IIRC the ones on sale were a scaled down version of industrial vertical pipe exchangers, which aren't very practical in a lot of houses. And they were way overpriced.
easy
thousands of pounds
They improve shower 'decency,' if your measure of decency is flow rate. 50% return would make your 7kW shower give the output of a 10.5kW one.
NT
But installing even a 7KW one would mean a rewire, or have you forgotten that you were advocating using the immersion feed?
I'm far from convinced that "knitting your own" is as simple as you seem to think. You've discounted vertical pipe ones which are probably the most efficient design (but a pain to install retrospectively) so anything you come up with will be less efficient to a greater or lesser degree.
Tim
I wasn't restricting the discussion of DHEs to one individual's situation, nor to only a 7kW unit. Surely it's clear that with any power of electric shower, the DHE increases the possible throughput.
Well, the design I settled on is simple.
they're just impractical unless you have a nice big drop to make use of
Not at all. Efficiency depends on more than solely whether the flow is bulk or film.
NT
One of the things I imagined was a retrofit to a shower base. A platform, say 50mm thick or less, which sits in the existing base and plugs into the existing drain. It has a 15mm water inlet and outlet on top as well as a drain. Inside is a zig-zag heat exchanger.
Then I thought, why not just make a complete base with the heat exchanger in. The drain part could be a series of walls forcing a zig-zag waste path with the copper pipe zigging and zagging along the middle. You'd need a weir at the end to keep the level up, and a bleed hole to allow it to drain when finished. You could make the top removable for unclogging.
It would take a while before the exchanger got up to temperature, so piss in the shower first. Zig-a-zig-ah.
Cheers
I suspect something liek that is how all showers will become. But that's not very diyable friendly, and cleaning would be an issue. Removing the top would really pong.
NT
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