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New boiler plans - combi, heating or system

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Our Viessmann has been trouble free for 10 years but yes, it wasn't cheap.  However, it does give effectively unlimited hot water at mains pressure while only storing 100L of hot water rather than the 350 you might typically have on a tank (that spends most of its time just gradually losing it's heat to your house). 

However, large tank and heat pump would be where I'd be going if I was fitting now.  


 
Posted : 15/03/2025 6:59 pm
phil5556 reacted
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Posted by: trail_rat

I realise they’re probably mainly for bigger homes but surely it fixes the main annoyance of waiting for the hot water to kick in?

 

I think it's also important to mention that the wait for ho****er you experience. Isn't you waiting for the combi to kick in. You'll have to wait regardless of combi or tank unless you have a circulation system fitted. 

 

This is true, I'm hoping to get the pipework shortened to the bathroom at the same time which I hope should help the initial heat to the tap time. It currently runs a slightly convoluted route via the 22mm pipework.

Do modern combis keep running at low flow rates? Because compounding my issue is that if I turn the tap turn to say half way it will go cold and then I have another 90 seconds waiting for the hot water to come back again.

 


 
Posted : 16/03/2025 6:00 pm
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15mm is enough for shower. For basins 10mm plastic pipe is sufficient and gives a decent improvement in “dead leg”. 


 
Posted : 16/03/2025 8:03 pm
Dickyboy and phil5556 reacted
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Vitodens storage owners...

What happens when the 46l tank is emptied? Presumably it just acts as a "normal" Combi and supplies hot water at a lower flow. It doesn't go cold until it can heat itself back up again... does it?

I don't think it does but it's difficult to find details!

 

And will it still provide hot water from the tank with the tap barely turned on, for when you just want a trickle of hot? So below the flow that the boiler would fire up for I can still get hot water out the tap?


 
Posted : 17/03/2025 6:50 pm
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