When your dad owns a construction company, you grow up knowing a lot about how buildings are built. My dad started taking me to construction sites when I was in the seventh grade, but he wasn't telling me to go into any of the construction trades. He was just showing me what construction workers did and how hard they had to work while doing it.
He said they made good money, but most of them were pretty worn out by the time they reached retirement age. It was the hard, physical labor that did it. He wanted me to go to college so I could work at a desk instead of working outside when it was ninety-eight in the shade or cold enough the concrete required an additive so it wouldn't freeze before it could cure.
I ended up going to college to become an electrical engineer and found a job with an architectural firm that specialized in industrial and office buildings. As one of the electrical engineers there, I designed the power and lighting systems for buildings.
The funny thing about my job was that even though Dad thought I'd spend all my time at a desk, I spent about half my time on construction sites. Construction sites require electrical work from almost the time a track-hoe or dozer takes the first bite of soil from the site until the building gets a certificate of residency - the inspectors final approval of the building construction. I was on a job site a lot to explain the electrical drawings, to inspect what the electricians had done so far, and to walk around with the electrical inspector when he made his inspections.
On almost all new sites, the electrical service comes from the power company's high voltage lines through underground conduits to a set of main switchgear. That means those conduits have to go in the ground before any foundation work is done. Once the building is weather tight, the switchgear has to be installed and secured in place and then the feeders from the power company pole have to be pulled through the conduits and connected to the switchgear. Then the switchgear is connected to the transformers that bring the line voltage down to the voltage used by the equipment to be installed in the building.
Usually that voltage is 480 volts, three-phase, and the transformers feed a bank of high amperage circuit breakers. From those circuit breakers, the electricians run more conduits that feed bus bars in the ceiling of the building for the connection of equipment. There are also conduits from those circuit breakers to transformers and circuit breaker panels that bring the voltage down to the normal household voltages for offices and other low-voltage equipment. At that point, what's left is other conduits and wiring from those low voltage circuit breaker panels for lighting and receptacles.
Any mistakes along the way can result in at best a lot of rework and at worst, a major electrical system failure when the system is energized. You don't get second chances if there's a short circuit in a thirteen-thousand volt line. The arc from that short circuit can reach thirty-five thousand degrees, will vaporize any metal and other nearby materials, and create a sonic blast wave about equivalent to exploding a pound of TNT. Any one of those is enough to kill anyone within twenty feet of the arc.
Yes, there are safety suits that OSHA requires for people working around high voltages. They're made of heavy canvas-like material that is supposed to keep the wearer from catching fire in the event of an arc flash. They don't do anything for the blast wave. In many cases they only serve to help make sure there's enough of the person left to identify after a high voltage arc flash.
Without the safety suit, even a short circuit in the normal four-eighty volt circuit creates an explosion and a fireball that can kill or severely burn people. As the design engineer, I had to be there to make sure the electricians had wired everything according to my electrical drawings before the system was energized.
The electricians on most jobs were well-trained and experienced in the common skills of digging in conduit, running conduit, pulling wire, and wiring panels, receptacles switches and lighting. It was seldom that I found an error in an electrical system.
Now, most of the electricians I worked with were free-lancing, meaning they weren't regular employees of the electrical contractor. They'd watch the various job posting boards on the Internet and pick where they wanted to work next. Many would work jobs in northern states during the summer, but then take jobs in the South during the winter. They were an independent bunch and a lot of fun to work with because they had some neat stories to tell.
}|{
I'd designed the electrical system from the power company pole down to every last receptacle and light fixture for a small warehouse and went to the site as soon as the contractor had finished leveling the building site. The electricians were laying out the path of the conduits from the power company pole to where the switch room was going to be and I had to make sure of three things before the concrete subcontractor could start any foundation work.
The placement of the conduits that came up out of the ground inside the building was critical. A conduit in the wrong place might not be discovered until the concrete floor was poured and the electricians attempted to place the switchgear. Correcting that error would mean ripping out a large section of the floor, rerouting the conduit, and then pouring the floor again.
Only one high voltage conduit was required on the job, but it ran under what was going to become a road around the building. That section of conduit had to be encased in concrete so heavy trucks wouldn't eventually collapse it, and I went to the site to make sure that job was done according to my design. That meant I had to get there before any concrete was poured.
I'd specified steel conduit as a riser from the pole down to the elevation the conduit was to be at going into the building, more steel conduit from the sweep, the elbow used to transition from vertical conduit to horizontal conduit, to across the proposed road and PVC conduit from there into the building. The steel riser was to protect the high voltage wiring from damage from lawn mowers and I used steel conduit to span the road because of a local code. I used PVC conduit for the rest of the run because PVC won't rust and it doesn't degrade over time like steel does. PVC is also a little easier to get any joints sealed against water intrusion.
In this case, I'd specified two, four-inch conduits from the pole to where the switchgear would be placed. I could have specified as small as three-inch conduits, but 500 MCM wire is pretty stiff and pulling it around corners is a lot easier in larger conduit. Considering the total cost of the project, the cost of the larger conduit wouldn't be significant.
One would hold the wiring from the pole to the switchgear. The other was a spare. It doesn't cost much to add a spare conduit when the first installation is being done, even if it's never used. It costs a ton to dig up an existing installation just to add one conduit.
Any conduit encased in concrete has to be supported by what are called "stools". Stools are pre-manufactured devices that keep conduits from sagging and also maintain a minimum distance between them.
I had a look and the number of stools was what I'd specified and the conduits were straight and level. All the joints looked properly done. They were just finishing up the forms that would keep the concrete in the area required. It all looked good, but I had a couple things I need to check before I authorized the pour.
The first thing I had to check was the soil compaction of the bottom of the trench. I found the lead electrician and asked to see the soil test data. He pointed to a woman standing beside the trench.
"Go see Evelyn. She keeps all the paperwork."
Evelyn didn't look like much. She had her red hair pulled back in a ponytail that stuck out the back of a ball cap with a fist holding a lightening bolt on the front. She had on the combination sunglasses/safety glasses that OSHA mandates for workers working outside in the sunshine so I couldn't really see much of her face other than her mouth. She was wearing a dark blue work shirt and work pants, neither of which fit her very well, and the standard electrician's work shoes.
I walked up and asked if she was Evelyn and she said yes. Then she smiled and asked me who I was and what I needed.
