A few electrical questions

[Matt Neil]

Exterior of the barn is done (mostly). I hope to wire the interior half (23' x 29') that will be the shop this Winter and have some questions.
1. I want to place a disconnect switch between the 200 amp main panel and the 100 amp sub that will power the shop. I have 4 year old triplets who will only get more curious around power tools. I'm not sure what a disconnect switch is, can someone provide a link or pic? I tried google but found a huge variety and not sure really what people on other threads are referring to.
2. How many 120 outlets do you place on a circuit if uncertain what tools will be on it? Do you stop at 10 duplexes or would you go more duplexes to cover more wall? 16?
3. I'm thinking of running 2 gang boxes with each duplex on a separate circuit. But I'm not sure if that's really needed. Would running every other quad on same circuits work just as well if the outlets are 4' apart? Basically, is there a benefit of having two 12/2 cables in each box to justify cramming the extra cable in there?
4. If I have light circuits running from main panel (before disconnect), and have extra capacity, should I place an outlet for the overhead dust filter? Or should I run that on the circuit of bench outlets for the chargers which also will run from the main panel?
5. If I place a wood floor on sleepers and insulation on top of slab, can I use romex under that floor? Does it need to be UL? Staple it to the sleepers or just lay it down on the slab?

The temps are cooling off here in South Dakota. Soon I'll feel no guilt for not working on things outdoors. Last week I called my state electrical board and asked if I add a few outlets to an old barn, if I needed a permit. Yes, I downplayed the scope of the project a bit. Adding outlets to existing circuits is ok, when adding new circuits they want a permit.

[Joseph Tarantino]

Exterior of the barn is done (mostly). I hope to wire the interior half (23' x 29') that will be the shop this Winter and have some questions.
1. I want to place a disconnect switch between the 200 amp main panel and the 100 amp sub that will power the shop. I have 4 year old triplets who will only get more curious around power tools. I'm not sure what a disconnect switch is, can someone provide a link or pic? I tried google but found a huge variety and not sure really what people on other threads are referring to.

something like this is probably what you are looking for:

http://www.homedepot.com/webapp/wcs/...0#.UHgmJm9_uSo

2. How many 120 outlets do you place on a circuit if uncertain what tools will be on it? Do you stop at 10 duplexes or would you go more duplexes to cover more wall? 16?

humbly suggest you check with your local building dept or electrical inspector. codes change over time. i've always kept 10 number to 10 on a 20A circuit.

3. I'm thinking of running 2 gang boxes with each duplex on a separate circuit. But I'm not sure if that's really needed. Would running every other quad on same circuits work just as well if the outlets are 4' apart? Basically, is there a benefit of having two 12/2 cables in each box to justify cramming the extra cable in there?

i don't see the benefit. i'd sooner intersperse the circuits. every other box is different than the one before it. like a/b/a/b/a/b.

4. If I have light circuits running from main panel (before disconnect), and have extra capacity, should I place an outlet for the overhead dust filter? Or should I run that on the circuit of bench outlets for the chargers which also will run from the main panel?

they draw so little i don' think it matters. personally, i'd want all power in my shop, for lights, tools, accessories, whatever, to come off the sub panel. that way, your proposed disconnect will disable everything, for the safety of your triplets. or you could run a power tool subpanel off your main sub-panel and power all tools off that second sub panel, with a disconnect. that way, the shop would have power for lights, heat/a/c and light duty applications (computer, radio, fridge, etc.) and you could kill all the circuits with potentially harmful tools.

5. If I place a wood floor on sleepers and insulation on top of slab, can I use romex under that floor? Does it need to be UL? Staple it to the sleepers or just lay it down on the slab?

i'm not an electrician, but i would put it in conduit. you don;t want a screw or nail accidently going through 3/4" plywood floor/subfloor and hitting romex wiring. but i'd check with my local authorities first.

The temps are cooling off here in South Dakota. Soon I'll feel no guilt for not working on things outdoors. Last week I called my state electrical board and asked if I add a few outlets to an old barn, if I needed a permit. Yes, I downplayed the scope of the project a bit. Adding outlets to existing circuits is ok, when adding new circuits they want a permit.

whenever it comes to plumbing and electrical, invariably, that which is safer is what gets approved.

[Steve Meliza]

1. I want to place a disconnect switch between the 200 amp main panel and the 100 amp sub that will power the shop. I have 4 year old triplets who will only get more curious around power tools. I'm not sure what a disconnect switch is, can someone provide a link or pic? I tried google but found a huge variety and not sure really what people on other threads are referring to.

Do you want do have a disconnect with a key or padlock or just have the switch too high for young people to reach? If you must have a key or padlock then you can get a disconnect that you stick a key into and rotate (as seen on Norm's garage workshop episode) or snap a padlock onto a big disconnect like Joseph linked to. If you don't need a key then mount the panel as high as code will allow and use the panel breaker (located at the top) to kill power to the whole panel, or just trip the breakers for the circuits of concern. By the time they are old enough to reach you will have had time to teach them shop safety.

2. How many 120 outlets do you place on a circuit if uncertain what tools will be on it? Do you stop at 10 duplexes or would you go more duplexes to cover more wall? 16?

I don't believe there is a limit for residential, but if this is considered a commercial application I think it may be something like 10 or 15? I'd ask the inspector or just limit the number to 10 or less so it isn't an issue. If you have two walls or a really really long wall then consider using 3 or 4 circuits for the 120V outlets.

3. I'm thinking of running 2 gang boxes with each duplex on a separate circuit. But I'm not sure if that's really needed. Would running every other quad on same circuits work just as well if the outlets are 4' apart? Basically, is there a benefit of having two 12/2 cables in each box to justify cramming the extra cable in there?

I've got 4" boxes every 4' and the duplex plug on the left side is from one circuit and the duplex on the right from another. This makes it much easier for me to know how my loads are balanced across those two 120V circuits and I don't have to mark or number each 4" box like you would if every other box was one the same circuit. Imagine trying to count outlet boxes to see if you're using the same circuit as the one on the far side of the shop. It is more work to wire up, but I find the convenience has long since washed away the memories of wiring up all those outlets. Just make sure you don't violate wire fill in the boxes. I used 2.5" deep metal boxes with metal faceplates that added another 6.5 cu. in. or so which allowed me to just come in under the limit, but I also had a third pair of conductors for another circuit passing through the outlet boxes which bumped up my fill a little (I was using 1/2" EMT and #12 THHN wires).

4. If I have light circuits running from main panel (before disconnect), and have extra capacity, should I place an outlet for the overhead dust filter? Or should I run that on the circuit of bench outlets for the chargers which also will run from the main panel?

I like to keep lights on lighting circuits and nothing else on there with them. I probably prefer it that way because I place a very high importance on keeping the lights on an not having a faulty motor plunge me into darkness while in the middle of a cut. Any how, depending on how you choose to implement your disconnect you may need a few circuits that are on all the time for such loads.

5. If I place a wood floor on sleepers and insulation on top of slab, can I use romex under that floor? Does it need to be UL? Staple it to the sleepers or just lay it down on the slab?

I'm really not sure how code applies to this situation and would ask the inspector, but you would need to staple the romex to something. You might also want to put in one or two runs of empty 1/2" conduit so that later on you can pull through more wire under the floor if you decide to add another circuit (eg. new 240V toy, err tool). If it were me I'd go EMT under the floor for the reasons mentioned by Joseph.

[Thomas Bank]

1. I want to place a disconnect switch between the 200 amp main panel and the 100 amp sub that will power the shop. I have 4 year old triplets who will only get more curious around power tools. I'm not sure what a disconnect switch is, can someone provide a link or pic? I tried google but found a huge variety and not sure really what people on other threads are referring to.

You don't really need a separate disconnect. You can put a main breaker in the sub-panel which would act as a switch for everything in the sub-panel. Then you can put a lock on the panel door. Or put a lock on the main panel door and just switch off the breaker to the sub-panel when you want to deny access. Not sure if the Borgs carry the kits, but you can get them at your local electrical supply.

2. How many 120 outlets do you place on a circuit if uncertain what tools will be on it? Do you stop at 10 duplexes or would you go more duplexes to cover more wall? 16?

The NEC does not have a specific rule for number of receptacles, but rather a calculation. For 15 ampere circuits, the calculation is as follows: 120 volts x 15 amperes = 1800 VA/180 VA = 10 receptacles, and for 20 ampere circuits, 120 volts x 20 amperes = 2400 VA/180 VA = 13 receptacles.

3. I'm thinking of running 2 gang boxes with each duplex on a separate circuit. But I'm not sure if that's really needed. Would running every other quad on same circuits work just as well if the outlets are 4' apart? Basically, is there a benefit of having two 12/2 cables in each box to justify cramming the extra cable in there?

In my shop, I went with alternating receptacles. The idea being that if I were using two tools at once (tool plus dust collector, for instance) I could plug them into alternate circuits if needed. Or, if I happened to trip a breaker, I could move over to the alternate circuit to finish my current job before having to go down to the panel to reset the breaker. It has worked fine for me for 14 years. I really doubt the alternate circuits on each double receptacle would be worth the trouble. Put a dab of paint on the screw to color code which circuit is which.

4. If I have light circuits running from main panel (before disconnect), and have extra capacity, should I place an outlet for the overhead dust filter? Or should I run that on the circuit of bench outlets for the chargers which also will run from the main panel?

I agree with Joseph on bringing everything into the sub-panel for convenience. Also, I think you're saying separate circuits for these items but just to be sure, I always have lights on a separate circuit from any receptacles. In the event of a tripped breaker, it is always nice to not lose your lights as well.

5. If I place a wood floor on sleepers and insulation on top of slab, can I use romex under that floor? Does it need to be UL? Staple it to the sleepers or just lay it down on the slab?

You would have to at least staple it to the sleepers - you can't leave it loose. Also depends on whether you're using furring or 2x material as sleepers. If you don't have 1 1/4" clearance from the edge of the framing to the wiring, you need to install the metal plates or run the wiring in conduit to protect it. Not sure what you mean about being UL - all wiring has to be UL approved. Do you mean UF - underground feeder? Like whether it needs to be water/moisture proof since it is on the slab? Again, you can't just have it laying loose on the slab and you should have a vapor barrier between the slab and floor, so it shouldn't be a problem.

Last week I called my state electrical board and asked if I add a few outlets to an old barn, if I needed a permit. Yes, I downplayed the scope of the project a bit. Adding outlets to existing circuits is ok, when adding new circuits they want a permit.

A sub-panel should have an inspection sticker on it. If you were ever to have any problems that could be traced back to the wiring and that sticker wasn't there, you may run into problems with your insurance. Electrical is something that I pretty much always do by the book.

[Phillip Bogle]

You don't really need a separate disconnect. You can put a main breaker in the sub-panel which would act as a switch for everything in the sub-panel. Then you can put a lock on the panel door. Or put a lock on the main panel door and just switch off the breaker to the sub-panel when you want to deny access. Not sure if the Borgs carry the kits, but you can get them at your local electrical supply.

The NEC does not have a specific rule for number of receptacles, but rather a calculation. For 15 ampere circuits, the calculation is as follows: 120 volts x 15 amperes = 1800 VA/180 VA = 10 receptacles, and for 20 ampere circuits, 120 volts x 20 amperes = 2400 VA/180 VA = 13 receptacles.

In my shop, I went with alternating receptacles. The idea being that if I were using two tools at once (tool plus dust collector, for instance) I could plug them into alternate circuits if needed. Or, if I happened to trip a breaker, I could move over to the alternate circuit to finish my current job before having to go down to the panel to reset the breaker. It has worked fine for me for 14 years. I really doubt the alternate circuits on each double receptacle would be worth the trouble. Put a dab of paint on the screw to color code which circuit is which.

I agree with Joseph on bringing everything into the sub-panel for convenience. Also, I think you're saying separate circuits for these items but just to be sure, I always have lights on a separate circuit from any receptacles. In the event of a tripped breaker, it is always nice to not lose your lights as well.

You would have to at least staple it to the sleepers - you can't leave it loose. Also depends on whether you're using furring or 2x material as sleepers. If you don't have 1 1/4" clearance from the edge of the framing to the wiring, you need to install the metal plates or run the wiring in conduit to protect it. Not sure what you mean about being UL - all wiring has to be UL approved. Do you mean UF - underground feeder? Like whether it needs to be water/moisture proof since it is on the slab? Again, you can't just have it laying loose on the slab and you should have a vapor barrier between the slab and floor, so it shouldn't be a problem.

A sub-panel should have an inspection sticker on it. If you were ever to have any problems that could be traced back to the wiring and that sticker wasn't there, you may run into problems with your insurance. Electrical is something that I pretty much always do by the book.

Everything Thomas has said is good. I only offer a couple of notes. NEVER use the tool disconnect and lights on the same circuit. Lights must be on separate circuits. If you need to make an emergency disconnect at the panel, you would kill the lights at the same time and not be able render first aid. If you are concerned about circuit security -- with children it is valid concern -- consider a lock out tag out system panel. There can be some small ones available at your electrical supplier.
Phil Bogle

[Jim Neeley]

"How many 120 outlets do you place on a circuit if uncertain what tools will be on it? Do you stop at 10 duplexes or would you go more duplexes to cover more wall?"

Matt,

I agree with Phillip that everything said here is good and I'd like to offer another consideration for you to mull upon.

The NEC has it's code issues and they should be met or exceeded but you also need to ask yourself how you are going to be using them and what / how many concurrent loads you will be placing on them. For example, if you are using a 15A router with a 11A shop-vac for dust collection on the running router, you need two separate circuits to handle the load.

If you also have old eyes, like mine, and like your work space flooded in light, this must be accounted for as well. I often used a 1000W double-headed halogen tripod-style light to flood my work area. If I want to use this with the router and shop vac, this will require a third circuit. You can always choose to install more wire and breakers than the NEC requires; it's up to you.

Every situation and user are different, and there's no need to get ludicrous here, but there's an old saying in the business: "Saying 'But it meets code!?!' is the same as 'This is the minimum I can get by with, doing anything less would be illegal.'". I recommend being practical, but conservative, unless you wish to be making changes / upgrades in the future.

Just my $0.02...

Jim

[Steve Meliza]

Be careful about locking doors to the panels as this prevents ready access in an emergency. For example, only lock the panel door if the whole panel has been de-energized. I believe that the NEC only allows locked breaker panels when someone with a key is always at hand.

[Joseph Tarantino]

........You might also want to put in one or two runs of empty 1/2" conduit so that later on you can pull through more wire under the floor if you decide to add another circuit (eg. new 240V toy, err tool).........

whatever you do electrically, leaving chases (with caps, if empty, until used) is a great idea. but i'd leave as large a piece of conduit that i could (e.g., 1.5") with 2 drags in the chase for future pulls. it's always easier to pull through larger conduit rather than smaller conduit.

[Thomas Bank]

Thanks for the catch, Phillip and Steve. Yes, the panel should only be locked if everything is de-energized.

[Matt Neil]

Thanks for the great feedback. The pic of the disconnect looks like something that would work well. I didn't think I really needed a lock, but one could be added so that as they get taller and I'm still too nervous, I can lock it later in life. I do plan to run lights from the main panel. I want to be able to get into the shop to grab tools so will need light but don't want to turn on the disconnect each time. I also need heat and battery charges going. It won't be inconvenient because the main panel is only 25' down the wall. I'm partitioning half of my 30' x 50' barn so I'm not conditioning the entire space. I've read other posts that recommend not using the breaker as a regular disconnect - the thought being that it will wear out sooner that way.

As I suspected, I may end up regretting wiring 10 duplexes on each circuit and will cut that back. I'd rather do the extra work now. I want to run romex in the walls, then closed cell insulation and 3/4" plywood screwed down over that. Then I have the choice of getting back into the walls if I wish or just run conduit for future expansion that I didn't think of now.

With regards to the romex under the floor, I was thinking UF when I typed UL. Good catch.