Garage Subpanel addition
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Garage Subpanel addition
I have a detached garage with a single 15 am circuit. I'd like to increase electrical capacity a bit.
What I need:
Lighting circuit for 3 overhead fixtures.
Outlet circuit for workbench outlets. I'm thinking 6 bench outlets plus 2 others already in place.
Single Outlet Circuit for 110v compressor. I can't find the amp rating for this particular motor. It is a rather old compressor. It is fairly high draw because I have to be careful what outlets I use it on and no extension cords or it will trip the breaker.
Single outlet circuit for 110v 13 amp Table Saw.
I could settle for one Single Outlet circuit for both compressor and table saw and just shut off the compressor when I'm operating the saw if this is necessary.
Physical layout: Electricity for the garage is provided through a 1 inch plastic conduit set in concrete (about 20 feet). From the conduit to the Main box is about 50 feet through the attic.
Possible solutions: One is pull a new wire from the main box. This is the most difficult choice but probably the most intelligent. If I choose this I would like recommended setup for this option. (Main panel breaker, subfeed wire gauge that will go through 1 inch conduit, etc etc)
Second solution is to use existing unused 240v/30a 2 pole breaker connected to outlet in laundry. I have a gas dryer so I don't need this outlet. If I pursue this option will it suit my needs and how would I set it up.
Third solution is to have new service established directly to the garage in which case I would call an electrician.
Any and all help is greatly appreciated.
What I need:
Lighting circuit for 3 overhead fixtures.
Outlet circuit for workbench outlets. I'm thinking 6 bench outlets plus 2 others already in place.
Single Outlet Circuit for 110v compressor. I can't find the amp rating for this particular motor. It is a rather old compressor. It is fairly high draw because I have to be careful what outlets I use it on and no extension cords or it will trip the breaker.
Single outlet circuit for 110v 13 amp Table Saw.
I could settle for one Single Outlet circuit for both compressor and table saw and just shut off the compressor when I'm operating the saw if this is necessary.
Physical layout: Electricity for the garage is provided through a 1 inch plastic conduit set in concrete (about 20 feet). From the conduit to the Main box is about 50 feet through the attic.
Possible solutions: One is pull a new wire from the main box. This is the most difficult choice but probably the most intelligent. If I choose this I would like recommended setup for this option. (Main panel breaker, subfeed wire gauge that will go through 1 inch conduit, etc etc)
Second solution is to use existing unused 240v/30a 2 pole breaker connected to outlet in laundry. I have a gas dryer so I don't need this outlet. If I pursue this option will it suit my needs and how would I set it up.
Third solution is to have new service established directly to the garage in which case I would call an electrician.
Any and all help is greatly appreciated.
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Sounds pretty straightforward. First of all separate service is out of the question and not necessary.
I would opt for pulling new wires from the main box. I trust this is not a continuous pull from one end to the other and that you could pull in at least two sections. You could use the existing wire to pull the new ones or pull a rope that would then pull the new wires. 1" conduit is a good size and using lubricant, which you can get at any supply or Home Depot, it should be a relatively easy pull. Just have someone there to help you. Pushing and pulling or at least making sure things don't get tangled at the input side.
I would recommend pulling a minimum of #8 and #6 is not out of the question. You will need 4 wires. Black, red, white, and green and single wires as opposed to UF or NM would be my choice but you can use them also.
There has been some discussion of late about the need for a main shutoff or breaker at the garage and it seems in the 2008 code that is required but check on that. Prior to the current rules if you had 6 or less breakers you could forgo the main shutoff at the remote location. In any event the spared double pole breaker from you dryer would work. you could have a couple of 20A and 15A circuits out there.
The red and black wires would go to the breaker, white to neutral and green to ground at the house end and if this is your main panel neutral and ground would be tied together. At the garage location they neutral and ground must not be connected. The sub panel needs a separate neutral and ground bus. Boxes have provisions for this.
While #10 would handle the load, the reason for using the heavier wire is twofold. One it gives you room for expansion should you need it in the future and two it gives you less voltage drop.
I would opt for pulling new wires from the main box. I trust this is not a continuous pull from one end to the other and that you could pull in at least two sections. You could use the existing wire to pull the new ones or pull a rope that would then pull the new wires. 1" conduit is a good size and using lubricant, which you can get at any supply or Home Depot, it should be a relatively easy pull. Just have someone there to help you. Pushing and pulling or at least making sure things don't get tangled at the input side.
I would recommend pulling a minimum of #8 and #6 is not out of the question. You will need 4 wires. Black, red, white, and green and single wires as opposed to UF or NM would be my choice but you can use them also.
There has been some discussion of late about the need for a main shutoff or breaker at the garage and it seems in the 2008 code that is required but check on that. Prior to the current rules if you had 6 or less breakers you could forgo the main shutoff at the remote location. In any event the spared double pole breaker from you dryer would work. you could have a couple of 20A and 15A circuits out there.
The red and black wires would go to the breaker, white to neutral and green to ground at the house end and if this is your main panel neutral and ground would be tied together. At the garage location they neutral and ground must not be connected. The sub panel needs a separate neutral and ground bus. Boxes have provisions for this.
While #10 would handle the load, the reason for using the heavier wire is twofold. One it gives you room for expansion should you need it in the future and two it gives you less voltage drop.
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Carrying this a bit further.... if a disconnect is required something like this
http://www.homedepot.ca/webapp/wcs/s...k=P_PartNumber
with a box like this
http://www.homedepot.ca/webapp/wcs/s...k=P_PartNumber
http://www.homedepot.ca/webapp/wcs/s...k=P_PartNumber
with a box like this
http://www.homedepot.ca/webapp/wcs/s...k=P_PartNumber
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The garage is detached therefore a disconnect of some form is required that will disconnect all ungrounded conductors. You can have a remote disconnect as Dsc has mentioned with an mlo upstream of it. Regardless the disconnect must be located at the nearest point of entrance of the feeder to the garage. Or You can have a panel with a main breaker or a backfed breaker and hold down kit to serve as your disconnect. Whatever you use for the disconnect in your description of the needed supply branch circuits.... the disconnect will need to be a minimum of 60 amps.
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You know this is all very confusing and personally I don't care cuz I don't have to pass any codes - e.g. no one is breathing down my back and I would just install the 4 circuit panel with upstream 220v 30A breaker at the main panel BUT I suppose we are to give out proper info here based on the current code.
So With that in mind.... why do you need a 60A disconnect with a 30A protection breaker in the main panel?
Also if this is the case I would just buy the cheapest 100 or 125A main panel for the garage you could find. Use #8 with inside main panel 40A double pole or #6 with inside main panel 50A double pole.
The 100A or 125A breaker in the sub panel os basically meaningless except it serves as a main disconnect to meet code.
This might also be the cheapest approach since a 100A or 125A main panel is probably less than a separate disconnect and smaller panel box.
So With that in mind.... why do you need a 60A disconnect with a 30A protection breaker in the main panel?
Also if this is the case I would just buy the cheapest 100 or 125A main panel for the garage you could find. Use #8 with inside main panel 40A double pole or #6 with inside main panel 50A double pole.
The 100A or 125A breaker in the sub panel os basically meaningless except it serves as a main disconnect to meet code.
This might also be the cheapest approach since a 100A or 125A main panel is probably less than a separate disconnect and smaller panel box.
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Rating of Service Disconnecting Means. The service disconnecting means shall have a rating not less than the calculated load to be carried, determined in accordance with Part III, IV, or V of Article 220, as applicable. In no case shall the rating be lower than specified in 230.79(A),(B),(C), or (D).
(A) One-Circuit Installations. For installations to supply only limited loads of a single branch circuit, the service disconnecting means shall have a rating of not less than 15 amperes.
(B) Two-Circuit Installations. For installations consisting of not more than 2-wire branch circuits, the service disconnecting means shall have a rating of not less than 30 amperes.
(C) One-Family Dwellings. For a one-family dwelling, the service disconnecting means shall have a rating of not less than 100 amperes, 3-wire.
(D) All Others. For all other installations, the service disconnecting means shall have a rating of not less than 60 amperes.
The 30 amp double pole in the houses' MBP is only for over current protection and isn't a disconnect because it is remote from the detached structure.
I had a chance to re-read Bruto's post (also this one) the day after when I was more coherent and it started to come back to me. I had forgotten about the distinction between a power panel and a lighting and appliance branch circuit panel. 95% of the time your subpanel will be a L&ABCP. Thus the need for a single disconnect. A really awsome electrician I worked under a couple yers ago (who taught me most of what I know) told me to always use a main disconnect. His reasoning, I think, was because your sub will more than likely always be a L&ABCP. If it's not, then you've just exceeded code and that's even better than just "meeting" it. Or rather, maybe he didn't tell me to "always" use a single disconnect, but sub panel after sub panel install in detached buildings, it was always a L&ABCP so I just made the leap in my head that you are always required to have a single disconnect.
So even if gumbeau happens to be on 2005 code still, he is required to have a main disconnect because of what he said he was going to run. It's also required to be no less than 60 amp.
Last edited by madpenguin; 09-21-08 at 07:17 PM.
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Exactly what are you wanting? An explanation as to why the disconnect must be rated 60 amps or are you wanting the code reference that requires it?
The feeder ocpd and conductors are sized using article 220 and must be large enough for the calculatedload.
Nec 225.39(D) requires the 60 amp disconnect based on the OP's description...but I think you know this. It also must be large enough for the calculated load served by the feeder but it cannot be smaller than specified in 225.39 A-D.
So is there anything to be gained by going into the rating requirement on a DIY forum...remember we have to stay with layman terminology here.....
MadPenguin
Though essentially the same language 230 is for services so we need to go to 225 for outside feeders to detached buildings....
The feeder ocpd and conductors are sized using article 220 and must be large enough for the calculatedload.
Nec 225.39(D) requires the 60 amp disconnect based on the OP's description...but I think you know this. It also must be large enough for the calculated load served by the feeder but it cannot be smaller than specified in 225.39 A-D.
So is there anything to be gained by going into the rating requirement on a DIY forum...remember we have to stay with layman terminology here.....
MadPenguin
Though essentially the same language 230 is for services so we need to go to 225 for outside feeders to detached buildings....
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Not sure why they didn't say "refer to 230.79"...
Thanks tho. Not sure why I always gravitate towards 230.....
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Well I guess industry has not kept up with the code as evidenced by the lack of hardware (panels) that meet this requirement. If someone wants to install a simple 2 or 4 circuit panel in a detached building by code they mine as well buy a 100A panel. I see little else that would economically and ergonomically fit their needs. If you need a 60A disconnect and have only 4 circuits with a 30 breaker at the main panel this seems rather ridiculous.
I stand by my previous statements. I'd buy a 4/8 circuit box and be done with it. Unless the man is breathing down your back. Better to ask for forgiveness then permission especially if you don't have to anyway!
I stand by my previous statements. I'd buy a 4/8 circuit box and be done with it. Unless the man is breathing down your back. Better to ask for forgiveness then permission especially if you don't have to anyway!
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Yea, it's best to go with the cheapest MBP you can find. Cheapest as in cost while retaining a degree of quality. By the time you used a MLO and a backfed breaker plus tie downs, your over what a MBP would have cost. Same with using a separate disconnect box on a MLO.
I would love to find a 60 amp 12/24 or 8/16 MBP but I don't think they even exist. 125amp MBP is the lowest I can find, altho I guess I admittedly haven't looked too hard.
I would love to find a 60 amp 12/24 or 8/16 MBP but I don't think they even exist. 125amp MBP is the lowest I can find, altho I guess I admittedly haven't looked too hard.
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Well I guess industry has not kept up with the code as evidenced by the lack of hardware (panels) that meet this requirement. If someone wants to install a simple 2 or 4 circuit panel in a detached building by code they mine as well buy a 100A panel. I see little else that would economically and ergonomically fit their needs. If you need a 60A disconnect and have only 4 circuits with a 30 breaker at the main panel this seems rather ridiculous.
I stand by my previous statements. I'd buy a 4/8 circuit box and be done with it. Unless the man is breathing down your back. Better to ask for forgiveness then permission especially if you don't have to anyway!
I stand by my previous statements. I'd buy a 4/8 circuit box and be done with it. Unless the man is breathing down your back. Better to ask for forgiveness then permission especially if you don't have to anyway!
As mentioned in other threads the inspector may in fact allow the small panel.. as is... without a building feeder disconnect. As for code you must have a 60 amp disconnect, if your inspector allows the 6 disconnect rule then you may total the breakers to reach the 60 amp minimums. Your reaching awfully far about economics in a disconnect. A simple fusible A/C pullout is just fine for your disconnect. About 15 bucks around my parts.
Op really has no reason for a sub-panel and feeder IMO as a simple 20 amp multiwire branch circuit would suit his needs.
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I'm kinda partial to running a separate (large) feed from the house panel as well. A 13 amp table saw and a compressor that trips 15 amp breakers along with lighting sounds a little iffy on a multi wire. Certainly won't leave any room for future expansion.
If you decide to add more tools or a fridge or anything else for that matter, you'll have to re-run new wire again. You'll have to weigh the costs involved and decide what to do yourself ultimately. What if it's winter and the ball and chain is nagging at you and you decide to retreat to the shop. A little space heater setting on the work bench would be pretty nice to keep the ole' hands warm. There are a million and one things to plug in out there that you might not be thinking about. Many of which that could run at the same time your doing something else.
Depends on how much cash you have I guess....
If you decide to add more tools or a fridge or anything else for that matter, you'll have to re-run new wire again. You'll have to weigh the costs involved and decide what to do yourself ultimately. What if it's winter and the ball and chain is nagging at you and you decide to retreat to the shop. A little space heater setting on the work bench would be pretty nice to keep the ole' hands warm. There are a million and one things to plug in out there that you might not be thinking about. Many of which that could run at the same time your doing something else.
Depends on how much cash you have I guess....
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I'm kinda partial to running a separate (large) feed from the house panel as well. A 13 amp table saw and a compressor that trips 15 amp breakers along with lighting sounds a little iffy on a multi wire. Certainly won't leave any room for future expansion.
Do you use any method other than overkill 101 when you design for a detached garage? .... what would your guess be as for what the OP's load calculation would be for his detached garage?
I'm starting to see where the MAD before penguin comes from.....
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Wow...what a response! I waded through all of that and come to several diametrically opposed conclusions.
Anyway. I've decided to go ahead and pull new wire. It seems to me the 1 inch conduit is the limiting factor in this whole business.
I think Bruto said I could get by with a single 20 amp circuit. That may be true but I'll describe the worst case scenario and possible plans for the future.
My workshop gets a wide variety of use.
I do automotive, woodworking and general upkeep type stuff.
Automotive requires the compressor to run nearly continuously especially during painting. I may want to upgrade to a 220v compressor as well.
Woodworking requires 2 motors in operation (one working machine and a dust collector). A 220v table saw is a possibility as well.
3 light fixtures plus individual incandescent work lights at each work station.
A dehumidifier is a possibility so I can get my working stock out of the house.
I'd like to wire the garage for the maximum capacity that will go through the 1 inch conduit. I'm not gonna scrimp on a few dollars either way on boxes so that really isn't an issue.
What I need is the Main panel to sub panel pieces and parts to get the most I can out of this setup. Obviously, I'd like to have 1 220v circuit in the box for the future as well as the previously mentioned circuits.
I won't be heating the garage. I live in Houston. I won't be air conditioning or putting in reefers.
Anyway. I've decided to go ahead and pull new wire. It seems to me the 1 inch conduit is the limiting factor in this whole business.
I think Bruto said I could get by with a single 20 amp circuit. That may be true but I'll describe the worst case scenario and possible plans for the future.
My workshop gets a wide variety of use.
I do automotive, woodworking and general upkeep type stuff.
Automotive requires the compressor to run nearly continuously especially during painting. I may want to upgrade to a 220v compressor as well.
Woodworking requires 2 motors in operation (one working machine and a dust collector). A 220v table saw is a possibility as well.
3 light fixtures plus individual incandescent work lights at each work station.
A dehumidifier is a possibility so I can get my working stock out of the house.
I'd like to wire the garage for the maximum capacity that will go through the 1 inch conduit. I'm not gonna scrimp on a few dollars either way on boxes so that really isn't an issue.
What I need is the Main panel to sub panel pieces and parts to get the most I can out of this setup. Obviously, I'd like to have 1 220v circuit in the box for the future as well as the previously mentioned circuits.
I won't be heating the garage. I live in Houston. I won't be air conditioning or putting in reefers.
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Ok the garage is now a workshop... Somehow I think you left out your desire for a welder.....
You have 4 options as I see it....
1.) 60 amp 4 wire feeder (H-H-N-Grd)to a 100 amp main breaker sub panel using #6 awg nm-b or SER from the house panel to a junction box (when you transition to the conduit) and then stranded thwn individual wires inside the conduit to the sub-panel. Equipment Grounding wire (EGC) may be #10 awg copper.
2.) 70 amp 4 wire feeder if you run conduit panel to panel using #6 awg thwn and the house panel rated for 60/75C terminations. Likely that it is not too old to require 60C but it is possible. Sub-panel will be 100 amp main breaker type. EGC can be #8 copper
3.) 70 amp 4 wire feeder using #4 awg copper cable (um-b or SER) and thwn in the conduit. 100 amp main breaker panel. EGC can be #8 copper
4.) 90 amp 4 wire feeder using #4 thwn copper... conduit is panel to panel and 60/75C rating on the house panel. 100 amp main breaker panel. EGC can be #8 copper
If your jurisdiction is on the 2005 NEC or before a 3 wire feeder (H-H-N) is allowed if there are no other metallic paths to the detached workshop like water pipes or electrical cables. You will bond neutral and ground at the sub-panel when using a 3 wire feeder. This is in contrast to a 4 wire feeder where you keep neutral and ground seperated electrically.
It is usually preferred to run 4 wires to a workshop as other metallic paths generally exist eventually.
You have a choice of building disconnects either remote on the outside or inside of the workshop nearest the point of entrance of the feeder with mlo sub panel up stream anywhere you want it or intergral to the panel in which case the main breaker in the sub will serve as the disconnect but sub panel must meet the location requirements for the disconnect since the disconnect is located in the sub-panel.
My choice #4 .. workshops tend to get added items like arc stick welders that use a lot of amperage.
It would also be very prudent to take a look at your house service rating....ie...100 amp service with mostly electric would require a load calculation for the dwelling to be sure the added workshop would be adequately supported by your homes service. Usually this works out fine but there is always the exception.
Also you will need to check the house panel if choosing option #4 to be sure its bus stab rating will accomodate a 90 amp breaker.
Here is a diagram of what your installation should comply with....it is meant as a guide... a complete understanding of this type of installation and the related code requirements is necessary for personal safety. Diagram based on 2005 NEC
You have 4 options as I see it....
1.) 60 amp 4 wire feeder (H-H-N-Grd)to a 100 amp main breaker sub panel using #6 awg nm-b or SER from the house panel to a junction box (when you transition to the conduit) and then stranded thwn individual wires inside the conduit to the sub-panel. Equipment Grounding wire (EGC) may be #10 awg copper.
2.) 70 amp 4 wire feeder if you run conduit panel to panel using #6 awg thwn and the house panel rated for 60/75C terminations. Likely that it is not too old to require 60C but it is possible. Sub-panel will be 100 amp main breaker type. EGC can be #8 copper
3.) 70 amp 4 wire feeder using #4 awg copper cable (um-b or SER) and thwn in the conduit. 100 amp main breaker panel. EGC can be #8 copper
4.) 90 amp 4 wire feeder using #4 thwn copper... conduit is panel to panel and 60/75C rating on the house panel. 100 amp main breaker panel. EGC can be #8 copper
If your jurisdiction is on the 2005 NEC or before a 3 wire feeder (H-H-N) is allowed if there are no other metallic paths to the detached workshop like water pipes or electrical cables. You will bond neutral and ground at the sub-panel when using a 3 wire feeder. This is in contrast to a 4 wire feeder where you keep neutral and ground seperated electrically.
It is usually preferred to run 4 wires to a workshop as other metallic paths generally exist eventually.
You have a choice of building disconnects either remote on the outside or inside of the workshop nearest the point of entrance of the feeder with mlo sub panel up stream anywhere you want it or intergral to the panel in which case the main breaker in the sub will serve as the disconnect but sub panel must meet the location requirements for the disconnect since the disconnect is located in the sub-panel.
My choice #4 .. workshops tend to get added items like arc stick welders that use a lot of amperage.
It would also be very prudent to take a look at your house service rating....ie...100 amp service with mostly electric would require a load calculation for the dwelling to be sure the added workshop would be adequately supported by your homes service. Usually this works out fine but there is always the exception.
Also you will need to check the house panel if choosing option #4 to be sure its bus stab rating will accomodate a 90 amp breaker.
Here is a diagram of what your installation should comply with....it is meant as a guide... a complete understanding of this type of installation and the related code requirements is necessary for personal safety. Diagram based on 2005 NEC
Last edited by Bruto; 09-22-08 at 11:27 AM. Reason: added #6 awg to first option
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Thanks Bruto. i appreciate the help.
I thought the reference to 2 workbenches,compressor, and table saw gave away the workshop status in the OP
Option 1. I'm assuming AWG 6. Is that correct?
If so, will I have any problems pulling 3 AWG 6 through 1 inch plus a #10 ground?
At present there are three way switches at the garage and back door that control exterior lights. I thought I would end that arrangement due to room in the conduit. Will the necessary wiring fit in the conduit with wiring for option 1? If not no big deal. I don't like the present arrangement in any case.
The other options I think you are saying I need conduit run from Main to Sub and I don't think I want to go that route. My MAIN is mounted outside on brick and no possible conduit route looks like much fun. I'd rather not if it can be avoided. Underground would go under pool plumbing,irrigation plumbing and around the pool. Through the house would involve opening walls up.
So if 2-4 involve conduit from Main to Sub I'll rule them out probably
I thought the reference to 2 workbenches,compressor, and table saw gave away the workshop status in the OP
Option 1. I'm assuming AWG 6. Is that correct?
If so, will I have any problems pulling 3 AWG 6 through 1 inch plus a #10 ground?
At present there are three way switches at the garage and back door that control exterior lights. I thought I would end that arrangement due to room in the conduit. Will the necessary wiring fit in the conduit with wiring for option 1? If not no big deal. I don't like the present arrangement in any case.
The other options I think you are saying I need conduit run from Main to Sub and I don't think I want to go that route. My MAIN is mounted outside on brick and no possible conduit route looks like much fun. I'd rather not if it can be avoided. Underground would go under pool plumbing,irrigation plumbing and around the pool. Through the house would involve opening walls up.
So if 2-4 involve conduit from Main to Sub I'll rule them out probably
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I thought the reference to 2 workbenches,compressor, and table saw gave away the workshop status in the OP
Option 1. I'm assuming AWG 6. Is that correct?
If so, will I have any problems pulling 3 AWG 6 through 1 inch plus a #10 ground?
If so, will I have any problems pulling 3 AWG 6 through 1 inch plus a #10 ground?
1 inch pvc will allow six #6 awg conductors at 40% fill. Here is my favorite link for determining this type of calculation and many others.....
http://www.jhlarson.com/ind_tables/ind_table.htm
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Just saw your other question.. option #3 is the same as #1 with 10 more amps by using bigger cable size and thwn in conduit.
You can also keep your 3 way switch set-up as is if you like but you really should have it separate from the new feeder.
You can also keep your 3 way switch set-up as is if you like but you really should have it separate from the new feeder.
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One last thing (I Hope) you mention going underground....is that from the house panel? If so you cannot use nm-b direct buried you will need UF style cable or wires in conduit.
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This should be the "you come to us and we will spend your money forum!!"
Reading the posers original message he needed maybe 1- 15A and a couple of 20A circuits. How that got to #4 wire heaven knows. I sure would not want your guys for my electrician, not that I would ever need one.
You have to remember there is a big difference between a one man shop and a factory. You cannot run more than one piece of equipment simultaneously except for maybe the compressor. You don't just add up all the tools you have even if they are plugged in at the same time.
Reading the posers original message he needed maybe 1- 15A and a couple of 20A circuits. How that got to #4 wire heaven knows. I sure would not want your guys for my electrician, not that I would ever need one.
You have to remember there is a big difference between a one man shop and a factory. You cannot run more than one piece of equipment simultaneously except for maybe the compressor. You don't just add up all the tools you have even if they are plugged in at the same time.
#21
The point where I think there is some confusion is that only two hots and a neutral(grounded conductor) can be run to a the OP's garage (Code 225.30 - a single multiwire branch circuit). The OP described a setup that would require more than two 20A circuits, although probably no more than six. More than two circuits means having a subpanel in the garage. More than six means having a subpanel with a main disconnect. If your inspector is working off the 2008 Code, the subpanel must have a main disconnect regardless.
A panel with a 100A main and up to 12 20A breaker slots can be bought for under $75. Going lower could save a bit of money, but isn't likely to save that much, and can result in fewer usable circuits. The 12 slots I mentioned above assumes using entirely twin breakers, two handles per slot, not full-size breakers.
We got to #6 or #4 wire and a 60A breaker in the main panel because all you need is an air conditioner, a refrigerator, and that compressor running on the same side of the feed, and you're passing 40 amps. Especially if you have a bigger compressor that can run for a while filling a large tank. And what about some heating? Doesn't need to be kept toasty, but even a small baseboard heater to keep it from freezing could put another 10A onto both sides of the panel at once.
One small note about cable fill. 1" PVC will allow six #6 conductors. That does not mean it will allow a cable with three #6 and a ground... a cable has to be treated as a single object, not the sum of its contents. Pulling four wires through a pipe is much easier than pulling one cable containing those four wires.
I'd run a cable with #6 wires (standard for stoves) from your main panel, through the attic, to the start of your conduit run. Then pull individual #6 black/red/white and a #10 green from there to the garage. At the garage you have a panel with 100A disconnect, 6-12 breaker slots. Drive a ground rod outside, close to where the panel is, and run a bare #6 copper wire from the rod to the panel's ground bar. Oh, and make sure that the neutral bar inside your subpanel is not electrically connected to the ground bar or the panel shell, it must be isolated. From there' it's all about hooking up your individual circuits. It might be a bit of overkill, but the alternative is two 20A circuits with zero expandability. Now if two 20's will serve, just pull a 12/3 cable attached to a twin-pole 20A breaker, or perhaps two 12/2 cables with two single 20A breakers. Then you have one circuit for the saw/compressor, and one circuit for... everything else at once. I'd spend a bit more time and money now and not redo it later. Especially the time, why risk doing all this work twice?
A panel with a 100A main and up to 12 20A breaker slots can be bought for under $75. Going lower could save a bit of money, but isn't likely to save that much, and can result in fewer usable circuits. The 12 slots I mentioned above assumes using entirely twin breakers, two handles per slot, not full-size breakers.
We got to #6 or #4 wire and a 60A breaker in the main panel because all you need is an air conditioner, a refrigerator, and that compressor running on the same side of the feed, and you're passing 40 amps. Especially if you have a bigger compressor that can run for a while filling a large tank. And what about some heating? Doesn't need to be kept toasty, but even a small baseboard heater to keep it from freezing could put another 10A onto both sides of the panel at once.
One small note about cable fill. 1" PVC will allow six #6 conductors. That does not mean it will allow a cable with three #6 and a ground... a cable has to be treated as a single object, not the sum of its contents. Pulling four wires through a pipe is much easier than pulling one cable containing those four wires.
I'd run a cable with #6 wires (standard for stoves) from your main panel, through the attic, to the start of your conduit run. Then pull individual #6 black/red/white and a #10 green from there to the garage. At the garage you have a panel with 100A disconnect, 6-12 breaker slots. Drive a ground rod outside, close to where the panel is, and run a bare #6 copper wire from the rod to the panel's ground bar. Oh, and make sure that the neutral bar inside your subpanel is not electrically connected to the ground bar or the panel shell, it must be isolated. From there' it's all about hooking up your individual circuits. It might be a bit of overkill, but the alternative is two 20A circuits with zero expandability. Now if two 20's will serve, just pull a 12/3 cable attached to a twin-pole 20A breaker, or perhaps two 12/2 cables with two single 20A breakers. Then you have one circuit for the saw/compressor, and one circuit for... everything else at once. I'd spend a bit more time and money now and not redo it later. Especially the time, why risk doing all this work twice?
#22
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You have to remember there is a big difference between a one man shop and a factory.
I'd like to wire the garage for the maximum capacity that will go through the 1 inch conduit. I'm not gonna scrimp on a few dollars either way on boxes so that really isn't an issue.
DSC
Aside from what he is asking for... you need to reread the threads he has some expansion needs that he has mentioned in post 14... a minmum 60 amp circuit is prudent. We already went through the two 20 amp circuits and he wishes to not do this. How your going to supply those needs in post 14 on 2 20 amp circuits and a 15 amp circuit is not possible with a small 30 amp or 40 amp 2 space sub-panel. If you can do that let me know what the magic is.......
If something has been said to upset you that was not my intention at all... he wants two 240 volt tools in the future thats 4 spaces plus his other branch circuits. Anything less than 100 amp panel will not provide enough spaces. The load requirement actually reduces for the 240 volt tools vs the same at 120 volts. At any rate we are responding to what he wants and making sure he has the necessary power at his workshop and spaces in his panel for his wants and any future expansion....like a welder....or a plasma cutter...better to design for this now than later and redo as mushansamonkey has mentioned.
He is in Houston...no heat required...
Last edited by Bruto; 09-22-08 at 05:56 PM.
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I've actually thought overkill would be a great middle name... If I had the extra money, I'd run a 100amp 1/0 feeder for that bad boy...
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I am not trying to be argumentative. I think this forum is basically for novices, although we do get a few questions from the trade about interpretation of the code etc.
When we answer questions we have to be understanding of the person we are responding to. Using terms and quoting scripture means nothing to them. They don't and won't have the code books. So enough of the lpty&z panel and 204.83 crap. Someone asks a simple question and we turn it into a who can sound the most authoritative but that often does not answer the persons questions.
Quite frankly I think the detached structure provisions are way out of whack and there is little or no good hardware out there to comply. No one wants to put a 100A main panel in there garage to run some lights and a few tools. I would be willing to bet my wallet that this is one code provision that will be disregarded more than any other. While I know they don't give reasons for these things and we often have to surmise what they are thinking when they do, I suppose the reasoning is that someone using the garage might not have access to the house even though they live there. While someone with a 5000 or more square foot home could have multiple sub panels with a main disconnect at each location some further apart then that little house with the garage
I know my rant on this is lame cuz it is the law but then laws are made to be broken sometimes!
When we answer questions we have to be understanding of the person we are responding to. Using terms and quoting scripture means nothing to them. They don't and won't have the code books. So enough of the lpty&z panel and 204.83 crap. Someone asks a simple question and we turn it into a who can sound the most authoritative but that often does not answer the persons questions.
Quite frankly I think the detached structure provisions are way out of whack and there is little or no good hardware out there to comply. No one wants to put a 100A main panel in there garage to run some lights and a few tools. I would be willing to bet my wallet that this is one code provision that will be disregarded more than any other. While I know they don't give reasons for these things and we often have to surmise what they are thinking when they do, I suppose the reasoning is that someone using the garage might not have access to the house even though they live there. While someone with a 5000 or more square foot home could have multiple sub panels with a main disconnect at each location some further apart then that little house with the garage
I know my rant on this is lame cuz it is the law but then laws are made to be broken sometimes!
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When we answer questions we have to be understanding of the person we are responding to. Using terms and quoting scripture means nothing to them. They don't and won't have the code books. So enough of the lpty&z panel and 204.83 crap. Someone asks a simple question and we turn it into a who can sound the most authoritative but that often does not answer the persons questions.
Your absolutely right. Most people don't have a code book, which is why it's good to post "scripture" here on the forum. So they can read any applicable rules pertaining to their setup without having to spend 100 bucks on a book for themselves.
Whether they decide to completely disregard it or not doesn't matter. Alot of people here are electricians by trade. It is scripture. It's the law of the land (after local codes) and more importantly, it's there for everyone's safety. You can't second guess it and assume you know more than the people who laid it down in the first place. Just about everything in that book is a direct result from people dying. With each revision, things get a little safer. If we as electricians don't follow it or advocate it's use, that's being negligent in many ways.
Anyway.... I'm not trying to be argumentative either. I absolutely love my job and actually feel guilty sometimes when I get my paycheck. I take it very seriously, so I personally really can't fathom blatantly violating the NEC because I've made a snap decision that it doesn't pertain to me.
Hopefully the OP gets as much technically sound advice as possible and then only he can decide what to do with it. That is the whole point of these forums after all.
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Anytime you see Bruto, myself and dsc in one thread, you can count on "diametrically opposed conclusions"...
I thought that was great also....nearly fell out of my chair when I read that... I was laughing so hard.
To add
I have been responding on DIY forums for many years and some posters are novices and some are not. Gumbeau is certainly no novice.
I fail to understand why anyone thinks that we must treat all as too unintelligent to follow a response from a professional or anyone knowledgeable in the trade. I will continue to respond with advice that is code compliant for the safety of all readers and posters. I cannot guarantee that all my responses to this forum will be "layman". It will depend on the poster and the question asked. I will follow the forums rules and policies and not provoke intentional disrespect or argument. I will not be told however what I can and cannot say by any member or any suggestions there of.
I will comply with any corrections from a moderator.
It is unfortunate that this thread has to deal with this childishness over novices and one person who seems to think the NEC is not something that needs to be followed cause it ain't being inspected..or the NEC is out of "whack". Frankly this project of Gumbeaus requires inspection by the local codes department and would be required to follow all local and national codes. The fact that it may not be inspected does not change that requirement. Imo I have said nothing that is so freakin technical that he cannot understand it.
I apologize to Gumbeau for causing diametrically opposed conclusions,.. ... however I do want him to get what he wants in both good design for his workshop for the future and his personal concerns for his workshop.
End of Story....
#28
I do automotive, woodworking and general upkeep type stuff.
Automotive requires the compressor to run nearly continuously especially during painting. I may want to upgrade to a 220v compressor as well.
Woodworking requires 2 motors in operation (one working machine and a dust collector). A 220v table saw is a possibility as well.
3 light fixtures plus individual incandescent work lights at each work station.
A dehumidifier is a possibility so I can get my working stock out of the house.
I'd like to wire the garage for the maximum capacity that will go through the 1 inch conduit. I'm not gonna scrimp on a few dollars either way on boxes so that really isn't an issue.
What I need is the Main panel to sub panel pieces and parts to get the most I can out of this setup. Obviously, I'd like to have 1 220v circuit in the box for the future as well as the previously mentioned circuits.
I won't be heating the garage. I live in Houston. I won't be air conditioning or putting in reefers.
Automotive requires the compressor to run nearly continuously especially during painting. I may want to upgrade to a 220v compressor as well.
Woodworking requires 2 motors in operation (one working machine and a dust collector). A 220v table saw is a possibility as well.
3 light fixtures plus individual incandescent work lights at each work station.
A dehumidifier is a possibility so I can get my working stock out of the house.
I'd like to wire the garage for the maximum capacity that will go through the 1 inch conduit. I'm not gonna scrimp on a few dollars either way on boxes so that really isn't an issue.
What I need is the Main panel to sub panel pieces and parts to get the most I can out of this setup. Obviously, I'd like to have 1 220v circuit in the box for the future as well as the previously mentioned circuits.
I won't be heating the garage. I live in Houston. I won't be air conditioning or putting in reefers.
That the key word " multi use " workshop
It will be wise idea to convert the air compressor to 240 volt circuit { as long the motor have dual voltage rating go for it., Trust me on this one because it will really reduce the amout of flickering when the unit kick on.}
But one thing I can't tell this OP what to do with the set up senice Bruto did gave few suggestions with the panel size and conductor { wire } size as well.
However all it will affect by house main breaker rating if have 100 amp main breaker 60 amp feeder is the max size you can safely use. If it have 200 amp then 90 amp feeder will work very well { keep in your mind the 90 amp will get ya by suprise if not pay attetion to the code cycle ( it is effected with 2008 NEC code )}
For one inch conduct # 6's you will have no issue with at all but #4's you may squeak by depending on the condition of the exsting conduit #2's will need 1¼ inch conduit { becarefull if you have PVC there is two diffrent inside diamaiter that will get ya if not watching it }
As for the subpanel the #'s of breaker typically I use 12 or more space type and yeah automatic main breaker on it.
Merci,Marc
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Thanks Marc for the reminder..
In my earlier post I failed to include the fact that 90 amp feeders wouldn't fly with 100 amp services. Way to much demand at the workshop for a 100 amp service to support in the event a 90 amp feeder was actually derived from the calculated load of the workshop.
In my earlier post I failed to include the fact that 90 amp feeders wouldn't fly with 100 amp services. Way to much demand at the workshop for a 100 amp service to support in the event a 90 amp feeder was actually derived from the calculated load of the workshop.
#31
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I really appreciate all of the advise and differing opinions.
It always helps to get differing points of view.
I'm probably going to go with the #6 through the attic and into the conduit option with a 100/125 amp main panel with a disconnect at the garage.
Why? Because I never know when I'm going to need serious power in the shop.
The compressor I have now is quite old. At least 30 years old and maybe older. I can't even find any technical info on the GE motor although I got word back from GE with an address to write too. I've owned it for 17 years and the guy I got it from bought it in a pawnshop 25 years ago. Campbell Hausfield makes one sturdy machine. Its built two airplanes and remodeled several houses. But it will get replaced one day with a 240v shop model.
Right now I'm setting up my shop for some big woodworking projects (Basically I'm going to take my woodworking skills from journeyman frame and finish carpenter to fine furniture maker while I build furniture for my entire house). If I decide to invest in a power jointer and thickness planer I want power for those things as well.
Welder? Never welded anything although i worked in a welding shop one summer. I was the guy who got to hold the galvanized bracket inside a closet sized cabinet while the welder tacked it in place. Chances of a welder are slim but I do have a 74 Harley FXE in pieces in the garage that is on my list of major projects so i may have to learn to weld to finish that one too.
Electricity has always been my weakest area although I have done more than my share of roughing in and basic wiring having done extensive remodeling of three houses over the years.
I'm thinking I'm going to eventually have to figure out a way to climate control the garage for the woodworking projects although I doubt heat will ever be necessary.
It always helps to get differing points of view.
I'm probably going to go with the #6 through the attic and into the conduit option with a 100/125 amp main panel with a disconnect at the garage.
Why? Because I never know when I'm going to need serious power in the shop.
The compressor I have now is quite old. At least 30 years old and maybe older. I can't even find any technical info on the GE motor although I got word back from GE with an address to write too. I've owned it for 17 years and the guy I got it from bought it in a pawnshop 25 years ago. Campbell Hausfield makes one sturdy machine. Its built two airplanes and remodeled several houses. But it will get replaced one day with a 240v shop model.
Right now I'm setting up my shop for some big woodworking projects (Basically I'm going to take my woodworking skills from journeyman frame and finish carpenter to fine furniture maker while I build furniture for my entire house). If I decide to invest in a power jointer and thickness planer I want power for those things as well.
Welder? Never welded anything although i worked in a welding shop one summer. I was the guy who got to hold the galvanized bracket inside a closet sized cabinet while the welder tacked it in place. Chances of a welder are slim but I do have a 74 Harley FXE in pieces in the garage that is on my list of major projects so i may have to learn to weld to finish that one too.
Electricity has always been my weakest area although I have done more than my share of roughing in and basic wiring having done extensive remodeling of three houses over the years.
I'm thinking I'm going to eventually have to figure out a way to climate control the garage for the woodworking projects although I doubt heat will ever be necessary.
#32
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I do have a question about the grounding rod.
The electricity goes in by the man door and there is no place closer than 8-10 feet from that point that is not concrete.
What is the procedure for grounding through concrete?
Or should I just run to get off the concrete?
The electricity goes in by the man door and there is no place closer than 8-10 feet from that point that is not concrete.
What is the procedure for grounding through concrete?
Or should I just run to get off the concrete?
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Glad things are coming together for you... sorry about the other distractions....
Some day get yourself a 240 volt miller wire welder (forget about the stick welders) these are absolutely easy to use and will be invaluable to you once you learn the basics. Yep I like Miller but others are fine.
Just don't let the neighbors now you have it.......
Just run a #6 solid bare copper as far as you need to the ground rod outside the garage. Use a 'ground rod clamp' to attach it to the electrode. Use sch pvc to protect the wire were it is subject to damage...usually this is where it exists the garage and enters the ground.
Some day get yourself a 240 volt miller wire welder (forget about the stick welders) these are absolutely easy to use and will be invaluable to you once you learn the basics. Yep I like Miller but others are fine.
Just don't let the neighbors now you have it.......
Or should I just run to get off the concrete?