Viessmann Vitodens 200 W System 26 KW Design Questions

Colmrenault

I was wondering if you can help me with the design of my heating system that I am upgrading. I plan to buy a Viessmann Vitodens 200w system 26 Kw (WB2C). Ideally I want to plumb the radiator flow and return to a System Zone 4 manifold, as I have very poor circulation down stairs compared to upstairs and want to run the pumps a different speeds. The beauty of the System Zone is that once the pump is off no flow will occur in that circuit, thus eliminating motorised valves, which I have had desperate trouble with unreliability in the past.

http://systemlink.ie/systemzone-product-ireland.asp

The copper cylinder coil will be fed separately from the boilers second set of flow and returns.

The System Zone manifold will be fed from the left with the boilers own pump. From the bottom of the System Zone there will be two flows & two returns, one set feeding upstairs & the other feeding down stairs & each will have it’s own circulation pump.

Upstairs & downstairs has conventional radiators. Both zones need to have separate time & temperature control. My original plan was to combine the pumps, time clocks & Zone thermostats with a System Lex wiring centre…

http://systemlink.ie/systemlex-product-ireland.asp



This can control up to 4 separate zones with individual time & temperature & individual pump control. It can produce a switched 220 volt call for heat or a zero volt call for heat. This would be no problem with the Vitotronic 100 standard controls on the WB2C version of the Vitodens 200W.
However I want to use the Vitronic 200 Advanced weather compensation module. This seems to talk digitally with the boiler and is constantly aware of the outside temperature and modulates up & down accordingly.

My plumber is under the impression that he can still use the System Lex to call for heat from the boiler with the didital Vitronic 200? Is this true?
If it is the System Lex can look after starting the pump.

Even if it can my problem with this though is that the traditional zone thermostat is only either on or off which doesn’t give the boiler the chance to modulate down as the zone approaches the target temperature.

Preferably I would prefer to use two Vitotrols 300A’s, one controlling upstairs & one controlling downstairs. Two of these will plug straight into the Vitotronic 200 doing away with the Sytem Lex altogether perhaps?

As they can communicate digitally with the boiler would I be correct in saying that the boiler can modulate down as the zones approach target temperature?

If so the problem I have now is how do I get the boiler to turn on and off the pumps for each zone?
There seem to be two electrical add-ons available, namely…

Extension AM1 & Extension EA1.

From the technical guide…

Extension AM1
Part no. 7429 152
Function extension inside the casing for wall mounting.

Using the extension enables up to two of the following functions to be achieved:
Function Rated breaking capacity of the relay output
– Switching the DHW circulation pump (only with the Vitotronic 200, type HO1A)
– Switching the heating circuit pump for a directly connected heating circuit
– Switching the circulation pump for cylinder heating (not for boilers with integral DHW cylinder)

Can two of these outputs be triggered by the 2 vitotrol 300A’s to turn on their respective pumps on the System Zone manifold?



Extension EA1
Part no. 7429 151
Function extension inside the casing for wall mounting.

Using the inputs and outputs enables up to 5 functions to be achieved:
Function Rated breaking capacity of the relay output
1 switching output (zero volt changeover contact)
– Central fault message output
– Switching a feed pump to a substation
– Switching the DHW circulation pump (only with the Vitotronic 200, type HO1A)
2(1) A 250 V~

1 analogue input (0 to 10 V)
– Set boiler water temperature default

3 digital inputs
– External heating program changeover for 1 to 3 heating circuits (only with Vitotronic 200,
type HO1A)
– External blocking
– External blocking with central fault message
– Minimum boiler water temperature demand
– Fault messages
– Brief operation, DHW circulation pump


What about this one?

---

Another question I have is what happens when the boilers internal diverter valve gives priority to the coil and cuts flow to the System Zone manifold and sends all the hot water to the coil (pumped by the boilers internal pump). I assume it’s no harm to leave the two other zone pumps running.

My next question is regarding part number 7408012 room temperature sensor. Would I be correct in saying that this is a hard wired sensor that can be mounted remotely from the boiler? I assume I do not need this if I order two Vitotrol 300A’s.



Regarding the …

Mounting base for programming unit
Part no. 7299 408
To be able to freely position the programming unit of the control unit
anywhere outside the appliance.
To be fitted directly to the wall or a surface box.
Distance from the boiler: Observe the lead length incl. plugs of 5 m.

Can I cut this lead and solder in an extension. 15m should do me?




I was going to put two grundfos alpha 2’s pumping upstairs and downstairs. As you may know this is a variable speed pump with high efficiency.
Would it be best not to go for the optional variable speed high efficiency pump in the boiler itself. Maybe they would confuse each other?


Finally do I need mixing valves on the heating circuits?

Thanks for your help with these questions. My main objective here is to avoid motorized valves at all costs and to have maximum modulation, thus increasing condensing duration/efficiency.

Colm (colmrenault@yahoo.co.uk)

Have you called Precision ( http://www.precisionheating.ie/ ) they should have all the correct answers for you on their product.

JohnnieK

The Vititrol 300 can control up to 3 seperate heating zones. I dont know if it would be compatible with a system link and if you are just using pumps it is possible the the internal pump in the boiler could circulate heat through the zones that are not in use. This control system is litrelly brand new and has only been released. As Gary has said the only way to know for sure is to call Stephen in Precision Heating (they are Viessmann in Ireland) and ask him and he will find out for you. There is no point in listening to post on this because you will get conflicting information so the best thing to do would be to call the horse himself.

P.S There great boilers.

Colmrenault

Thanks for your prompt replies Gary & Johnie. I was onto the sales department in Precision Heating during the week alright. He mentioned Extension AM1 but he wasn't really sure. I will try to get through to their technical department on Monday.

Colmrenault

Colmrenault wrote: »

Thanks for your prompt replies Gary & Johnie. I was onto the sales department in Precision Heating during the week alright. He mentioned Extension AM1 but he wasn't really sure. I will try to get through to their technical department on Monday.

Send a copy of your first post to them and it should make it easier for them to come up with answers, also tell them that Gary would be able to answer all your in depth questions for one of his boilers and you may go with the manufacture with the best answers(keep them on their toe's:)), Gary.

Carlow52

3 comments.
Why not use the system link setup to do the HW coil?

Seems to me that combining what seems to be a pretty advanced boiler with the electronics of the system link is perhaps not the way to go.

The other point is that I use a separate time clock for the HW and have the water heated before the CH comes on in morning and afternoon.

This allowed me reduce the boiler size and achieve more condensing as the condensing on the HW loop on its own will be poor enough if tank temp is much above 60

What I did with mine was I bought the manifold and built my own electrical controls

I used the alpha pump only on the zones that have TRV's

Colmrenault

Carlow52 wrote: »

3 comments.
Why not use the system link setup to do the HW coil?

Seems to me that combining what seems to be a pretty advanced boiler with the electronics of the system link is perhaps not the way to go.

The other point is that I use a separate time clock for the HW and have the water heated before the CH comes on in morning and afternoon.

This allowed me reduce the boiler size and achieve more condensing as the condensing on the HW loop on its own will be poor enough if tank temp is much above 60

What I did with mine was I bought the manifold and built my own electrical controls

I used the alpha pump only on the zones that have TRV's

Yes I was toying with the idea of using the manifold to power the coil. However this means trying to integrate another pump with the digital controls of the boiler (version with Vitotronic 200) so that put me off. What advantages can you see in doing that?

My house is a 10 year old detached block built two storey with 6 inches of isulation in the attic and 2 & 1/2 inches of aeroboard in the 4 inch cavity. Double glased PVC windows.

I just entered my details into a boiler sizing website (http://www.idhee.org.uk/calculator.html) and it said I only need a 15Kw boiler. This seems small to me, but alot of websites say that boilers were traditionally over specced in the past which leads to a lot of cycling. Would you think 15Kw is enough?

Carlow52

Am not skilled in advanced boilers so cant help with the digi output question.{ am of the butterfly carb era)

I concur with the over-spec theory, u don't ever need to have all rooms at 21 and the tank full at one point in time.

I time-shift the HW as discussed and then manage the timing for the 3 remaining zones I have.

I would double the insulation in the attic and make the access hole 100% airtight and insulated: best value money spend ever.

Cant comment on the 26 vs 15.
where did the 26 come from?

I heat 2500 with 22

Colmrenault

Cant comment on the 26 vs 15.
where did the 26 come from?

The Vitodens 200W (WB2C) comes in 19Kw, 26Kw, 30Kw & 35Kw versions so I was worried about buying one to big or too small so I had the 26Kw in my head. By the sounds of things, the 19Kw would be better suited to my house, and would modulate down lower than a bigger boiler when necessary.

I heat 2500 with 22

Had you enough output last winter? If so I'll definity go for the 19Kw.
By the way is your house block built like mine or timberframe?

Carlow52

All external walls insulated internally ( retro job)

Yes was warm enough because when I sized the rads I used 60 and 70 as the input temp to see what rad sizes where required and erred on the side of 60, which means the rads are a little bigger but then when it was really cold I raised the boiler temp to close to max if required and kept the grandchildren away from the rads.

I can also zone by room:)