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7 Strange Lessons & Tricks I Learned Installing a Shop Subpanel

 

To do it right, I decided to install a workshop subpanel.  I re-wired my shop some time ago, but I compromised on the 240V circuits since I could get by with one outlet.  But ultimately, before I close up all the walls, I want it done correctly and to account for future upgrades.

To do it right, I decided to install a workshop subpanel. I re-wired my shop some time ago, but I compromised on the 240V circuits since I could get by with one outlet. But ultimately, before I close up all the walls, I want it done correctly and to account for future upgrades.

In my previous article, Wiring Up Your Shop, I mentioned that I eventually wanted to put in a subpanel, but I didn’t feel like messing that deeply into electrical work.  Well, now I kinda need to.  I’ve got a bunch of 240V circuits that I need, and with my ideal shop layout, I just can’t have one breaker. 

Previously I had re-wired my Table Saw, Jointer, and Drum Sander with a longer power cord.  I ran these along the dust collection flex hose up to the ceiling, and then to a common 240V outlet. 

Since I used these tools one at a time, all was fine.  But my Drum Sander really belongs on the other side of the shop, so now I need at least two 240V outlets.  I don’t want to put two 240V outlets on one circuit, but I don’t have any more room in my Main House Panel.

I started reading on how to install a subpanel, looked through a few electrical books, and realized I could totally do it.  Now that’s not to say it’ll be perfect.

I wanted the cabinet to be firecaulked so it’s sealed out from bugs and drafts.  Behind this will be a radiant barrier and poly-iso insulation.  I also don’t want this to be a major leak for sound.

I wanted the cabinet to be firecaulked so it’s sealed out from bugs and drafts. Behind this will be a radiant barrier and poly-iso insulation. I also don’t want this to be a major leak for sound.

Why You Want a Subpanel

Running out of room in my House Panel was the main motivator in doing this, but there are a bunch of other reasons you’d benefit from a subpanel.  Below is a list of things to think about.

  • You may have (or need) multiple 240V circuits, and these take up a lot of room in a panel.
  • One disconnect shuts down the whole shop.
  • You can bring your shop circuits inside when your main house panel is outside.
  • Future expansion for circuits.  You may eventually want:
    • Dedicated media circuits (DVD player, iPod dock, radio, TV)
    • Heating unit
    • Cooling unit (AC units need dedicated 20-30A 2-pole breakers usually)
    • Air Compressor
    • Welder
    • Machine upgrade from 120V to 240V model – Table Saw, Drum Sander, Wide Belt Sander, Jointer, Jointer-Planer Combo Machine, Upgraded Dust Collector
    • Small CNC dedicated circuit(s)
    • To add an additional dust collector
The Main House panel just lacks enough space for multiple 2-pole breakers.  Any future tools or air conditioning I add would mean a subpanel anyway, so I might as well just do the whole thing now.

The Main House panel just lacks enough space for multiple 2-pole breakers. Any future tools or air conditioning I add would mean a subpanel anyway, so I might as well just do the whole thing now.

To me, it’s just cleaner to have a separate panel just for the shop.  I have access to it indoors, and I know I can expand my electrical system at any time.

I have a lot of circuits to avoid tripping breakers.  By having things like the shop vacuum on the same outlet as another tool, you risk popping a breaker.  My air compressor, dust collector, lights, the shop vacuum, the TV/ DVD player, and each of the 240V machines are all on their own breakers

“Isn’t that a lot of individual circuits?”, you may ask.  True, but the whole thing is protected by a 60A breaker.  Even if I ran around the shop like a wild animal turning everything on at once, this breaker would trip and protect the feeder wires.

Click here for the woodworking plansElectrical Plan, Revised

1.  A Good Panel is Hard to Find

I didn’t expect this one.  When I started to plan for a subpanel, I figured I’d just go to Home Depot and pick up an electrical panel that had enough space for the circuits I mapped out. 

But finding a panel that can take 8-10 breakers at 240V (this means 2-pole breakers), plus 10 more 120V single-pole breakers isn’t easy.  In conventional panels, 2-pole breakers take up two slots, and single-pole breakers take up one space.  So that means I needed 26 spaces! 

My existing house panel is a GE model, so their “slim” breakers can be used.  Sometimes called “half size” or “wafer” breakers, these model THQP breakers save tons of space.  You can fit twice the number of breakers in a panel since single-pole takes ½ slot, and 2-pole takes only 1 slot.  The house panel already uses these, and I’ve never had an issue with them.  The house is 18 years old and all’s ok.

What I needed was a panel that can take 20 individual circuits, but has 26 “spaces”.  By using the GE panels, I can use the slim breakers which they make in 2-pole and single-pole models.  With other brands I just couldn’t find the slim style in all the varieties I needed to make it work. 

Home centers don’t seem to have a good variety of useful panels, so I had to special order this one.  Depending on how many separate circuits you have, you may find it easier than I did choosing a panel.

This panel comes with a 200A breaker as the “main”, which in this subpanel will simply function as a disconnect; the 60A breaker in the House Main panel will be what protects the feeder wires.  Some panels don’t have this option.  I wanted it because it’s convenient to be able to shut down the shop from the inside (one light will still be on from the House Panel, though).

This panel comes with a 200A breaker as the “main”, which in this subpanel will simply function as a disconnect; the 60A breaker in the House Main panel will be what protects the feeder wires. Some panels don’t have this option. I wanted it because it’s convenient to be able to shut down the shop from the inside (one light will still be on from the House Panel, though).

Some panels are labeled 20/40 for example, which means “20 circuits, 40 poles (or slots)”.  So I needed, at minimum, a “20/26” panel.  Of course I want more than that for future expandability, so picked a 200-Amp, 40/ 40 panel. 

This way I can fill up one bus bar with 240V circuits (the panel can fit 9 of these on one side), and have plenty of room on the other side for the ½ size single-pole breakers (it can fit 20 of them).

The 200-Amp label is just the size of the main (or just the disconnect in a subpanel), but I don’t really need 200 amps, nor will it ever see that load.  I’m protecting the feeders from more than 60 amps, which is going in the main panel.  I wanted a “main switch” in the subpanel, which acts as a disconnect for all the circuits below it.

WoodChip Tip: Since my subpanel serves the same building (a standalone building is different), I removed the tie bar that connected the neutral bus bar and the ground bar.  The neutral bar is isolated from the electrical panel cabinet, and the panel uses the ground from the main panel which is connected to water pipes and a ground rod installed by the original contractor. 

Read the NEC (National Electrical Code) and some forums/ books, then talk to your area’s building inspector or plancheck office.  They’ll probably have a checklist for you, and some diagrams that will help you comply with local and national codes.  This will save you trouble when you have your inspection.

I needed to find a panel that would allow enough individual breakers.  I want many individual circuits because I want to make sure that I don’t have two tools on at the same time on the same breaker, such as a dust collector and bandsaw, or the air compressor firing up while I’m using a circular saw.

I needed to find a panel that would allow enough individual breakers. I want many individual circuits because I want to make sure that I don’t have two tools on at the same time on the same breaker, such as a dust collector and bandsaw, or the air compressor firing up while I’m using a circular saw.

2.  Underestimating Wire Length is Too Easy

In my hurry to hook everything up, I started out by connecting the outlet, then rolling out the Romex to the panel area and then cutting the wire.  After cutting it short once, I always left a bit of slack and let it be.  In the future, you may need to disconnect things and that extra wire will come in handy.

You might thicken your walls for more insulation, and have to move your outlet box forward (and need more wire), or maybe move it over one stud bay to accommodate a tool.  I’ve been glad many times during this particular electrical update that last time I left extra wire and just zig-zagged it in the stud bay to keep it neat.

I don’t like splices and junctions where one continuous wire should go.  I actually rewired my entire air compressor circuit because of that.  There wasn’t enough to make the connection to the new subpanel, so I used a new continuous line.  Keep in mind that any junction box has to be accessible, which means an ugly access panel.

WoodChip TipWhen you send the non-metallic (NM) wires through wall studs or top plates, do two things.  One is protect them with metal plates (they sell these things at home centers, with small spikes you can hammer over the studs), and secondly firecaulk the holes to keep your studbays sealed.  I don’t want air movement in my stud bays due to my wall design, and also I don’t want flames spreading so easily from bay to bay.  I definitely don’t want flames to go up thru the top plate into the attic space, so those will get extra attention.  I used intumescent fire sealant, rated for 3-hours.  You want to try to leave 1-1/4″ minimum of wood in front of any hole you drill in vertical studs.  I’m furring out the studs with 2×3’s, that’s why I wasn’t so worried about notching for conduit or drilling holes close to the edge.  Make sure you’re not compromising your structure and that the wires passing thru studs are protected by wood or plates. 

The feeder wires from this 60A breaker are #2 copper so in the future I can upgrade the subpanel to 100A, which is what I would do when upgrading my main house panel to 200A.

The feeder wires from this 60A breaker are #2 copper so in the future I can upgrade the subpanel to 100A, which is what I would do when upgrading my main house panel to 200A.

3.  Organize the Panel First = Good…But the Panel May Not Cooperate

I just wanted to run wire from an outlet then pop in a breaker and hook it up, then do the next circuit.  But take a minute and plan the order you want the breakers to appear in the panel.

I chose to put all the 2-pole 240V breakers on the left side, and the single-pole 120V breakers on the right.  Then I put those in some sort of logical order.

When I went to the panel to put in the breakers for a test-fit, I discovered I couldn’t put a 2-pole breaker as the first one due to a notch in the bus bar being absent.  I’m pretty sure it’s not legal or advisable to alter it. 

I was forced to put in a single-pole slim breaker as the first one.  So, I put the Main Lights first, which kind of makes sense, even though I preferred all the 240V ones on the left side.  The last breaker on the left side of the panel is the Secondary Lights breaker, which also kind of makes sense too.

Don’t marry yourself to your plan 100%; be prepared to run into whacky problems that may require you to change course.  Just like test-fitting furniture parts and joinery, do a test fit of your breakers, preliminary wire runs, etc. before tightening up cable clamps, cutting wires, or making final connections to outlets and switches.

Here’s the panel schedule; the first item being the disconnect/ subpanel circuit breaker protected by a 60 Amp breaker.  Circuits 2 thru 9 are the 240V, and 11 thru 20 are the 120V, plus the two light circuits 1 and 10.  The reason the lights are in those slots is due to the panel design; it doesn’t allow 2-pole breakers at the beginning and end of the bus bars.

Here’s the panel schedule; the first item being the disconnect/ subpanel circuit breaker protected by a 60 Amp breaker. Circuits 2 thru 9 are the 240V, and 11 thru 20 are the 120V, plus the two light circuits 1 and 10. The reason the lights are in those slots is due to the panel design; it doesn’t allow 2-pole breakers at the beginning and end of the bus bars.

4.  Running Feeder Wires Is Like Wrestling a Wet Panda

My house panel is 125A, which is light, but it works.  I don’t feel like re-doing this panel at the moment.  For my subpanel, I won’t be using more than 40 amps at a time, since I’m one person.  The dust collector, 3 hp table saw, air cleaner, and lights will be on at the same time, and it’s possible the compressor could kick on, too.

But, I still wanted to size the feeders to deal with at least 100A for the future, just in case.  This means #2 copper, and I bought it with THWN insulation.  The ground is #4. 

Since I only needed 6 ft. of wire for each of the 4 (1 neutral, 2 hot, and 1 ground), the price difference was minimal to me.

However, the thicker the wire the harder it is to deal with.  I used PVC conduit from panel to panel, and even with the gentle sweeps of the elbows, it took 20 minutes of struggling and fighting, and some slamming stuff on the ground to get it through. 

I used balled-up masking tape on the ends of the wire to prevent the copper strands from getting caught on the conduit seams as it rounded corners, and it worked.  Snaking it through the main panel with all the existing wiring meant running back and forth from the exterior main panel to the interior subpanel to push and pull its way to the main lugs.

So, pre-plan the panel-to-panel route carefully.  Don’t use too many direction changes.  I used two conduit bodies with access panels which helped me shove the wires from a better angle.  Looking back I can see several other configurations I was considering would have been impossible to push all 4 wires through.  Using LR vs. LB conduit bodies, upsizing the conduit from the code minimum are examples of things I should’ve explored better.  A pro, of course, would have already gone through these mistakes and would know all the options available.  That is part of what you pay for when you hire one, which is probably the way to go anyway. 

I used 1-1/4” conduit, and in retrospect I’d probably use 1-1/2” to make it easier.

The panels are close to each other so that actually makes it more of a challenge for conduit routing.  The cable TV device is below the subpanel so I can’t feed from underneath, and overhead is where all the 12 ga. Romex comes into the box.  So that left a side-tap.  The main panel didn’t have any convenient knockouts that made sense on the top so I opted to enter this way.  I’m furring out the wall pretty deep anyway so this will be flush to an access panel.

The panels are close to each other so that actually makes it more of a challenge for conduit routing. The cable TV device is below the subpanel so I can’t feed from underneath, and overhead is where all the 12 ga. Romex comes into the box. So that left a side-tap. The main panel didn’t have any convenient knockouts that made sense on the top so I opted to enter this way. I’m furring out the wall pretty deep anyway so this will be flush to an access panel.

5.  Label As You Go – Not Because You’re Dumb

I figured I could keep track of 18 circuits, but I was wrong.  I had to trace wires several times, and even got that wrong when things crossed or passed through areas I couldn’t see.

Since I have a lot of individual outlets on their own circuit, it’s easy to have multiple wires along one wall and that gets confusing when I’m at the panel.  So, I used blue masking tape and just took a Sharpie and wrote what wire serves which outlets.  That way, when I go to do the final connections, I can see what would be the best order to connect to the ground and neutral bus bars, and which wires go to what breakers quickly.

When you’re all done, use a real labeler to identify the circuit numbers and have a plan adhered to the inside of the panel door so you and others will know what circuit serves what.

Also, when I finished I neatened up the conductors within the panel box.  As Michael suggests below, the neater you do these the more the inspector will trust your work.  I admit I could’ve taken more time to make the conductors more parallel, etc. but I did arrange the neutral and ground conductors along the bus bars so that they would be more parallel and neat-looking.

WoodChip Tip:  Prepare the wall behind the subpanel for insulation.  Don’t leave this stud bay uninsulated!  I put my radiant barrier foam board with a 1” airspace between the foam board and exterior sheathing and sealed it.  Then I added extra framing to furr out the wall to 6” total. 

Next I put in the subpanel.  I sprayed expanding foam insulation into the gap between the panel and rigid foam.  To keep the foam from sticking to the panel (in case I want to ever remove it without a mess), I carefully laid plastic-wrap over the back sheet metal box and taped it in place. I also sealed all the electrical panel’s holes, gaps, and seams in the sheet metal enclosure with firecaulk.  This is just to keep out bugs, and to prevent air leakage.  I can feel the air infiltration at my house main panel; I’m now working plug these up too.

I put temporary tags on all the home runs to the panel box.  This is especially helpful when spreading out this project over several weeks.

I put temporary tags on all the home runs to the panel box. This is especially helpful when spreading out this project over several weeks.

 

This labeler is extremely useful.  I’ve labeled reference binders for project design, this website, and storage containers.

This labeler is extremely useful. I’ve labeled reference binders for project design, this website, and storage containers.

 

6.  Some Stuff Still Belongs on the House Panel

At first I was going to put the future outbuildings on the subpanel, but decided to reserve those in the house panel.  It’ll be two circuits, one for spray equipment/ compressor(s), and the other for lighting and small receptacle loads.

I’ll also put a few lights on the house panel too so I can still see when I throw the shop panel disconnect.

The plug that is used by the sprinkler timer goes on the house panel, too. 

Now that I’ve created more room in the house panel, I can split up some loads for the house, like put the computer on its own, and maybe reserve separate-circuit outlets for hair dryers, etc.

Even something as simple as the conduit routing from the main to the subpanel took a long time to figure out.  At first I thought all I need to do was run some wire from the outlets then hook them up to the breakers.  But to truly do it right, take your time and slow down.  Give yourself time to catch mistakes throughout the process.

Even something as simple as the conduit routing from the main to the subpanel took a long time to figure out. At first I thought all I need to do was run some wire from the outlets then hook them up to the breakers. But to truly do it right, take your time and slow down. Give yourself time to catch mistakes throughout the process.

7.  Plan Many, Many Small Work Sessions

I thought, “How hard can this be?  I’ll just use this weekend and route the wires in the morning, then hook up the subpanel in the afternoon.”  Yeah, it takes a bit longer than that.  It’s not too hard to figure out, but it’s a re-work of the electrical, so let it take its time.

Just hooking up outlets alone takes time to do it right, and then thinking ahead for the wire routing, knowing what my plans are for the walls and ceiling in the future just took some time to noodle over.  Give yourself this time.

Working in 1-1/2 to 2 hour blocks works well; I just take breaks and then go back and do some more. 

Crayon the Shop Cat likes it because there are no power tools on, which means she gets to roam the shop and explore.

At least someone appreciates the mess I make...

At least someone appreciates the mess I make…

I purposely did all the non-hazardous prep work before having to finally turn off the power. 

I wanted the majority of the shop to be “live” so I could still do woodworking, so I started with the new circuits first, since there is no power to those.

Then any wiring that had to be connected to an existing circuit (such as adding an outlet to a circuit) I did within one day so the power wasn’t off too long.

I took 4-5 hours to do the “main panel to subpanel” routing, and some connections, but did not connect the feeder neutral, 2 hots, or ground at the subpanel itself, only to the main panel. 

I shut off both the main panel breaker to the subpanel, and the subpanel’s disconnect.  The rest of the house I could turn back on.  Then the final connections within the subpanel to all the breakers could be done with the lights on (being on the house panel still) but the subpanel is not powered or live at all.

The next-to-last step was to do the subpanel feeder wire hook-ups (2 hot, 1 neutral, and 1 ground), then slowly test one circuit at a time to make sure I didn’t mislabel anything.  Then I tested each outlet with the tester device to make sure no loose or crossed wires existed.  I bought one designed to test GFCI outlets as well.

Final labeling was the last step before fastening on the cover. 

Now I have an indoor panel, labeled the way I want it, and with dedicated circuits serving what I need.  There’s plenty of room for future expansion for an AC unit or whatever else I decide to add, and the wires are sized to handle future upgrades.

So start diving into improving your shop’s electrical system!  There’s really no reason to live with a frustrating and deficient electrical arrangement; it’s really not that hard of a process.  Some parts you may have an electrician do, but at least you’ll know what you want by doing a bit of reading and drawing out your ideal workshop’s plan.  At the very least, by diving into the design part of this you’ll know what you want and can speak more intelligently to the electrical contractor.

Each breaker is assigned a number, and that corresponds to a panel schedule I’ll put on the inside of the door, along with an 11x17 color copy of the electrical plan.

Each breaker is assigned a number, and that corresponds to a panel schedule I’ll put on the inside of the door, along with an 11×17 color copy of the electrical plan.

Click here for the woodworking plansElectrical Plan, Revised

Related Articles:

Wiring Up Your Shop

Fast Fixes for  an Under-Performing Workshop Layout

Resources:

How-To Book from Black & Decker (really helpful and complete)

Mike Holt’s Illustrated Guide to Understanding the NEC Volume 1, 2011 Edition  (suggested by Michael in the comments below)

Rex Cauldwell’s Wiring a House 4th Edition: Completely Revised and Updated (For Pros By Pros)  (suggested by Michael in the comments below)

Wire Stripper

Labeler

Test Kit

GFCI Tester

A bunch of wire

 

I tried to keep the wiring relatively neat; grounds on the left toward the back, neutrals on the right toward the back, and the hots on either side but more toward the front.  It won’t be perfect but make it so you can easily trace wires from the breakers to where they enter the panel without sticking your hand in there.

I tried to keep the wiring relatively neat; grounds on the left toward the back, neutrals on the right toward the back, and the hots on either side but more toward the front. It won’t be perfect but make it so you can easily trace wires from the breakers to where they enter the panel without sticking your hand in there.

 

Testing was the last phase; I went breaker by breaker to make sure all was connected to the right outlets and breakers, then I made sure that I’m getting the correct voltage (120 or 240).

Testing was the last phase; I went breaker by breaker to make sure all was connected to the right outlets and breakers, then I made sure that I’m getting the correct voltage (120 or 240).

 

I just bought this device, designed specifically for GFCI outlets.  I use another one from Greenlee as well for non-GFCI outlets.  I tested each to make sure it trips properly.

I just bought this device, designed specifically for GFCI outlets. I use another one from Greenlee as well for non-GFCI outlets. I tested each to make sure it trips properly.

 

The NM (Non-Metallic) cable clamps hold the Romex wiring in place so they don’t move around an get scrape up the insulation.  It’s easy to nick it and get a tear so be careful when pulling wire through areas where metal edges are nearby.

The NM (Non-Metallic) cable clamps hold the Romex wiring in place so they don’t move around an get scrape up the insulation. It’s easy to nick it and get a tear so be careful when pulling wire through areas where metal edges are nearby.

 

You can tell by my previous articles I like to seal the hell out of everything.  This project is no exception.  I firecaulked all penetrations into each stud bay, and also used regular acrylic caulk (DAP 35-year) on the studbay itself.  Then a radiant barrier panel with 1” square spacers behind it went in, and was also sealed airtight.  This provided insulation and a radiant barrier behind the subpanel.  I used sprayfoam insulation around the panel, but used a plastic wrap barrier so that the foam doesn’t stick to the panel itself, just filling the stud bay.  I then caulked around the panel box to the stud framing forming a tight envelope.

You can tell by my previous articles I like to seal the hell out of everything. This project is no exception. I firecaulked all penetrations into each stud bay, and also used regular acrylic caulk (DAP 35-year) on the studbay itself. Then a radiant barrier panel with 1” square spacers behind it went in, and was also sealed airtight. This provided insulation and a radiant barrier behind the subpanel. I used sprayfoam insulation around the panel, but used a plastic wrap barrier so that the foam doesn’t stick to the panel itself, just filling the stud bay. I then caulked around the panel box to the stud framing forming a tight envelope.

 

The prep of the box before bolting it to the wall framing took a while.  I carefully applied firecaulking to each hole and knockout that I wasn’t planning on using.

The prep of the box before bolting it to the wall framing took a while. I carefully applied firecaulking to each hole and knockout that I wasn’t planning on using.

 

…aaaaaand….done.

…aaaaaand….done.

 

Crayon amongst the chaos and loving it.

Crayon amongst the chaos and loving it.

For more guidance in assembling your Workshop Design, click on the Starting? Go Here! category and read those first.

Connect with me on Facebook, and follow me on Twitter for more ninja tips to Optimize Your Woodshop!

And, if you’re on Twitter, be sure to follow #woodchat every Wednesday night, at 6:00 pm, PST.

Gotta get more clamps,

 

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7 Responses to “7 Strange Lessons & Tricks I Learned Installing a Shop Subpanel”

  1. Bill says:

    Bobby,
    I did the one circuit thing for a few years (to many). Only had one light which would dim when I started up TS. Electrical was a direct overhead run from the house, of course the ever present extension cords. House built in the 40’s.

    Needed to upgrade the house service so at the same time ran an underground service to the shop. As I was doing a total remodel at the time, decided to run exterior conduit throughout, worked great and don’t mind the conduit showing. I ran dedicated outlets to all my power tools, lighting, and put in 12 wall outlets on their own circuit. I have at least 2 or more outlets on each bench and several at convient locations throughout. Overkill yup, but no extension cords.

    In the finish room overkill once again, dedicated run for the lights, and separate run for each side of the rooms outlets.

    Now I can run DC, TS or whatever at the same time no dim lights. Cost a little more for copper but will worth it to me. The only thing I would do different would be to run larger conduit, minimum of one inch, so much easier to pull wire through than the half inch I used, live and learn. Now need a run to the attic for lighting and fan.

    Bill

    PS: Enjoy and am learning from your blogs. Thanks.

  2. Michael says:

    Bobby,
    I am right now immersed in completely rewiring my shop, and the adjacent playroom, both in the same detached building that has had 40 years of bad, and repeated electrical modifications. Like you I have taken things down to the studs, so I feel the pain you have been going through. I was very impressed at how dedicated you were to drawing up Class-A plans. Major Kudos. I even have the 2012 version of Autocad but have been too lazy to use it –no excuse, I know. In looking over the pictures it seems that you have done a heroic job. However, at the risk of sounding like a wet-blanket I thing I see a few glitches (Disclaimer: I am a licensed physician, NOT electrician, so anyone reading this please take care and do your own research.)

    1. I am assuming this is NOT a permitted renovation and thus there will be no inspections. This is good because were you to get inspected, the panel is an absolute NO-NO. Either the subpanel or the cable equipment would have to be moved as you need 72″ of dedicated vertical space, measured from floor, where locating the subpanel (i.e. no other equipment) NEC 110.26.E.1.a “(a) Dedicated Electrical Space. The footprint space (width and depth of the equipment) extending from the floor to a height of 6 ft above the equipment or to the structural ceiling, whichever is lower, must be dedicated for the electrical installation. No piping, ducts, or other equipment foreign to the electrical installation can be installed in this dedicated footprint space.”
    2. Another issue if you were to be inspected is that the panel is MESSY. I have learned the hard way that inspectors, at least around here in sunny California, consider a sloppy panel to be a sign of careless work elsewhere and will go out of their way to look for violations (this is doubly true for us DIYers getting inspected). For example, all individual conductors should have gentle sweep 90 bends then run parallel to one surface of the panel, no odd angles or twists that look like spaghetti. I can’t upload images, but there are a zillion on the web of what a clean panel looks like, here is one of them: http://www.aplushomeinspections.ca/ESW/Images/Panel.jpg
    3. Other NEC issues that may or may not be an issue – the picture are a little hard to judge.
    a. Cable must be set back no less than 1 ¼” from edge of framing members, joists or studs NEC 300.4.D
    b. Where multiconductor cables are stacked or bundled together longer than 24 inches, the allowable ampacity of each conductor must be reduced in accordance with NEC Table 310.15(B)(2)(a).
    c. Where more than two cables containing two or more current-carrying conductors pass through the same opening in wood framing that is to be fire or draft stopped using thermal insulation, caulk, or sealing foam, or if the conductors are installed in contact with thermal insulation without maintaining spacing between cables, the allowable ampacity of each conductor shall be adjusted in accordance with NEC Table 310.15(B)(2)(a). Note there is no 24-inch provision in this requirement.
    d. Don’t forget that devices with motors designed for continuous running (e.g. air-conditioner or heatpumps) need to have wiring sized for 125% of ampacity requirements, after derating for bundling or ambient temperature
    e. Runs through attics where it goes over 85F require deratting
    f. It looks like one of the side is deeply notched. Load bearing studs notched more than 40-60% require sistering another stud, non-bearing can be notched 60%.
    g. Not relevant to your install since you are going to cover everything with drywall, but anyone reading this should be aware that exposed NM-B is NOT allowed along the vertical framing members
    4. Yes the conduit fill table says that you can use #5-2AWG in 1 ¼” schedule 40 PVC, so using four conductors is allowable, but that is just too hard. What you have on the main panel is a type LB conduit body. Instead of the funky question mark you should have used a 1 ½” type LR body. The LB would join the LR with a sngle vertical conduit. If the depths are differnet then a vertical would extend up from the LB about half way. The LR would be rotated out to join the vertical at 45 degrees, using a gentle sweep connector. You would then measure the lengths of wire and feed them vertically through from one conduit body to the next, ten made your two 90 degree bends in the conductors. If you really were struggling then you could feed them one at a time through the short nipples. BTW: the best way to bend these monsters is using the back end of the handle of a crescent wrench. That smooth hole will hold the conductors and the wrench will give you added torque.
    5. For what its worth I think the two best books for anyone contemplating this same undertaking are:
    a. Mike Holt’s Illustrated Guide to Understanding the NEC Volume 1, 2011 Edition
    b. Rex Cauldwell’s Wiring a House 4th Edition: Completely Revised and Updated (For Pros By Pros)

    Sorry, if all these critiques make me sound like a jerk, but I have been suffering this for a while and thought others shouldn’t make the same mistakes I have.
    Mike

    • Bobby says:

      Michael,

      No worries I appreciate the input. Most of the photos were of the panel in progress; before putting on the cover the conducters were neatened up a bit, and I went back and adjusted where everything was connected on the neutral and ground bus so that it didn’t look as random. You’re right it could have been done more neatly for sure. As for the cable box below the panel, that wasn’t mentioned at all; didn’t know that. I don’t see the “real life” issue, though it does appear to be clear in the NEC. I could move the panel or the cable box over one bay I suppose but would be a pain to do it.

      The studs will be furred out with additional 2×3’s fastened to the 2×4’s so I wasn’t too worried about the 1.25″ clearance on the stud holes; I’ll have over 2″ of wood in front of most holes when it’s done. I may also add the nail plates were it’s at “picture-hanging” height. My understanding that this 1-1/4″ requirement can be violated if you put a protection plate in front of the penetration location. I did that on the north wall already, knowing that in a shop I’ll be attaching many things to the walls in the future. The additional 2×3’s are also why I didn’t mind notching for the conduit structurally. Ultimately I want a lot of room for insulation in each stud cavity, so I’m adding these 2×3’s all along the south and north walls which face the exterior.

      The original existing 14 ga. house wiring is bundled together enmass (like 10+ conductors) from the main house panel though the garage wall and into the house; I guess I’m not clear on what is meant by “bundling”. The NEC chart says where the number of current-carrying conductors in a raceway or cable exceeds three. So I’m not sure what is meant by “raceway”. If it means “close together” then most houses have that condition. I’m not sure that I’d be required to use 10 ga. conductors for a 20A circuit; currently most are 12 ga on 20A receptacles.

      All wiring in my shop is currently (or will be) sealed with 3-hour fire-caulk intumescent sealant for top plates, horizontal fire-breaks, and vertical studs as well. I’m trying to keep each stud bay contained for airflow (and fire) as much as possible. That’s the yellow sealant you see in the photos.

      For AC, I haven’t run those conductors yet; I just left a space for it in the panel. That will be installed by an HVAC contractor, probably a mini-split heat pump system.

      For things like the dust collector that are somewhat continous, it can work on a 15A circuit, but I’m using 12 ga wiring, and same with the other receptacles. For the 240V, 15A outlets I’m also using 12 ga. The only 15A breakers I’ll have will be for the lights, but I may still use 12 ga for that as well.

      In both the existing house and the shop, there is some wiring that is in the unconditioned space (attic). In the existing house it’s mostly 14 ga. wiring and 15A receptacles. The shop has mostly 20A receptacles and 12 ga. wiring.

      You’re right about the exposed Romex; everytime I see it I want to accelerate the insulation project and get that done. I also am in the process of neatening up the Romex that comes out of the panel, using plastic-covered staples. The existing 14 ga. wiring is too taught to run those any neater, and thank goodness they’ll be covered up. I left some slack in the new 12 ga. shop wiring knowing that I’d want to move the receptacles inboard to accomodate the wall-furring, and when that’s done I’ll re-anchor the Romex.

      You’re also right about the 1-1/4″ conduit being difficult; I’d have been better off doing it the way you said. It was a pain to get all of those #2’s to follow the sweep. I was dealing with the existing main house panel being offset in two dimensions, so it was quite a puzzle. An electrical contractor would’ve known the best option, I’m sure.

      Thanks again for your detailed look! When I explored the electrical forums I knew that I’d get some critiques. But that helps me correct things I didn’t see when I was doing it. I’m especially interested in ways I can improve the install. I’m inspired to go back into the panel and further neaten up the conductors to be more parallel. I may also look at relocating the cable box; I think that might be easier than doing the panel.

      I’ve put a reference to the books you mentioned in the Resource List and in the post itself. Thanks again, Michael!

      Bobby

  3. Bobby says:

    Andrew,

    I like it; I went diving into electrical stuff a few years ago to add extra circuits but finally realized a subpanel is the “right way”. Definitely mention what things have to go on their own breakers, like air compressors, dust collection, etc. so you don’t trip one when something turns on while using another tool. Also keep the lights separate, and maybe have a dedicated “media” outlet for TV, DVD, computer.

    Then think about how many 240V 2-pole circuits you might need later; any possible upgrades like a more powerful lathe, AC or electric radiant heat, or 3 hp table saw.

    By the way, loved your recent Lego post! I like giving Legos to my friends’ kids, and I’ve kept all of mine. I just got back from Disneyworld, and went to the Lego store in Downtown Disney. They had an awesome giant dragon made from Legos; I’ll post it on Twitter this afternoon.

  4. Bobby says:

    Jeff,

    Cool! I’m glad to see you’ve got a good electrical set-up. I still remember my one-car garage with the lonely 15A outlet that I had to be careful about using more than one thing at a time. I am putting most of the lights on the subpanel, but I am leaving some on the house panel for the back-up scenario you talk about so that I can lock it out.

    I kept my bus tie just in case I ever wanted to have a separate service or something like that; not sure what Southern California Edison would say about whether that’s allowed. But bill separation is a really good point. I could put that $ on the LLC and then prove it.

  5. Andrew says:

    I’ve got a bit of house remodeling going on here this summer, including redoing the main electrical service to the house. I’ll be hiring an electrician for that since they’ll have to work with the power company for that piece but I’m having him add a subpanel for my shop/utility room area. I’ve been suffering in my shop for a few years not having this.

  6. Great tips.

    I rewired my shop with a subpanel a couple years ago and put only the wall outlets (tool circuits) on the panel. The lights and overhead door are still on the original circuit from the house panel. That way I can shut off all the tool circuits and lock the panel to keep the kiddos from firing up the tools. Also if I happen to overwhelm the 40A 240 in the subpanel the lights won’t shut off. My panels are further apart than yours but it’s very similar to what you did.

    Since you have a full size panel you could always get a separate service put into that panel (200A right) and then replace the bus tie and nix the feeder from the main panel. If you ever needed to seperate the bills for the shop and home (for tax purposes) this would be the way to go. We ran two panels at our lake place. One for all the normal circuits in a house and the other panel is for the electric baseboard heaters. We have off-peak rates for that and it’s a cheaper tier of electricity. I’m doubting you could rely on off-peak as your only supply for the shop though.

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