Viessmann 200w WC and room t/s

[ridk1]

Hi,

I would like to install the Viessmann 200w with the weather compensation, but, I would also like to have an internal sensor.
Can it be setup in such a way that the boiler is being conrtrolled by the wc probe and the internal thermostat?

I have read several posts on here about this subject and I understand the different views as to whether or not an internal sensor is required but these posts do not answer the above question.

Thanks.

 

[Agile]

The disadvantage with this model is that as designed it does not take into account the internal room temperatures.

Now that does not mean that with a little knowledge of electronics applied that it cannot be done, but its just not supplied that way in the box.

Of course if you just wanted an on/off internal thermostat then that should be possible.

Tony

 

[ALEC1]

the vitotronic 200 sits in the boiler or on a wall and gives all the functionality you need..bit chilly boost the target room temp with the party button, going out press the set back button, chnage the time programmes..

No you dnt need a room sensor...why do you want one?

 

[ridk1]

Thanks Agile for your explanation. Alec1, thank you foir your explanation as well.

No you dnt need a room sensor...why do you want one?

My thinking behind an internal sensor is to be able to override the wc for when there is somehting happening in the house that is the exception to normal use:
-We have family/gangs of kids around (extra heat from watching telly, playing console games). Sometimes gets so hot we need to open a window (in winter).
-Drop in temp from open door/windows (during and after showers and baths or for heavy cooking)

Would the wc controller alone handle these situations?

..bit chilly boost the target room temp with the party button, going out press the set back button, chnage the time programmes..

That is the issue I'm having - how does the system know if the target room temp has been attained if there is no sensor to see what it is?

 

[ALEC1]

It all supposes of course that radiators are correctly sized... the latest controller will allow you to reduce the temperature very easily for when the kids come round...and when you open the windows..


I seems you just need a user interface, and that the vototronic 200 is I woild go to their website and look at their instructions


It may be a good idea to put a trv on some rooms, but certainly not all....

 

[Agile]

It may be a good idea to put a trv on some rooms, but certainly not all....

Not just a good idea but required under the Best Practice for installations now.

However, why dont your TRVs already control the max room temps already?

As for opening windows in winter, thats both expensive and probably mostly unnecessary.

I wonder how big a "modicum" is?

Tony

 

[ALEC1]

Tony, Have you done he 200 series trainig, read the instruction book or even installed one...you don't need TRVS with this boiler when it uses the vitotronic 200 weather compensator

Best Practice are UK guidelines, the boiler is developed in Germany to German standards... the two probably have nothing in common...

 

[ridk1]

I wonder how big a "modicum" is?Tony

Alec1, Myteryman, could you clarify please, do you know how the 200a would influence the boiler when used with WC?

The house is a shell at the moment. No plumbing done at all yet.

The house has been extended, old part of the house has solid walls, the new is cavity wall (100mm block, 100mm insulation, 100mm block). In terms of house volume of old to extended, I'd say its about 60% old 40% new. I was planning to have a trv on every rad.

 

[Agile]

The 200a is effectively the part of the boiler which controls it. Not an external component which "influences" it !

Remove it and you cannot operate the boiler ( without some other type of controller )

If W/C is being used, then TRVs have no effect UNLESS an additional heat source is provided in a room like a large TV for example.

If fitting a new system I would normally wish to fit TRVs as well with a W/C boiler although would not add them to an existing system. Some people like cooler bedrooms for example. W/C assumes a very well externally insulated thermal envelope and the same internal temperature in all rooms.

Yes, I have fitted the 200 series boiler! Also done the Viessmann domestic boiler training and the solar as well Alex!

Tony

 

[ridk1]

The 200a is effectively the part of the boiler which controls it. Not an external component which "influences" it !

Remove it and you cannot operate the boiler ( without some other type of controller )

What I was trying to ask was what does the 200a do when used as well as the Ho1B wc controller? I wasn't planning to use the 200a on its own.

If W/C is being used, then TRVs have no effect UNLESS an additional heat source is provided in a room like a large TV for example.

Sorry, I'm a little confused by this - so you are saying TRVs would be a waste of money in a Viessmann WC setup?

W/C assumes a very well externally insulated thermal envelope and the same internal temperature in all rooms.

All rooms will not have the same level of insulation (becuse we have extended). The old part of the house has solid walls, but we have added 50mm celotex to them internally where possible which helps.

 

[Agile]

The 200W boiler needs a controller to work at all. It can either be used with a vitotronic 100 or 200.

The 100 is a basic constant temperature controller and can be used with a room stat. Part Number HC1B.

The 200 is the W/C controller and its Part Number is HO1B.

You only need ONE of these plus the outside sensor for the HO1B.

Earlier boilers were supplied with the basic controller which you had to throw away to fit the W/C. Now you can order the boiler fitted as required.

W/C works by measuring the outside temperature and providing a predetermined amount of heat to the building which should result in the required internal temperatures.

In theory a TRV is not needed BUT they do limit the temperature of a room if heat is being added such as from a large TV or cooking etc. I would recommend them at least in the living room. Even without a TV, five people generate say 100 watts each of heat each if they are having a lively discussion, more if dancing! [ Alex will disagree at his own risk but will probably just say open a window if its too hot! ]

Its very important to get the best from W/C that the heat output of EACH rad is adjusted to provide the exact heat output needed for that room to maintain the target temperature. Doing that will enable lower temps in bedrooms if required.

W/C can be good at doing what it is designed for and if used correctly can result in a gas saving of perhaps 5-6% and an increase in comfort.

But W/C is not without problems! These include:-

Different people perceive the temperature differently at different times! Today for example I say its too warm. Its actually 20 C but I have a slight temperature due to a virus. I need anti viral drugs and not any adjustment to the W/C.

Go out for a 30 min jog and you come back feeling hot at 21 ° C. Sit still looking at the internet and you could be feeling cool because you are not producing much internal heat. Same watching a boring old film. W/C does not respond to how YOU are feeling. If you live alone thats no problem.

As far as I know, no domestic W/C takes into account the rate of change ( Δ T ) outside. If its 7 am there is no point in pumping vast amounts of heat into the house when the sun is rising in 2 min and the outside is increasing at 20 ° per hour.

A house can cool significantly in 30 minutes but underfloor heating takes 1-2 hours to respond. Also an hour to cool as well.

Many houses can get very hot on the sunny side and remain cold on the north face. That only applies on sunny days and W/C does not respond to that.

But these are usually lesser issues and do not seriously detract from the advantages of W/C.

Your house sounds reasonably well insulated so should be fine but heat output balancing is very important and time consuming. I replace the sensor with a potentiometer so I can set the output flow temperature of the boiler and then have some USB temperature measuring memory sticks which can give a time/temp graph of a rooms heat up profile!

W/C wil only work if its very carefully set up and then NOT TOUCHED apart from whats available as a user function !

Tony Glazier

 

[ridk1]

Agile - what a fantastic post, thank you for taking the time to write all that up! Lots to take on board and think about.

 

[ridk1]

I have over 50 installed and my clients are very happy with it...

Thanks Alec1. Hope this isn't against the rules, but how can I get ahold of you outside of the forum if I wanted some help with my install?

 

[ALEC1]

I have messaged the OP...

Tony thats a great post...a first from you actually on this subject, a source of great frustration as I consider you with your background and thoroughness a very able technician... your negativity about heating technology has been a source of constant amazement to me..

Tony makes a valid point about perception of temperature, the best way to check this is of course with a independent thermometer.

My clients comment on the stable even temperature, the fact they can tell how cold it is outside from the radiator temperature, the lack of over heating...several of them have pointed to 20% savings on the gas bill when I have up graded on-off controls with weather compensation...Viessman say this is to be expected, vaillant say 10-15%.... I would only add that savings will relate to how well you interact with the programmer...(which is actually very intuitive!)

 

[Agile]

It defies UK understanding, but you can run mult zone heating systems with one outdoor sensor and NO indoor sensing, and it works very well..

It works ...

But that is only BECAUSE ( or shall I say IF ) each radiator heat output has been carefully balanced to meet the room temperature required.

That is an essential aspect of installing W/C.

The Germans having a reputation of obeying instructions and being fussy about getting things right are probably better at it that the typical UK bodge it installer!

Tony