Buderus Comparisions to Viessmann

Wow!

!

Leo G

Back to Jules

Go here:

http://www.viessmann.ca/web/canada/ca_publish.nsf/AttachmentsByTitle/docVitodens-Features/$FILE/Vitodens-Features.pdf

here:

http://www.viessmann.ca/web/canada/ca_publish.nsf/AttachmentsByTitle/docVitodens-Article-FlueGas/$FILE/Vitodens-Article-FlueGas.pdf

and here:

http://www.viessmann.ca/web/canada/ca_publish.nsf/AttachmentsByTitle/docVitodens-Article-Weather/$FILE/Vitodens-Article-Weather.pdf


If you like technical reading and really want to understand the engineering involved in a Vito, those links should keep you busy for a while..ENJOY!

Brad, jp and all

I was told at one of the training sessions I attended that the Vito's control does have the processing power to "learn" the house. It does this from what I understand, based solely by looking at the target supply temp and the rate that it is changing relative to what it should be. If lot's of heat is lost out in the system, it see's the target temp dropping and reacts accordingly. If the house is up to temp, or thermostats/TRV's are not calling, it will see the target temp stay the same or start to rise causing the control to modulate down....At least that's what I understand about what I was told.

It "remembers" how the supply temp acted at a corresponding OD temp while coming out of setback at 6AM yesterday. Having that info on hand, the control bases the burner operation on that, adding in the factor produced by today's temperature. Sounds more complicated than it is but the control does have "fuzzy logic" capabilities.

Yes, this is my kind of thread.

I see

At least I think I see what you're driving at but your analogy has been leapfrogged by Big Silver Logistics Co:) Big Silver came to the table and proposed building a continuous trolley arrangement that took the widgets directly off the assembly line, transported them the 7.5 minute trip and returned without ever wasting energy applying the brakes to stop at each place and then start up again. The trolley was variable speed so it could exactly match the capacity of both the producing plant and the plant using the product. The trolley system used about 40% less energy than the big truck starting and stopping many times a day and about 30% less than the smaller truck that ran all the time. Everyone lived happily ever after:)

Thanks, Steve

That makes sense and explains the machine's abilities well.

Thank you.

Brad

Not sure, Uni

The gas valve setting is known, agreed. The flow is at best interpolative from motor Amps or Hz. but the actual portion of flow or resistance (both of which will affect Amperage) cannot be reliably broken out. Without knowing return temperature it therefore cannot calculate BTU's. It can approximate flow and maybe that is good enough.

Again, my observations are entirely internal conjecture. This is bringing out some excellent thoughts from the group including some actual Viessmann data. My stated thoughts on a HWR sensor were my musing, "how would I do this if it were my blank sheet of paper and did not have a room sensor?" The HWR sensor was the missing variable I was playing with, that's all.

Soon enough though, I will have a room sensor and will see what difference it makes. Maybe take in one season without it (it is working that well), then install the RTS in the spring and track from there.

Steve Ebels' explanation I have heard during my own Vitodens classes (looking at my scrawly notes but it did not sink in) and it was good to have it reinforced.

Target temperature over time and what it takes to achieve it. Simple in essence.

That and

flue gas temperature! Another blank entry- such a tease.

We are a hungry lot for information, are we not?

Not real valid for boilers

Subcooler:

Your analogy is the perfect reason why automobiles and boilers should not be compared - in any manner.

Automobiles have a number of wear items - such as tires and brakes - that do wear out as a function of use. Most Boilers do not.

On the other hand, if you just look at the engines - a good diesel engine will be in better shape if it runs continiously for many months - than if it stops and starts multiple times a day.

The fact is that for many types of equipment continuous operation promotes longer life of the components. This is actually true of the heat exchangers that are the heart of any furnace or boiler (and heat exchangers in general). Thermal expansion from starting up and shutting down takes a toll. Now many of the old cast iron or heavy wall firetube boilers were so overbuilt that they almost never fail from thermal expansion induced fatigue even after many decades of use.

Unfortunately, The same condition is not going to be true of the modern lightweight household boilers; and I suspect that you will start seeing HX failures tied to thermal expansion fatique cracking down the road. The less often you start and stop firing them the longer they will last. I will also say that the Vitodens HX impressed me as one of the most fatique resistant HX designs that I studied as I was looking for a replacement boiler for my house.

I have spent much of my teenage years in coal fired home furnaces and boiler service and cleaning and much of my adult life operating and maintaining Naval steam propulsion, power plants, and other commercial equipment where long term reliable operation was needed. The plants that were baseloaded always had fewer equipment problems and wear and tear than the cycling plants.

So give me a boiler that will run all the time... Please (I.e: we need smaller mod/con boilers than are currently available).

I will keep you analogy in mind if I decide to go into the trucking business. Cept' right now - tending power plant heat exhangers (my primary responsibility) and other equipment pays very well.

Perry

Mr. Ebels

You said a mouth full, marketing for some can cure all.
Maybe I have been in the control biz to long.

Very good points...

No question, most warranties are written to protect a manufacturer as much as possible, while still giving the marketing department a crack at convincing the consumer that there is this great warranty even though it shouldn't be needed (our products don't fail, right?).

For some pretty graphic examples, look no futher than the roofing industry. All sorts of "50 year" warranties abound, but almost none cover labor, most are pro-rated, etc. Anything beyond the first year is basically not covered. Roof shingles are dirt cheap, not much exposure there for the bean counters to have to build reserves against.

I'm with Perry and Steve, the best warranty is the one you don't have to excercise. All devices have failure rates associated with them and how quickly a manufacturer steps up to the plate to get replacement parts and gives good technical support is probably more important than the cost of the parts themselves.

Allow me to correct myself...

You are absolutely correct about the units having the tappings, my bad. However the non-combi units will require the DHW production kit part# 7134 214 or 7134 215 in order to run the indirect. My point was that many of the other mod-con boilers ie Prestige and IBC to name a couple have built in domestic priority. Presitge with the built in tapping and IBC by selecting it in the load configuration. Once again, I'm not trying to knock the Vitodens, it definately has its place in the market, I'm just trying to say there are less expensive alternates that do a very good job aswell.

I would say

1) Yes, longer run-times supports longevity and efficiency. Cycling on-off entails warm-up time with every cycle which is incurred almost equally regardless of outdoor temperature (cold starts excepted).

Modulation gives the boiler the option of down-firing rather than the only other option, being "off". All ModCon's enjoy this feature.

2) The Lochinvar Knight is the same in principle to most modulating condensing boilers in that it a. Modulates and b. condenses. Much as a car has a. Wheels and b. an engine, transmission and chassis. End of automotive analogies!

3) I am not clear on what you mean by "low initial temps while adjusting the boost to slowly raise output temps..."

Outdoor reset simply matches the output to the load as best it can. Boosting simply over-rides that to get you to temperature more quickly, possibly defeating condensing for the time period in the process, possibly not. But the temperature you put out at any time has to at least meet the heat loss, (otherwise why bother heating?)

No reason it has to be crude, just meet your temperature keyed to the outside temperature.

Is your Knight perchance

oversized??

That is another thread entirely! Maybe it has been?

I suppose if it is oversized, any safe strategy that prolongs cycle time is good.

But if it forces you to underheat your building for the sake of using boost to play catch-up, what does that do for your quality of life?

do i hear buffer tank?

sounds like the need for a buffer tank?????

Best way

Set your curve so it meets your room temp and gives you just a tad more for recovery from setback. While this won't keep the boiler running constantly, the run time should, if all things are appropriately sized, be nice and long.

If however, your boiler is over sized or your radiation is a bit light, you will probably not achieve good run cycle times at all. If that's the case, your best option would be to add a buffer tank as suggested by JP. This kind of defeats the purpose of having good response time from the boiler and in addition, may allow the boiler to ramp up to high fire when it really doesn't need to. Correct sizing of not only the boiler but also the radiation is CRITICAL to achieving maximum system efficiency.

tTowne, kind of sounds like.

kind of sounds like your system is not set up correctly, sounds like the target temp is too high?

If i remember right, a couple yrs ago you had a DHW heater heating your place and it couldn't keep up?

what are your supply and return temps? and method of transfering heat? baseboards, infloor etc....?

might want to start your own thread so everyone will put in their 2 cents and you can buy lunch!

I waiting

For the list.

Guys

I apologize if I changed the direction of this thread. I guess in the end I just wanted to optimize as much as I can with what I have. I needed to know if the consensus was for long cycle times=increased effeciency & increased longevity. Knowing this may be true I will come up with solutions not to a problem but to an ideal. Thanks to all for your thoughts and opinions

Here is the list:

I will start the list by listing all of the items in a household that need to be on 24 hours a day.

1) Heating in the right climate and time of year.

2) Cooling in the right climate and time of year.

3) Hmmmm... I can't think of another home appliance or personal use item that may need to be operated round the clock (or even a solid 8 hours).

Perhaps someone can help me with items 3, 4, 5, and more...

If not, then I guess this concept only applies to heating and cooling in the right climates and time of year. I do note that there are probably hundreds of industrial examples of equipment and processes that run better and more efficient if never shut off and restarted.

Keep in mind when comparing apples to other things - that the other things are indeed an apple. Otherwise you get fruit salad.

Perry

Tekmar is certainly not "crap"! I have never and will never even suggest such. They are however quite limited in what they can do--mainly to the secondary (emitter) side of a primary/secondary system with mod-cons.

While I believe that their TN4 system can take control of modulation in some mod-cons, I will say that their programmers would orgasm over the prospect of variable speed circulation in the primary (boiler) loop. Then they'd start pulling out their hair trying to figure out how to make a simple feedback mechanism that would work with any boiler...