DHW heated by modern CH boiler, what stops it cooling it?

[ericmark]

It does not affect me, as I don't have a condensing boiler, but the whole idea today is to vary the water temperature rather than simply turning boiler on/off.

So I know we want DHW stored at over 60ºC, but not much more, but how does it ensure the boiler warms DHW and not cool it?

 

[Razor900]

Thats the essence of hot water priority.

The system knows whether its doing space heating or water reheat and has more than one flow temp built into it to suit

 

[ericmark]

Thank you, I assume that means there needs to be some wiring to say either CH or DHW, this is clearly built in with a combi boiler, but with a system boiler, it would need extra wires, so all my wiring diagrams for S and Y plan must now be redundant? I assume C plan is simply no longer used?

 

[Razor900]

There are various ways of doing it. Some controllers have it built in now and some boilers use an NTC sensor and so it natively

Any boiler that can use weather compensation or opentherm can be made to work on priority hot water as can individual makes like Worcester which is why you need to use their own controls

 

[Exedon]

Thank you, I assume that means there needs to be some wiring to say either CH or DHW, this is clearly built in with a combi boiler, but with a system boiler, it would need extra wires, so all my wiring diagrams for S and Y plan must now be redundant? I assume C plan is simply no longer used?

Look up X plan designed for hot water priority.
C plan was very rarely used (in this area anyway) fully pumped S plan way more normal.
Y plan is horrible for several reasons!

 

[ericmark]

I have never heard of X Plan, I need to look it up, thanks.

I have had a quick read, seems similar to W Plan. Except connection to boiler to auto lift temp when on DHW.