On 28 Jul, 00:50, Mike Holmes wrote:
Many thanks for the replies



If there's a risk of
scalding you need a TMV at the point(s) of use. A TMV on the store
outlet is no good.

TMVs at the point if there is a risk of scalding.
TMVs at the store outlet are no good at preventing the isk of
scalding.
You still need to distribute at 60degC ish to avoid legionella in the
pipes.
The TMVs at the outlets are usually set at a maximum of 43degC (I
think) which won't cause scalding to any 'at risk' users.

The idea for the TMV just after the PHE is because if your store is at
75degC say, and you open a tap to give a moderate-low flow rate, then
you're probably going to get water output from the secondary
approaching 70-75degC and - dangerously hot - hence the TMV so you
have a steady maximum temperature in your DHW system - unaffected by
the store if it is at a higher temperature or flow rate through the
PHE. You don't store your DHW, with a heat bank, you store the system
water - check the many threads on heat banks or the wiki link above.

I know. The TMVs are being used for 2 different purposes.

1)Mix to a safe temperature at the store outlet, whilst keeping above
the legionella-friendly temperature.

2) Mix to a non-scalding temperature at the point of use which is
below the legionella temperature.