vitodens 200 control

Andrew Hagen (ALH)

Just a note, the bypass in the boiler is not designed to be the only bypass in the system. You should have a separate differential bypass. You're probably already aware of the pump speed coding that needs to be changed.

The RS indoor temperature feedback is advisable if you're running completely on boiler reset. If you're zoning with thermostats and zone valves, it's probably unnecessary. Of course additional control of your heating system only gives you more options once it's up and running, even if you just rough-in the wires.

-Andrew

RadPro

vitodens 200 control

Thanks for your help on my last post guys……Now re the control of this 6-24, what is going to be my best option for control during days of high solar gain when is cold outside …lets say 0 degrees. Will I need the RS indoor thermostat with potentially other room thermostats wired to it. I want to keep the comfortrol mounted in the vitodens. Just picking the brains of you guys that do know thanks Paul (Oh BTW my application is about 1200 sq. ft of radiant…50% staple up and the other 50% in gypcrete with ceramic tile.,,I’m trying to run without the LLHeader and use the onboard vito/grundfoss pump.Again my goal is efficiency but as good a control as possible from the vitodens)

RadPro

vitodens

yes Im aware of the coding...Yes Im aware that all of the zones will pump continuously from the vito pump but I'm hope to balance them temp wise by adjusting the flow. If this just isn't right I'll buy the LLH and control a second pump( the other heating circuit)from the vitodens. Am I off track on this?????? thanks Paul

Andrew Hagen (ALH)

Flow

It sounds as if you are on track. Of course I'm unfamiliar with the details of your system. If you have only one zone, which will circulate continuously, you should not need the dp bypass. If you were to begin to zone the system with zone valves you would need it.

Hopefully the "staple-up" is in some sort of extruded aluminum plate. Otherwise the floors will likely want different temperatures.

Whether or not you need the LLH is based on the head loss at the "design" flow rate. 6-24's and 11-44's are the only Vitodens that can ever be run without the LLH. Not every 6-24 or 11-44 does not need the LLH. Many do need them. These are reasons why people work with experienced trained installers and/or designers. Whomever sold you the boiler should have some experience with it and with hydronic system design. It's really difficult to comment over the internet for obviousl reasons.

I recommend using the indoor sensor feedback for a system such as yours with no other direct indoor temperature control.

-Andrew

Paul Pollets

2 temps

Sounds like you'll need to separate temperatures, which requires a mixing station piped off the LLH. Review the Viessmann drawings for the piping, which are included in all installation instructions. The "A" pump does the med. temp and the "B" pump circuit controls the mixing valve.

If the design temperature between the 2 types of radiant panels is within 10 degrees, it may be possible to use a single temp., and balance at the manifolds...for serious hydronic experts only. Not providing 2 temperatures for the system, could result in very uneven and unbalanced zoning, not to mention $$ energy costs. I've never seen a "staple-up" and gyp application have similar design temps...usually a 20-40degree difference!! Do the math and design and pipe for the required (2) temps.

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heatboy

What.......

are your Delta T's and GPM requirements? I advise against using the internal pump for heating anything. You will need at least one more pump down stream of the mixing valve. Without the LLH, a primary loop will be needed and set your mixed temps as a secondary off that loop. The primary loop should have some sort of air elimination device, so by the time you add up all of the costs the LLH is a much better option.

Simply Rad_2

efficiency

If you are looking for efficiency you mught also look at the "staple-up" application. Especially, with zero or below design temps as you stated earlier. Do the math knowing the output of "staple-up" is limited to around 15 btu's per sq/ft. Also, the name of the game of efficiency is lower supply temps. Gyp is ideal,around 120(depending on loads and floor coverings) but with staple-up you supply temps can range from 140-180 degrees. Might want to re think "staple-up" by simply doing the math.
Jeffrey

Ron Schroeder_3

Vitodens control

Sorry, double post.

Ron Schroeder_3

Vitodens control

I have installed a 6-24 into a RFH home of 2400 Sq ft. The onboard pump is the prime mover. There is no mixing valve, there is no LLH. The boiler is controlled internally. The system operates with a homeowner satisfaction rating of 95%.

The distribution system consists of a 1" copper main distribution manifold that feeds three Heatlink sub-manifolds. Floor piping is 1/2" Heatlink pex with no loop length exceeding 250 feet. All loops are balanced for return temperature. There are no zone drive motors intalled at this time. The home is prewired for statlink control.

The missing 5% customer satisfaction arises in the library, where a combination of sedentary activity and a ceiling height window connected to a skylight provides a comfort challenge that the strategy cannot meet. The missing 5% means I have not met my objective. The client and I now have to strategize how we will resolve the deficit.

I do not recommend that you install a heating system inthe manner that I did unless you are prepared to own the system.

I also do not recommend that you use a room temperature sensor with the Vitodens boiler in RFH applications.

The boiler accuracy without a mxing valve is only 15C and with a mixing valve shrinks down to around 2C. A room temperature sensor is recommended only with fast acting emitters like wall panels or baseboards. In RFH applications think S L O W W W W. A slow boiler, changing room temperature slowly in response to slow outdoor temperature changes maximizes occupant, read customer, comfort.

The LLH will save you a lot grief. Think of it as your friend. It allows the boiler and onboard circulator to operate optimally independant of changing flow conditions at the emitter level. It also provides a smoothing effect to teh heat transfer from boiler to system. the literature shows some graphics illustrating how this works. Please use the insulation kit.


Paul has already addressed multi-temperature installations.

If you have questions that I havenot covered, please call me at 604-533-9445.

Mike T., Swampeast MO

Your Library Problem

Will toss out an idea:

Provided this doesn't put your flow over the edge, why not install some high-output fin baseboard beneath that ceiling height window? Control with a wall thermostat operating a simple zone valve. While I presume your operating temperature is very low, you'll still get some output from that b/b. Not sure if you'll find ratings for such low temperatures, but you should be able to make a reasonable guess as to output via interpolation. Someone at Slant Fin told me that they were seriously considering studying low-temp output of their b/b. Perhaps they could offer assistance.

Andrew Hagen (ALH)

I tend

to look at low mass radiant (extruded plates and to a somewhat lesser extent gypcrete) as a faster acting heat emitter.

I've always thought slow reaction equals discomfort. If the floor is instantaneously the same temperature as the fluid temperature as the boiler changes temperature the comfort will be maximized. A floor that lags the boiler by too much will not work as well.

If he has bare tube stapled up, he should pull it down and install some extruded aluminum plates. The Vitodens likes low system temperatures...staple-up does not.

-Andrew

Ron Schroeder_3

a good suggestion however

then I would need to set up a multitemp system. Additionally, the BB would add an aesthetically most unappealing component.

How about this: I will ramp up the supply temp a few degrees overall. Then I will temperature limit the bedrooms and living room with wall stats and thermomotors. In theory the stats will limit the output to the areas where additional heat would cause dicomfort. The library will emit a few more BTU's per square foot. Comfort should increase. The wild loops in the WC will just make those rooms a little toastier and give the excessive water and warmth some place to go.

What do you think?

Mike T., Swampeast MO

Since you said 95% satisfaction, I presumed that the library was a touch chilly--not cold. B/B will have some output even at very low supply temperatures and the high-output versions would maximize output with minimal length. Would not have suggested if I thought that it would require a multi-temp system.

If cost is no object, you could possibly use bare fin tube sunk into a chamber in the floor with a nice cover. Pre-made units with extremely attractive covers are available.

Have you considered a large, TRVd panel radiator or even a TRVd cast iron radiator in the library? Again, sized to work at the available supply temperature providing somewhat more than your estimated "missing" heat?

Do though run the flow numbers carefully as such will probably be a relative wide-spot in the road compared to the underfloor loops.

Not saying at all that your remedy is bad or even poor. Am however still thinking of 95% satsifaction so presume that the rest of the house is near perfection. Might be bad to monkey with everything else when the problem is confined to one area.

Ron Schroeder_3

we are running supply temps

of between 85F and 100F and only run up on the design days. At this extremely low temp BB would not contribute enough to offset their ugliness.

Have considered radiators.

You are right that we only need to top up the temp as the room is only a little too cool.

FYI this is a wet install. Underfloor insulation would be a better solution but I do not want to volunteer.

Ron Schroeder_3

slow temp changes

allow the occupants to become gradually acclimatised. Discomfort arises when bodies begin to radiate or absorb heat rapidly.

I assume constant flow and outdoor reset and weather responsiveness in all of my designs.

RadPro

Staple up issues

thanks for the replies . I'm re thinking the LLH and running the second pump for all the other zones. Can I just add 3rd loop between the joists for the staple up application to add the extra BTU's or do I absolutly need 140 degrees under the wood floor to get proper temp at the floor surface. Again I'm looking for COOL return in the Vitodens for condensing and Max efficiency...Paul

Mike T., Swampeast MO

What is the design loss of the library? The presumed deficit? System head loss? Presumed (or known) max flow?

How much space is available for an iron radiator? Space for a tall one in view of the glass?

Ron Schroeder_3

I have less than

tewlve inches of wall space between the top of teh window sill and the floor. This large expanse of glass is doing precisely what I thought it would do when we installed the system; it is sinking the heat.

I'll think about this a bit more. Perhaps I'll just increase the gpm to this room a little. Then I will have a slightly lower delta T but we are still well within reach of condensing.

BTW, I have to reiterate: do not install these little boilers without a LLH and mixing valve unless you consider all of the implications. I did not say that this was my first choice knowing what I know now. When this went in there was no LLH available yet.

Mike T., Swampeast MO

Here's an exceptionally simple fix, but it might not pass the aesthetics.

An oil-filled electric radiator-type heater.

There's another possibility if you're not using the boiler for DHW. Use the built-in capability to drive such to give yourself a high-temp zone. You'll need a buffer tank and another (tiny) circulator to provide high-temp water to a TRVd radiator. You have exhaustive control of the DHW side on a Vitodens. Think high temp and high differential in the buffer tank.

You can temper that glass heat sink by putting the radiation in full view, but you'll need a higher temp than currently available in the system.