Overall, the practice seems to be very heuristic based, with every installation being a bit different and rules of thumb being the norm. Our system seems to work fairly well in practice, but I've been curious to get a professional's opinion on it (the only pro that's seen it was the gas guy who did the final hookup, who seemed impressed but didn't really offer any specific criticisms).
Repo at https://github.com/mtrudel/boiler
I've since added an elixir based graphing system to it, at
You will never find one of those houses still using it. Doesn't matter who built the house, where, when, what make of components or which fuel. Usually electric, but there were quite a few gas. Effectively all have been ripped out now. You might find evidence of ducting when rewiring.
This was quickly condemned when we got it inspected - it had a crack in the heat exchanger and - these things were apparently only designed to last 25 years. Lasting 50 was pretty impressive/dangerous.
You can get replacement heaters for them, but it's pretty niche, needs to be imported from Europe, and because of the age normally involves dealing with asbestos insulation. It's also apparently virtually impossible to get the venting cleaned, as it's embedded in the flooring (under concrete for the group floor). (Edit: And this caused real problems for Asthma sufferers)
While it worked though it was pretty good, it heated rooms extremely quickly.
Also, the heat in Santa Fe is much different than that in New Orleans.
With 3/4" PEX at a relatively slow 1.5 GPM flow rate, that adds about 1.4 seconds to 'hot water delivery time', though that's not entirely accurate, because the loop itself has some heated water trapped in it.
It's a bit like people from 200 years ago debating what to make the candle holder from so that it lasts 100 years.
The whole house is built (and maintained) with a different mindset.
(I think they removed the last knob-and-tube light socket a couple years ago)
My concern is not so much that a sample of 100 PEX heat traps installed today will all burst on the same day in 2059 or 2159. It's more that if the average lifetime of PEX under those circumstances is only, say, 50 years, maybe there will be a few percent that burst in 5 or 10 years, depending on how variable the corrosion rate is. So if you can protect yourself from that with 45 centimeters of copper, which will cost a heck of a lot less than the water heater does, maybe you should.
>Newer water heaters have built-in heat traps.
So it's "no, they're just done by default and hidden". Seems like a reasonable thing to do.
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