Iam not an electrician, but I am trying to learn what will be involved (purchasing of material) for my project. I am powering an outbuilding that will need approx 200 amp service(all the loads added). I want to utilize a 200 amp double pole breaker off the main to service a 200 amp sub panel to accomplish this. I plan to bury the cable from the main to the sub panel. Can you help me understand the type, and gauge of the cable to make this connection? I am assuming from what I am reading that this is the best way to accomplish this, or if anyone has any suggestions I am all ears.
Yes, I will be hiring an electrician to do this, but I want to know what my expenses will be as well as be able to save some money by doing the grunt work (ie the trench for the cable, and burying the cable, mounting the sub panel, and pulling a lot of the wire that the electrician will wire the sub panel with.

Why are you think the simple task of connecting the wires to an electrician. The stuff you want to do is the complicated part.
You are basically asking how to do this whole job. Why not get an electrician there, ask him what you can do to save money, and then go from there?

Just so you know, you cannot come from a 200A service with a 200A sub-feed. I have never seen a residential panel that was rated for more than a 125A branch circuit/feeder breaker.
Also, how do you know you need a 200A service to a home shop? That is a huge load, did you do a demand load calculation, or did you just go around and add up every piece of equipment you have?

Stan,
Thanks for your response. As I stated in my Question, I am not an electrician. I am simply trying to learn here so that I can be as involved in the project as is safe. I already have an electrician coming out to provide some guidance on getting started.
This is a fact finding, and learning effort.
Your comment about what I wish to be able to do may have been misunderstood. I want to be able to help this process, by being able to do a lot of the tedious tasks like drilling chase holes, running wiring, digging the trench etc...

As for your question regarding how much Amperage that I need is exactly why I am here asking you. Yes I added the potential loads, and clearly that is the incorrect way of calculating this. I think that's where you come in. Would love to know more about how to do a demand load calculation. This shop will be running more than power tools. I will have a fridge, AC, as well as a probable entertainment center. An article I read said that you add amps of your appliances to determine the load. I assumed (again really wrong) that if the total of the load was 175 amps then I needed 200 amps supplied to the sub panel?
Work with me here!! Lol not an electrician, but not an idiot.

Sorry, that first line in my reply seriously typo'd. I meant that connecting the wires is the easiest part.

Think about the load. If you add everything up, you need to take into account 120v loads as opposed to 240v loads. So if you add up things like lighting, refrigerators, small appliances and tools, etc, these are all 120v loads, so you have to divide them in half to get the 240v load on the service. By this I mean typically those loads will be pretty well split up in the panel, so half will be on one leg and vice-versa.

A real demand load calc will be hard on something like this so adding things up, and using experience in curving that number are you best bet. Remember that tools will only be used by those in the shop. So if you are alone unless you have a large dust collector or something similar that will run simultaneously with other tools you'll only be running one tool at a time. A welder is a good example of this. If you are alone in the shop welding there is not much else going on 'cept maybe an exhaust fan.

In my experience 100A is more than enough to a residential shop of even a moderate size.

I have done a Demand load calc, and it revealed 120 amp calculated. I know the main is pretty full. Is there a way to have the power company or an electrician (not sure who would be responsible for doing this) run power between the meter and the house to another panel or some sort of 120 amp circuit breaker box that supplies a 120amp sub panel? If so, with 120amp computed load, what size breaker (between the metter and the feeder cable), What size sub panel, and wire between the two would you use. Also I am assuming that I will be using 4 conductor cable (2-hot, 1 neutral, and one ground).

Can you recommend any suppliers that sell buriable cable that will fit my needs

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Originally Posted by lsblpn

can you recommend any suppliers that sell buriable cable that will fit my needs

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Home Depot or Lowe's has the cable you need. It is quite pricey. I agree with the fellow that said 100 amps might be enough. Unless you anticipate multiple loads running simultaneously. Only you know that.

I think a 3/0 gauge would be sufficient for 200 amps. The smaller load service panel would be cheaper on the wire too. You might dig the trench and save some money. The hookup, I think you probably realize you should get someone with experience.

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Originally Posted by Happyfrenchman

Home Depot or Lowes has the cable you need. It is quite pricey.

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A real supply house would also be a good place to check. They'll have exactly what you need.

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Originally Posted by Happyfrenchman

I think a 3/0 gauge would be sufficient for 200 amps.

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You think? Wouldn't it be good to know for sure before you give electrical advice to someone?

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Originally Posted by stanfortyman

A real supply house would also be a good place to check. They'll have exactly what you need.



You think? Wouldn't it be good to know for sure before you give electrical advice to someone?

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Wow... do you feel better now? I made one post and you... with about a thousand... have to be like that... what is wrong with you?

Oh excuse me... 4000 posts... most of them not like your last I hope.

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Originally Posted by Happyfrenchman

wow.... do you feel better now? I made one post and you... with about a thousand.... have to be like that.... what is wrong with you?

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HAHAHAHA... like what? Making sure people get correct and safe electrical advice?
Yeah, I have to be like that.

Happyfrenchman,

The issue Stan has with your advice, is that your guessing, evident by this statement:

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Originally Posted by Happyfrenchman

I think a 3/0 gauge would be sufficient for 200 amps.

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And you do not mention either it should be copper or aluminum.

Providing advice for electrical issues is not anything to be guessing at.


To lsblpn, you need #4/0 aluminum 4 wire URD cable, 4 wires twisted, and ready for direct burial.

This will be sufficient for a 200 amp feeder.

It will need conduit to sleeve it where it comes out of the ground.

If you have roads, driveway, etc, or rocky soil, you may want to consider using 3 or 4 inch PVC conduit to sleeve and protect the wire underground.

I am sure there is an electrical distributor in your local area, or perhaps several. The large box hardware stores do sell the #4/0 URD cable, check prices at all.

Gentlemen,
Thank you for your input! I can assure you there will be no guessing. My electrician will have the final say so about all this, and will do all of the work that required his expertice. I am merely learning what I need for budgeting purposes, and to be able to speak intelligently with my electrician.
What about my question concerning power to the feeder:

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I have done a Demand load calc, and it revealed 120 amp calculated. I know the main is pretty full. Is there a way to have the power company or an electrician (not sure who would be responsible for doing this) run power between the meter and the house to another panel or some sort of 120 amp circuit breaker box that supplies a 120amp sub panel? If so, with 120amp computed load, what size breaker (between the metter and the feeder cable), What size sub panel, and wire between the two would you use. Also I am assuming that I will be using 4 conductor cable (2-hot, 1 neutral, and one ground).

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Sorry for the delay in responding. I get busy.

The electrician needs to do the load calculation for a service feeder.

Since your not an electrician, I have to question how you did the calculations.

TK,
Thanks for the response. Apparently some experts feel that if your not an electrician, you're an idiot. I have no delusions what so ever of trying to do any part of this project that is over my head. If I were an electrician I wouldn't need to be on here asking any of you questions. I am trying to determine what I have to purchase, which parts of the project me or my back can do to save me some money with my electrician.

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Originally Posted by tkrussell

Sorry for the delay in responding. I get busy.

The electrician needs to do the load calculation for a service feeder.

Since your not an electrician, I have to question how you did the calculations.

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A few follow up questions:
1. I was looking at the service entrance meter box, and it appears there is a 200 amp breaker that I assume supplies the 200 amp main. There appears to be an expansion slot on the service entrance box. Could this possibly where another 200 amp breaker could be placed to service a sub panel (or would that technically be another main)? FYI: these areas of connection will be done by the electrician not me, but I need to know what my costs will be.
2. If it's a sub I'll need #3/4 correct? Or what ever gauge an updated Demand load calc revealed. If it is actually a main then a three conductor?
3. What are your sugestions as far as burying the cable? Is direct buryable cable inside of conduit over kill? Should the cable be in a separate trench from the water lines if it is in conduit?
4. For safety, what gauge and type wire do you recommend for the interior wiring? What gauge and type for larger appliances that require 240 (ie. AC unit, and water heater).
5. I have some doubts as to how accurate my Demand Load calc may be. Used the Demand load calc tool from electrical knowledge.com. It gave me a calculated value of 120 amps, but everybody seems to think this is excessive. This will basically have everything a single family dwelling would have (AC, Heat, Refrigeration, and a washer and dryer, not to mention numerous 120 outlet need for appliances, tools and electronics. What are your thoughts? Can you make any recommendations to arrive at an accurate Demand load calc.

Happyfrenchman. Stanfortyman is a professional. He gives accurate, valid advice which is helpful to the problems or projects which the original poster requires. Your careless opinions about wire size is not helpful, it's actually dangerous. Unless you can offer advice which is helpful, accurate and legal it's best that you rethink your comments before you post them. This is a do it yourself forum which often discusses methods and situations which could be potentially dangerous. It is irresponsible to offer information which could cause a possible dangerous conditions or harm to persons or property.

You people are in a dream world... I used the word "think" but actually I looked it up. But that is besides the point. This is an amateur online site. If you are a professional electrician, giving supposed expert advice on here to stated amateurs is more irresponsible than me, an ex aircraft electrician, giving an opinion, clearly stated as such.
The guy was not asking for anything but information. Why don't you go out to his place and hook him up personally if you guys are so careful and responsible?

You guy's are amazing! You are spending more time back biting each other than answering my questions. Isn't that what this forum is supposed to be for?
So, Far TK is the only one that has given me any meaningful information. I have already clearly stated that the important aspects of this project will be handled by a professional. I am merely trying to learn what I need, and what parts of the project I can safely work on.
I am not an idiot. I am a medical professional that has enough sense to figure out what I can do safely and what I can't. So get off your high horses and either answer my questions or shut up. If you all are so professional, and so concerned about amateurs safety then you shouldn't be on this site at all. Not asking you guy's to sign a waiver, just a little advice. If I were an electrical professional, I would have no need for any of you. That's the point of this site site. A disclaimer or advice about where to have a professional help is fine, but you guy's are trampling on my questions, and not helping me at all.

Isblpn, busy now, but will address your last questions later today.

Wow, uptight much?

We are here, giving our free time, to help make sure folks attempting to do work way outside their level of expertise do not go doing things they should. THIS is why we are here. It is quite obvious that most folks will do these projects either way. No one here is looking for the work, we are just helping out.
When I call someone out on guessing or giving incorrect advice you'd better be damned sure I will stand behind it. I have seen way too much bad, even dangerous, advice given out to just sit back and not say something.
This is what I do for a living. I am pretty good at it. I have no delusions that lots of folks are out there doing things themselves. In fact I get pretty regular service calls from folks who screwed something up by trying to do things maybe without asking questions first. At the same time, maybe there are some things that most folks should not be doing at all.

If this puts me on a high horse I am OK with that. The view is better from up here anyway.

TK is a VERY calm and diplomatic person. I am amazed sometimes at what he puts up with and how he handles folks. I am not him though.