thermostat on circulating hot water

23 Jan 2010
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United Kingdom
I have an indirect unvented cylinder with a secondary circulation bronze pump. I want to fit a thermostatic limiter to reduce circulating temperature and associated heat loss. Also to limit tap temperature to 45°C while maintaining cylinder above 60°C.
I have shown three non-return valves to prevent cold water entering the cylinder's warm inlet, to prevent warm water entering the cold water inlet and to prevent warm water from the cylinder entering the thermostatic mixer.

My idea is that the bulk of the circulation bypasses the cylinder and goes from the bronze pump into the cold inlet of the thermostatic mixer. Only sufficient hot water would be taken from the cylinder to maintain the circulation temperature. Warm circulating water would enter the cylinder's warm inlet to balance the hot water leaving.

When there is demand from the taps, the cold feed pushes hot water through the cylinder to the mixer's hot inlet and it also joins the circulation into the cold inlet.

Have I missed a trick? Or do I really need three non-return valves in the circulation system?
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