Sub panel for wood shop garage

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Old 12-17-13, 06:08 PM
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Sub panel for wood shop garage

Hello all, Mike here from Cranston, Rhode Island.
I have a home built in 1920 with a detached garage.
Originally had a 60 amp service with the old tube wiring.

I have since had a new service professionally installed. 200 amp with 1 60 amp subpanel. The subpanel feeds the attic which I converted into 2 bedrooms and a full bath. Currently light usage.

The main panel is full. I have a woodworking shop in my basement and filled up the main panel with 2 240 and a bunch of 120 circuits.
Can I add 2 more subpanels?

I would like to add a 60 amp 8 breaker subpanel to feed the basement lights and receptacles. I'll leave the electric dryer in the main panel.

Then I want to add another subpanel for my 10' x 20' detached garage as I am moving my wood shop to it next summer once the renovations are complete.
The garage is a 75 foot run from the main panel.

I want to add a 100 amp subpanel in the garage. I will install a grounding rod for the panel.
The garage is a tinder box. I'm rebuilding it. The walls are old and dry 1x6 sheathing covered by 1/2" new plywood and red cedar shingles. The interior will have southern yellow pine on floor and eastern white pine on the walls and ceiling. No sheetrock! Yeah, I got a big fire extinguisher. Replacing the overhead door with 2 carriage doors. More wood. And I'm adding a side door. Wood. I'm adding a fire alarm.
Here are my questions.

Should I use 2 50 amp breakers in the main panel to feed the sub?
I happen to have a new spare 100 amp main panel with a 100 amp main breaker and 20 breaker slots. Can I use it?

Run 6/2 wire from the main to the garage sub?
Cerrowire 125 ft. 6/2 NM-B Indoor Residential Electrical Wire? Found on HD site.
Then add a ground to one neutral bus to the copper grounding rod? Or do I need to purchase another actual subpanel without the main breaker?

I need to run the wire under ground. I realize there is UF for this purpose.
But can I run a pipe through my basement wall and underground to the garage? If so, Metal or PVC?

The garage subpanel will power a dozen 4 foot 2 bulb florescent lights and 2 240 volt tools. A table saw and a wood/sawdust collector.
Plan to have 10/3 30 amp dedicated circuits for each.

I will continuously run a dehumidifier, an air filter and small oil filled heater when necessary.
The sawdust collector runs whenever any other tool runs. The air filter will run whenever I am in the shop.

All the other tools and accessories are 120 volt and tend to run one at a time.
I plan to run 3 12/3 circuits for the 12 lights.
I will also add 16 receptacles on 4 12/3 circuits.
Do the receptacles need to be GFCI?

I'm sure I didn't think of everything here but it's a start.
Oh yeah. When the main breakers in the main panel are turned off, what's the risk factor?
I'm assuming the hot bus bars are dead?
But the neutral bus bars could in theory still be dangerous assuming something goes wrong at the pole?
Trying to plan this out correctly so I don't need to place any calls with my insurance company or the family undertaker.
Thanks.
 
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Old 12-17-13, 07:19 PM
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The feeder will be sized for the loads and will need to be 4 conductors.

The lighting cannot be on a 30 amp circuit.

PVC is to work with and does not rust out.

For a 120 circuit you will only need xx-2 cables, not xx-3. The ground is not counted.

Receptacles in the outbuilding will need GFI protection.

Even with the main breaker of the incoming lugs will still be hot in the service panel.
 
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Old 12-17-13, 07:36 PM
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Run 6/2 wire from the main to the garage sub?
Cerrowire 125 ft. 6/2 NM-B Indoor Residential Electrical Wire? Found on HD site.
You cannot use NM-B cable outside or underground in conduit. The preferred wire would be 4 - THHN/THWN separate conductors. If you are running a 60 amp feeder, I'd suggest 3 - #6 (1 Blk, 1 Red & 1 Wht) and 1 - #10 Grn ground in 1" PVC conduit buried with 18" of cover. You can use the 100 amp main breaker panel in the garage, the 100 amp main breaker will be the disconnect.
 
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Old 12-17-13, 08:11 PM
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If you want use the 100 amp breaker to feed the garage you will need to use #3 THWN wire (#6 ground) It is allowed to feed it with a small breaker in the main panel.

If it was me, I would install the 100 amp breaker in the main panel, feed a 100 amp sub panel in the basement (fed with #3, main breaker not required) then feed the 100 amp main breaker sub panel in the garage with a 60 amp feed. That feeder could come from the main panel or the 100 amp sub in the basement.
 
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Old 12-17-13, 08:17 PM
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ok total wattage
table saw 220 x 12 = 2640
air cleaner 115 x 3 = 345
chip collector 220 x 12 =2640
dehumidifier 115 x 4.8 =552
lights 24 40 watt tubes 960
heater 1500
--------
8637 total wattage
8637 x 1.25 =10796 /230 = 47 amps

So, I don't need a 100 amp panel? Sell the one I have on craigs list?
A 50 amp panel would suffice assuming I run everything listed above concurrently and nothing more. Add a little safety factor and call it 60 amps?
So 2 30 amp breakers in the service panel? Connect to sub with 8/3 cable with a ground? That's considered 4 conductor cable?
The lighting will be on a 20 amp circuit. Yeah, I said 12/3. meant 12/2. You got me, I was counting the ground.
I would imagine the incoming lugs would be hot unless the street service was pulled. But not the hot or neutral bus bars if the main breakers are off? Not that I would touch the hot busses anyway. Just need to understand it.
 
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Old 12-17-13, 08:22 PM
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Oh, more great information! Thanks!
I'll ponder all this and update my plan. Got all winter to figure it out.
But time to say goodnight Dick.
Yeah, I'm old enough to remember that show.
 
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Old 12-17-13, 10:04 PM
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So, I don't need a 100 amp panel? Sell the one I have on craigs list?
You can keep and use that panel. Feed it from a 60A 240V breaker. The 100A breaker in it will serve as a service disconnect.

A 50 amp panel would suffice assuming I run everything listed above concurrently and nothing more. Add a little safety factor and call it 60 amps?
50A might be a little low. 60A will suffice.

So 2 30 amp breakers in the service panel? Connect to sub with 8/3 cable with a ground? That's considered 4 conductor cable?
No. Even if you tied them together you'd still only have 30A. One 60A 240V 2-pole breaker in your main panel.

No cable. 3 #6 AWG THWN copper conductors in PVC conduit, plus one #10 ground.
 
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Old 12-18-13, 07:01 PM
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Call me anal but I donít like to make assumptions. Latest draft of my wiring project.
Wire confusion. THHN wire and THWN wire seem to be grouped together as outdoor wire. But in detailed web views, the thhn/thwn is classified as thhn. That leads me to believe THHN can be used for wet applications? Additionally, for example, thhn 3 awg is rated at 110 amps, not 100 amps. Is this a safety thing whereby the panel load cannot draw 100% of the wire amp capacity using a 100 amp breaker?

Main panel: 200 amp with 100 amp double pole breaker to feed basement sub panel.

Basement subpanel: No breaker. Install next to service panel. Feed with indoor Electrical Wire 3 AWG wire. 1 black, 1 red, 1 white, 1 green ground. Some confusion here. I don't find this wire jacketed. So, use 4 separate strands? If so, I would imagine I need to run it through a metal conduit?
Use 15 amp breakers on the 14/2 to feed basement lights and receptacles.
Add a 70 amp (a little more wiggle room vs 60) double pole breaker for the garage subpanel.

Garage subpanel: Use my service panel box with the 100 amp breaker already installed.
Run 75' of THHN/THWN 4 AWG wire through a PVC conduit underground.
If I run a red, black, white and ground from house subpanel to garage subpanel with 100 amp breaker, where do I hook each wire? Black and red to 100 amp breaker lugs? White to neutral bus? Ground to what? See where Iím going here?
Outbuilding needs its own ground and not grounded to main service panel?
My 100 amp panel box has 2 neutral bus bars. The green ground screw is not installed. But the neutral bus bars are connected. Do I run all white wires to 1 bar and bare copper grounds to the other? Does it matter? And then run a 10 gauge ground to the left bus using the supplied connector and then outside to the grounding rod?

Add a double pole 20 amp breaker and connect to a 240 volt receptacle via 12/3 with ground for each 240 volt appliance.
Almost there! Thanx!
 
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Old 12-18-13, 07:28 PM
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THHN wire and THWN wire seem to be grouped together as outdoor wire. But in detailed web views, the thhn/thwn is classified as thhn. That leads me to believe THHN can be used for wet
THHN is not rated for wet areas, but since most THHN is also dual rated as THWN, it can be used in wet areas, but it must be shown as THHN/THWN. The "W" is the key.

That leads me to believe THHN can be used for wet applications? Additionally, for example, thhn 3 awg is rated at 110 amps, not 100 amps. Is this a safety thing whereby the panel load cannot draw 100% of the wire amp capacity using a 100 amp breaker?
Use the 75 degree column, #3 is rated for 100 amps. #4 is too small for a 100 amp branch feeder with few exceptions.

If I run a red, black, white and ground from house subpanel to garage subpanel with 100 amp breaker, where do I hook each wire? Black and red to 100 amp breaker lugs? White to neutral bus? Ground to what?
Install an accessory ground bar in the subpanel. DO NOT install the green box bonding screw or jumper in this panel because the neutral and ground must be isolated.

Black and red to 100 amp breaker lugs?
Yes.

My 100 amp panel box has 2 neutral bus bars. The green ground screw is not installed. But the neutral bus bars are connected. Do I run all white wires to 1 bar and bare copper grounds to the other?
Throw the green bonding screw away, see above comment. The new white neutral conductors from the new branch circuits terminate on the neutral bar. The ground wires will terminate on the new accessory gtround bar you are installing. From this ground bar, install a #6 copper (solid or stranded - insulated or bare) GEC to the ground rod. I prefer 7-strand bare #6 copper secured with Jiffy 105C 1-hole straps.

Outbuilding needs its own ground and not grounded to main service panel?
The outbuilding will have both a connection to the ground rod and to the main service panel ground, both terminate at the accessory ground bar you will install. That's why you need to run a 4-wire feeder from the main service panel.

Add a double pole 20 amp breaker and connect to a 240 volt receptacle via 12/3 with ground for each 240 volt appliance.
For a 20A, 240 volt appliance you need to run 12-2 w/G NM-B cable. For a 20A, 120/240 volt appliance you need to run 12-3 w/G NM-B cable. A pure 240 volt circuit only needs 2 insulated conductors and 1 ground conductor, hence, 12-2 NM-B cable.
 
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Old 12-18-13, 07:47 PM
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ok total wattage
table saw 220 x 12 = 2640
air cleaner 115 x 3 = 345
chip collector 220 x 12 =2640
dehumidifier 115 x 4.8 =552
lights 24 40 watt tubes 960
heater 1500
--------
8637 total wattage
8637 x 1.25 =10796 /230 = 47 amps
Your wattages are off because you are using the wrong numbers. Your electrical service is 120/240 volt not 115/220.
 
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Old 12-18-13, 09:22 PM
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ok total wattage
table saw 220 x 12 = 2640
air cleaner 115 x 3 = 345
chip collector 220 x 12 =2640
dehumidifier 115 x 4.8 =552
lights 24 40 watt tubes 960
heater 1500
--------
8637 total wattage
8637 x 1.25 =10796 /230 = 47 amps
table saw 240W x 12V = 2880A
air cleaner 120V x 3A = 360W
chip collector 240V x 12A =2880W
dehumidifier 120V x 4.8A = 576W
lights 24 40 watt tubes 960W
heater 1500W
--------
9156W total
9156W x 1.25 = 11445 W/240V = 47.68A


Because you made the same error on both sides of the calculation your answer came out close. A 60A feed should serve your needs well.
 
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Old 12-19-13, 07:54 AM
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Thanks for the great input!
More to digest and update my run book with.
So, all appliances marked for 220 are now considered 240?
I did read that in the electrical book I purchased by failed to incorporate that in my calcs. Black & Decker The Complete Guide to Wiring, 5th Edition. Lots of good info but definitely not complete.
 
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Old 12-19-13, 08:32 AM
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So, all appliances marked for 220 are now considered 240?
It would be pretty unusual to see an appliance marked 220 volt. What types of appliances are you referring to? The only 240 volt residential appliances I can think of quickly are a large window A-C units, central A-C units, electric water heaters, baseboard heaters, electric furnaces, large air compressors, some electric ovens and some electric cooktops. Electric ranges and electric dryers typically are 120/240 volt appliances.
 
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Old 12-19-13, 08:41 AM
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I'm using the term appliance generically.
I checked the small "spec" plates on my table saw and wood chip collector as they are the 2 biggest power consumers in my shop. And the collector runs whenever any other wood removing tool runs.
I could swear they both stated 220. But I could be wrong. I'll double check tonight as I'm now curious as to possibly needing glasses. They are both over 5 years old.
 
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Old 12-19-13, 09:12 AM
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I could swear they both stated 220. But I could be wrong.
If they say 220 volts on them, I am betting they are from offshore manufacturers from maybe China, Korea or may be even Taiwan. Regardless, they'll still run on 240 volts.
 
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Old 12-19-13, 09:26 AM
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Grizzly tools. Def made in China.
 
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Old 12-19-13, 11:21 AM
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I did read that in the electrical book I purchased by failed to incorporate that in my calcs. Black & Decker The Complete Guide to Wiring, 5th Edition.
We recommend Wiring Simplified from Gardner Bender. It's continually updated and tied to the NEC. It's also easy to read, comprehensive and inexpensive. It can be found in the electrical aisle at many home improvement centers.

Between the two you should be in pretty good shape for reference material. Of course, you have to actually implement the guidance.
 
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Old 12-19-13, 11:26 AM
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I'll check out the book.
And yeah, this will be a completely safe (hopefully) installation.
I can't really do anything but make detailed plans for my garage for the next 3 months. I did a guy thing and ripped my lower bicep tendon from the bone. Had a bolt installed a month ago. Lifting 2x4's and the like is out til spring.
 
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