Boiler controls changed

We've just had our annual boiler service done and when I asked the guy if it had a clean bill of health, he said yes but it needed a bit of tweaking to get the emissions to where they should be.
I've just been in the loft to move stuff back to where it was and I noticed that he's altered both the hot water and central heating controls on the boiler. The guy who installed it five years ago set both controls to No.7 (they go from 1 to 9) and they've never been altered since, neither by me or by any engineer who's serviced the boiler, but today's engineer has moved both controls to No.9
Now, I freely admit that I'm no heating engineer but for most things in life, if you turn something up to maximum, then you use more of something. Given gas prices and especially the latest round of ripping off, sorry, price increases, I don't want to be using more gas than I have to. Our heating and hot water have always been hot enough for us with the controls set at No.7, so can I turn them back down, or is there some engineering reason (to do with the emissions and tweaking he had to do) to leave them at max?
Cheers
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If this is the boiler temperature, you want it to be as low as possible, whilst it can still maintain the house temperature. That's the most efficient for boiler operation (particularly for a condensing boiler).
The trouble is that this ideal setting changes when the outdoor temperature changes, and whilst you're heating the house up from cold, and in some cases if it's also running a hot water cylinder. So in practice, you'll want it a bit higher than the ideal setting so you don't have to keep adjusting it, particularly if that means a trip up to the loft each time..
Boilers with weather compensation do this adjustment automatically for you, to keep the boiler operating at its most efficient temperature all the time (in theory).
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Andrew Gabriel
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Andrew Gabriel formulated on Tuesday :

Thanks Andrew, I'll turn them back down then I think.
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在 2012年10月16日星期二UTC+8下午8时24分12秒,John写道:

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