boiler with separate flow temperature settings for HTG + HW?

[blubs]

Morning,
I have a problem at home that i know is pretty endemic: When heating DHW, i want my condensing boiler to forget about condensing for a while and ramp up the temp so as to heat the cylinder as quickly and efficiently as possible, its only ever topping it up 10 or 20 deg, ..
However, in HTG mode, i want luke warm rads, so as to max the benifits of condensing latent heat gain and prevent overheating due to stinking hot radiators kicking out after stat satisfied....
My problem is exasperated as i have a thermal store, which really needs to be 65-70deg.

Anyone know which boilers, old or new, can do this????

I have been reading the viessmann stuff, and i like to think their system boiler, that does know which circuit its heating, (it has 2 flows) is this clever, (allthough i cant find where to set flow temps for DHW?????) It is however, ridiculously big!
I also still dont know how its outdoor sensor only can effectively regulate indoor temp without knowing about windows open, strong wind chill etc???, but thats a different subject.

I believe the ideal system is a simple one (mechanical room stat!, or programmable if theres a chance anyone will work out how to use it!!), where users know to keep flow temp as low as possible, naturally turning it up when the snow falls.. the problem being that they they then have a lovely condensing boiler, that unfortunately never reaches target temp on cylinder, pumping and firing in vain, for hours...especially on long runs between the two, i see it alot...
any thoughts?....
thanks.
Paul.

 

[Dan Robinson]

Intergas, Vaillant, Ideal Vogue, Veissmann, Keston

My thermal store only runs at 67 degrees.

Heating runs at whatever the weather sensor tells it to.

I have a Coopra which also is perfect for the job.

The problem with some boilers is you HAVE to use their own controls (Veissmann and Vaillant for sure).

Intergas we have done this many times using off the shelf components.

Any boiler can be made to do this AS LONG as doesn't need to use propriety controls and doesn't mind the weather sensor suddenly vanishing from its "awareness" during hot water cycles.

Like the Intergas and Coopra.

 

[ALEC1]

if you are thinking of changing the boiler you might as well get rid of the thermal store assuming it only does hot water.

I can't think of any advantage of them over regular hot water unvented cylinders, apart from no discharge pipe.

Viessman vitodens 200s are well worth investing in but only if you go for their weather compensation, which is an automised way of doing what you want. Correctly set up it really does give you a fantastic heating experience, stable room temps and always tries to work at its most efficient, with a flow temp around 50c for heating.


Using proprietary controls simplifies installs, guarantees you have a seamless system with no mismatches...

You may be lucky with your thermal store and it may work ok at lower flow temps, but beware...viessmann max flow temp is 72c, vaillants with its proprietary controls is 80c...

 

[Dan Robinson]

Forgot to mention Worcester.

But Intergas or Vaillant would be my recommendations for off the shelf or proprietary.

 

[blubs]

thanks.
The main reason i have a thermal store, is that i am hooking up a wood stove..
its very difficult and overly complicated to do that with unvented..
I have to disagree with you ALEC1, i've bought a lot of dripping and faulty valves servicing unvented cylinders. and expansions vessels= very expensive stuff, my thermal store with internal DHW coil is devilishly simple, nothing really to go wrong and it can store more energy per litre, as it will go to 90 plus deg!!....but thanks for heads up about viessmann flow temp..
with the solar coil too it does a fantastic job, at 85deg C after a sunny day i have loads of hot water at mains pressure..
The boiler is rarely used to heat store, but when it does, its not required to do much, but i need a high flow temp..
My Keston Celsius has been doing a sterling job for the best part of a decade, however in winter, I have to turn flow temp up and down daily!!! Could i train it to have 2 flow temps?? i know it has outdoor sensor facility

I am going to replace keston with an inter gas combi one day, so glad to here they have this facility. (does the combi version have facility to heat indirect cylinder at different flow temps to heating demand?, even though its a combi??)
I haven't decided whether to plumb it up to hot out on cylinder, use a solar thermal DHW blending valve or just have 2 lever valves to switch between various combinations of thermal store hot, combi hot, or both in line!!! , one things for sure, when i'm dead and gone, no one will know how to use system!!

I have never fully investigated outdoor sensors , but i know my favourite manufacturers and indeed installers! recommend them.. I just feel that there are so many customers with systems they just don't understand, and consequently don't use them correctly AT ALL!! so i try to keep things simple,
I just don't see how they can regulate indoor temp with no feedback as to what it is ????????????? I am guessing they simply regulate flow temp to match outdoor temp/heat loss.. nothing else???? does this mean that unlike normal stat system, the boiler is never 'satisfied', but always on during heating times?. if so, surely this leads to more heat lost through flue, and energy on pump???

big pros and cons with proprietary controls for sure... i like to tailor my choice of controls to suit customer, a lot of them would never work out some of the viesmaann stuff!!

will look through my keston manual in a mo.... and look into what a coopra is?
ta.

 

[Dan Robinson]

The intergas boiler was born for this kind of thing and is easily achievable with a simple relay or two.

If your preferred installer isn't up to speed tell them to register with the combustion chamber section of this forum and find half a dozen of us at that can do it in our sleep and can give them instructions.

Or even better there are professional members already here that would no doubt cover your area.

 

[Dan Robinson]

P.s. to this properly with a combi would require an outdoor sensor really.

 

[Dan Robinson]

In fact I think I have just found my next project at home

 

[blubs]

Thanks, i think i have my answers now?!, shame there isn't a boiler with a simple '2 switched live' setup...
.. Obviously I will be doing the installation/wiring myself!! most electricians i know can't handle this sort of thing! or even a honeywell y plan!, unless its wired from scratch by themselves!!