Modulating or not???

Dave_13

O.k., I've learned a lot about condensing or non-condensing boilers pro and cons-now what about modulating and non-modulating burners? It seems like modulating would be the way to go. What are some pluses and minuses about each????

munchkin-man

The addvantage is

Efficiencey. MODULATION, The Munchkin boiler has the ability to to modulate. This means you can control the BTU input in to the combustion process based on the return water temp. The higher the return water temp the less BTU'S sent to the combustion process. On a conventional boiler using cold start you have a high limit with a differential that is on off with full BTU input in to the combustion process. The addvantage of the modulation is less fuel consumption.

CONDENSATION, The Munchkin condensates because we channel the return water back through a pre-determined number of coils depending on the BTU rate of the unit behind the target wall of the combustion chamber. The hot flue gas's are exhausted passed the rear coils and out to the atmosphere. The return water sucks a great percentage of the heat out of the flue gas's and transfers it back in to the return water to be reheated. This action cause's the flue gas's to condense because of the temperature differance between the water or surface of the coil and the flue gas's. This is called the dew point a physical action that occures when the temperature diffrence between two temperatures is at a certain ratio to each other. This physical action results in very low flue gas's being exhauted in to the atmosphere. We get a 92% AFUE (Anual Fuel Utilisation eficiency) because of this. The stack efficiency will change in relation the the flue gas's temperature and co2 levels. Any condensating boiler under approximately 82.5% (if I am not mistaking) is not a true condensateing boiler it is classed as near boiler condensing heater only and condese's very little. The Munchkin condense's in both the stack and the boiler.

Dave_13

Modulating????

So why would anyone buy a non-modulating boiler like the Mz Boiler? Sounds like a good boiler but it doesn't modulate. Is modulating really that important or does it depend on the application? I plan on having radiant, HWBB and Indirect domestic.

munchkin-man

Re read my staement on MODULATION

You will find the answer to your question is in the story behind the story of Modulation. No matter what type of media you are suppling for space heating modulation is the way to go to help conserv fuel.

When heating domestic through an indirect one would want to go right in to high fire without using the step up modulation sequence available in the Vision One package that is energized when cenral heat is demanded. Then let the modulation work it's magic.

Mike T., Swampeast MO

MZ is modulating in Europe

A bit of info from an MZ engineer.

"Until it is available in North America, the on-off version, PROPERLY CONTROLLED, will deliver an annual fuel-use profile within one or two efficiency points PLUS OR MINUS of the modulating version. The on-off version will often beat the outdoor reset contol if indoor feedback is not properly incorporated in the control. The primarly benefit of modulation is the longer life of inexpensive,
easily-renewable, already very long-life components, not efficiency.

To the best of my knowledge, the modulating version of the MZ in Europe is either DC or controlled in such a way so that it does not "surge". Gas is mixed down-stream of the blower in the burner. The mixture is always just barely on the lean side of stochiometric. If one wishes, one can trim it to within the limits of one's measuring tool's ability to count CO. In the real world, not the lab, the
constant fluctuations in such things as barometric pressure, gas pressure, moisture content of the air, moisture content of the fuel, variations in incoming electrical current, normal +/- variations in component parts' manufacturing tolerances conspire to introduce very, very small variations and instabilities that irritate
perfectionists and deprive some of them of sleep at night. Out of the lab, however, the modulating MZ passed Germany's Blue Angel standard, the world's most-stringent air-quality rule at that time (now equalled in toughness by Southern
California's South Coast Air Quality Management District's regulations) long before many of its competitors did (and some have not yet!).

Burner technology is evolving fairly rapidly out of environmental concerns as much as anything else, as I understand it. Building a pre-mix burner that doesn't scream, buzz, howl or moan (LOUDLY) under certain conditions, that won't flash-back (burn the pre-mixed gas and air upstream of the burner face instead of downstream, even when the combustion process is slammed with a sudden, sharp backpressure as can happen on startup if the initial mixture is too lean, etc.), that doesn't encourage NOX formation and that accomplishes all of those things at a five-to-one turndown ratio or better is not something that every manufacturer has been able to do. Patents on the burners that do are guarded and protected.

The MZ has HUNDREDS OF THOUSANDS OF EQUIPMENT-YEARS
BEHIND IT SINCE 1981 AND IS EXTREMELY WELL DOCUMENTED AND UNDERSTOOD. No surprises! The scheduled maintenance on the MZ is required by European environmental laws, not the nature of the MZ. I would schedule a condensate-drain
cleanout (three-minute procedure, including two minutes to remove and replace the unit cover, one minute to unscrew, dump, rinse and replace the condensate cup) every two years even though it will only be necessary in one out of every two or three hundred units in the three years after that interval. I would also schedule an ignitor replacement every ten years (thirty-minute job, including figuring it
out from scratch if you forgot what you were told about the ten-minute job) just for good-order's sake. There is a 50/50 chance that it will be needed between the 15th and 30th year. That's it! All equipment requires service eventually."
------------------------------------------

This statement, "the on-off version will often beat the outdoor reset contol if indoor feedback is not properly incorporated in the control" is HIGHLY IMPORTANT!!!!

Remember that, when reset, early Munchkins really did not modulate as reset essentially circumvented its brain. The new control of the Munchkin sounds incredible however.

I would imagine that the amount and level of modulation varies greatly with the system to which the boiler is connected.

When a proportional (AKA modulating) boiler is connected to a system controlled digitally (AKA wall t-stat(s)) proportional control of the burner is particularly difficult as the "perfect" goal would be to keep the t-stat(s) just a tiny bit UNSATISFIED. The lower the mass and volume of such a system, the more difficult this becomes. A battle ensues: too much modulation and the space may not heat sufficiently or be extremely sluggish as outside temperature falls; too little and temperature flucutation in the space grows. Team this with multiple zones (circulators or valves) and even heat sources of wildly varying output characteristic and the task becomes extremely difficult. I would imagine that the Munchkin (being engineered for the American market) would be geared to do this as well as possible.

When a modulating burner is connected to a proportionally controlled system (TRVs, pneumatic, etc.) it becomes somewhat easier to fully modulate the burner--even to the point that it almost never stops burning at some level. The "trick" will be to keep a steady delta-p (perhaps delta-t or a combination) across the boiler at the lowest possible return (perhaps supply or combination) temperature. I would imagine that the Veissmann is geared to do this as well as possible as it comes from an area where TRVs are the norm.

Mike T., Swampeast MO

Where it gets amazing

Proportional flow devices (TRVs, etc) provide near perfect feedback for a modulating boiler--even to the point that it can determine the comfort desires of the occupants!

Reset temperature on such a system is NOT an absolute--it is part of a learning curve and serves mainly as a reference point. The controller strives to learn the delta-p (delta-t, both) of the system when it is MAINTAINING indoor temperature at any given outdoor temperature.

Once such is established a rapid decrease in delta-p (increase in delta-t) can ONLY mean ONE THING--an occupant has requested a temperature rise in some space--and not only will the burner rapidly increase firing, but the supply temp will rise even if the outside temp remains steady. This allows response to be as rapid as possible. The remaining proportional flow devices will merely modulate down automatically until the one(s) wanting to raise the temperature are satisfied.

Conversely, a rapid increase in delta-p (decrease in delta-t) will mean that an occupant has "turned down" some area and the return (supply) temps will slowly fall and the burner decrease fire as the controller "learns" a new maintenance level.

Do any modulating boilers allow you "tell" them during setup whether they are attached to a digital or proportional system?

ken_6

are you a contactor? or?

Mike T., Swampeast MO

a writer who understands heat?

a businessman/contractor who detests "business"?

an artist who loves plumbing?

a conservationist who looks for reality?

a craftsman who can't comprehend not producing silky smoothness with his hands?

an **** who could NEVER be a politician unless he betrayed his essence?

a person who just "sees" things?

a phantom?

Please tell me what I am...I REALLY want to know...

Steve Ebels

Mikey

Your just a wetheaded geek like most of the rest of us. You eat, sleep, walk, talk and think and "feel" hydronics 24/7.

We have had phenomenal success with the Vitodens running panel rad systems. These are all equipped with TRV's.

Example: The house we just finished Tuesday. 5,000+ sq ft. It was amazing to see the Vito throttle down to a whisper and run those rads at 90* water temp with outdoor air about 53-54*. Constant heat output, exactly matched to the load. It takes some calculating and a good heat loss to size the rads correctly, and then a little seat of the pants fine tuning to get the curve balanced between just enough heat and enough to recover from setback. But BOY! let me tell you it works slick. Modulating burner, modulating flow rates from the Vito controlled primary pump, modulating flow into the rads from the TRV's. Throw in a little under floor tubing to warm the floors and you're darn close to hydronic nirvana in my book.

Mike T., Swampeast MO

You got it Steve...

Don't ask me how or why but somehow everything seems to be related to hydronics (or is that hydronics is related to everything) in this stupid head of mine. It just seems a perfect balance between art and science where neither holds the advantage.

"Throw in a bit of underfloor..."

Now you're REALLY talking...pay attention to your numbers and run it "wild!"

Matt Connolly

If I can attempt to add anything to Mike's eloquence...

it's that the European fully modulating MZ is only 1% more efficient than the non - modulating US version in most cases. When a burner modulates, it runs for a longer time but burns less fuel. The on / off type burns at a set rate then stops and burns no fuel. For the given heat load, the same net BTU enters the system. Think of a four cyl. engine vs. an eight cyl. of the same displacement. The eight essentially modulates since it uses less fuel per cyl. but has twice as many as the four. The four uses twice as much but fires half the time. Bottom line, at any given throttle position, the same net horsepower goes to the rear wheels. Just like the same net heat into the home.

A few important points, though. If the heat source isn't properly sized or the system incorrectly controlled, the modulating unit's advantage will grow, since it will cover the design and control mistakes. The on / off burner in a low mass, fully condensing boiler like the MZ has the advantage of fewer and less moving parts, no circuit boards to complicate operation or troubleshooting, and the ability to maintain its efficiency with loads 1/5 the output without short cycling.

Having said that, don't get me wrong - I like modulation and think it is a good thing. The MMZ (modulating MZ) is in the US now getting tested and approved. It is the most popular of its kind in Europe, with a variable speed primary pump (same as the Vitodens) and full outdoor reset built in. The announcement will be coming soon about its debut...

Is this a great industry to be in or what?

By the way, Mike isn't a wethead geek, just a man who understands who he is and what it's all about. An Objectivist, maybe?

Matt

Dave_13

Modulating?

Thanks Matt, that's what I was looking for- a simple explanation. I can see how it would run longer at low fire with a modulated burner. They definitely have a lot of good products out there! It's hard to choose! I really like the Veissmann though (And the Munchkin, and the MZ, etc!!!!!!!)

Ted_5

The Vitodens

has it all by far!! The HX is 1.5mm thick 316Ti stainless
steel. The HX wieghs almost as much as the whole Munchkin.
Try and find one to look at before you make up your mind.

Ted

Mike T., Swampeast MO

\"Objectivist\"

Thanks Matt, I like that!

hot_rod

Modulating depending on

the loads. Plenty of applications where modulating would not be needed. Consistent loads, snowmelt for example, DHW production, large commercial slabs perhaps. Modulation adds complexity to the equipment, which translates into more potential breakdowns, I'm not sure it's "right" for every job.

Micro loaded, multi zoned jobs have modulating written all over them. Nice to match output to load in this case, typically all zoned residential could benefit from modulating equipment. Or large well insulated buffer tanks

Match the heating device to the application.

hot rod

Steve Ebels

\"throw in a little\"

That's exactly what we did Mike. We are runing that 500 sq ft of underfloor wild. No stats, no zone valves, just 4 loops constantly circulating a little warmth. Running on the same curve as the rads. That way the floor is always getting a little warmth while the trv's on the rads actualy react to the temp changes in the room. So far, it's been working sweet. We had that part up and running about the middle of April and had a few 20* mornings to check the floor temps under a little load. At 22* outdoors the room temp was 67* (felt like 70-72) and the floor temp was running a couple tenths over 73* on the part we had insulated. The rads were barely flowing, just enough to heat the whole surface. It sure felt nice in there.

Mike T., Swampeast MO

Amazing

how much mechanical complexity can be eliminated with careful design.

Have my shower floor (3/8" copper tube encased in garden hose for insulation) hooked up but won't know the result until November/December. Am shooting for a surface temp around 82° or so but the calculations were theoretical to say the least.

Three other baths (all with different types of exposure) all work as designed.

"No stats, no zone valves, just 4 loops constantly circulating a little warmth. Running on the same curve as the rads." Using a 0.9 reset ratio bath floors vary from about 77° @ 50° outside to 82° @ 8° outside.

Attachment is my heating "bible" for this house. Note the high level of imbalance of the rads--this was inherited--yet the TRVs seem to handle it in stride. The upstairs (bedrooms, study, sleeping porch) are the most oversized--kind of the opposite I would expect in a gravity system where heat wanted to go up--but good (I suppose) for "airing" during the morning and keeping the bedrooms warm at night without refueling.

This is a composite of theoretical heat loss data, HVAC-Calc, and actual data from actual radiator temps at maintenance condition on fairly still nights of steady temperature. Note the "85%" notation after heat losses--this is the adjustment I used from HVAC-Calc numbers based on "reverse engineering."

Also note that "Req. H2O Temp" does NOT include delta-t and "headroom." Actual "curve" is set about 20° above this temp, 10° for delta-t and 10° for wind/ability to raise space temp rapidly.

All radiant areas (baths) run "wild" off of this supply. Only the master bath has a rad (it also uses electric floor warming instead of hydronic)--the most exposed bath has electric BB, but have found it completely unnecessary.

(Table rather large, about 2 meg, so click to see.)

Matt Connolly

Mike, I could hear John Galt...

talking as I read. Who is John Galt, anyway? Maybe it was Howard Roark!
Matt

rich pickering

maintenece

Our current boiler inspector, saint that he is, comes from Holland, where they rented their boilers from the utility.I forgot to ask what make they were, but they were wall hung modulating. What I found real interesting is that once a year the utility came by and changed the boiler, taking the old one back to be cleaned and checked.After seeing the picture of the acid cleaner for the hx, and then hearing this, I'd really like to talk to their maintence guys.So far we are installing Trinity's(no one wants to spend the money for the vitodens)but something keeps nagging in the back of my head.Any one else feel this way?

Matt Connolly

The factory in Europe

has sent us pictures of the Munchkin / Trinity heat exchangers after a few years use (they are made in the same factory). Because of their parallel passage system and small tube diameter, they can clog very easily. Any impurities or minerals will attach themselves at the slowest, hottest point of flow. That is probably why the Munchkin requires the HX to be cleaned on the water side every 2 years for the warranty to remain in effect. I don't know about the Trinity's requirements.

I was told that most service companies over there have HX replacements and simply switch them out with ones that were cleaned at the shop, saving the need to roll out the acid pump at the home. When I get the pictures of the HXs, I'll post them.

The MZ has none of those restrictions, it has proven itself for 23 years with nothing more than a 15 minute clean and check every 5 years. It's been modulating in Europe for the last 10 years, and that model will be available here soon.

Matt

hot_rod

If the system is

cleaned and filled properly from day one, including appropiate inhibitor chemicals, AND if the system is tight and doesn't tak on additional fill water, AND o2 barrier tube is used.. Tell me where these impurities, scale, sludge, etc comes from?

It doesn't magically appear, osmosis thru the components.

This is why I keep harping on the need to flush, clean, and treat the systems properly from day one.

This procedure should apply to any hydronic system, be it cast iron, copper, stainless, aluminm, what have you.

Certainly the boilers with small passage ways are more prone to problems, the installer is the one responsible for creating this. I doubt the boilers are shipped with blockages!

You clean and maintain your boiler for the same reasons you maintain your motor oil, or be prepared to pay the piper down the road. I feel these cleaning procedures are more for DHW production units that see fresh water on a continous basis.

Mt 2 cents worth

hot rod

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Doug_7

Why Modulating improves efficiency

From what I have read Modulating improves condensing boiler efficiency in two ways:

1) Modulating eliminates the heat losses that occur on start-up and shut-down purge cycles of on-off boilers. Frequent boiler-cycling at lower and lower heat load increases these heat losses for on-off boilers.

2) Modulation gives higher boiler efficiency when operating at low fire than at high fire on the same boiler because of the so called "inverse efficiency curve". Efficiency actually increases at low load because the condensing section is less heat loaded and runs cooler, condensing more. It is called "inverse" because conventional non-condensing boiler efficiency drops off dramatically at low load.

Modulating condensing boiler efficiency increases at low heat-load compared to on-off boilers. An important point especially since gas prices are going up dramatically this summer, fall and winter.