Mod Con Boiler sizing

leed

Mod Con Sizing

If the lower outputs are desirable, why are the Viessmanns 100's often considered one of the boiler"s of choice with a 34K low firing rate? 

CMadatMe

Why Vitodens

Because it has the best hx with the best warranty and will produce more condensate then every condensing boiler out there with there 25 degree boiler delta pump that comes in the box.



Is anyone even thinking about or considering the effect of the downstream mix formula in the equation. Until someone can rebuff how a Vitodens WB1B10-26, 35 or WB2B-26 or 35 can have rated outputs well above the max flow rate of 6. 2gpm based on a 20, I'll keep my hat on the 40 delta. I must be seeing things when at a 160 water supply condensate is pouring out of it. Heck it even flows at 170 supply temp..

Gordy

Viessmann 100

The 100 is designed to compete in a lower price range. In short it's minus some control logic that it's 200 line has. Lower modulation requires a little more high tech controls. But even the 200's do not modulate real low. The Germans apparently don't feel the need. Maybe do to higher heat loss structures that are much older across the pond.



Mike t. Swamp east had some very detailed observations he posted on his viessmann 200 which was piped into his converted gravity system with rads. If you do a search under euro cave you will pull up the posts. Viessmanns pumping control strategy is unique. At least at the time he installed his.

TonyS

Just because they have a good

cheerleading squad doesnt necessarily mean they have the best product. Google "Viessmann trouble" youll find plenty of dissatisfied owners.

Im not knockin on them, but I get tired of hearing the chant. They are an ok boiler but I prefer the triangle tube exchanger and evidently quite a few other manufacturers do to. Imitation is the sincerest form of flattery.

TonyS

Oh No not the downstream mix

formula again!! Im going back to ZeroHedge. Good night guys.

CMadatMe

Triangle HX

Tony, the only reason why you see that hx in everyone elses warehouse is becuase the polish mfg of that hx caught wind ACV was going to another mfg to produce it due to quality control and their inability to make a larger btu output. Just because everyone is using it doesn't make it sliced bread. There is always a monetary reason.



How do you think that boiler would react to seeing a return temp just a few degrees above supply temp at a 2 degree outdoor temp? I'm talking a 3-5 degree delta...

TonyS

While we were trying to figure out

who is buying all the Greek bonds I pulled these articles out for your reading pleasure.

As you'll see even Siggy has to revisit this argument every so often because there is such a strong misunderstanding!

SpeyFitter

They do now

The "Germans" are feeling the need to introduce some smaller stuff pretty soon. Rumour has it they will introduce in North America a smaller Vitodens in the next year with a plate exchanger and storage tank for DHW (e.g. like the Vitodens 222 accross the pond) with a smaller Inox-Radial heat exchanger and smaller burner that modulates down to something like 16,000-17,000 BTUH or there abouts. They are recognizing the need for these low heat loss structures in green buildings and/or the fact that not everyone in more moderate climates such as in the west coast needs a minimum firing rate that is in the 30,000 BTUH range.

With respect to Delta T's - we have to be careful with too low flow aka high Delta T's because they could cause more laminar flow which would reduce effective heat transfer to the space if they are used on the system side. I think the only place higher Delta T's should be worked with is in high head loss water tube heat exchangers like the Vitodens or Giannoni where you are simply trying to get the heat out of the boiler at higher firing rates to the low loss header where the flows on the system side are more tuned towards the traditional 20 degree delta T in mixing with this water. But this does mean that no matter what the lowest water temp returning to the boiler will be whatever comes out of the system. So whomever is advertising the superiority from a Delta t standpoint of higher Delta T's like 40 degrees is false advertising it if they are advocating this as being more efficient; these 40 degree delta T designs to get the heat to the system need to go 20 degrees higher than whatever you want the system to run at and then you drop a further 20 degrees giving off heat to the system to get your 40 degree difference from return to supply.

TonyS

I dont know how the boiler would react

but I know how I would react if my return was coming back a few degrees higher than the supply. I would be so happy I would pipe it up to my neighbors house LOL

Jean-David Beyer

I know how mine would react.

Message displayed: Return water temperature greater than supply temperature.



Condition causing automatic reset: Set if heat exchanger inlet temperature is higher than heat exchanger outlet temperature by +10F.



Reset action: Reset when return temperature - 9F is less than supply temperature or reset with manual reset.



I do not know how this would happen for very long, since I do not have a perpetual motion boiler. I suppose if the boiler were supplying the indirect at 175F and it were satisfied, and it switched to the radiant slab zone with 75F supply, the returning water in the piping might be hotter than the supply briefly.

TonyS

Seriously Chris I like the viessmann boiler

I just dislike the way they advertise...INOX RADIAL

INOX is a french synonym for inoxidable or stainless steel

Radial means round

Lambda sensor- o2 sensor

316TI- off the shelf titanium alloyed stainless

I expect this kind of stuff from water softner salesmen but I think by trying to make simple generic things sound wonderful insults our intelligence.

gennady

LAMBDA

Actually there is no O2 sensor, and this is a beauty of it. there is an electrode, measuring ionization rate of the flame, and this ionization rate is a measure of flame quality. Titanium alloy stainless steel resists acidity much better than standard stainless steel. Regarding condensation, think about boiling point of the water near atmospheric pressure. It is somewhere 212F, and if saturated steam in combustion products is exposed to lets say 140F surface, it will condense. the rate of this condensation depends on size of contact surface and duration of contact. Here comes in play Viessmann's much larger gas side passages surface. As of fire tube heat exchangers, since coal fired trains it was old news.

using LLH or buffer tank resolves short cycling issue on low loads, It is all in the boiler manuals

gennady

fire tube HX

Actually fire tube HX is in a sense a buffer tank as an boiler element.

Jean-David Beyer

As of fire tube heat exchangers, since coal fired trains it was old news.

Coal, oil, and even wood-fired railroad locomotives were generally fire-tube boilers, though the firebox was surrounded by water as much as practical. Dry base, I guess you would call them. But some had a "thermo-siphon" in the firebox that amounted to a single water tube. Large steam plants, and ships seem to have used water-tube boilers. As far as I know, only one steam locomotive was ever built with a water-tube boiler, and it was not a success. I am not, and never was, a boiler engineer (designer), but it seems to me a water tube boiler would be more efficient, and safer, than a fire tube one, but only in very large size ones. I.e., never in a home heating system and not even in a railroad locomotive. A water tube boiler does not even need a superheater; or you might better say, it does not need a separate superheater. In fact, I very much doubt you need a superheater at all for heating purposes. You get really dry steam with them, though.



I do not know what you would call the heat exchanger in the W-M Ultra series boilers. No tubes at all. It is an aluminum casting that completely surrounds the burner that is near the top. Maybe it is a wet-base downdraft boiler. The fire goes down and is exhausted from the bottom. I assume the flame is mostly around the burner and only hot combustion gasses lower down, and, I suppose, fairly cool combustion gasses as they exhaust. There are pins on the fire side of the casting. The water side has no pins. The return from the system goes in the bottom of the casting and the supply comes out the top. Counterflow heat exchanger, if you will. I found the size of the thing surprisingly small.

gennady

Firetube

I'm a authorized weil mclain installer and I did install and corrected installations of ultra boilers, and it is a very good boiler, I also graduated polytechnic university with major in power plants. I have seen firetube boiler on the historical part of the textbooks, and a real one when I started to work in USA. I worked at various power plants and never seen firetube boilertgere. They are cheap and simple. and so for me it is old news.

SWEI

condensing

I've got a PS399 (pre-Trimax) running DHW only on a SMART 120.  It's keeping the outer tank at 146F using the onboard CH controls (not DHW priority.)  Temps cycle from about 138F to 155F and it condenses all day long.

SWEI

fire-tube HX

The specific HX in question was a groudbreaking design at the time.  The fact that multiple manufacturers immediately adopted it the moment it became available says something, and I don't believe for a moment that cost was the primary driver.



Viessmann makes fantastic stuff, but they don't sell their HX to other manufacturers.  As to the alloys used, both 439 and 316Ti seem to be holding up better than 316L has, though some of the issues there were at least as likely due to the HX design as to the alloy from which it was made.

SWEI

deltas tee

Increasing ∆T on the boiler side is usually a good idea, and can save quite a bit on pumps and piping, especially on larger systems.  TT specifies minimum flow rates that equate to ~38F differentials and starts lockout at 72F.  We aim for 35F, which seems to work well.



On the system side, we try to widen the ∆T when we can.  This works well with oversized plate radiators or big iron (sometimes.)  In-floor is another story.

Jean-David Beyer

Fire tube heat exchanger.

I saw a tiny fire tube hot water heater, or maybe it was a boiler. The fire tubes were vertical, and it seemed as though you could put anything that burned beneath it. It was around a foot in diameter with perhaps 10 fire tubes. It was a couple of feet high. It has an ASTM stamp, but I do not recall which one.



The people that owned it were considering making a steam-powered railroad car from it. They could not do it unless Hartford would insure it, but they thought that would not be a problem. They already ran three steam locomotives, so they knew what needed to be done. The thing was no longer (if it ever was) usable for domestic heating because its evaporative surface area was too high, and would require a New Jersey Black Seal license to operate it. These guys had all kinds of licenses, Black, Blue, Red, and one Gold Seal license.

leed

Low fire

The heat loss for the house is 43-44K. Will the 34K low fire be to high?  

Mark Eatherton

It wil cause short cycling during the shoulder seasons...

If you have the room and the money, adding a buffer tank to the mix will help alleviate the short cycling, which is hard on seasonal efficiency.



Heres one of many SIegenthaler articles on the subject.



http://www.pmmag.com/Articles/Column/BNP_GUID_9-5-2006_A_10000000000000351457



ME

SWEI

throttling back

On the load side you can throttle back as much as you want - if it satisfies the demand, it's all good.  If the system runs well through a winter at the lower flow rate, it might be worth considering a smaller circulator, perhaps even a smart circ depending on the system.

NYplumber

More?

Tony, would you know where to find the other sections to that series from Siggy?

TonyS

NY PLumber

Sorry I didn't get back sooner. On vacation using a iPad, . Screen is to small for my eyes.

I purchased a disk from Siggy, he has it for sale on his website. It has all the articles he wrote for PM and I think Domestic engineering. I don't have my computer with me or my bookmarks or even my passwords, so I can't help you till I get home. It looks like this hurricane is going to hit us in the keys so I'll be home by Monday if you can't find it