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JoshuaZ comments on Procedural Knowledge Gaps - Less Wrong
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After having about 50 different housemates, I'm shocked by how few people have basic home-maintenance knowledge. Things like:
Ok. I confess that this one more than any of the others makes me seriously worry about how good my theory of mind is. How do they think their heating systems work?
They think that the furnace burns at a different temperature depending on how high the thermostat is.
Couldn't it just be an erroneous application of (an intuited version of) Newton's law of cooling, which says that heat transfer is linearly proportional to heat difference? They assume that the thermostat temperature is setting the temperature of the heating element, and then apply their intuited Newton's Law.
Seems pretty rational to me.
For example, this absolutely works with say, an electric stove.
This is actually implementation dependent. Though the most common implementation of a thermostat is just an on-off switch for the heater, it is possible to have a heater with multiple settings and a thermostat that selects higher heat settings for greater temperature differentials.
Also, turning the thermostat up extra-high means that you don't have to go back and make the temperature higher if your initial selection wasn't warm enough.
Even with an ordinary thermostat, cranking it up can be effective in some realistic situations. If some corners of the house take longer to heat up than the location of the thermostat, they'll reach the desired temperature faster if you let the thermostat itself and the rest of the house get a few degrees warmer first. Or to put it differently, scoffing at people who crank up the thermostat is justified only under the assumption that it measures the temperature of the whole house accurately, which is a pretty shaky assumption when you think about it.
As the moral of the story, even when your physics is guaranteed to be more accurate than folk physics, that's still not a reason to scoff at the conclusions of folk physics. The latter, bad as it is, has after all evolved for robust grappling with real-world problems, whereas any scientific model's connection with reality is delicately brittle.
That's an important lesson, generalizable to much more than just physics.
This general point is seriously deserving of a top-level post.
Since about 50 years ago all but the lowest-end thermostats are designed to be "anticipators" — they shut off the heat before the requested temperature is reached, then gradually approach it with a lower duty cycle. More often than not, the installer doesn't bother to fine-tune this, in which case it can take a long time to reach equilibrium. Turning it a few degrees warmer than you actually want isn't a completely stupid idea.
(reference: http://en.wikipedia.org/wiki/Thermostat)
Thank you for reassuring me that I'm not crazy :)
Do you actually think a typical person has a coherent theory of how a heating system with a thermostat works?
It's a very human and intuitive way of thinking. People bundle together various things that seem like they should somehow be related, and assume that if something has a good or bad influence on one of these things, it must also influence other related things in the same direction. When you think about it, it's not a bad heuristic for dealing with a world too complex to understand with full accuracy.
I would imagine it's simply an application of the extremely general (and useful) rule of thumb "if doing something has an effect, doing it a lot will probably have a lot of that effect".
Depending on the type and size of the heater relative to the area to be warmed that statement could very well be false.
I have lived in some places where turning up the heater produced much hotter air than at a lower temperature, which would heat a house much more quickly. These houses had relatively modern central air conditioning systems with electric furnaces, or really good gas furnaces.
I've also lived in places with radiators or really crappy wall mounted heaters where it wouldn't make any difference at all.