Buderus Comparisions to Viessmann

No Probalamo Brad

When you count the number of recips, screws, scrolls, centrifs and what the heck absorbers installed, centrifs. will be less than 1% of the total installs. That is just shear size vs. numbers.

A second thanks to you Brad I have a computer in the shop and this thread has kept me busy cleaning all day.

My boiler was installed by a heating contractor who had never

installed one before. There are no "Viessmann" contractors in my area. I would be best if you did work with someone who has installed these before as it makes things go faster.

As for results: after 2 months I have a 45% fuel savings - and I have not even started to setback the unit at night and on weekends when I am gone.

Call it elitist or whatever - the dang thing works - and works as advertised.

Perry

Ehemm As A Homeowner

As a homeowner myself You are way out of line in your point of view Jules.

Gordy

#4

Refridgerator

Install whatever you want; I hope that you got your Q answered.

Jules: You came here looking for an answer to a question on why the Vitodens cost more - and found that your question created several subgroups of discussion on issues related to the how and why of the Vitodens - and it's usefullnes. Not exactly what you were looking for.

Yet, I hope in the end it answered you questions,

I am a homeowner as well, and also an engineer who has been working with industrial scale boilers for most of my life. I work in a power plant and do not sell or service boilers; but my expertise is heat exchangers and I have a lot of experience with them in all their various sizes shapes and functions (and my job title is Heat Exchanger Testing Engineer - yes large power plants employ a person full time to care for and ensure HX's are replaced in a timely fashion with ones that last a long time). My sub specialty is controls.

While it is true that the old style cast iron based boiler does indeed last a long time - please do not extend that concept to modern non-cast iron boilers. There has been a huge change in boilers in order to: 1) Reduce Mfr cost. 2) Gain efficiency. 3) Minimize size. Research will tell you that the first real attempt at this; the condensing boilers - produced boilers that in most cases failed in 5 to 7 years (a few select brands did not). Modulating burners are now the newest technology on the block - and is largely being used in modulating condensing boilers. They haven’t been around long enough for anyone to make any really good estimates on boiler life; but I expect that several of the current brands will also be short lived boilers (personal opinion after studying the design of a number of them).

So I would caution you that your statement of: "boilers last a long time." Old cast iron boilers last a long time. But they tend to be limited in efficiency.

I would also caution you on the second part as well: "and all the manufacturers stand behind their products." Can you provide any evidence of that - or is that someone’s general statement. Fact is, my research indicated that when a boiler brand does not work out it tends to disappear - along with Mfr support. That is true of many other products. Even when the product is in production you will find a wide range of how well the Mfr stands behind their product and in the level of customer (or contractor) support.

Each Mfr decides up front what the design intent of their boiler will be: The cheapest thing that possibly can be built while getting past the very limited warrantee period, the best and most highly engineered boiler designed for long life regardless of cost, or some degree of balance between those two extremes (and I would propose that the two most discussed boilers on this form represent those two extremes: The Munchkin, and the Vitodens).

In addition, many people - especially people with a lot of history and experience working in technical industry forms opinions and habits on how and why things work. They do not want to consider something new and change is hard for many of them (and having seen many new things flop they challenge new things all the time). Unfortunately, you stumbled into a group of people who are clashing over the benefits of something new versus the old. On review I personally do not think that this has been an "elitist" based argument. People have been debating technical things, and modes of operation. No one is saying (with their nose up in the air) - Well buy a Vitodens because it is just the best (regardless if it is or not – is a Mercedes the best… I think not). Several people are saying that the Vitodens is the best built and engineered product out there (from several perspectives – and I am one who believes that) - and then debating the need and function of those features with people who are willing to challenge them on it.

I came in clean without a lot of background, did a lot of research and looked at a number of issues and chose the Vitodens as the most likely to last a long time - which given the cost of installation is very important (the HX design is superb for longevity and function, and the burner design is very rugged). How long will it really last in general, how long will any other mod/con boiler last is unknown. They haven’t existed long enough for people to say anything with real life confidence.

The second thing that I found was that only the Vitodens had the built in controls – or optional parts necessary to retrofit into my house and work properly (and I had a Munchkin rep literally scratching his head on how he would retrofit a Munchkin to my heating system). For every other boiler out there I looked at I would have ended up with a collage of parts and components from different Mfr’s – and hope that they all did in fact work together properly for maximum efficiency (and the cost of assembling that collage of components was not going to be much cheaper that the Vitodens and could have cost more). So why does a Vitodens cost more…? In many applications it doesn’t – if you are really interested in having a boiler work to its maximum efficiency (and not a boiler with a theoretical efficiency that is only achieved under certain conditions). Many heating contractors are not going to tell you that you need another $1000 control box to make your new boiler perform up to its full capabilities in your house (and actually, many heating contractors don’t even know it is needed for the boiler they are selling).

Now I will concede that not everyone needs all the features built into the Vitodens; but if I were to start selling boilers I would stick to the Vitodens because it is one package that can really work well in most every application. There is no way I could look a customer in the face and tell them that some of the other boilers will provide a long life with minimal expected maintenance.

I wish you well with whatever you chose to install – be it one of the design extremes or something in the middle; and I hope that long term it works out the way you are expecting it to work out.

Peace.

Perry

Exactly!

I have yet to hear something positive from subcooler in all of his posts. Negativity pervades them.

For what it's worth, appliance designers would love to be able to use variable-speed compressors, etc. if they were available and if the bean counters let them. The performance benefits are indisputable as a modulating compressor can take advantage of much larger HX's relative to the load it is trying to cover. It is the main reason why the mini-splits with variable-speed compressors achieve the very high SEER ratings they do, without the benefit of a huge cabinet/HX like most US split systems.

Many washing machines also have variable-speed drives because the electronics have become cheap enough to allow the omission of a transmission - just drive the motor to whatever speeds you want and garner performance benefits in the form of better control, more options, etc. as well.

Variable-speed drives have also made their entry into air handlers, allowing them to deliver great cooling and heating performance while keeping the occupants comfortable. Being able to ramp up and down (i.e. modulate) is a key feature.

Some high-end electric cooktops have very sophisticated controllers built-in that allow the modulation of the heat input the same way a VFD motor is controlled. The big benefit is the ability to maintain certain temperatures consistently at the bottom of the pot, as opposed to the "on-off" cycles the older electric stove tops "feature".

The bottom line is, the only thing to fear about modulation is the added complexity of controlling it and the higher initial cost (along with later repairs). On the other hand, most everything in nature modulates (from your heart beat to the rate with which you inhale/exhale), and nature is usually pretty good at figuring out which is the most efficient way to do things.

I do know that the Vitodens "learns" based on cycles--both space heating and DHW production. It's considered "fully educated" when it has information regarding 60 cycles of operation. Any program change of the heating curve causes "learning" to begin from scratch. The sun and moon dials are "special cases" and changing them does not necessarily cause learning to begin from scratch.

Such "learning" is related to the emitters and/or structure. One goal of the learning is to avoid abrupt and "energy robbing" changes in burner output. To me it seems only logical that part of the learning has to do with how rapidly boiler temperature changes after the burner stops firing. In an odd sort of way, this DOES give the Vitodens a "return temperature" sensor--as long as it's not firing... If you're not firing "boiler temperature" is now "return temperature". Hmmm....

A very good Viessmann tech described the learning process to me as "black magic". Either he and other techs don't know or they can't tell.

What I can surmise though is that burner shut-downs are very important events to the Comfortrol™. The first thing it probably wants to learn is, "Why did I have to shut down and how can I avoid it in the future?" Then, "If I utterly must shut down, how do I most efficiency cycle myself?"

Intentional shut-down do occur in a special circumstance. After the boiler has fired continually for about 24 hours it shuts down for a brief period.

When I first noticed this in my datalogs, the shut-downs were occurring at midnight. I don't use timed supply temperature setback and honestly thought that the boiler might be switching to reduced mode for one minute either before or after midnight. Then I scoured the manual and found mention of a "test" after 24 hours of continuous firing but of course it didn't describe just what happened during the test...

I then noticed that the time of the test changed. It jumped forward considerably and then kept coming a bit later and later each day finally "settling in" at roughly mid-morning. Odd.

This was the first year with the Vitodens and my datalogging system. I kept having problems with the wireless solar-powered outdoor temperature sensor. It had very limited range compared to all of the other sensors and would "drop out" for hours and even days at a time. I kept experimenting with placement and found the ONLY place for reliable transmission was on the South side of the house (room with receivers is on the SW corner of the house).

At least I found a location for the sensor where it only sees full sun for a couple hours in the afternoon and even then its design reduces direct solar influence.

I have another temperature sensor on the North side of the house. While not logged I do look at it very frequently--especially when checking current operation of the boiler via the sensors.

To my surprise I found that the intentional "test" boiler shut-down coincided almost perfectly with the time that the south-measured temperature began showing a sharp increase over north-measured temperature on sunny days.

Then as winter progressed and days became longer, the boiler "test" occurred earlier and earlier coinciding almost perfectly with the onset of significant solar gain.

You MUST remember that such test only happens if the boiler has fired continually for 24 hours. If it is forced to cycle anytime during a 24 hour period, I find no evidence of the test occurring. If the day is sunny, the weather has to be quite cold for the boiler NOT to shut down at least once in the "heat" of the afternoon.

After seeing the timing of the "test" with onset of peak solar gain, I noticed something else.

Previously, were this a sunny day and the boiler had been modulating continually since the later afternoon before, the boiler temperature would rise quite sharply and significantly above target after the onset of peak solar gain, then the burner would shut down.

Now, on a sunny day the burner would shut down shortly after boiler temperature began its rise above target but before the differential between boiler temp and target was as great as before. The sunnier the day, the more quickly this seemed to occur. It's as if the boiler were thinking, "Hmm. Must be a sunny day. I'm going to shut down before I'm forced to fire well above target even at my minimum rate."

My apologies both for my near ignorance of PID and use of hyperbole.

After a bit of refreshing--well more studying--about PID, the main thing I remembered was confirmed: That PID in its simple state is not particularly well suited to HVAC control because it's an inherently linear control method attempting to operate an inherently non-linear system.

While you may well have wonderful understanding of PID logic, you don't seem to have the same level of one of the most basic portions of anything hydronic--delta-p.

Have you verified for yourself how and why both head loss and flow rate will vary between an underfloor circuit with one 200' loop and 3 200' loops using the exact same circulator?

BTW: I probably would take a fairly high-speed camera to understand just how that snail manages to move with only a single foot...

Here

I offer this peace offering. Brad Stole my spot.
Brad isn't that something that PID control was first used on a wide scale in the 1950's. Once old is new again.

Homeowner Jules:

It almost sounds like you had made up your mind before asking the question.

The bulk of the messages in this thread are from HOMEOWNERS--including me. Some of them have a Vitodens--including me--and some don't. One has a different Viessmann boiler using oil for fuel and at least one is still shopping for the "best" boiler for their particular system.

Of those homeowners, most--but NOT me--are highly and formally educated and have or do work in some field related to energy production and/or energy utilization. My Vitodens came first and they have initiated private communication with me for my opinions. I give such--good, bad and indifferent. THEY HAVE MADE UP THEIR OWN MINDS!!! If there is any narcissism involved, it's me and my big iron rads with TRVs as I do believe such to be truly ideal for a Vitodens.

ALL of these homeowners had the SAME questions. How can it be that different? Is the greater cost really worth it? When they saw, felt, examined, and operated the Vitodens they knew...

These are JUST the sort of homeowners to whom you should be listening! They're not being narcissistic. They are however the type who actually take the time to observe, measure and report about a device that most people take for granted.

I'm only positive of true contractor status of one regular contributor this thread. His reputation is excellent and he is NOT "exclusively" Viessmann.

At least two of the other frequent contributors to this post are known for two things: negativity and anonymity. While I doubt that either has actually seen a Vitodens in person, one did finally admit that he'd never observed one in operation...

The ONE THING that I notice binding EVERYONE in this thread is skepticism.

"How can the Vitodens be that different to justify the price?"

Do you want to listen to those who actually have one or those who have never observed?

Homeowner Jules

I am not here to question why you came to this site or you level of formal education. The mechanical industry has always been plagued with a lot of (black magic) when it comes to how things really operate. In this case it happens to be how to most efficiently run a boiler. Most of this (black magic) is derived from people who don't grasp all aspects of the entire process of what does it really take to heat this space. I read a book when I was a school boy called Dare To Be Different. Those lessons have stuck with me throught the years. One lesson was trust your instincts and another was sometimes you have to swim upstream and my favorite the mob may rule but that does not mean they are correct. I want to thank-you for visiting and commend you on whatever desicion you make. The Sub

It's less than you think...

According to the ACEEE list of the most efficient boilers, the Vitodens' 6-24 or 8-32 consume ½ or less than their high-eff. boiler peers (mod-con or not). At 48kWh a year, you're looking at less than 2 therms of energy needed to power these units. Compare that to the ~45% (degree-day adjusted) energy savings that at least two participants here have posted for their Vitodens.

ACEEE

I just took a look at the ACEEE site. All I could find is the statistics that show Dunkirk, Monitor, and Utica all edge out the Vito in efficiency. Did I get the wrong ACEEE site?

The list of boilers with 95 or greater AFUE is quite short.

AFUE of the Vitodens 200 was very recently re-certified at 95.2 (previously it was 94.2).

> Andrew: Will proportional flow increase

> efficiency over constant flow if no LLH is used

> apart from the extra miniscule watts to drive the

> pump?. A BTU is a BTU is a BTU when the correct

> ammount is delivered the load should be satisfied



If you're not using primary/secondary or a LLH you have to pay extremely careful attention to flow rate--it can be neither too low nor too high. All mod-cons appear to share this requirement of an acceptable range of flow and I suspect this is much of the reason that primary/secondary or a LLH is highly recommended by most mfgrs and also why they frequently supply the appropriate primary circulator with the boiler.

Ensuring a range of flow with a single zone system isn't much of a problem, but it gets significantly more complicated when zones are added.

If you use proportional flow control for the emitters (TRVs, FHVs, pneumatics) and add a differential pressure bypass valve you can solve the zoning problem as even though the system acts like each space is individually zoned, the boiler only sees a single zone. Of course TRVs, FHVs certainly add to cost and retro-fitting them to some systems can be quite difficult. Pneumatics really aren't practical for typical residential systems. In this instance with a single directly connected circuit with inherent proportional flow, the use of a VS circulator is mainly about electrical savings as the TRVs/FHVs have already done the job of regulating flow. Constantin once posted a chart showing the "typical" electrical consumption of various boilers operating actual systems. The electrical consumption of the Vitodens 200 was WAY, WAY, WAY below all others.

I'll certainly agree that, "A BTU is a BTU is a BTU when the correct amount is delivered." [emphasis added] If by "correct amount" you mean delivering as close to the exact number of BTUs as possible to just meet the load, the job is MUCH more difficult than most imagine.

If you're trying balance output to loss by direct connection to a mod/con with fixed system flow, then your only chance of reasonable success is if the boiler modulates the burner to a target temperature from some sort of reset mechanism (outdoor or indoor). In this case, indoor reset with a proportional room temperature controller would be highly preferrable, but I'm not sure if any currently available mod-con allows this (direct connection and proportional indoor reset). Personally, I'd use the Tekmar TN4 system and choose a mod-con who burner can be directly controlled by the TN4. If not using the TN4 any "boost" function as is quite common in mod-cons is counter-productive at it will just keep boosting output until it forces the thermostat to be satisfied. While such is good if you regularly change the thermostat setting significantly, it's in complete opposition to modulation to the actual load. Fortunately such function can usually be limited or even defeated if desired.

When primary/secondary (preferrably in the form of a LLH) is used variable speed primary circulation truly shines. In fact, it's the only way to ensure that boiler output closely matches system load in any but the simplest of systems where direct connection could have been used to begin with...

Huh?

What mob?

This homeowner came on this site for an opinion. I would dare say that 80 percent of the heating contractors out there do not install Viessmann products, or even know about them.

This site happens to include as it's "regulars" guys in the business who are familiar with the Vitodens and what it is capable of, and I include myself in that bunch.

Why the attitude?

I will say, as many of your so called elite have reiterated that Jules the homeowner asked a specific question "Buderus compared to Viessmann".

I have no problem specifying, and installing another brand, and do many times. Budgets, ROI, clearances, and application drive the decision.

Both Buderus, and Viessmann both make fine boilers. As a homeowner I would first find a good contractor and install what he is comfortable with.

Ok, I tried to stay out of the thread because there are enough of us "elitists". But the attitude I am reading is funny at best, but I would say more inappropriate. I thought only politicians made a point by making fun?

As to the homeowner, you asked the question and got some great responses. Use your judgement as to who you think is telling the truth.

I am going to go sip my orange koolaid in a silver cup, have a Merry Christmas, and Happy New Year....


Cosmo

Andrew, However if emitters are properly sized to the heatloss,room by room using a mod con with ODR would it not be possible to tweek the curve to match the heatloss without the added cost and head loss of TRV's(in the case of a munchkin where 8/gpm is needed at high fire)

I admire your emphisis on simplicity and also think that a home heating system should be user friendly.

I dread the evening noon or night when one of the prioritized components in my mod/con will malfunction.

Thanks for all your posts