How to build a rocket workshop (part 8: judgment day)

I alluded to the fact in the last two posts that there are some laws and regulations applicable to electrical work.

Among other things, your city or state will require you to obtain a permit (and pay a fee) before you can even begin the work. In Washington state, this is the Department of Labor & Industries. The work needs to be done in accordance with certain requirements, and then an inspection is required once it’s complete. At that point, you notify the Department and schedule a date, and an electrical inspector will come on site to review all of the work.

It’s not uncommon to fail an inspection and for remedial action to be required. An inspector can fail you no matter how small the violation, relative to the overall work done.

Judge not, lest ye be judged – amirite? Unfortunately, it’s literally the inspector’s job to judge – and he or she has significant power and discretion.

front of shed with door and new exterior light
purely cosmetic

What are the requirements governing electrical work? There are several, and they are no joke. I had to bring myself up to speed quickly.

First, there’s the National Electrical Code (“NEC”), which is published by the National Fire Protection Association (“NFPA”), in NFPA 70. Interestingly, this is the same NFPA that publishes the Code for High Power Rocketry (“HPR”), in NFPA 1127. But that’s a whole separate topic, worthy of its own blog post.

The NEC is “national” but is not technically a federal law. However, it has been adopted in all 50 states, which can also modify it as they see fit – so the rules can and do slightly vary from one region to another.

In Washington, there are state-specific statutes and regulations further modifying the standard NEC rules.

view of electrical panel in shed
where the magic happens

So what are these rules, exactly? There are far too many for a comprehensive list, but here are a few examples:

  • Conduit minimum depth underground. Copper wire must generally be enclosed inside conduit (metal/rigid or PVC) and, if horizontal and running across the ground, must be buried so the top of the conduit is at least 18″ underground.
  • Securing conduit. Conduit that is vertical and runs along walls (indoor or outdoor) must be secured with straps (plastic or metal) at no greater than 36″ intervals.
  • Conduit bends. You can physically bend conduit – with heat, if it’s PVC, for example – or you can attach 90 degree (or 45 degree) PVC “elbows” for turns. But the total turns cannot exceed 360 degrees. That means, for example, you could have a maximum of four 90 degree “elbows” or PVC pipe bends.
  • Panel clearance. Installation of a new electrical panel or sub-panel must have a certain minimum amount of clearance in front of it. Specifically, a minimum width of 30″, depth of 36″, and height of 60″. Visualize a telephone booth-like invisible box in front of the panel that must be completely unobstructed to ensure access to the panel.
  • Tamper-proof outlets. Electrical outlets (or “receptacles”) inside a dwelling unit (e.g. a house) must be tamper-proof. Inside a shed, which is not a dwelling unit, they don’t need to be – until the 2020 version of the NEC takes effect this summer, at which point even the shed would need all outlets to be tamper-proof.
  • GFCI outlets. For safety reasons, a ground fault circuit interrupter (“GFCI”) is required. Either the electrical panel needs to have a GFCI circuit breaker, or at least one outlet needs to be a GFCI outlet.
  • Ground rods. The new electrical panel for the shed requires at least one copper ground rod, and depending on the soil quality (specifically, its electrical resistance), possibly requires two. A ground rod comes in a standard length of 8 feet and has to be driven completely down into the ground. A bare copper wire (not insulated or inside conduit) connects the ground rod to the electrical panel. This is again for safety reasons, to redirect excess current.
close up view of junction box with outlets
junction box/ outlets

The NEC and its state and local variations of the electrical code have many more rules that must be followed. The above list is just a small fraction of things I learned during the course of this project – all from my friend Darrin, noted electrical expert and lifelong student of the electrical code, among other titles.

Again, the reasons for these rules are often pretty self-explanatory. Clearance in front of a panel is important so that a person has unobstructed access to the panel. Copper wire should be inside conduit when buried, in order to protect it from future damage – and that conduit should be buried pretty deep, for the same reason. The rules are mostly about safety and common sense.

As soon as we completed all the work, I scheduled the inspection. This was on a Sunday afternoon, incidentally, and the inspector showed up first thing Monday morning – record response time.

Judgment day!

The inspector was friendly, and he seemed quite impressed with all the work and how thoroughly it was done. He agreed it met all the applicable requirements in the code, with just a couple of very minor issues to address. These were promptly fixed, and the project officially passed inspection.

All I need to do now is a bit of final cleanup work – fill in that huge trench; clean up the mess everywhere from sawing, drilling; get the landscaping back in order with about a hundred wheelbarrows of mulch; and so on.

I think at this point, the backyard garden shed can officially and rightfully be called a workshop.

How to build a rocket workshop (part 7: the burial)

Step #2,352: dig a trench.

In order to run electrical wire and conduit from the main electrical panel in the house out to the shed, the electrical code requires (more on this later) that the conduit be buried a minimum of 18 inches underground.

digging completed – view from above

This requirement is totally understandable, given the nature of electricity and the danger of someone accidentally digging into it. It is also burdensome. It fact, is much more burdensome than it seems. This is partly because 18 inches is deeper than it initially sounds, and the difficulty increases exponentially as you get further down. If you’ve ever done any digging in your yard, even just to replant a small plant or bush, I’m sure this will resonate with you.

The minimum depth applies to the top of the PVC conduit, and you need to err on the side of too deep rather than too shallow if you want to make sure it’s up to code and will pass an inspection, so the trench really needs to be about 20 inches deep.

But the most difficult problem you immediately run into – if you’re me – is the soil quality. This is soil that nobody has touched in many decades. It’s dense and compressed, like clay, and also rocky. I mean extraordinarily rocky. There were points during which I achieved maximum rock, i.e., there was no soil at all and just pure rock.

pile of large rocks and stones, with a Starbucks cup for scale
sample of large rocks I dug up, with cup for scale

I had nothing other than a simple garden shovel. I went out on a limb and halfway through the project bought something that is specifically made for digging trenches, which looks just like the shovel except it’s somewhat narrower. This was helpful, but the digging was still brutal.

I’d estimate digging this trench by hand took about 50 percent of the total time for this electrical project, with the other half being everything from drilling and cutting and bending conduit to actually running the copper wire inside it and installing outlets and light fixtures (for which, as mentioned in the last post, my friend Darrin was invaluable and did all the heavy lifting, literally and figuratively). In retrospect, maybe I should have brought in some kind of heavy machinery to dig this trench.

Did I mention the sheer quantity of rock?

another large pile of rocks
maximum rock

Anyway, the trench was simple enough, conceptually. And from the main electrical panel in the house to the shed, only about half had to be underground. The other half is above ground and runs along the outside of the house.

Below is a picture of the trench mid-project, when I was busy naively underestimating the 20 inch depth requirement. It’s getting there, but by no means complete yet. You can see where the conduit comes up out of the trench, above ground, in between the door and the gutter downspout. We also installed a new junction box with electrical outlets and weatherproof cover there, just because we could.

View of L-shaped trench dug in ground, surrounded by piles of dirt and stones
a straightforward trench

Below is the view underneath the front of the shed, where the 1″ diameter conduit goes up inside the shed to a sub-panel. The smaller 1/2″ conduit on the left here contains copper wire, running from the shed’s sub-panel to the copper ground rod that you can see here.

As an interesting aside: with any electrical panel, you need to have at least one copper ground rod, and this comes in a standard length of 8 feet. The metal rod must be buried underground and attached via copper wire to the panel. In other words, you have to drive the rod straight down into the ground.

If the soil quality is good and its resistance is low enough, you may be able to get away with just a single 8′ ground rod. In our case, the soil was abysmal, and we needed to drive two separate 8′ copper rods into the ground. You’ll never be required to use more than two rods.

Outside shed, close up view of pvc conduit in trench and copper grounding rod
pvc conduit and copper grounding rod

Here are two final pictures of the trench once it was dug further down to the required minimum depth, and we laid the conduit inside.

view of trench from house, with PVC pipe laid in trench
trench from house

As this project went on, we needed to leap across increasingly wide and deep trenches, countless times. Particularly awkward was the trench needed to pass directly in front of the shed door, which required Olympic-level gymnastics to vault across the ditch but also simultaneously duck your head to avoid hitting the top of the door frame.

Eventually we realized it would just be easier to throw together a few wooden bridges made from lumber (2x4s or 2x6s). This prevented more injuries and also was a good idea for the inspector who still needed to come on-site after all the work was complete.

view of trench continuing to shed, with PVC pipe
trench continues to shed

If you look closely (and maybe squint), you can also see in a few of these pictures that we came across some unexpected pipes and drain tiles. We called 811 before digging – required by law – and the various utility companies came out to ensure there was nothing buried underground in this area.

But there were drain tiles, which are not part of any utility but are just part of the property. These were loosely connected and immersed entirely in tons of rock, to facilitate water drainage from the house, and we hit them in two separate locations as they cut across the trench. We also encountered some other pipe (about the same size as the drain tiles, roughly 4 inches in diameter) whose origin and purpose were unclear. We just dug around and beneath it, without disturbing it, and continued on our way. That pipe remains shrouded in mystery.

The conclusion here is simple and painfully obvious: digging sucks. But it was a necessary step to bury the copper wire and conduit in order to comply with the electrical code. This was the most backbreaking part of the project but also allowed for the more fun electrical wiring to be completed in the shed (covered in the last post).