seasonal efficiency variation puzzler (new Munchkin vs old CI)

[Deleted User]

I wrote numerous articles dealing with this very phenomenon just recently. One of them is missing from the link, and I will post it as an attachment to this post. It's obvioulsy too late to diagnose the efficiency of the replaced boiler, but not too late to begin getting good data on the new system. For a few hundred dollars, youtoo can own the equipment necessary to perform in filed real time energy audits.

The article archives is at

http://www.contractormag.com/articles/columnist.cfm?columnistid=6

The relevant articles began in June of 05.

Enjoy!

ME

R. Kalia_6

We moved to a house in 2003 that had a CI boiler, and over the winter of '03-'04 I used the gas bills to calculate therms per degree-day. I subtracted the baseline determined from the summer gas bills. The boiler got more efficient when it was really cold (less short-cycling is my guess, it was really oversized), but it had almost the same therms/dday in October and April, which are about equally cold.

We got a Munchkin in Fall 2004 and I did the same thing for the winter of '04-'05. It started out in 10/04 with excellent efficiency: it used about 65% of the gas used by the CI boiler (per dday) in 10/03. Over the winter it got progressively worse, but not due to the weather getting colder. It just got worse every month. In 4/05, it used almost as much gas per dday as the CI boiler in its best month.

I was worried that something was going wrong with the Munchkin, and I had a combustion test done (everything OK). Moreover, I now see that therms/dday for the Munchkin in 10/05 is back to what it was in 10/04, i.e. 60% of the old CI boiler's October usage.

What could be happening? Maybe it's because the ground is colder in April than in October, and this cools the house through the foundation. But why wouldn't that affect the CI boiler also?

ALH_4

More Info

Do you have a plot of therms and degree days for both years? Domestic hot water production affects your energy usage, and will throw off the ratio more during low degree-day months.

-Andrew

Constantin

Nice to See you Again!

We can speculate about a number of issues that could be at work here. More environmental factors are likely to be required.

At the outset, the wide divergence between the Ci boiler and the modulating Munchkin are to be expected. The seasonal efficiency of a CI boiler during the shoulder seasons is notoriously bad. As the winter progresses and the temperatures drop, the CI boiler ought to improve in performance while the modulating boiler should hold steady.

Is this a high-temp system? I.e. what is the design-day temperature of the emitters in your home?

Does the Munchkin have a Vision 1 controller, outdoor reset, and a proper heating curve programmed into it? Don't assume that the contractor did all these things, I found lots of the settings on my Vitola untouched. Is your OR sensor working?

Do you have a local source that can normalize for the BTU content that the gas company delivers per CCF? This, ladies and gentlemen, ought to be a law, BTW, that the utility can only charge on a per BTU basis, not volume.

I recently downloaded 5 years of weather data for Boston from NOAA, and I am currently in the process of massaging it into shape for my purposes. I plan on trying to tie boiler consumption to hourly bin data consisting of dry bulb temp, humidity, wind speed, gustiness, etc.

Christian Egli_2

The boiler of Munch-hausen

Something seems disturbing, although I don't think it is the stuff of horror movies. The Munchkin is saving you considerable fuel for one reason mainly, I would guess.

Not because of the 92% efficiency vs. the degraded cast iron boiler at 85%, that's all the stuff of glossy brochures. The savings are real, indeed, but not ever as gigantic as hoped.

You still made a good choice with your Munchkin.

Where I think things are really paying off is with the optimized control system that came with your new boiler compared to what you did not have with the old one.

Running the Munchkin with the old controls would have produced the same U shaped curve you witnessed for the old system, except that it would have been a little lower to account for the higher advertised efficiency. This is exactly what you see from February on to the end of the season.

The missing down slope on this U curve, I would attribute to better control. With better controls you don't overheat and you can better account for thermal inertia.

Coming out of the summer, your home is still full of heat. Not much would be really needed to fight off the cold. This is hard for old ON-OFF systems to anticipate. But your Munchkin senses all this and only adds tiny bits of heat until December.

Then everything just gets cold, and home heating is the same old business.

Modern control on the cast iron boiler would have yielded the same pre-season savings, transforming the U curve into a up up and away curve.

What happens at the end-season that did not happen in the pre-season? Your home is now fully cold.

What do you think?

R. Kalia_6

answers

Many thanks for thinking about this problem! Some answers:

a) Yes, hot water use can be different in the dead of winter. I subtracted the summer gas bill rate, which was 30 therms/month with pilot, 18 therms/month with Munchkin. But that doesn't explain the difference between October and April.

b) The design-day temp is about 170F, because of a modern addition with a minimum amount of baseboard. But that doesn't explain the difference between October and April.

c) We have Vision I and I have access to all the parameters. Water temperature varies from 90F to 170F. Again, whatever the reset curve may be, the boiler uses the same region of the curve in October vs. April.

d) I don't know the real BTU of the gas. The gas company applies a correction factor to the cu. ft. that is always between 1.00 and 1.01 (and which I included in my calculations) but it may not be an honest correction.

e) The "house is holding heat in fall" explanation is similar in effect to my "ground is warmer in fall" explanation. But I don't quite understand why "modern controls" (reset?) would reveal this phenomenon while bang-bang control will be unaffected by it. Let's look at the CI boiler in October vs April. It had the same (bang-bang) control in both months. If the house needs more heat in April, why didn't the CI boiler use more gas in April? Everything else is the same.

Thanks again,

Christian Egli_2

Doggie bag? not at an all you can eat boiler

Nothing wrong with your intuition on e)

The house full of heat shows itself to the boiler by returning water that is hotter. Thus, return temperature will be higher in pre-season than in end-season. Another way to look at it is delta T will be smaller in pre-season and larger in the end-season.

I know, in the design phase, we always pick a set delta T as though it was set in stone. But it is not.

Not considering variable flow, with a wide delta T, a hot water system can ferry away lots of heat from the fire before it goes up the flue. With a small delta T, much less; the rest goes up the flue. If you can't take it away as fast as it is burning, you lose it. It helps to reduce your boiler water temperature, less will go up the flue.

Lots of fancy things a bang bang system can't do. At its worse, a simple ON OFF control does not directly react to how much heat is taken away from the boiler, it just maintains a set supply temperature and whatever is not consumed on the spot gets wasted up the flue.

It's an all you can eat boiler. But what happens to the leftovers in the pre-season when your home is not very hungry for food? The sensorless chef doesn't know that, he cook for a full army.

And since you can't can heat...

The Munchkin tailors the portions to the appetite of the customer.

Incidentally, steam boilers do this all the time, ever since prehistoric times. You monitor pressure, you monitor the instantaneous customer appetite. Simply beautiful and gadgetry free.

When you switched boilers, why didn't you go for steam?!?

Chuckles_4

I think I understand. In brief, if the "true" efficiency (BTU out per BTU in) is the same in Oct and April (Munchkin), the therms used per deg-day will be worse in April because of more retained heat in the house in Oct. But a CI boiler becomes MORE efficient when more therms are needed, so BTU out per BTU in is actually better in April and worse in October. The two opposite trends tend to cancel each other out in a CI boiler.

I am not convinced that this is the explanation, but now I understand the argument, thanks!

Chuckles_4

The $64K question is, do newfangled boilers really have the nasty seasonal therms/dday trend I showed in the graph above? In terms of therms/deg-day the Munchkin uses OVER 40% MORE GAS in the spring than in the fall! I have never heard anyone describe that kind of trend here on the Wall or anywhere else.

Of course the "retained heat" or "heat loss to the ground" would depend on the house and its construction, and is not the fault of the boiler (our house is 1920's brick with good windows and attic insulation, but uninsulated foundation). But, if anyone here has an older house with a condensing/modulating boiler, then maybe that person would volunteer to see if his/her boiler behaves the same way as my Munchkin.

I realize it will take some work, but I hope it will be interesting for you. You would need to have your gas bills on file and they will need to tell you the deg-days for each billing cycle. The July or August monthly gas usage would have to be subtracted from all monthly bills.

ALH_4

Data

Trying to work backward from a ratio is difficult without the raw data. I still think the fuel usage and climate data is the key. How about solar gain? Is it cloudier in the spring than in the fall? You could have degree-days without much heat load if you have higher solar gain. If the heat load is low when the temperature is low, the boiler will stay hotter more of the time.

There is an answer somewhere, but I doubt it has much to do with the condensing boiler directly. I would say it has more to do with the weather and the structure. Does the Munchkin have an indoor sensor option? Have you set the heating curve as flat as possible?

-Andrew

Alex Giacomuzzi

Very Interesting Thread......... Some Interesting Thoughts.

I agree this is the $64K question in several ways..

I am going to make some assumptions here given that you have a 1920's home with a 170 deg. F. design day temp. I presume the majority of your emitters are either cast iron radiators, cast iron baseboard, and some fin tube baseboard with a minimal amount of radiant tubing. I am also assuming that your Munchkin is operating effectively with tuning / setup correctly. Regarding the previous CI boiler ---- how much oversized was it?? I am just curious.

Regarding the CI boiler ---- the oversized CI boiler the terms of "short cycling, seasonal efficiency" , standby losses etc. are extremely relavent and make a huge impact in understanding the great data that you provided to the wall. In looking at the CI alone, it is understandable that as the call for short demands of heat start in the fall contribute to increased short cycling which is very inefficient especially for an oversized boiler. Therefore the therms increase (temporarily), until the calls for heat become more frequent or the boiler may run longer. The standby losses, short cycling etc all decrease and the CI efficiencies improve just as your data suggests for the colder weather. This is expected and nice to see charted. As the weather starts to change, so does the efficiencies and we start to return to the October conditions in April / May. Seasonal effects are very pronounced on a CI boiler especially an oversized one.

Now lets look at a Condensing / Modulating Boiler. I do not have any comparison operational specs on a Munchkin to compare against, but I do believe that your data speaks for itself and I can offer some interpretation. First of all, Vitodens 200 specifically the WB2 11-44 has a great instruction manual with some great data included that may help us with your data.

The note worthy data says the exhaust temp of the Vitodens is 86 deg F when the return water temp is 91/95 deg F. and is 140 deg F when the return water temp is 149 deg F. This tells me ---- if you have a traditional hight temp emitter system, you will probably be running higher exhaust temps and therefore running higher therms per degree day for the same system input heat as if you were running low temp returns for radiant for example. This will cause the therms per day to increase just as your chart suggests. This is the $64K question that there have been several assumptions made about. In this particular circumstance --- with an existing high temp emitter base, I do not agree with an earlier comment that a modulating system will hold steady in colder weather. For an ideal design (where you can specify everything) ---- yes, but not for every existing application out there.

Back to the favorite "It all Depends" on the design data and the type of emitters your boiler is serving. For example.... if you had an excessive amount of emitters, you could possibly reduce the return water temp slightly, but all in all...... There definitely appears to be a decrease in efficiency the hotter you need to run the system. I believe you have captured that point very well.

Now lets look at another data point.... Condensate FLow.
For a supply / return of 104/86 we get 3.7--5 gal.per day
For a supply / return of 167/140 we get 2.9--4 gal.per day
The less condensate, the less efficient. There is a 20% to 25% difference here depending on how you calculate.

I do not know if Munchkin has any of this data available, but it would be interesting to compare......

When we start coming into spring time, I think both boilers are short cycling a bit and this can drive up the therms in both cases. Interesting data....... Thanks for posting it.
I am sure there will be several interesting responses..

Regards Alex

Chuckles_4

I will try to collect the raw therms and deg-days data, but since I didn't enter them into a spreadsheet but rather scribbledd the calculations on the bills themselves, it will take a day or two before I can get to it.

I don't have wind or sunshine data; the angle of the sun may also be relevant. I agree that this could skew the results. Each year is probably different from the next. But those are huge variations in efficiency...

I've set the curve as low as I could, but not as flat as possible. A flat curve would have to be level at 170F i.e. no reset at all.

Chuckles_4

answers

Most of the house has CI radiators (enough to heat that part of the house with 150F water on a design day). But an '80s addition has CI baseboard and needs 170F. No fin tube, no radiant.

The Munchkin is set as correctly as I know how. If I am doing something wrong, I don't know it.

The old CI boiler was 160,000BTU input. The Munchkin is 80,000BTU (I absolved the contractor of any liability if the new boiler was too small...it is not too small!) This is a 1800sf house (not counting basement) in the Chicago area.

I did not collect the condensate (and I must admit I have no desire to do so!)

>There definitely appears to be a decrease in efficiency

>the hotter you need to run the system. I believe you

>have captured that point very well.


I did not follow that. The therms/deg-day of the Munchkin continues to decrease in spring when it is running cooler again.

Chuckles_4

> Most of the house has CI radiators (enough to

> heat that part of the house with 150F water on a

> design day). But an '80s addition has CI

> baseboard.

>

> The Munchkin is set as correctly as

> I know how. If I am doing somethign wrong, I

> don't know it.

>

> The old CI boiler was

> 160,000BTU input. The Munchkin is 80,000BTU.

> This is a 1800sf house (not counting basement) in

> the Chicago area.

>

> I did not collect the

> condensate (and I must admit I have no desire to

> do so!

>

> _There definitely appears to be a

> decrease in efficiency > _the hotter you need

> to run the system. I believe you > _have

> captured that point very well.>

>

> I did not

> follow that. The therms/deg-day of the Munchkin

> continues to decrease in spring when it is

> running cooler again.

leo g_13

2 questions

Is your DHW a tankless or is it a seperate gas fired unit?

Is your potable water supply surface, well or ground source?

Leo G

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Guy_6

Simple

Something simple to look at as well- the outdoor reset curve. If the boiler output temp is dropping too low for the radiation, or if there is something ie:sunlight, affecting the outdoor sensor in the different season.

Just as an expiriment, try disconnecting one wire from the outdoor sensor, disabling it, for a month and check your therms/ degree day.

GW

GW

Chuckles_4

Separate gas fired unit. Municipal water supply.

hr

The wider the delta T

the more efficient the boiler. Regardless of conventional or condensing boiler design. Although condensors run more efficient when condensing. Be interesting to connect a data logger to supply and return boiler connections, to add this curve into your number crunching somehow.

hot rod

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S Ebels

Good point

A municipal water supply will run upper 50*-lower 60* range by the end of summer. Come spring time when the frost is going out of the ground I've measured incoming water temps in the mid 30* range for municipal water supplies. This would be adding a sizeable BTU load depending on the gallons of DHW that you use daily. Lower incoming water temps could be adding as much as 20% to your DHW load without any actual increase in gallons of consumption.

Steve D._2

another theory

Aprils are wetter than october with snow melt and rain. The wet brick will go through an evaporative cooling effect if brickbound moisture is evaporating. This could explain your difference.

You could also have more consumption for hot water use. Your ground water could be coming in at different temps in april vs october. A couple of therms difference in a low degree day month will muck up your calculations.


I also went through the same exercise as you recently and noticed that in low degree day months I could have 9-18 therms for hot water only. Picking a number to subtract to arrive at a baseline can give very wild numbers in a month when there is 1 degree day and 7 therms used!

I will look more closely at your graph and see if I can identify anything.

Best of luck

Steve

Steve D._2

R,

This is my data in CT. You can see the spikes in warmer weather base on variation in the baseline / actual difference when I tried to remove my water heater consumption. I would tend to not rely on the warm mo's for decisions.

What has me puzzled is that I have a CI atmospheric boiler with no reset and it does pretty good compared to the munchkin.

Steve

leo g_13

Uh-huh!

Yup Steve, what got me thinking the same way was "Chicago". Can be quite chilly during them winter months. The other factor would be the chimney effect of the stand alone. As the temp outside goes down, I feel, more heat is lost from those tanks vent. Heat to cold and all of that.

I think that you are going to have to graph both appliances to get a better understanding!

Leo G

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R. Kalia_6

data

Here it is. Sorry, I don't have any of all that other data people want! By the way, a 20% change in the baseline isn't going to have a large effect. This is Chicago and it's cold.

R. Kalia_6

> What has me puzzled is that I have

> a CI atmospheric boiler with no reset and it does

> pretty good compared to the munchkin.


Therms/deg-day depends on the house . You can't compare two different houses. Also, I can't really see what the numbers are because the y-axis range is so large. I would suggest taking the spikes out and plotting the curve so as to show the winter data more clearly.

Enough

You are right

I cannot compare your house to mine. That is modern communication for you - think after you click send. The reason I made the comment is that I don't consider my house energy efficient and the numbers were close. If you had a 6000sf uninsulated victorian I would indeed be extremely high in consumption.

Here is my graph which will only be useful to you based on it's shape, not it's values. Warm month values are out to lunch because my baseline goes from 9-18 in warm weather. I also add 1degree day to the calculation so I don't divide by zero.

Aside from the phenomenon you have discovered, do you feel that you will get a reasonable payback of your additional expense?

Steve

Mike T., Swampeast MO

Degree Days & Use

Were your thermostat settings identical in October and May? Is daily setback used? If so, when, for how long and how much?

Basic degree day calculations assume that heat is required any time the outdoor temp is below 65°. There's a few problems with that:

First, it's a simple average of the lowest recorded hourly temps. 1 minute of 64° temp relates to 1/12th of one degree day...

Second, it does not account for occupancy load. In my experience most houses don't need heat until the temp drops to the 55°-60° range and stays there for a decent period of time. This tends to exaggerate degree days when the outdoor temp is fluctuating around 65°--paricularly in the fall.

Third, there is no accounting for periods of time with outdoor temp greater than 65°. Again, this tends to exaggerate degree days in the fall.

Christian Egli_2

Naaaa, it can't be cold in Chicago, that's impossible

I think your first plot would look much less drastic if you carried the ordinate all the way from zero up to where you need it at 0.3 - 0.4

The way you have it is the way hot stock tips are marketed.

All you were expecting when you installed a higher efficiency boiler was to have the new curve appear a margin below the old one, while keeping the same shape.

You could be rightfully furious if the new curve had risen above the old one. That did not happen.

There was an additional bonus for you, the fall part of the new curve with its missing chunk gives you additional savings.

Visually, what is important with your curves is the gap between the two in reference to the gap between each of them and the ground line.

Keep warm.

Chuckles_4

Very useful. He's got a boiler whose gas consumption is increasing by nearly 50% over the course of a season, and you are telling him to not worry his pretty little head and to be grateful it's not even worse.

Not a great advertisement for hydronics, is it? I mean, wetheads make all kind of efficiency and savings claims, but then they don't want them analyzed too deeply by the customer.

Constantin

On the other hand,

Some suggestions have been made regarding the possible causes of this discrepancy. For example, does it make a huge difference if the potable water supply temperature drops from let's say 55°F to 35°F?

A quick, back-of-the-envelope calculation seems to show that a 20°F drop in the supply temperature could result in an additional load of ~8,800 BTUs per day if you have 200 liters / 53 gallons of hot water consumption. Across the 30 days per month (on average) that comes out to about 2.6 therms/month extra. Not much.

... on the other hand, a slow leak in the heating system may become more noticable as time goes on. I'm not suggesting that this is happening, and presumably, the system is tight as a drum.

Other explanations such as the exterior walls acting as a heat sink in the fall and a cold sink in spring seem more likely. The only way to really know is to instrument house and the Munchkin to make better sense of the environment vs. the boiler. That is, capture HDD, insolation, wall temps, etc. locally, monitor supply and return temps, flow, vent temps, also the BTU content of the gas being delivered. Only then can you remove issues by the process of elimination...

Alex Giacomuzzi

Other Explanations

Given some of information expressed here, we could certainly make a design experiment out of this with instrumentation that would make any PHD scientist druel..
It would certainly gather a ton of useful data.

I would like to offer another explanation for which I have no data ---- now that sounds real good from the start..doesn't it??

I would really like to have some things explained to me. On the sales literature for example and the application literature that is available on the more efficient condensing boilers which state efficiencies from the low to the high 90%. I can grasp that very well. This is mostly what I hear spoken about. Now lets take the device and apply it in a real world situation as we have described here.

I am not asking people to measure condensate for example or measure flue gas temps, but I am saying this reflects and is an indication of the efficiency of the device.

There are a few manufacturers that publish some relavent data. I went to the this boilers web site and viewed their manuals, found tons of important information on installation, troubleshooting, parts etc, but I could not find a data sheet on the flue gas temps, or the condensate quantities for various load or temperature running conditions. Nor was there any kind of a graph of chart which gave you an indication of % load and operating temp as it relates to efficiency. This data would be invaluable to help understand what might be happening here.

For example...... I am presuming that this 74K output boiler is probably running in the 70% to 100% range as far as loading is concerned. Ok ---- what happens to efficiency when we load this particular boiler? Can anyone help us here? What happens to efficiency when we load a CI boiler and visa versa?

Secondly the setpoint temp for operation is 170 deg. F. What happens to efficiency when running at this supply temp value versus say 110 or 120F.? Any ideas?

Both of these conditions are occuring in this particular application. If this were radiant in floor, it would be a completely (partially that is anyway) different opportunity.

Another thought.......... I understand very well the desire to size the boiler at or near the load. This fits a CI unit to the tee, but in reviewing how a condensing unit deals with increased load, is this still the appropriate application philosophy??

I really think this is a great thread, and would really hope someone has boiler test data to share on an application described above ....... If I could have found it, I would have provided it.. sorry.

Thanks for letting me partake... Alex

S Ebels

Correction in terminology

His gas consumption is NOT increasing by 50%. What he is saying is that more CCF of gas seems to be used per degree day as the winter wears on. It's an interesting puzzle since the boiler operates at XX% efficiency pretty much regardless of outside conditions other than water temp provided to the system. I doubt that there is anything the boiler itself could do to generate this discrepancy unless it became severely out of tune.

The big variable to me is still the hot water heater. One would have to track gallons of hot water used and factor that into the equation to isolate what the boiler is doing.

S Ebels

Another thought

Degree days are basically a measure of indoor vs outdoor temp. My gut level assumption has always been that while DD numbers tell a large part of the story, they can't tell it all. There are some other factors that influence the load on the heating system. These would be things like wind, both speed and direction, humidity levels in the house, the depth of frost in the ground and actual ground temperature. Someone else mentioned evaporative cooling of the structure brought about by a cold spring rain. I can see where this would be a factor especially in a high mass (brick or concrete) house.

While the Munchie does indeed tick upward in the spring, your graph shows that the CI boiler did also. I think to get a meaningful set af data on this, a person would have to track it for 5 or more years and look at the average DD/therm.

Anyhow, I'm just saying that DD's are not the only factor in looking at heating costs. Other things can have quite an influence on your system than just outdoor/indoor temps.

Constantin

Ain't it fun?

I agree that it would be nice if the manufacturers published curves that showed the efficiency of their units as environmental factors change. However, it also isn't that hard for homeowners to do their own sleuthing...

For examble, the HOBO series of dataloggers can measure multiple temperatures, store thousands of data points, etc. and also capture when the circs are running, etc. So if it really interests you...

One thing to keep in mind with this modulating/condensing boiler is that unlike its CU cousins that it will achieve 94% efficiency across a broad range of firing capacities (100%-20%). Only when the heating demand falls below the minimum firing levels does the mod/con boiler start to behave like a single-stage boiler (i.e. cycling on and off).

One thing in the favor of the mod/con boilers though is that they have very little mass and that the time of year when their minimum capacity exceeds the heating demand of the home the return temperatures will be very low and hence combustion efficiency high.

At the coldest time of the year when the highest emitter temperature are required, the efficiency will suffer as the return water temperatures rise above 140°F. However, how much of the year is that cold to require emitter temperatures that hot? What about the rest of the year?

I also agree that highly-modulating boilers give contractors more leeway. If 16;1 boiler turndown ratios become the norm, then one boiler model will be able to cover a very wide range of heat losses with perhaps less rigorous analysis requirements beforehand. But a properly-sized boiler will always be better than a grossly-oversized one, IMO.

Chuckles_5

I think you may have missed on of Alex G's points. There is a claim (I don't know true or not) that modulating boilers are MORE efficient when not running on full fire. In other words, if your max heat load is 80,000 BTU, don't get the Munchkin 80, get the next one up (Munchkin 140)---it has a bigger HX and so it'll be more efficient than the 80 on cold days when most of the gas is consumed anyway.

[Deleted User]

Yeah... like

clear night sky re-radiation. If one year was more cloudy at night than another, that will have a BIG influence on heat loss, and we DON'T typically take it into consideration...

ME

Constantin

Interesting Idea...

... a flue gas temp sensor could tell you quickly whether the flue temps drop as the load drops for a given return temperature and the boiler modulates down.

Presumably, it all depends on how much more efficiency a HX can gain as the HX surface area increases relative to the firing rate. There has to be a diminishing return there somewhere, which is why having a low return temperature is so important in the first place.

leo g_13

OK here's your answer!

Like all great jumps of knowledge, this resolution to Mr. R. Kalia's question happened when I was not even pondering this riddle. Intuition just jumped in and solved it!

From the start of the heating season until the winter solstice, the days are getting shorter (well actually the days aren't, just the sunlight!). After Christmas, the days (light) begins to lengthen. Almost exactly as your Munch graph shows! With the legthening of the days, guess what? People tend to start to rise earlier, and stay up later, therefore the heating is "on" for longer and longer periods!

Mr. R. Kalia, you may now go to sleep with a peace that only descends upon those whose questions have been answered! ~

Leo G

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R. Kalia_6

Yes, that makes sense. We always blew the flame out at sunset and then lit it again at sunrise. I didn't think to mention that because I figured it was like 'dog bites man', everyone does that.

leo g_13

OK 'nuff funnin around

R. is the munchkin a T-80?

Leo G

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R. Kalia_7

I don't remember if it's a T80 or T80M, whichever one is the wall-mount.

leo g_13

OK

R. the reason why I asked is because the T80 has a lower turndown, 19K as compared to the 80M, 27K. If yours is the wall mount, you have the T80.

It would be interesting to get someone to "tap" into your munchie with a laptop, and see what exactly it has been doing!

Leo G

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