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Old 01-13-2010, 05:43 PM   #1
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Sub Panel install


Im looking to install a sub panel into my shop. The distance from the main panel is about 80' what gauge wire do i need to use? The subpanel will be used to power two wielders, a plasma cutter, drill press, outlets, additional shop lighting, and future additions. Ive seen that i cant put the neutrals and grounds on the same buzz bar what else should i know?

Thanks, i want to do this on my own but will probably have an electrication check out the work before turning it on.

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Old 01-13-2010, 05:52 PM   #2
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You need to compute the total load of the devices, you need to know how many circuits you want, you need to know the capacity of the main panel, and you need to know how to wire. This is not a good DIY project to start on, kind of advanced, and based on your question (don't take offense), but it sounds like you don't know much about wiring, let alone code, and its pretty tough to learn what you need over the internet. There are pros on this site who can answer essentially any electrical question, but teaching you how to wire a subpanel over the internet? I don't think so. Just my two bits.

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Old 01-13-2010, 06:02 PM   #3
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Originally Posted by Daniel Holzman View Post
You need to compute the total load of the devices, you need to know how many circuits you want, you need to know the capacity of the main panel, and you need to know how to wire. This is not a good DIY project to start on, kind of advanced, and based on your question (don't take offense), but it sounds like you don't know much about wiring, let alone code, and its pretty tough to learn what you need over the internet. There are pros on this site who can answer essentially any electrical question, but teaching you how to wire a subpanel over the internet? I don't think so. Just my two bits.
Thanks and this isnt a project that im "starting on" ive done other wireing. Wired up our old shop with no problems just never done a subpanel. I know how to wire, main panel is a 200. I can compute the total load of the devices. Not sure how many circuits maybe 10.
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Old 01-14-2010, 12:26 AM   #4
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Sub Panel install


Installed a subpanel for a workshop/garage is a very common topic here. I just did mine with the excellent help of folks here. Suggest to do a search and you will find a wealth of information. Look at Stubbies diagrams and you will find a 4 wire to detached building example. After doing reading and research, ask remaining questions and clarificaitions.
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Old 01-14-2010, 12:41 AM   #5
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Sub Panel install


Ok to cover the basic .,

For welder which type of electrique welder you have the stick type or MIG or others ?? The reason why I ask due there are few diffrent requirement for circuit sizing so read on for the rest of details.,,

Plasma cutter I will need the info plate I am pretty sure that need at least 50 amp circuit but verify with nameplate so I can able come up with correct size.

Drill press that set up for 120 or 240 volts ?

For general purpose receptale you will need 20 amp circuits the number of circuits will depending on the layout and how many items will be on that circuit.
Normally I will recomened at least 2 or more 20 amp circuits and they have to be RCD'ed { GFCI'ed }

Keep the light circuit seperated so if any thing on genral circuit will not affect the lights when the breaker trip.

Yes that correct with subpanels you MUST keep the netural and ground seperated and keep in your mind some subpanels do not have grounding bussbar that you will have to get it anyway they are only few Euros { Dollars }

As far for load demand figures do the house part first and see how much leftover you have.

I know you will say something about this part but please do understand this part first due I always address the house part first to see how much leftover from exsting 200 amp panel I know the load demand is good so it will cover typically worst case situation.

Once the load demand for house part is done then do the load demand for shop part to see what you come up.

and once you answer my above question then we will go from there.

Merci,Marc
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Old 01-14-2010, 07:46 AM   #6
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Sub Panel install


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Originally Posted by frenchelectrican View Post
As far for load demand figures do the house part first and see how much leftover you have.

I know you will say something about this part but please do understand this part first due I always address the house part first to see how much leftover from exsting 200 amp panel I know the load demand is good so it will cover typically worst case situation.

Once the load demand for house part is done then do the load demand for shop part to see what you come up.

and once you answer my above question then we will go from there.

Merci,Marc
The shop and house are on different main panels coming from the meter. Im gona ask but thinking that in this case i need to know the load demand from the main shop panel and that the house panel doesnt matter since its split at the meter and not a subpanel.

One mig, one stick, plasma requires a 50 like you thought, current drill press is 120 would like to upgrade to a more powerful one or maybe a mill in the next few years. The main box covers most of the lighting and outlet needs we have, so im visualizing one circuit of each.

Main box is less then a year old were just moving the metal fab part of our shop to the other end and would rather install install a subpanel then run low gauge wires all that length and give us more flexability in the future.

I have done a search and read quite a bit on this site, i just havent read anything where the subpanel would be powering things such as wielders and thought that might make a difference.

Thanks.
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Old 01-14-2010, 09:53 AM   #7
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Sub Panel install


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Originally Posted by eagertolearn View Post
The shop and house are on different main panels coming from the meter. Im gona ask but thinking that in this case i need to know the load demand from the main shop panel and that the house panel doesnt matter since its split at the meter and not a subpanel.

One mig, one stick, plasma requires a 50 like you thought, current drill press is 120 would like to upgrade to a more powerful one or maybe a mill in the next few years. The main box covers most of the lighting and outlet needs we have, so im visualizing one circuit of each.

Main box is less then a year old were just moving the metal fab part of our shop to the other end and would rather install install a subpanel then run low gauge wires all that length and give us more flexability in the future.

I have done a search and read quite a bit on this site, i just havent read anything where the subpanel would be powering things such as wielders and thought that might make a difference.

Thanks.
Ah, I think most folks thought this was a subpanel going into a detached workshop and to be connected from a house subpanel. But rather it's a subpanel to a main panel in the shop and the shop has a separate service entrance, meter, etc. - the current shop main panel and proposed new sub panel are under one roof - all correct?
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Old 01-14-2010, 12:44 PM   #8
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Sub Panel install


Actually I think he means a single meter with a shop and house fed from the meter. The shop is likely detached from the house. Something like this.... he will have to verify. I suspect 3 wires to each structure from the meter. If he has the meter out on a pole (farm pole) then this is a common setup for rural areas in missouri.
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Old 01-15-2010, 07:02 AM   #9
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Sub Panel install


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Originally Posted by Stubbie View Post
Actually I think he means a single meter with a shop and house fed from the meter. The shop is likely detached from the house. Something like this.... he will have to verify. I suspect 3 wires to each structure from the meter. If he has the meter out on a pole (farm pole) then this is a common setup for rural areas in missouri.
This like your diagram is what i have.
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Old 01-15-2010, 01:16 PM   #10
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What you have is service equipment located at the house and workshop both have 3 wire service entrance. Probably have a 200 amp service I can't imagine the utility would have ran 100 amp service to the meter in your situation but let us know if they did.

Assuming 200 amp service what is the main breaker size in the shop panel?

What you want to do is determine what tools and loads you have in the shop and list them by individual load requirements. This information is on the nameplates. Then determine the load that the main breaker in the shop panel will need to handle calculating in the expected load being used at the sub-panel. The main breaker needs to hold the demand from both panels. I think you understand that quite well.

The key in a shop is how many tools or pieces of equipment and lights etc will be operating at one time. Usually if a one man shop this is generally no more than two tools plus lights and heat/ac etc. If more than one man shop where multiple tools then you may have to be more aware of load management to keep from tripping breakers .... common sense really.

What I'm saying is if the shop main panel has a common demand of 30 amps per hot leg and it has a 100 amp main breaker then I have 70 amps per hot leg in reserve. So my sub panel cannot have a load of over 70 amps on one hot leg of its feeder from the shop main panel or I will trip the shop panel main breaker. If I run a welder at max output setting placing 50 amps on the two hot legs of the sub-panel feeder then my main breaker in the shop panel is 20 amps from its maximum rating. So I think you see the thinking.

There is a calculation called demand load that you can do but frankly you likely will only get confused having never done one. So just stick with real load figures from what you operate in the shop at one time..

From your description your wanting to move your main 120 and 240 volt power tools to the sub-panel. So you need to determine what the max. load those tools will place on the sub-panel after considering how many will operate at the same time. Once you know that in amps of load then you can determine your wire size for the feeder to the sub -panel. Example .. if at the most I am having a hole drilled by the 120 volt drill press with a helper and that drill press has running amps of 12 amps shown on the nameplate. In the meantime you are welding a steel plate and using 35 amps from your 240 volt stick welder. One leg of your feeder to the sub is 47 amps and one is 35 amps. Your also operating 30 amps per hot leg from your main shop panel .. heat, lights etc. so the 100 amp main breaker is holding 47 + 30 = 77 amps on one leg and the other leg is 35 + 30 = 65 amps.

Your sub-panel feeder is going to have to have an ampacity that will carry the load you calculate. In this case 47 amps is your highest load on one leg of the sub panel feeder. Your going to need at least #6 awg to carry the load. And you would likely install a 60 amp breaker in the shop panel to protect your sub-panel feeder. Voltage drop should not be any issue at 80'. You also want to consider giving yourself some extra ampacity if possible for added equipment in the future.

So if you can get us the main breaker information of your shop panel and the figures you feel will be the highest loads the sub panel and shop panel will be using we can get on with wire size and how to wire your sub-panel. Use the 'rated input current' for your welders and plasma cutters. Remember this is a calculated loadof what you feel will be the maximum load at any given time not a sum of all your tools operating at once. Don't forget that air compressors come on and off as they cycle.

BTW this is absolutely doable as a DIY project. Being handy and having wiring experience this should not pose any problem for you. Several of us here can answer any questions you have and we will help get that sub-panel installed safely.

On more thing .. since your not adding more load to the shop just moving tools to a different location there really isn't any issue with the service capacity but I would just like to know what it is so you can plan for the future.
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Old 01-22-2010, 05:11 PM   #11
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Originally Posted by Stubbie View Post
What you have is service equipment located at the house and workshop both have 3 wire service entrance. Probably have a 200 amp service I can't imagine the utility would have ran 100 amp service to the meter in your situation but let us know if they did.

Assuming 200 amp service what is the main breaker size in the shop panel?

What you want to do is determine what tools and loads you have in the shop and list them by individual load requirements. This information is on the nameplates. Then determine the load that the main breaker in the shop panel will need to handle calculating in the expected load being used at the sub-panel. The main breaker needs to hold the demand from both panels. I think you understand that quite well.

The key in a shop is how many tools or pieces of equipment and lights etc will be operating at one time. Usually if a one man shop this is generally no more than two tools plus lights and heat/ac etc. If more than one man shop where multiple tools then you may have to be more aware of load management to keep from tripping breakers .... common sense really.

What I'm saying is if the shop main panel has a common demand of 30 amps per hot leg and it has a 100 amp main breaker then I have 70 amps per hot leg in reserve. So my sub panel cannot have a load of over 70 amps on one hot leg of its feeder from the shop main panel or I will trip the shop panel main breaker. If I run a welder at max output setting placing 50 amps on the two hot legs of the sub-panel feeder then my main breaker in the shop panel is 20 amps from its maximum rating. So I think you see the thinking.

There is a calculation called demand load that you can do but frankly you likely will only get confused having never done one. So just stick with real load figures from what you operate in the shop at one time..

From your description your wanting to move your main 120 and 240 volt power tools to the sub-panel. So you need to determine what the max. load those tools will place on the sub-panel after considering how many will operate at the same time. Once you know that in amps of load then you can determine your wire size for the feeder to the sub -panel. Example .. if at the most I am having a hole drilled by the 120 volt drill press with a helper and that drill press has running amps of 12 amps shown on the nameplate. In the meantime you are welding a steel plate and using 35 amps from your 240 volt stick welder. One leg of your feeder to the sub is 47 amps and one is 35 amps. Your also operating 30 amps per hot leg from your main shop panel .. heat, lights etc. so the 100 amp main breaker is holding 47 + 30 = 77 amps on one leg and the other leg is 35 + 30 = 65 amps.

Your sub-panel feeder is going to have to have an ampacity that will carry the load you calculate. In this case 47 amps is your highest load on one leg of the sub panel feeder. Your going to need at least #6 awg to carry the load. And you would likely install a 60 amp breaker in the shop panel to protect your sub-panel feeder. Voltage drop should not be any issue at 80'. You also want to consider giving yourself some extra ampacity if possible for added equipment in the future.

So if you can get us the main breaker information of your shop panel and the figures you feel will be the highest loads the sub panel and shop panel will be using we can get on with wire size and how to wire your sub-panel. Use the 'rated input current' for your welders and plasma cutters. Remember this is a calculated loadof what you feel will be the maximum load at any given time not a sum of all your tools operating at once. Don't forget that air compressors come on and off as they cycle.

BTW this is absolutely doable as a DIY project. Being handy and having wiring experience this should not pose any problem for you. Several of us here can answer any questions you have and we will help get that sub-panel installed safely.

On more thing .. since your not adding more load to the shop just moving tools to a different location there really isn't any issue with the service capacity but I would just like to know what it is so you can plan for the future.
This post really helped. I got the sub panel installed today. I had to move a few breakers in the main 200a panel so i didnt have to much other stuff on the leg that i put the 100a sub panel on. Ran 2-2-4 from the main to the sub and used a 125 lug panel for the sub. Right now it has 2 220 circuits and 2 20 one with lights and the other with outlets. Its a 12 circuit panel so i can still add on, i anticipate needing at least 1 more 220 in the near future. Everything works.

The air compressor (on the main) didnt kick in while i was using the wielder or plasma cutter, but i dont think itll trip the main panel when it comes on. Only way it might is if were using both wielders and the plasma cutter at the same time when it flips on and i dont see a situation where wed be using all 3 at the same time in what is normally a 2 person shop.

I meant to take pictures before i put the panel on but forgot to take my camera to the farm today.

Thanks for the help, other then the first poster everyone was very helpful.

One final question, why do you have to hook up the neutral and grounds seperate on a subpanel?
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Old 01-22-2010, 05:38 PM   #12
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Sub Panel install


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Originally Posted by Stubbie View Post
Actually I think he means a single meter with a shop and house fed from the meter. The shop is likely detached from the house. Something like this.... he will have to verify. I suspect 3 wires to each structure from the meter. If he has the meter out on a pole (farm pole) then this is a common setup for rural areas in missouri.
Stubbie do you have any pics of a farm pole, esp one that feeds several areas? Could use some for a class. Thanks in advance.
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Old 01-22-2010, 07:34 PM   #13
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One final question, why do you have to hook up the neutral and grounds seperate on a subpanel?
There is to be only one current carring return path. Multiple/redundant grounds are ok. So the sub panel ground and neutral are separated.
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Old 01-22-2010, 11:20 PM   #14
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Originally Posted by eagertolearn View Post
Im looking to install a sub panel into my shop. The distance from the main panel is about 80' what gauge wire do i need to use? The subpanel will be used to power two wielders, a plasma cutter, drill press, outlets, additional shop lighting, and future additions. Ive seen that i cant put the neutrals and grounds on the same buzz bar what else should i know?

Thanks, i want to do this on my own but will probably have an electrication check out the work before turning it on.
sounds like you need a 200a service just to feed what youre adding there,welders can put a major load on system depending on size of machine.
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Old 01-22-2010, 11:56 PM   #15
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Stubbie do you have any pics of a farm pole, esp one that feeds several areas? Could use some for a class. Thanks in advance.
I'm sure I have some but I'll have to take a look. Check back in a few days to this thread. I'll do my best to have them posted but I'm not sure at this point if I can locate them. I have lot of pictures....


You might look in the NEC NFPA 2008 handbook at art.547 they have some nice illustrations of farm pole distribuiton points. They do not have an example of a meter with double lugs where they feed a home and barn or other building from a pole. But what we do is install sub feed lugs to the cl 200 meter like below and feed the barn panel 100 amps (service equipment at the barn) and same with the farm home. Or we will catch service disconnects at the pole and run feeders to the buildings and home.

http://www.milbankmfg.com/products/c...pConnector.pdf

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