Recommendations for a decent boiler with external temperature control?

Not quite everything...

You can have an unpressurised mass of water in a tank, which you can heat from a pressurised primary via a heat exchanger (if you want to do it fast - you could also do it via a conventional indirect coil) - you have a secondary pump to take water out of the bottom of the tank through the HE and back into the top to extract the heat from the boilers primary flow.

Then on the extraction side you have a similar arrangement with a big plate HE. Again a secondary pump passes hot water from the top of the store store through the HE and back again, to heat incoming cold water from the mains.

In effect you get a combi type of effect where the heat comes from the heat bank. This gives you mains pressure hot water, at any flow rate the mains can deliver rather than being limited by the rate at which the boiler can supply it.

You could do it with less hardware using a vented primary boiler (no need for the charging HE, the boiler can just circulate its primary water into the cylinder. However that does not suit my application since I have no loft space for header tanks[1], and much prefer sealed primaries anyway.

[1] There is currently one cupboard suited to the location of the header (and that is where it currently is), but I want to turn that into an ensuite shower, so both tanks in it need to go.
Reply to
John Rumm
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The fastest way to heat it is via a plate heat exchanger - it will also heat top-down, not bottom up as a coil will do. It will also combine the outputs of the heated water and the boiler. These do something similar, explaining.

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a plate and pump is cheaper once the cylinder gets largish. It also means smaller cylinder can be used when upping the boiler kW, as the boilers output is put at the top of the cylinder where the hot water is drawn-off.

I have used this method when a body jet shower was installed. It saved the cost, and space, of a new large cylinder. A body jet would have exhausted the existing cylinder of water. Effectively it makes your cylinder larger.

Advanced Appliances do not have header tanks in their standard thermal stores. They have a brass ballcock directly in the water saving space. A sealed insulted lid caps it. It means you can get inside the cylinder easily. Look here they will supply with coils and put extra tappings in. They will make a short wide cylinder, to save height. Or a square heat bank to any shape you want. All stainless steel.

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DIYer did a SS pressurised heat bank. Worth looking....piccies too.
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was guided through on the forum. His comments on its performance is worth noting. Some aspects I would have done differently, but an excellent job from his angle.

Reply to
Doctor Drivel

Typo: should be they will supply without coils.

Reply to
Doctor Drivel

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