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.


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 ([email protected])

 

[Gray0689]

It's a very complicated system the way it is 5 pumps!!!
If you have pumps at different speeds won't the pump at higher speed just starve the others
Why do you have bad circulation downstairs??
The pumps is an old way of doing things if you have good motorized valves should have no problem?
And I got to say I never saw so many compression joints in my life in one area!!!
Also the expansion relief valve should be pipped to out side if that blew off there your going to have a big mess!!

What your doing is good zoneing areas off but your doing it an old way
You should have mot valves linked to room stats per zone not pumps

 

[doitmyself]

I plan to buy a Viessmann Vitodens 200w system 26 Kw (WB2C).

How big is your house?
Have you sized the boiler using Boiler Size Calculator

I have very poor circulation down stairs compared to upstairs and want to run the pumps a different speeds.

How many rad upstairs and downstairs?
Has the system ever been balanced?

eliminating motorised valves, which I have had desperate trouble with unreliability in the past.

Decent valves, i.e Honeywell will work for years without any problems. You can't say the same about the cheaper ones.

Your proposed solution is a very expensive sledge hammer to crack a nut.

If you want maximum modulation this must be designed into the system from scratch, which includes installing the correctly sized radiators.

 

[colmrenault]

It's a very complicated system the way it is 5 pumps!!!
If you have pumps at different speeds won't the pump at higher speed just starve the others
Why do you have bad circulation downstairs??
The pumps is an old way of doing things if you have good motorized valves should have no problem?
And I got to say I never saw so many compression joints in my life in one area!!!
Also the expansion relief valve should be pipped to out side if that blew off there your going to have a big mess!!

What your doing is good zoneing areas off but your doing it an old way
You should have mot valves linked to room stats per zone not pumps

Thanks for your thoughts Gray. The picure of the System Zone 5 is not actually in my house. It's just a picture of one I took in someone elses house. I'll let them know about their blow off valve. I will be using a smaller version of this a 4 zone (it's the smallest available, one flow & return will be blanked off). I'll only have 3 pumps, one in the boiler itself powering the manifold & coil and two more, one powering upstairs & one powering downstairs.
According to Systemlink.ie the pumps can be run at different speeds without starving each other. Even though using pumps may be a old method, someimes an old method can still be good. I'm not sure why I have bad circulation downstairs. One plumber I had over said the pipework is too small & just poorly designed. The main flow (3/4")goes from the boiler to the hot press upstairs where the pump and Copper cylinder is (8m away) then tee's off with one side going to the coil and the other going to the all the radiators in the house. All the upstairs rads get fed first (6 big singles) and then the 3/4" has to meander it's way downstairs (15m to the first rad) to feed 6 big rads, two of which are doubles. It is currently an open vented system.
My plan is to pressurise the system, run an extra flow & return upstairs for the coil. The down stairs pipe run will be shortened considerably (by 23m) with the new layout taking it's feed from the system zone which will be dowstairs too beside my new boiler. Maybe that will improve downstairs flow?
After the trouble I had in my previous house with motorised valves, I just won't touch them again, even though it would make my design simple and cheap.

 

[colmrenault]

How big is your house?
Have you sized the boiler using Boiler Size Calculator

How many rad upstairs and downstairs?
Has the system ever been balanced?

Decent valves, i.e Honeywell will work for years without any problems. You can't say the same about the cheaper ones.

Your proposed solution is a very expensive sledge hammer to crack a nut.

If you want maximum modulation this must be designed into the system from scratch, which includes installing the correctly sized radiators.

Hi doitmyself
My house is a 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.

I just tried the boiler sizing website and it said I only need a 15Kw boiler. Would you upsize a little from this or is it usually fairly accurate?

Even with all the rads turned completely off upstairs the pump seems to be under a lot of pressure pumping downstairs with cavitation noises coming from the pump also. It's a 6m head pump on speed 1. The expansion tank is about 3.5m above the pump.

What formula do I use to work out if my existig rads are the correct size for their room? Thanks for your help.

 

[Gray0689]

Thanks for your thoughts Gray. The picure of the System Zone 5 is not actually in my house. It's just a picture of one I took in someone elses house. I'll let them know about their blow off valve. I will be using a smaller version of this a 4 zone (it's the smallest available, one flow & return will be blanked off). I'll only have 3 pumps, one in the boiler itself powering the manifold & coil and two more, one powering upstairs & one powering downstairs.
According to Systemlink.ie the pumps can be run at different speeds without starving each other. Even though using pumps may be a old method, someimes an old method can still be good. I'm not sure why I have bad circulation downstairs. One plumber I had over said the pipework is too small & just poorly designed. The main flow (3/4")goes from the boiler to the hot press upstairs where the pump and Copper cylinder is (8m away) then tee's off with one side going to the coil and the other going to the all the radiators in the house. All the upstairs rads get fed first (6 big singles) and then the 3/4" has to meander it's way downstairs (15m to the first rad) to feed 6 big rads, two of which are doubles. It is currently an open vented system.
My plan is to pressurise the system, run an extra flow & return upstairs for the coil. The down stairs pipe run will be shortened considerably (23m) with the new layout taking it's feed from the system zone which will be dowstairs too beside my new boiler. Maybe that will improve downstairs flow?
After the trouble I had in my previous house with motorised valves, I just won't touch them again, even though it would make my design simple and cheap.

From what I can see this system zone manifold is for 2 heat sorces
Why do you need it if only working off 1 boiler your plumber could very easily make a manifold up and if you use good motorized valves instead of pumps if you ballance all the rads it would be better in long run
I'm a plumber from northern Ireland
And I know what some of the plumbing is like in the south so be carefull of who you get!!!!!

 

[tamz]

What you are proposing is a bit over complicated for a domestic situation but whatever floats your boat. Basically the "system zone" thing is nothing more than a low loss header.
You maybe should listen to the plumber who told you the existing system was badly designed and get it done correctly this time around.

So far as connecting the proposed system up to the Vitronic 200, ring Viessmann technical and explain what you are proposing. They would be the best people to advise.

 

[Avatar]

err - for the cash you are going to spalsh on this excessive installation, you could instal two smaller combis to service your 'zones'.

I personally would look at a good sized combi (28-32kw) and spend your money on removing and replacing the old pipework. Then a motorised valve or two should be fine . . . .

You problem is an old and crappy system. If you want to solve the problems, rip it out and start from scratch - with a combi boiler system. This gets rid of all of the problems potentially, and delivers fairly high pressure hot water as well!

Putting a brand new boiler cobbled on with an excessive amounts of pumps is not going to solve the problems you have got - its like putting a sports car engine into a moris minor!!!

You are going to waste your money this way matey!

 

[doitmyself]

My house is a detached block built two storey with 6 inches of insulation in the attic and 2 & 1/2 inches of aeroboard in the 4 inch cavity.

I just tried the boiler sizing website and it said I only need a 15Kw boiler. Would you upsize a little from this or is it usually fairly accurate?

That's a well insulated house. I would be inclined to up the boiler to, say, 18kW. This would allow for the colder winters we seem to be experiencing at the moment (The usual assumption is a minimum temperature of about -1C.)

Even with all the rads turned completely off upstairs the pump seems to be under a lot of pressure pumping downstairs with cavitation noises coming from the pump also. It's a 6m head pump on speed 1. The expansion tank is about 3.5m above the pump.

Is the pump installed into vertical pipework and is it pumping up or down?

Why is the pump on 1? Have you tried the other speeds?

What formula do I use to work out if my existing rads are the correct size for their room?

The correct way is to use a heat loss program such as Stelrad Stars. But you could get a rough idea by allocating the total boiler output to each room in the ratio of room floor area to total house floor area. You should deduct 2kW from the calculated boiler size, which is the allowance for the hot water cylinder.

For example:

Boiler output = 18kW - 2kw =16kW for heating
Total floor area = 80m²
Requirement = 0.2kW per m²
Room area = 12m²
Heat required = 12 x 0.2 = 2.4kW radiator

You can find the output of your existing rads from a manufacturer's catalogue. There is very little difference between manufacturers for the same size and type of product so the Stelrad Elite Catalogue is as good as any.


If you want to have the boiler condensing as much as possible the return temperature needs to be below 55°C. Now rad outputs are measured under defined conditions: Flow temp = 75C, Return temp = 65C, Room temp = 20C. If you alter any one, the output will change. You have to allow for this when sizing your rads. So for flow = 75C, Return = 55C, Room =21C , you will have to oversize the radiator by 20%. This is because the rad will be giving out less heat than the mfrs literature says. So, if the size of the rad works out at 2.4kW, you install a 2.88 rad (say 3kW).

In you later posts you describe the paths taken by your pipes, the changes you intend to make and suggestions that the pipes are not the correct size. Read Small Bore Heating Systems and Copper Tubes in Domestic Heating Systems. They will explain why you need different size pipes and how you calculate the correct size.

Note: you still calculate on the actual rad output not the size. So, in the example above you use 2.4kW not 3kW. The same is true for the boiler size you don't need to increase this by 20% to allow for the lower temperatures.

You say that you definitely don't want to use motorized valves due to poor previous experience. What make valves did you have problems with?

 

[colmrenault]

err - for the cash you are going to spalsh on this excessive installation, you could instal two smaller combis to service your 'zones'.

I personally would look at a good sized combi (28-32kw) and spend your money on removing and replacing the old pipework. Then a motorised valve or two should be fine . . . .

You problem is an old and crappy system. If you want to solve the problems, rip it out and start from scratch - with a combi boiler system. This gets rid of all of the problems potentially, and delivers fairly high pressure hot water as well!

Putting a brand new boiler cobbled on with an excessive amounts of pumps is not going to solve the problems you have got - its like putting a sports car engine into a moris minor!!!

You are going to waste your money this way matey!

I had considered a combi, but when one of my mates put in a 30Kw combi, I didn't really like the result. For me it just takes too long for the hot water to get to any of the taps. To make it worse it's even a storage combi which is supposed to improve that problem. I suppose the boiler position will not usually be as central in a house as a copper cylinder. My copper cylinder is very well positioned at the moment and I like the quick response from it so that's why I'll stick with my choice of a system boiler instead, but i appreciate your thoughts.

 

[colmrenault]

Is the pump installed into vertical pipework and is it pumping up or down?

Why is the pump on 1? Have you tried the other speeds?

First time trying multi-quote, hope it works.
The pump is installed on horizontal pipework on the flow, just after the combined expansion & topping up pipe. It is on speed one because the cavitation noises on any other speed is just unbearable to listen to. I suppose it is pumping horizontally servicing upstairs but then eventually the water has to go downstairs vertically to service downstairs. I'm not sure if I've answered your question fully there.

You say that you definitely don't want to use motorized valves due to poor previous experience. What make valves did you have problems with?

My original valves were made by EPH, well that was the name on the motor anyway. The first motor stopped closing the zone when the zone thermostat asked it to so I brought that back and they gave me a replacement motor made by sauter. That lasted 6 months but then stated emmitting a constant buzzing so I returned that and thay gave me another sauter under warrenty. I was getting on fine for awhile with this then one night i looked up at the ceiling and there was a brown stain. I went up to the hot press and low and behold water was leaking out of the spindle of the motorised valve. That just finished me with them.

 

[colmrenault]

From what I can see this system zone manifold is for 2 heat sorces
Why do you need it if only working off 1 boiler your plumber could very easily make a manifold up and if you use good motorized valves instead of pumps if you ballance all the rads it would be better in long run

The beauty of the the System Zone manifold compared to one made up by a plumber is that no flow will occur in a zone if it's respective the pump is off, even if the pump beside is still on. I will try and upload the technical data sheet later.

 

[doitmyself]

The pump is installed on horizontal pipework on the flow, just after the combined expansion & topping up pipe.

If it is in horizontal pipe you need to make sure that the shaft of the pump is horizontal or very slightly higher at the vent plug end.

It is on speed one because the cavitation noises on any other speed is just unbearable to listen to.

If your tank is 3.4m above the pump, I doubt if it is cavitation.

Do you have separate feed and vent pipes, if so where do they connect to the system. If just before the pump, how far apart are they. A pic of the pipes and connections would be helpful.

I suppose it is pumping horizontally servicing upstairs but then eventually the water has to go downstairs vertically to service downstairs.

The fact that the water has to go up, down or horizontal is of no consequence. All the pump has to do is overcome the friction caused by the water travelling through the pipe. See the two references I gave.

Never heard of EPH

 

[Gray0689]

The beauty of the the System Zone manifold compared to one made up by a plumber is that no flow will occur in a zone if it's respective the pump is off, even if the pump beside is still on. I will try and upload the technical data sheet later.

Non return valves do the same thing
Myson motorised valves are good never had a big problem with them
Yes all valves can fail but never saw a myson one leak from centre

 

[Avatar]

If your friend combi didn't work i presume it wasn't plumbed in properly.

Like I said - spend the money on ripping out the old pipework and cylinder ect, and put brand new in.

How far is your kitchen/bathroom going to be from the site of the combi. If you can have the combi sited within 5 meters of both, you will have lovely hot water pressure. Although you will have to remove the old pipework first.

The type of set up you are looking at is like for an 8 bedroom house or something!

I do commercial plumbing in office buildings and the like (with multi zone valves), and what you are proposing would be rediculous for them - an office with 40 employees/8 tiolets an a huge space to heat!!!! In this office the combi is supplying 6 hot water outlets at once, that are with 5 meters of it though.

Really think it through, have some plumbers over to disguss it and wiegh up your options before you spend.

 

[Avatar]

Just to requalify, you have a 3-4 bed house with 1 kitchen and 1 bathroom right??

 

[maul]

you really need to find why you have bad circulation in your lower house circuit.
my guess is sludge restricting the flow or airlock or incorrect pipe sizing somewhere .
once you have that problem sorted all you need is 2 port zone valves (honeywell ) to control the seperate circuits.
valves do fail in time they are a moving part but they are cheap to replace.
pumps fail as well
thermostatic rad valves will also be a real godsend for efficiency as will proper balancing and pipe sizing.
simple solutions are the most reliable a multi pump system sounds a nightmare to me and its just not needed. also valves use much less power than pumps.

 

[ecowarm]

the 200w is a very efficient boiler and with the vitatronic control it will do all you ask of it without that system wiring centre thing. Bin the multi pump setup and use zone valves.
Call viessmann technical .......... very helpful and will put you right.

Also get one of their unvented cylinders to compliment the boiler.