Vitodens 333, Greenstar 550 -VS- Thermal store system advice

[PaulH79]

Hello, I'm planning to install a new heating & DHW system to our edwardian aged semi detached house, and looking for a bit of advice on what kind of system to go for...

We currently have an old Baxi Bermuda back boiler and 120L DHW cylinder.

I'm currently weighing up the following options, and would greatly appreciate any advice, issues or alternatives.


Option 1:
A thermal store based system, with Dunsley Yorkshire woodstove and gas fired boiler feeding a thermal store, with provision in the store to accept a solar circuit at a later date. From what I can gather the pro's would be a hugely reduced energy bill, and DHW at mains pressure.
Cons would be the huge expense, and I'm not sure that the 300/350L models (largest unit I'm gonna fit in the loft) are suited to heating.

Option 2:
A Large combi with high DHW output, such as the Viessmann 333F or Worcester 550. In this case we would install a stand-alone wood fired burner in place of the baxi boiler and firefront. Obvious pro's would be a simpler an cheaper installaiton, but with the drawback of being unable to use renewables.


If anyone could advise on the functionality & practicalities of the above, or offer any alternatives that would give a high DHW output, it would be much appreciated.
Cheers

 

[PaulH79]

Does anyone have any experience of owning or installing either the Viessman or the Worcester unit? Or an equivalent from another manufacturer?
What are these boilers actually like in practice, do they really deliver 19-25 litres of hot water per minute as advertised? What is the pressure/flow like when 2 outlets are in use?

Similarly for the termal store option, is a 300L store big enough to be useful in a combined CH/DHW install? Or is this size of tank only really good for DHW?

Any other issues to consider?

Any advice would be great cheers!

 

[ServiceNumpty]

Albeit the cost of installing a 333 or 550 would be cheaper, (I have fitted the hiflo's). The only pro as I see it, is to save space. I personally would install a conventional heat only appliance with a twin coil unvented cylinder, this allows for thermal solar panels at a future date, you also have the Viessman 242f which is in effect a similar set but all housed in one unit.

I have a Worcester System Boiler, 210ltr twin coil unvented, connected to solar panels. I have the solar controller , with 3rd sensor next to my programmer, this tells me the temperature within the cylinder at the top & bottom.

Solid Fuel at the moment can be just as if not more expensive than gas, I have removed at least 1/2 dozen systems this year alone.

But there are factors to be considered when going down the unvented route, cold water flow rates, cold water dynamic pressure, dhw piping etc etc. A full site survey would need to be conducted.

 

[mehran]

no one can really give you a clear answer. there is loads of way to do it and the more money you have the more you can have.

get a few people around and dont go with the cheapest option I know I would do it differently to most other RGI's