Heat exchanger for shower fitting immersion boss?

[John Stumbles]

Anyone got a link or any info for those heat exchangers comprising a bundle of microbore that fit into an immersion heater boss on a standard vented DHW cylinder, to give mains pressure DHW for a shower?

[Cicero]

=================================== Do you mean a 'venturi shower'?

[John]

No he means a heat exchanger.

[kevallsop]

The 'Micraversion', made by Yorkshire Fittings, fits the description (Page 22 of pdf):

[Onetap]

I think that may be an old Yorkshire fittings pdf file. I'm fairly sure that neither the Micraversion or the Sidewinder are still made; this would be because they were crap.

The Micraversion was intended to heat the HWS cylinder up, not provide mains pressure hot water. The surface area would be inadequate, as would the temperature differential for that application. You'd need a plate heat exchanger, heated by the boiler primary water, with a pump to shove the boiler water through the primary side of the PHX. You could use a tube-in-shell heat exchanger similar to the Micraversion, but I suspect it would work out at 20 feet long to achieve the heat transfer surface area.

The old Range Powermax combi boilers (not the current Potterton HE ones) generated mains pressure hot water like this. If you're thinking of building something from parts, you could look at the Installation & Maintenance manual to see how they'd done it.

[Onetap]

I think so. And good riddance, too.

search draws a blank for both. That pdf on the latenightengineer site must be 5 years old, at least; probably 10.

You'd find their surface areas to be very small in comparison with that of a modern British Standard DHWS cylinder. They were used in the days when 'short-coil' cylinders were the standard replacement supplied to clueless householders.

[John Stumbles]

What about the 'sidewinder'? Was that another manufacturer's version of the same think (i.e. indirect heating element)?

I'm sure I've seen a more recent beast along similar lines but definitely intended as a thermal-store-type adaptation for providing mains pressure DHW for showers from a standard gravity cylinder.

However I just had a go at a DIY lashup with 10m of 10mm pipe in a tub of water at 60C and although it gives a decent heat transfer when the HW in the tub is agitated a bit it quickly drops off when the water is standing still.

I was interested to see what the commercial version looked like to get an idea how much copper I should be using.

It must be possible to get adequate transfer from a suitably-sized and laid-out exchanger in a cylinder since thermal stores such as boilermates use this principle, but my crazy-idea-but-it-might-just-work experiment didn't.