Heat traps?

On 21 Jan 2007 03:27:20 -0800 someone who may be snipped-for-privacy@care2.com wrote this:-

The arrangement of connections to a UK hot water cylinder limit the amount of gravity circulation of hot water.

then?

You might need them on some installations, e.g., serving secondary heating zones.

One I had was a thermal store serving a HWS storage cylinder & with a mid position valve. The mid-position valve was normally open to the HWS with the power off; gravity circulation caused the HWS to overheat. It wouldn't happen with a simple boiler, because there's little heat stored.

I fitted a swing-check non-return valve to stop it. No effect at all. With hindsight, should have been a spring check NRV.

Changed the 3-port Y plan to 2 off 2-port zones S-Plan valves, both normally closed; problem solved.

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