but it looks to be EMT when. It comes through the wall. It is also very old, so it might be none of the above. I've run a metal fish tape through it and not encountered any resistance of note, it also shows no signs of moisture intrusion and my basement has a spring continuously filling a cistern in the basement, the soil is very wet. The fact that there is no trace of water makes me think it is structurally intact, but I intend to run the new wires inside of Kevlar sleeving as an added measure. (Oh the fun things you can get for free when you work in weird industries)
 
Well, if I offended you, don't think you are somehow in a small group of people. I offend a LOT of people.
That being said.
First question I would ask on this, why do you need to bury the cable to begin with? Is there a law that says it can't be done with areal cable?
Poles are reasonably cheap if needed and you could run areal wire out to the building and eliminate the trench and rigid pipe path.

Now for a bit of reason to do as much as you can instead of going with a minimum.
Say you feed it with the 3 runs of 12/2 that someone suggested. And then a killer deal on a larger lathe that needs 30 amps to run falls in your lap. 12 gauge wire is good for 20 amps not 30.
Point here is finding machines on the used market is sort of funny when you are on a budget. First the little table top 110 units are there. The Central Machinery stuff from harbor freight and similar low buck low quality gear. Then you get into the mid sized gear that people want new prices for (at least in my area of central Ohio and you aint far enough away that Ohioians aren't buying there) and it's 40 years old or better. But that's what everyone wants so they will pay the premium. Then you get into the bigger industrial gear that is heavy and hard to move and the price goes back down. But that stuff uses bigger motors and requires more power. But it's cheap to buy. Dragging something home to find out it can't be used sucks alot more than not having it at all. Trust me. I too know about being broke. Watching stuff rust away that I didn't have the money to invest in at the time and it sat and was ruined.

As far as how to do it on a shoestring.
First it doesn't ever happen overnight. It takes time to put together everything you need to do a project. Electrical systems don't come in a box that you buy and assemble. And that's actually a good thing, because you can buy your wire this week or month or whatever and maybe get some 4 square boxes to put outlets in and then next week get the outlets and faceplates. Once you have that stuff then it's the panel. and then later the breakers. do it slowly and it will come together.
The other thing to do is check the scrap yards for rolls of wire and long sections of cut wire.
As long as it's long enough and the correct gauge then it will work. Color isn't important. If it's all orange, so be it. You grab a roll of white, black, red and green tape and mark your conductors.

So don't be offended,,, be motivated to figure it out. Or be offended and let that motivate you. Yes, family comes before all else. Don't assume I don't know about that either.
 
That reminded me of something...

Buy one roll of wire!!!

We needed to put a sub panel in shop off of shop panel and cable distance was say 50 feet.

Buying by foot cable in 4 colors was one price but buying 500 foot roll of black was less...much less.

Used tape to mark each conductor and all is good and we have substantial amount left on roll for large load outlets for welders someday.

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Not exactly on topic but ..

I just changed out my workshop (cubby hole) lighting for led flurecesent fitting of 50w, it has a maintained live and a battery that will keep half the lights on for upto 3h if the power drops might be worth considering if your going to be working at night in the dark surrounded by spinny and sharp things :)

They have got a lot cheeper, and you can get a small bulk head light as a very cheep one juat to give enough light to find your way out.

Stuart

Same, but mine are fluorescent rescued from the skip when my (very eco-conscious) workplace went over to LED lighting - positioned to light the main breaker panel for house and shop as well as the spinny sharp things, cost me not a penny apart from the twin & earth to wire them in!

Dave H. (the other one)
 
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