Proposed Solar Thermal System. Ok, what if I.....

21 Sep 2008
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United Kingdom
Ok, so the plan is to connect solar primary circuit to lower coil in a solar unvented cylinder, which will provide the DHW. So far so good, all as normal. The twist is that I have a 300l Megaflo Direct cylinder that i want to use as a thermal store (because I got it for free).

What would happen if I used the upper coil in the solar unvented to take heat from the solar unvented cylinder and pump it into the Megaflo which would be a tank containing the space heating primary circuit water? This would only happen when the DHW cylinder has satisfied temperature. The upper coil is in the middl so there should still be a bit of hot DHW in the top.

The upper coil in the solar twin coil cylinder s meant to be used the other way round, to put heat into the cylinder (from a boiler or whatever), so i wonder if it will be effective to 'steal' heat from the heated up DHW unvented solar cylinder?
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Thanks for your clear and concise reply!

Please expand upon your musing. Is there a fundamental design problem here or are you incorrectly assuming I would be using this system in the UK in winter?

If I use a circulating pump to pump water from the "heat store" around the upper coil of the solar cylinder (while it is still being heated from the solar primary circuit in the lower coil) it will surely bring some heat from the twin coil cylinder to the direct cylinder?
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Well yes I I'd jumped to the conclusion you wernt planning to raise the temperature of you're house in July!
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And yes your theory will work

You will get "SOME" heat into your "heat store"
Ok, I'll try it as I build it can change it later easily. Thanks.

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