On 2006-08-18 00:25:40 +0100, "Doctor Drivel" said:


"Andy Hall" wrote in message ...
On 2006-08-17 22:22:52 +0100, "Doctor Drivel" said:


"Andy Hall" wrote in message ...
On 2006-08-15 00:48:54 +0100, John Stumbles said:

On Sat, 12 Aug 2006 14:29:14 +0100, Andy Hall wrote:

Then unless the heater can be set to 75 degrees or more, the energy
storage will be more limited vs. running at boiler flow temperatures.

This is exacerbated in systems using external (plate) heat exchangers
because the pump circulating water round the PHE runs at full bore
regardless of the demand, so if you draw a gentle shower or run a hot tap
at part flow you're liable to lose most of your hot water capacity through
mixing within the cylinder long before you would have done if you were
drawing only enough to provide the amount of DHW demanded. It should be
easy enough to fix this either cleverly by modulating the pump or
brute-force by restricting the flow with a TRV type affair. Either way
would have the added benefit of doing away with the need for a TMV on the
output of the PHE.

Starting to get complicated, though, isn't it....

No.

Would you be willing to subsidise the extra cost??

Matt, what are you on about.

Meaning if you think it's not such a big deal, would you be willing to
subsidise the installer for the additional cost of the components? Do
you know what the additional cost, including the cost of diagnosing and
replacing them as a result of failures during the system lifetime?