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Vitoden exhaust run distance

marc Member Posts: 203
The venting manual for the vitodens does not show a SS liner as a acceptable venting alternative. I read the current Venting manual on line today. The Vitodens can be vented in Either Viessmann's Venting or approved ss venting. Flex venting is not one of them. Someone must be confusing the name of the manufacturer with the type of venting.


  • Heatmeister_2
    Heatmeister_2 Member Posts: 88
    Vitoden exhaust run distance

    I will have 4 90 degree bends to get my exhaust pipe up my chimney with a total run close to 50feet. I am looking at the GB142 and the Vitoden. I know the GB can go up to 100feet but is the Vitoden limited to 33feet? I prefer to use my existing chimney vs. cutting a hole in my rim joist and having a PVC pipe sticking out the side of my home.

    Also, I hear the Vito can service 3 different temps. My set up will be 1) In floor in basement, 2)Indirect Water heater and 3)either staple up or panel rads. Is this feature that big of a deal over a GB given the fact that mixing valves will address this issue AND that the Vito cannot service all 3 temps simultaneously?

    Can someone spell out in plain English the advantages of each unit PRICE INDEPENDENT. Both are great units, but the overall cost of the project far outwieghs the marginal difference in price between the two units.
  • Empire_2
    Empire_2 Member Posts: 2,343
    NY codes

    I don't know about your area, but Hi Eff. equipment cannot be vented into a chimney due to the lo temps and condensation. The manual should be able to answer all your questions.

    Mike T.
  • Constantin
    Constantin Member Posts: 3,782
    Some, but certainly not all, answers...

    Heatmeister, the Vitodens is limited in the length of the concentric exhaust/intake to a relatively short distance. If you look into the installation manual, you'll see that you have the option of just installing a stainless flue into the chimney and attaching the Vitodens to that. Then, the Vitodens will draw it's combustion air from the basement. IIRC, that stainless liner can be an eqv. of 60' long.

    If "sealed" combustion with a setup like that is desired, simply place the Vitodens in its own room or build a small room around the Vitodens and run an external air supply to it. That room could also hold all the piping, etc. protected from the vagaries of basement users. Hermetically seal the room, and you should be done.

    Another option to consider is placing the boiler in an attic space or on an upstairs floor. Both the GB142 and the Vitodens have the reputation to run virtually silently, so there is no adverse impact from placing them inside the living space. If an attic space, ensure that the space is part of the conditioned space, no venting etc. so that the temps don't drop into the dangerous zone. Our sealed attic holds an AH and part of the sprinkler system. Works great.

    What I like about the Vitodens is the stainless HX, the burner, and the control system, among other things. It's reportedly very easy to service. Plus it can handle multiple water temperatures with the built-in controller via a 3-way or a 4-way mixing valve. I doubt you'll need more than 2 temperature capability, because most installers assume that the boiler will run the indirect water heater on priority whenever there is a call for more DHW.

    From an efficiency standpoint (independent of the boiler you choose), the panel rads may be preferable since you'll probably be able to size them to run at 140°F on a design day and hence condense all-season. That is a lot harder to achieve with staple-up construction, even if you use plates, unless you have a very low heat loss to contend with.

    The Buderus GB142 is also a fine piece of equipment. I'm sure one of the experts here can pipe up about the capabilities of it and it's various controller options (RC10, et. al). If it is an option, I would wait until the outdoor-reset capable Buderus controller is released later this year. The Vitodens already has ODR built-in.
  • ALH_4
    ALH_4 Member Posts: 1,790

    Constantin is correct, except a radiant floor with plates will run very cool. We have systems heating well-insulated homes with 105F water at -30F outdoor temp. This is with extruded aluminum plates. Bare staple-up will not perform the same.

    The Vitodens has the ability to control one external 3-way mixing valve with the on-board control, and you can add an HK control for a 3rd temp. Three temperatures are a relatively rare requirement whan you have the ability to design a system from scratch. You have the ability to choose and size the heat emitters for a particular design temperature. Usually the two temperatures will be a low-temp radiant floor coupled with higher-temp panel radiators.

  • Mike T., Swampeast MO
    Mike T., Swampeast MO Member Posts: 6,928

    The Vitodens requires a Viessmann mixing valve to provide the second (lower) temperature. Control of ONE mixing valve is inherent to the boiler. The indirect is served via a built-in diverter with the two smaller models (called DHW priority); with the two larger models DHW handling is determined by coding. In either regard, the domestic hot water is a built-in function of the control unit.

    The Vitodens stainless steel heat exchanger and radiant burner are unique. The burner is especially noteworthy. The air and fuel are mixed via a self-correcting, non-mechanical, proportional link. Adjustments to such are neither allowed nor required. Combustion analysis is for verification only. Ignition is through a direct spark system.

    The Vitodens is very quiet. Service access is very good and REQUIRED routine (typically annual) cleaning/maintenance is very easy.

    An accessory device called a low-loss header is typically used in American-style systems. This isolates the boiler from the system flow while maintaining return temperatures as low as possible.

    The Viessmann Comfortrol™ provides outdoor reset.

    Some installers resent the "Viessmann way or no way" of the Vitodens system.


    The Buderus GB comes with a pre-made manifold that provides for proper flow through the boiler. Mixing valve(s) [appear] to need external control, e.g. not directly controlled by the boiler. DHW is similar to the larger Vitodens models, e.g. function determined by coding. DHW control is inherent.

    The heat exchanger is cast aluminum. Aluminum may be more sensitive to water conditions (particularly naturally soft, acid water) and the water may require treatment, monitoring and maintenance to ensure the maximum life of the heat exchanger. (Stainless steel is generally considered less sensitive to water conditions, but treatment, monitoring and maintenance may be required in exceptional cases.)

    The air-fuel mix is intended to be adjusted during setup. Fortunately a built-in function facilitates this adjustment. The air-fuel mixing is not as sophisticated as the Vitodens and may be less able to compensate for unusual conditions in the flue. Since wind/ice [seem] to be more of a problem with horizontal venting, every attempt should be made to use vertical venting. Ignition is via a hot surface ignitor.

    The Buderus is very quiet. REQUIRED routine cleaning/inspection access appears to be easy.

    Indoor reset is provided via the dedicated RC-10 room temperature controller. While technically a superior reset scheme, many here report problems using the RC-10 with American-type systems, instead using conventional thermostats. This [may] compromise efficiency. An outdoor reset controller is rumored to be available soon. As with the Vitodens (or any system of outdoor reset) careful setting of the reset curve is required for the most efficient operation. The beauty of the RC-10 indoor reset scheme is that the ideal curve is automatically learned.


    Both of these boilers are intended to operate with a MAXIMUM supply temperature of 75°C (167°F). These limits can be subverted but only by accepting significantly lower efficiency.

    With that in mind, you would be well advised to use panel radiators (preferrably with thermostatic radiator valves-TRVs) as opposed to "staple-up" unless heavy conduction plates are used. The panels should be sized to operate at the lowest temperature space and budget will allow (the lower the design temp, the bigger the panels).

    Both brands enjoy a well-deserved reputation for exceptional quality. Both brands tend to have very passionate followings. Properly installed and controlled in a well-suited system, both will achieve extreme energy savings.

    While this is personal opinion, the more you follow "European-style" system design, the better these boilers will perform.

    If you can learn to accept generally lower space temperature (made MUCH easier with systems delivering a high portion of their heat via radiation) you can achieve truly fantastic energy savings.
  • Simply Rad_2
    Simply Rad_2 Member Posts: 171
    Vent lenght

    One thing to remember is the Vitodens vent lenghts are not the normal equivalents of 5' for an elbow. The 87 degree elbow has an equivalebt vent length of 1.6' and a 45 degree elbow is 1'. So the 33' maximum is actually longer than what it seems. The whole venting system is very user friendly also.
  • Simply Rad_2
    Simply Rad_2 Member Posts: 171
    2 temp system

    You would use a two temp system. High for panel rads and mix the low temps for the slab. The DHW is on its own piping and temp control. The great thing about the Vitodens is the ability to have two separate heating curves for high and low temps. THe Vitodesn is a heating package not just a boiler.
  • Constantin
    Constantin Member Posts: 3,782
    I'm confused...

    ... but as my wife will tell you, that's pretty easy to accomplish. :-P

    Your post seems to be in response to mine, yet where do I mention flexible liners once? All I mention is stainless liners, which could potentially be flexible I suppose.

    Viessmann allows the products from a number of manufacturers and gives detailed instructions in the manual you mention from page 30 onwards. In any event, the exact allowable eqv. length of liner/flue depends on the appliance as well...
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