Viessmann Weather Compensation and Separate Zones UFH

Hello, I'm hoping that somebody may have experience of how the following works in practice and I'd be grateful for any input.

To set the scene, the project is a 4 bed, 2 bathroom Victorian mid-terrace insulated to current Building Regs. We're looking to use a Viessmann 200-W 19KW system boiler with a 210 litre 200-V cylinder set up as a 4-pipe system, controlled using a Vitotronic 200 H01B weather compensation controller. Ideally, we would like 3 zones: 1. ground floor UFH (a Speedfit single room pack with its own adjustable blending valve and circulation pump); 2. ground floor rads; and 3. first floor and loft floor rads. The ground floor UFH zone and radiator zone are in practice open-plan.

Getting the weather compensation to work when there is more than one zone seems to be the main problem. If we compromise and combine zones 2 and 3 (the radiators) then Viessmann Techical have suggested the solution of using the optional sub-mounted mixer kit or, as we already have fitted the UFH valve/pump, an actuator and a brass bodied mixer turning it into a 6 pipe system. The Speedfit valve/pump would be wired into the actuator and I'm guessing the actuator then wired back to the boiler. I'm also guessing that there will be no other zone valves necessary and all wiring can be done at the boiler. Likewise, there will be no internal thermostats required and all controls for the two zones and the hot water will take place from the HO1B controller.

1. Is this correct so far? Have people had experience of this working satisfactorily in practice?

2. Would all of the rads have TRV's, save for the two bathroom towel rails?

3. Would it however be advisable/is it possible to keep a room stat for the UFH zone (to act like a TRV)?

4. I'm waiting for a price for sub-mounted mixer kit and/or an actuator and brass bodied mixer (they don't seem widely available). If it turns out to be unnecessarily expensive then what are the pros and cons on losing the weather compensation on the UFH zone and simply using a room thermostat and a 2 port valve to give separate circuit with individual control from the thermostat?

Thanks in advance.

thr brass bodied valve with the right mixer motor is much the same as submounting kit...

You can't use any off controls with the vitotronics 200, and you save a lot by not buying the controls, thermostats pump and mixing valve from the UFH manufacturers...

If you want a decent heating system stick with the weather compensation and forget the zoning...

are you and installer seeking help or a member of the public...

The OP's expectation of combining different systems and controls and expecting them to work properly demonstrates that he is an ( over active ) owner .

I expect that he is/has employed a basic plumber to do the installation but one for whom the complexity of controls is totally outside his capabilities.

The totally different characteristics of UFH make it difficult to control at all and particularly not in conjunction with radiators!

Food for thought: how does UFH with a time constant of two hours cope with WC when the outside temperature increases from 0 C to 10 C within two hours?

Tony

Yes Tony whilst not rocket science its it does require specialist knowledge to integrate UFH with weather compensation and radiator circuits and you do need to know what you are doing.

I do a great deal of it in London and many a time I have to clear up other peoples messes...

But aren't you struggling with the appropriacy of weather comp...let alone how it works with UFH, just like so many other heating engineers in the UK...

I would suggest that the OP looks on the internet for integrated heating for a professional installer!

You can't use any off controls with the vitotronics 200, and you save a lot by not buying the controls, thermostats pump and mixing valve from the UFH manufacturers...

Click to expand...

Sadly, the UFH valve/pump is already installed (but I will take it down and save for another job/ebay if the sub-mounted mixer kit is not much more expensive than buying the Viessmann actuator and brass bodied mixer (and solder kit) separately)...

If you want a decent heating system stick with the weather compensation and forget the zoning...

Click to expand...

I would have thought that in the event of losing one or 'tother the one to lose would be the weather compensation as it would not be a good idea to put the UFH and rads on the same zone?

The OP's expectation of combining different systems and controls and expecting them to work properly demonstrates that he is an ( over active ) owner .

Click to expand...

My proposal is an entirely Viessmann system (save for the UFH pump which is a Grundfos unit which would be wired back to a Viessman actuator to integrate it into the system and, re Q3 above, a UFH roomstat might be a nice addition if it could be made to work with the system). Your deduction that I am an over active owner is correct though (albeit a general builder by day, who finds it prudent to have some idea of what is going on!).

I would suggest that the OP looks on the internet for integrated heating for a professional installer!

Click to expand...

I have a Viessmann installer lined up but I'm not sure if he has installed this exact system before, so I though it would be a good idea to canvass opinions from people who may have done this particular, or similar installation several times before and would have experience of the ins and outs and how well it works in practice.

ALEC1 said:

But aren't you struggling with the appropriacy of weather comp...let alone how it works with UFH, just like so many other heating engineers in the UK...

Click to expand...

I dont think so Alex, I am a great fan of WC but I do understand the problems associated with using WC with UFH.

The bigest problem the OP seems to be creating is trying to use WC on UFH together with rads BOTH on the same zone!

OP, I am not even convinced that your proposed system even has any provision for applying WC to the UFH.

UFH in concrete floors needs 1.5 - 2.0 hours to warm up and so needs to be started early to reach the required temperature at the appropriate time. During that time the external temperature will vary a lot if its the morning. So the correct control is an intelligent system which has learnt the characteristics of the floor as well as the typical weather changes during this time.

Rads warm up in 10 minutes so cannot ( efficiently ) be used on the same timed zone as the UFH.

Its not really that complicated but it does need to be properly designed to operate properly.

A friend has just has a system installed in his house with all UFH and with 26 zones. A castle? No just a five bed house with seven toilets and with a pool in the basement. He has a 500 li thermal store for the hot water and another for the pool although he has never been able to give me an explanation of why he thinks thats needed.

Tony

Thank you for responses so far.

Tony, I think my original post is getting a bit confused - I am trying to use WC on the UFH but with the UFH separately zoned from the rads (I completely agree with what you are saying about response/warm up times of rads versus UFH).

The Viessmann sub-mounting kit (or the actuator and the brass bodied mixer coupled to existing UFH pump) should create that separately controllable zone for the UFH. Both ways its Viessmann kit so it will be controllable from the H01B (which can do two zones) and the WC should be applied to the UFH (hopefully, if I understand it correctly!).

Ooops - too slow on the keyboard. Mysteryman has beaten me to it. Oh well, will post anyway...

Mysteryman - would you put a seperate room thermostat on the UFH (this bit I don't really understand)?

A room stat on UFH is another hot chestnut!

Many ( most/better ) WC systems also look at the room temperature as well as the outside temperature.

By the time a room stat would turn off, the floor is already too hot! It then continues to give out too much heat for the next 30 min!

Tony

gosh here we go... you don't need indoor sensing with a viessmann weather compensated system nor for radiators or for underfloor heating or both....

why is everyone so hung up on indoor sensing... the 150 or so systems I have installed all work fine with NO indoor sensing...

To be clear with the viessmann system you do NOT need indoor sensing but you can buy indoor sensors from viessmann that communicate with the boiler, it depends on how much you want to spend!


all you need is the correct heating curve on the UFH zone....its that simple!

and yes if you have a pump on site the brass body mixer is the better option....

ALEC1 said:

To be clear with the viessmann system you do NOT need indoor sensing but you can buy indoor sensors from viessmann that communicate with the boiler, it depends on how much you want to spend!

Click to expand...

I would put it differently!

The Viessmann system will work without an indoor sensor!

Adding an indoor sensor will enable it to take account of the increased temperature when you have the local society members round all producing a lot of hot air!

Sorry to drag this thread out of its grave! I'm looking at installing a very similar system in my house. Viessmann Vitodens 200w System boiler, Vitocell200 300l unvented cylinder and the HO1B weather compensation.

Downstairs we're looking to install polyplumbs overlay UFH which is installed just under the tiles and has a quicker response time than traditional UFH in screed (had it in last house too). Upstairs will be radiators.

Will this system work with the above equipment and weather compensation?

Is the 4 pipe system much cop?

Mixing rads and UFH need significant controls and installation knowledge!

Separate timing as separate response times too!

Its not an easy job so choose carefully who you get to do it for you!

Tony

Anyone have any recommendations for installers in the West Midlands(Solihull)?

Thanks for the input Tony!

I've been lurking for a while trying to find the answer I'm looking for and have read with interest the Agile/ ALEC1 posts on Viessmann and UFH.

I started with a Viessmann 222F 35kW with WC controlling the radiators (all with TRVs) in my fairly large, extremely old and inefficient house. When we redid the kitchen I bought a Nu-heat 2 zone overlay UFH for the kitchen and utility rms (on the strength of it's low buildup under the tiles). This included the wiring centre and roomstats for the two zones, pump and mixing valve.

It was only after the plumber (not a Viessmann trained - my mistake) tee'd off the radiator feed and return for the feed and return to the UFH mixer that I realised there was no way to call for heat from the wiring centre back to the 222F. I eventually went for omitting the call for heat and programming the UFH timer to only be on when the boiler was on. I accepted this meant there could be times when the UFH is calling for heat but merely circulating luke-warm water.

So to the point:
1. Am I correct- the wiring centre cannot call for heat from the boiler (there's no external volt free contacts)? I've scoured the wiring diagrams but can't find anything obvious.
2. If the boiler senses a flow around it's heating circuit (using the UFH pump- not the internal boiler pump) will it see the water temp dropping internally and then kick in to heat up? (It doesn't seem to be so far)
3. Is having two pumps in the same loop going to cause issues? (again, no obvious problems so far).
4. Is there a smarter way to do this? I appreciate the posts saying the controls are complex and I'm willing to go to the needed level. It seems 2 supposedly premium products are struggling to speak to each other though!
5. In the rambling below- can the 222F take a pre-heated supply from a solar thermal system?

It's been in for a year and has been ok although often the floor doesn't feel subjectively warm. There's still a radiator in the kitchen which works away (stat set to 21), but the utiilty room seems to rarely need heat to reach 19 as it's set. The boiler house itself is set to 19deg on a fairly low (2.2 I think) curve in an effort to save our horrific heating bills and I'm looking at pre-heating the water into the boiler with a solar thermal setup to try and reduce the bills a bit further. More secondary glazing is also in the works.

thanks for reading the rambling and for any advice offered.

W