I‘m a big believer in the “law” of unintended consequences, having been its “victim” many times. Our actions, however well intentioned, often have follow-on implications that may actually be contrary to that original intention and, in fact, undermine it. It's a consequence of the impossibility of fully seeing the ripple effect of our actions, of feeling that the original goal as stated is so important that any unforeseen consequences don’t matter, or of that eternal vice of hubris.
I saw this again the other day, when a friend’s electric water heater began to show signs of age and wear-out after about 15 years of service. No big deal, he thought; just get a new one of same capacity rating. Yes, there’s the expense, but other than that, it’s a straightforward -replacement operation.
Except it is not straightforward, and here’s why: new energy-efficiency regulations recently went into effect in the U.S. and to meet them and as a first step, these water heaters are being jacketed with few extra inches of insulation. The most-common sized water heaters at 55-gallons (210 liters) and below are only slightly affected, but above that size the changes are significant.
This increased diameter due to insulation means that a 70-gallon heater which previously measured about 23 inches (60 cm) across now measures about 27 inches (about 70 cm). Two immediate problems: first, it may be hard to get that new heater to whatever room or basement corner it needs to go to, as the access to the heater area is often full of twists, turns, narrow doorways, and steep stairs. Second, once you get it there, the new and improved heater may not fit into the available space since these units were often stuffed into a very tight corners or closets. So now, the homeowner has to somehow make a bigger place for the new heater, a costly and often very difficult process.
The unintended consequences don't end there. For the larger non-electric heaters, the exhaust manifold outlet is raised a few inches to improve combustion efficiency, a laudable goal. Problem is that, again, many actual installations have no headroom, and changing the path is difficult or nearly impossible—and certainly costly. Electric water heaters also have new requirements which increase their height, as well.
Long story short: any potential energy savings due to the increased efficiency of these units may be completely “wiped out” or worse by the physical installations issues, and that doesn’t include the headache and hassle issues associated with “reconstruction.” Those are unintended consequences, for sure.
Fortunately, for most electronic systems, circuits, and especially power supplies, higher efficiency may come with an increase in BOM cost but not physical size. In fact, most higher- efficiency designs are smaller than their lower-efficiency predecessors, for various reasons—but there are exceptions, of course. Further that new switching supply may be a form, fit, and functional replacement for an existing unit, but operate at a different frequency and so have a new set of system-level EMI/RFI issues.
What's the next “unintended consequence” scenario I am looking at? New York City passed new rules mandating that all battery-powered smoke detectors must have a sealed, 10-year battery, rather than user-replaceable ones, see here and here. The reason given is that homeowners let the batteries go bad, but then don't replace them. Seems like a good idea, but still, so do many other things which have unforeseen consequences in the real world.
[On the other hand, I never understood the public-service announcement reminding everyone to change smoke-detector batteries every six months with the roll-back/turn-ahead of the clocks—that always seemed quite excessive to me. Fresh batteries last two to three years at a minimum, so I wondered if this “change your batteries” admonition was a contrivance spurred the battery vendors.]
What been your experience with and exposure to the “law of unintended consequences” in technical areas? Have you ever had to live with – and perhaps fix – the results of those well-intentioned but naïve decrees of others?