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Issue #213 April 2008
What Makes an Engineer?
by Steve Ciarcia
A couple of weeks ago, I was having the screened-in lanai at the “cottage” converted to a Florida room. Since this involved considerably more than slapping in a couple of windows from Home Depot, I called in a contractor. On the building permit, I had to certify that I was just replacing the screens with windows and that I wasn’t air conditioning or heating the room. Doing that would have been adding more (taxable) square footage to the house and a simple lanai screen/window swap was considered tax free.
One of the ironies of home improvement these days is how much the government really doesn’t trust us. Putting in a glass window on a screened porch became a major project. Even though I was just replacing screens with windows, because everyone else supposedly lies and actually makes it into an added room, the law required that the renovation be constructed like a genuine addition and structurally equivalent to any other supporting wall in the house. The new glass enclosure had to follow current building codes that included adding inside and outside electrical outlets and lighting where none had been before. This was considerably more than just rerouting the one existing floodlight, so the contractor sent a couple of electricians to rewire the whole place.
The electricians arrived like the chosen ones. Their trucks blocked the whole driveway and their equipment was spread all over the place. The lanai was filled with ladders, extension cords, and tools with no regard for the convenience of the occupants. No one even asked me how or where I wanted switches or outlets. Soon there was just a trench along the side of the foundation, a new conduit pipe sticking out an adjacent wall of the house, and two guys merrily drilling large diameter holes in all of the structural stuff that the contractor had already installed.
I came out on the lanai and watched them for a few minutes. I started to wonder about the effect of drilling holes in the support beams and how close these holes could be before it actually affected support calculations. I noticed that they were daisy-chaining all of the outlets and I wondered about the attenuation between outlets at 120 kHz used for X-10 and the voltage drop from one socket to the next with applied loads. I saw that they had found the CAT-5 cable for one of my web cams and wondered, despite its twisted-pair conductors, how much induced EMF there would be when these guys stuffed all of the AC and DC wires into the same wiring tract. Finally, when I noticed one electrician using the space between my rain gutter downspout and the house as the fulcrum of a 20' piece of conduit pipe he was trying to bend, I did a quick calculation on the length of the moment arm and force about to rip off my gutter and said, “Should I be concerned about only using one circuit for these three plugs?”
He instantly realized I was watching and stopped using my gutter pipe as a bending tool. Obviously disturbed at my questioning whether he was following code (he was), he replied, “The AC power has a lot of juice and it will take care of anything you need to plug in. In fact, please step back, Sir. One hundred twenty volts is a lot of power and I wouldn’t want any electrical arcs hurting you while these boxes are open.”
Talk about gratuitous putdowns. I stared at him and said, “By the way, I’m an electrical engineer. Given the dry air and drought conditions, I suspect you’d have to put a bloody screwdriver across the wires to get a spark today. I guess the ‘juice’ just isn’t what it used to be.”
He scowled and went back to work. As he turned, I could swear I heard him utter, “Great, all I need is an engineer.”
I went back in the house and tried to forget the surly man who might be a great electrician but probably had no concept of my other observations. For that matter, even though I am an engineer, I wasn’t sure I could still calculate all of the answers anymore. There was a time when I could calculate the induced EMF of twisted and non-twisted wires, but I think my current knowledge got rusty after figuring the voltage drops along the daisy chain. Heaven forbid we throw in the capacitive effects of the loads and do it for 120 kHz.
Certainly, management tasks have dulled the sharpness of my math skills, so I determined to refresh some of that lost expertise by going back to school—not literally, but virtually. A quick search on “college video lectures” revealed hundreds of free online college courses, including engineering classes. For the last couple of weeks, I’ve been watching electrical engineering and physics classes at MIT (http://ocw.mit.edu/) and other colleges. The good news is that I’m actually remembering a lot. The bad news is that I’m also remembering how much I hated some of those equations the first time around.
So, just how much does a guy have to know to still call himself an engineer? My conclusion is that engineering is qualitative, not quantitative. Engineering is a mindset and training to know there are losses in electrical conductors, stresses in support members, and electrically induced energy in magnetically coupled conductors. Until I finish all of these courses again, however, knowing exactly how to calculate it is an exercise for those who remember all of the equations.
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