Integrating UFH with exisitng Yplan system, & new boiler

[lchris21]

I'm about to embark on the great adventure of fitting a new boiler to my extension I'm building. I've removed a small rad from the kitchen and installed approx 10m2 of UFH.
A couple of questions:
My exisiting Ideal boiler is coping, just about, with the system I have at the moment and gives plenty of HW and the CH don't take long to warm up. Its approx 15KW. Shall I take the opportunity to go up to say, a 18KW just to be on the safe side ? I'm going to change to a Vailliant Ecotec plus as they seem to have a good rep on the tinterweb. The boiler is approx 14yrs old and I may as well change it when the kitchen is like a bomb-site.

The kitchen has now become part of the dining room and I want to keep one rad in place and somehow integrate this with the UFH? Is this possible with Y-plan? I'm thinking a two port valve tee'd off the pumped flow of the new boiler feeding the dining room rad and then down to the blender of the UFH. Is this OK? Will I have to fit another valve into the pumped return to stop the exisiting pump playing havoc with the UFH?

I'm hoping to have a room stat in the kitchen/dining room extension to control this and somehow integrate it with the exisiting Y-plan setup I have, which I've yet to get my head around. Basically ending up with two zones, one being the rest of the house and the other, the new extension.
I don't really want to go down the road of completely redesigning the system to S-plan which I believe might make things a little simpler???

On the subject of integration Vailliant seem to have a selection of "add-ons" for their boiler range which might help simplify the process.. Or am I completely mad and suffering over googling syndrome ?
I'm hoping to just whack in the new Valliant, do away with the exisiting CH&HW timer/programmer, plug in some superduper add on from Vailliant that will control my two zones, HW and take commands off two room stats?

Confused? I am now

Cheers

 

[lchris21]

Cheers, already got the the UFH mixer, exisiting pumped system etc so really don't want to go down that route.

Looking at 3 channel programmers at the moment. Any suggestions?

 

[lchris21]

Had a quick look at their sub mounting kit. Will it fit inside a normal wall hung kitchen cupboard ?

 

[DeltaT]

The separate UFH mixer can't be weather comped.

Oh I love this forum!! You never heard of a 4 way mixing valve then??

 

[mysteryman]

It mounts immediately below the boiler with a matching casing. It would need to be a big kitchen cupboard.

 

[mysteryman]

You shouldn't use a 4 way mixer with a condensing boiler because you don't want a raised return temperature.

I was making my replies for the DIY man, not for commercial jobs!

 

[Boilerman2]

Methinks Mysteryman has an unhealth interest in Viessmann i.e on the payroll???

 

[ChrisR]

I wouldn't worry too much about weather compensation for a v small system. 2 parts complication and 9 parts baloney. You can always use an optimising thermostat. You can use a programmable one like a Honeywell 937. Saves buying a 3 channel programmer too.

If you use a 3 port, it''ll always be open somewhere, so if another zone calls for heat, your 3 port will send heat where you don't want. I'd lose it.

 

[lchris21]

I'll probably have both the existing heating on plus the new extension UFH loop & rad in there at the same time. But it would be nice to be able to just have the UFH loop on earlier to warm up

Is there much hassle changing from a 3 port to two 2 port valves? While the kitchen is in pieces, running in a few more bits of pipe and wiring will not harm in the grand scheme of things