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Buderus Comparisions to Viessmann
ALH_4
Member Posts: 1,790
What you are describing is very possible. I have watched 6-24 Vitodens systems work exactly this way with Thermofin radiant floors and radiant walls. Fine tuning of the balance among the rooms can be accomplished via flow setters on the manifolds. However all of this is contingent on at least similar specific heat loads on all of the rooms and solar gain can cause certain rooms to overheat at times. With the TRV's you still have a governing control that will shut down a room if the solar gain takes over.
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Comments
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Why does Viessmann cost more?
Isn't an efficiency rating enough? Isn't 90%+ the same regardless of manufacturer? What is Viessman doing that nobody else is doing? Can someone please justify this to me before I spend my hard earned cash?
Thanks,
Jules0 -
Quality of Materials and Engineering for One Thing
When you hold the MatriX burner in your hands and the heft heat exchanger, feel the weight of that compared to other brands.
The stainless they use is 316T (not L for low-carbon but T for Titanium) which has a longevity and resistance to corrosion greater than 316L. (I assume you mean the Vitodens but the 316T is used across their condensing line.)
All of that material and quality just has to go toward longevity. Peace of mind.
The integration of the variable speed on-board circulator with the controls is another. I cannot explain it, but the Vitodens maintains interior temperature dead-nuts with little assistance from TRV's and WITHOUT an indoor sensor. (Such will be installed but in the meantime it buzzes along with barely a sound and heats predictably to temperature with a minimum of fuel consumption.)
Sure, the principles of combustion and efficiency are the same across most consensing boilers, much as the principles of automotive engineering can be found in common between Yugo's Hyundai's, Beemers and Mercedes. All things have a quality range.
Fit, finish, quietness of operation, ease of installation all play a role. Nothing against the others -they all have their niche and price point.
I made a concious choice after kicking quite a few tires.0 -
Quality
Brad "Dead-Nuts" White is exactly right as usual. ;-)
My view of what differentiates the Vitodens:
1) Titanium stabilized stainless steel. (also in the Vitocell 300's)
2) Standard control functions others do not offer standard or even offer at all.
3) A very highly engineered product. Remove the cover and it is evident.
4) The Matrix burner. It is unlike any other.
5) The coil heat exchanger design, quality and thickness.
6) Internal variable speed pump in the 24/32 models.
7) Internal solenoid to switch from heating to DHW mode with no additional pump on 24/32 models.
There are probably more, but those are pretty significant.
What is the origin of the term "dead-nuts" anyway?0 -
Probably comes from a well-placed kick...0 -
After
you hold a Vitodens heat exchanger or Vitocell 300 coil in your hands you would know the answer. The quality is incomparable.
To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"To learn more about this professional, click here to visit their ad in Find A Contractor.0 -
Triangle Tube Prestige
Has a 439 Stainless Steel Heat Exchanger does that enter the debate? It's self-cleaning where the Buderus must be cleaned annually. Is Viessmann self-cleaning? Thanks for your responses.
Jules0 -
The "dead nuts" accuracy is built-in. The Vitodens is the ONLY boiler out there that's able to modulate boiler output to system load on a real-time basis.
Others modulate to either achieve a supply temperature target or to attempt to maintain some fixed delta-t.
Some may think this is the same. Here's how it's different:
Imagine that heat loss is a hilly road that must be traveled in the most efficient manner possible.
A "normal" mod-con uses its reset function (either outdoor or indoor) to compute the velocity required to JUST CREST the hill ahead and using the velocity gained while on the way down the hill just before. This is NOT "cruise control"! Your car speeds up considerably on the way down and JUST BARELY makes it over the next crest--your speed is FAR from constant.
A "normal" mod-con uses its modulation like a team of earth movers just ahead who keep chopping off the tops of hills and piling the debris into the next valley. Unfortunately these earth movers lack a surveying team and have no idea how much to cut and how much to fill to produce a level path. Why? Because the vehicle does not know the CONSTANT speed to follow were the path perfectly level. Even if the earth movers get just right, you're either traveling too fast or too slow. This is what happens with ANY form of primary/secondary when primary (boiler flow, e.g. your speed) is fixed!
Vitodens says "screw this". I WANT A SURVEYOR! It simply uses outdoor temperature to find the average elevation of the terrain ahead--then and ONLY THEN can it determine the amount of energy required to just maintain velocity or INDOOR temperature.
Instead of a team of earth movers ahead, it has gang of tunnel borers and a team of bridge builders. BUT, the higher the average elevation the harder the tunnel borers and the bridge builders have to work because they had to bring their materials and food up from the bottom!0 -
The fact that I have
not fathered any children knowingly despite years of trying (and begging if that counts) bears some truth here... Now I have to figure out the origin -and to lose that moniker!
My dad used the term (Navy, 1943-45), my uncle (USNA Annapolis '46 and USN 1942-80-something.... They both had kids.... Mmmmm.0 -
Something you might not have considered Jules is what components come with each boiler and what must be "added on". While the Triangle tube boiler (Prestige) has domestic priority built in, the Viessmann (Vitodens) needs a Domestic Hot Water kit, as well as several other add ons (ie: low loss header, etc.). While I would never try to compare the two boilers as being the same, I have a hard time justifying the huge price difference with the value difference. Is how much more you pay for Viessmann worth all the extra engineering they have done? Well thats up to you to decide. If you are looking for a fast payback on investment you will simply not get it from either of these products. Your gas bill (the portion of it that is gas) will probably only be going down by 20 - 25 percent at the most. At that rate you will need several more than 3 - 6 years to recover the cost. The real value of these boilers is dependability and longevity and in that sense either one (Viessmann, Buderus, or Triangle Tube) can provide that.
As for the "self cleaning" heat exchanger it is highly recomended that it is serviced after the first year of operation and then every 2 - 5 years after that. Just like any other major appliance if you take care of it, it will last for a very long time indeed. Hope that helps.0 -
sorry,
mike, PID is REAL time. otherwise it would make no sense.
you are suggesting these systems are predicting tomorrows weather
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It's not "predicting the weather" but it is making a reasonable assumption:
Namely that the weather in the next hour or so won't be that much different than the present. Even when the weather DOES change rapidly the surveyors know the proper level but it takes a while longer for the tunnel borers and the bridge builders to adjust their work rate.0 -
j.p.
You missed the point of the analogy altogether. While PID may be "real time" down to the nonosecond, a "normal" mod-con with fixed primary flow cannot find BOTH the average elevation AND the required throttle position to maintain an even speed.0 -
Exactly right
The variable speed circ on the 6-24 and 8-32 Vitodens is also weather responsive allowing the boiler to perfectly match btu input to flow rate to outdoor conditions to heating curve. It's the only boiler currently set up in this manner. It NEVER puts out more heat than needed.
Mike: I have never asked anyone at Viessmann the question but I have always assumed that the circ speed is a function of OD temp and the "mysterious" room temperature dial. I'd like to find a device that would measure circ RPM's and watch what happens when the dial is turned up or down.0 -
A more complete answer
Some people forget all the details of how and why things work.
You need to understand what boiler efficiency numbers really mean - compared to what a boiler normally can do.
A boiler is not just a heat exchanger that can get 90+ (or 83+) percent of the heat from the fuel. Yet that is what is reported by the efficiency numbers. Under ideal operating conditions - the boiler is capable of getting 94.2% (or whatever).
The real question you need to ask is: What must be done in order to operate the boiler so that it is operating as efficiently as it can in all the other situations. To operate at maximum efficiency for any give situation requires a good control system.
The Vitodens 200 comes complete with a very advanced control system built in that can handle almost any home or small business situation that you are likely to run into - to maximize the "ACTUAL" efficiency of the boiler.
No other boiler that I looked at this year has this. Some have a basic outdoor reset built in (not nearly as advanced as what is built into the Vitodens, and some of them are really crude and would not be appropriate for my house at all); but often you need to buy an external control system. Now you can buy a cheap basic one for a hundred or so - or spend $1000 or more for one that really runs the boiler very efficiently (please add the cost of this control system to your other boiler cost, and the cost of wiring it).
While it is true that in many cases the Vitodens does not even need an indoor temperature sensor if it is set up properely - it is also true that such setup can be a trial and error process that takes time (without an indoor temperature sensor). And what if you need an indoor temperature sensor for the house for other heat gain or loss situations - or for areas in the house... No problem. The Vitodens has them available. If you use one for the whole house - it automatically adjust which reset curve the boiler should be on (ending the trial and error process). If you need to control zones separately - that is not a problem either.
Bottom line: The Vitodens comes built in with a very highly sophisticated control system and options that works without having to buy anything else. That control system will allow the Vitodens boiler to work at the most efficiency point it can for each stage of operation - and not just work a peak efficiency under certian specific conditons.
Some people get distracted by how well this can work in some cases that you don't even need an indoor temperature sensor that they miss what the system can do in the other cases and why.
Hope this helps,
Perry0 -
Steve:
The best way I've ever been able to "measure" the speed of the circulator is via that wonderful little Grundfoss "indicator for magnetic fields" key fob.
By intentionally setting the boiler to operate at fixed speed and then changing that speed I know that the speed of the little rotating disk on the indicator does vary and give at least a rough indication of circulator speed.
That said, I can only relay that the speed of the circulator is somewhat related to outdoor temperature and generally increases with decreasing outdoor temperature but neither completely nor absolutely.0 -
I have asked about the operation of the circulator.
Main thing I know is that "boiler circuit" and "system circuit" modes of circulator operation are VERY different! Once the remote temp sensor used for the LLH is plugged in, the boiler AUTOMATICALLY switches to "boiler circuit" mode where the circulator varies speed to maintain the conditions specified in the low loss header illustration in the Technical Guide.
Personally I've ONLY observed "system circuit" operation as I do not use a low-loss header.
I once asked about using the connections for the LLH temp sensor but without the LLH. Reason: The odd difference I find between "boiler temperature" and the supply temperature that I measure in some circumstances. Answer: Don't because you'll ALSO change the circulator function0 -
Wow, this is fun!
Now, is this circ's speed continuously variable, like a VFD fan motor on a VAV system, or just multiple speed taps?0 -
Continuously variable
AFAIK0 -
"engineering can be found in common between Yugo's Hyundai's, Beemers and Mercedes. All things have a quality range"
I hope they are not like a mercedes. Mercedes parts are expensive and Consumer Reports doesn't even give them a good report. Expensive does not always equal better. A Honda or Toyota get higher ratings and are more reliable then a Mercedes.0 -
Hmmm...
The Viessmann Vitodens offers two dedicated nipples for DHW and the controller has DHW-priority built-in (enable, disable, or blend at your discretion). The low-loss header is a neat option, but not required on every system. For example, Mike T. in Mo runs his Vitodens w/o any additional circulators and reports a 43.6% fuel savings, DD-adjusted.
I agree that few boiler swaps (if the extant plant is still working) can be justified on economics alone. However, when the time comes to install a new boiler or replace a dead old one, I would focus on the marginal cost of upgrading to a mod-con, not the absolute cost. Then see where the 30-45% savings reported here get you in terms of a payback.
I would clean and inspect any boiler I own at least once a year - I clean mine bi-annually. Furthermore, reviewing warranties on Aluminum-based HX blocks coupled with postings from EU-based installers regarding failures of such boilers is interesting indeed. On a new system, there may be little risk. On a CI-based system, there may be more opportunity for the pH to go bad and the HX to spring a leak. Given how few HO's, maintainers, etc. will test pH as often as stipulated in some warranties, they may not be as valuable as marketing tries to suggest.0 -
Tekmar crap?
""""It's not "predicting the weather" but it is making a reasonable assumption:"""
yep, thats the "D" in P.I.D., its the whole idea.....Derivative!
cute story though.
so are you suggesting that Tekmar controls constantly over shoot?0 -
Now Bordy....
That was for metaphoric, analogic discussion only.
Cartalk.com is down the hall, second door on the left.
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Mike
If it's any consolation, I liked your analogy!
I don't know a lot about Viessmann, but their marketing/reputation has done its work. My perception is that they are the " Chrysler New Yorker" (I don't like Cadillacs)of all boilers. Some guys would say I've bought into a bunch of sales talk, but to the consumer, perception is reality. Kevin0 -
Only on the combi...
Just to clairify, the combi version does have the dedicated tapings for domestic, however up here in the great frozen north (Calgary, Alberta) we don't use these models as the amount of domestic falls far below the standard demand for the average household (less than 2gpm for 90% of the year.)
Rudnae0 -
Scott
If the vitodens is sooo weather responsive why do we have to select a heating curve?
Why cant it operate solely from the outside sensor?
I don't think there is any great mystries here it is just sensing the emiter return water temp via the sensor in the LLH, Less heat given up less heat needed
Or Is my assumption off the wall0 -
NO COMPARISON
> If it's any consolation, I liked your analogy! I
> don't know a lot about Viessmann, but their
> marketing/reputation has done its work. My
> perception is that they are the " Chrysler New
> Yorker" (I don't like Cadillacs)of all boilers.
> Some guys would say I've bought into a bunch of
> sales talk, but to the consumer, perception is
> reality. Kevin
VIESSMANN V BODERUS
You cant compare them Viessmann by far has the best product in the industry. Boderus makes a great product and has its place in the market. But they still have alot of work to do till they catch up. You can also be sure when they do viessmann will introduce there new version and put them back in the stone age.Boderus systems are good I have one in my own home and sell them alot. But I also have a Ford in my driveway and would mach rather have a Bently Turbo R.
Mike A0 -
Fair question
Given that the internal programming of the Vitodens is still a mystery to those outside Viessmann (and to some within the sphere to be fair), all I can offer is conjecture. That and knowing the machine works extremely well.
The heating curve gives the Vitodens -or any controller for that matter- a place to start, a frame of reference, from which the PID logic can attach and depart. Without a heating curve, any device using PID logic will have to create it's own experiential database. Sort of re-inventing the wheel.
Something as relatively predictable as a heating curve is, as you know, selected by the user based on calculated heat loss and calculated radiative surfaces.
This ratio dictates maximum supply temperature at minimum outdoor temperatures. Within this curve is a decent predictable algorithm. (Once you adjust it after some weeks of running, the PID logic has to start all over with the new curve.)
You cannot do outdoor reset with just an outdoor sensor, you need at least the second controlled variable and feedback to do this, such as the radiation supply temperature. (I know that you know this so assume an oversight in asking about just using the OD sensor.)
Other OD reset strategies involve space temperature, rate of rise or drop and parallel offset or oblique offsets during warmer or colder periods. (Some reset curves can make a space seem a tad cool when it is in the 40's and 50's so a skewing to an off-curve higher temperature is sometimes indicated. That is a whole different discussion.)
One thing about the Vitodens that defies logic to those of us who have discussed this is, there is as far as we can tell, no return water sensor. There may be but no one at Viessmann has confirmed that.
The hypothesis to those of us in the conjecture business is that the HWR temperature relative to the HWS temperature can over time develop an algorithm via PID logic to determine the rate of heat removal, hence building heat loss. A certain HWR temperature we surmise, compared to the HWS temperature sent out moments earlier, could obliquely indicate a corresponding room temperature.
Without a HWR sensor somewhere, I have NO idea how this happens. It is just my best guess at how it would be done. I could be completely wrong. But do I have fun thinking about it!
The LLH sensor reads, as far as I can tell, the boiler output and/or more likely, the radiation outflow temperature. The sensor extends deep enough into the spot common to both the boiler water inlet and the radiation circuit outlet, both near the top. I would think it more likely that the thermistor tip is the real point of measurement and that is the deepest part so my default judgement says that it measures the radiation outflow. This makes sense to me because the heating curve is so dependent.
It does not measure return water temperature which, (when properly set up with higher radiation than boiler flow), skips merrily along the bottom of the LLH. System return temperature is thus boiler return temperature.0 -
So Munchkin would be in the same league as A Burdeus?0 -
No, Steve.
No.0 -
Which is better?0 -
Allow me to disagree...
Have a look at page 6 and 7 of the Vitodens TDM. Both the smaller and the larger Vitodens have tappings for dedicated DHW production built-in. The combi units can be attached directly to the domestic water system whereas the non-combis have to be attached to a indirect water heater.0 -
If you do not know the answer to that
Well, you should.
Each has it's place and price point. You get what you pay for basically. Take it from there! 0 -
brad, a simpler approach
its my understanding that there is a supply temp sensor and the OD temp sensor and no head pressure sensor.
so, the PID controller has no idea of flow, unless the pump is positive displacement. therefore no power, btu's or heatloss can even be assumed.
you set the curve, the PID then keeps the differential between supply and OD sensor at a porportional offset.
the PID tells the boiler, higher,lower,higher,lower. the boiler then either varies pump speed or burner pressure to keep supply temp where PID wants it.
EDIT: therefore, it could careless what the return temp is, only interest is supply temp. i would guess this is where the variable pump comes into play, quickier to vary pump
speed/volume than burner control, though they do work together. my guess is the pump is the fine tuner.
a complicated but simple tracking one dimensional control.0 -
then let me ask -
why is a RTS necessary? If we have several known mathematical points via slope etc, and the burner is continuously variable within its range, and the circ is the same. The temp sensor will report internal values - the CPU will then - with reasonable quickness calculate infinite varieties of function relative to required output - all of that within a time weighted calculation of temp rise or fall. After consulting with the ODS of course. (and to offer an opinion re the tekmar - it does not over shoot. Most boilers (other than the vito 200 and a few others) are slow hogs and cannot respond quick enough, eg they are large hunks of CI, non modulating & over pumped at a constant gpm - hence the overshoot.) The tekmar will do its best to match firing to load - but it too can only do so much under those conditions. Great thread!0 -
Brad
Great response I will have to reread that one a few times to digest it fully.
However we both agree you should have more flow (up to 30%) in the emitter loop than the boiler loop. That agreed upon the extra 30% makes a left turn and blends with the boiler discharge water in the area where the sensor is located, hence telling the boiler what the return temp must be.
if you know the boiler discharge temp and you know the blended temp it is easy to figure the emitter return temp0 -
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Americans Score Again Mike
The very reason that Vitodens stand alone is because the Americans already knew that over controlled modulation provides no real benefit and is actually detrimental to the life of the equipment.
I am also so glad that you dared step into the car type analogy. Here we go. Here is you control strategy in a (nutshell).
A manufacturing plant needs 96 pallets of boiler parts per 24 hours to keep its production plant running. They require 1 pallet every 15 minutes to keep the line running. The warehouse they are hauling from is 7.5 minutes from the plant. ***This is important pay attention.
Orange Trucking Company decides that it can make a round trip every 15 minutes and haul 1 pallet at a time. The plan seems simple and flawless. The truck runs 24 hours a day and never stops to take a breather. After a few years Blue Trucking Company wants to try the run.
Blue Trucking Company decides to buy the exact same truck. Nut for nut and bolt for bolt she is the same rig. Big Blue decides to try a little different strategy. In their plan they haul 8 pallets every other hour from 7:00am to 5:00pm. In the evening starting at 7:00pm to 7:00am they haul 4 pallets every hour.
Now Ill do the math for you. Big Orange made 96 trips a day to fill the quota. Big blue made 18 trips a day to fill the quota. They had hauled the same load. Could that be possible? A few zingers come to mind, The lights are on but nobody home, or going to school uphill both ways, or spinning your wheels. I dont think I need to explain which truck you would like to buy after a few years.
That my friend is why you would never ever set-up a control strategy for us .0 -
JP and Glen, you both make
very good points which I cannot refute, nor would I want to.
[EDIT- I agree with your point, JP about the circulator being a fine tuner but at some level I think it takes a stronger role. For example at minimum flow (sub-modulation range where the Vitodens "pulses") the circulator seems to go to high speed. Seems so to me anyway but hard to tell with the burner making the little noise that it does. Anyway, the discharge water temperature seems to drop for just a second by a degree or two then goes up. Thinking is, more flow, more BTU extraction, longer run time. Multi-dimensional. But not being a the designer of the machine, only a guess.]
There is one twist I have been watching and that is, I opened the TRV's on all of the radiators that have them (two in the bathrooms do not and will not, one in the living room and one in the kitchen will, but not just yet).
The house still maintains 68 degrees, the exception being when sun comes in one room or when my Susan has some cooking going on which is often. (She fully grasps the concept of overheating, let me tell you.)
The program is set up to about a 5 degree setback (parallel shift) overnight and on certain days. My data logger has shown the temperature is met at the time prescribed (5 AM for example) within five minutes and without a room temperature sensor. It is almost like smart recovery with a Honeywell thermostat, so there is some self-educating going on. How it knows when the room is at temperature, I do not yet know.
So yes, Glen's point about the curve is well taken, a great place to start. It may well explain how temperature can be maintained so well without an RTS. The use of "By Exposure" reset illustrates this on larger buildings but those are really higher mass structures and the intent is to cancel out skin losses only. Houses are more dynamic, I will submit, with greater envelope to floor area ratios and infiltration as a very high percentage of heat loss.
But in my case, the tuning of output to meeting the time schedule without apparently measuring the room. is pretty neat.
Yes, this is a great thread!0 -
Sub
I didn't catch what you were saying at all. Call me dense.0 -
Mr. Ebels
Maybe I0
This discussion has been closed.
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