Combi question

My Sime combi has an annoying habit: If CH is off and I run some hot water - when I stop the DHW the boiler switches its diverter valve back to the CH circuit, but then continues to run the pump for another 30 sec or so. I presume this is to prevent temperature over-run.
What it does mean is that if I stop/start the hot water, the water temperature goes from hot (water in pipe) to cold then back to hot again as the boiler regains temperature. It's a PITA when topping up a bath or using the shower. Do other combis do this?
Another (academic) question: Is it illegal to modify the controller electronics in a boiler?
Nick
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Another Nick wrote:

In a word, nope...! (Sounds like this is the designed behaviour for yours, but it is certainly not standarad behaviour for all of them).

Not in itself.
The only legal requirement if you are going to make alterations to gas appliances is that you be competant to do so.
(although there is no legal definition of what competant means in this situation!)
--
Cheers,

John.

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On Sat, 25 Feb 2006 22:04:14 +0000, John Rumm

So in theory it'd be possible to 'chip' a boiler to boost performance?
sponix
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On Sat, 25 Feb 2006 22:03:30 +0000, sponix wrote:

You're not too far from the mark. my boiler controller contains fairly rudimentary electronics - for a few quid in parts a simple microcontroller chip can add a bit more "intelligence" to the design. E.g. NOT running the pump for so long when the CH is cold, modulating flow based on incoming water temp. dispalying flow/return/DHW temps etc. etc.
Of course it'd take some time reverse engineering the existing boiler, then building/programming a replacement. Time I don't have (too many other jobs!) hence it's just an idle thought at the mo...
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