On 16/12/2019 07:53, MM wrote:
On Sun, 15 Dec 2019 22:59:43 +0000, John Rumm
wrote:

On 15/12/2019 11:34, MM wrote:
On Fri, 13 Dec 2019 14:00:44 +0000, John Rumm
wrote:

On 13/12/2019 09:19, MM wrote:
On Thu, 12 Dec 2019 12:02:30 -0800 (PST), wrote:

On Thursday, 12 December 2019 18:31:00 UTC, MM wrote:
On Thu, 12 Dec 2019 10:11:06 -0800 (PST), tabbypurr wrote:
On Thursday, 12 December 2019 09:15:48 UTC, MM wrote:
My heating engineer, who is very good and always does a good job,
fitted a new 3-port valve in the airing cupboard last week. He
replaced the Danfoss with a Honeywell. The Danfoss has lasted 15
years. He explained how these valves work and said that it was always
better, if possible, to have the hot water switch off AFTER the
heating, because this guarantees less wear on the valve due to the way
the valve positions itself when the hot water is switched off. Even if
one has the central heating on and it is then turned off, it's a good
idea to switch on the hot water briefly, even for only 30 seconds, so
as to reposition the valve beneficially.

MM

That ain't right. The 3 position valve's positions are, in this order: HW only (resting position), both on, CH but no HW. So the way to minimise wear is to not turn the HW off at all, jus leave it move between HW and both.

But then I'm going to have far more hot water than I know what to do
with. One hour with the Wallstar gives me enough water for a hot bath
AND the washing-up.

MM

Once it's hot it stops heating it.

Sure -- but only for a while, as the temperature will inevitably fall
and the boiler will kick in again. If I've had my bath that day, how
can I justify having a copper cylinder full of very hot water until
the next day? Seems daft to have piping hot water at 3:00 a.m. at
night.

With good lagging, relatively little heat will be "lost". However also
keep in mind where it is lost to - i.e. it ends up leaking into the
house in most cases, where it will simply reduce the amount that needs
replenishment from the CH at this time of year ans so is mostly cost
neutral.

It "leaks" upwards (where all heat leaks...) and upwards is the loft,
as the airing cupboard is on the first floor.


Sure, do whatever works for you. I only mentioned it since people often
get overly concerned about the costs of DHW production, when in reality
they are typically dwarfed by the space heating costs.

Absolutely. During the summer, when the CH is off, the HW burns a very
small amount of oil to get me my tankful of very hot water. The
heating oil lasts a very long time.

MM


My DHW is about £100 a year. In winter CH is £100 a WEEK.



--
€œThe fundamental cause of the trouble in the modern world today is that
the stupid are cocksure while the intelligent are full of doubt."

- Bertrand Russell