Design conditions...

Mike E_2

Well, the topic of your thread was "Design conditions", and the first sentence of your original post was "It is currently zero degrees F outside. Design conditions." You then went on to say that you were running at 16,193 BTU output.

So, this means that at design conditions, your house only needs 16,193BTU. If your calculated heat loss shows 40,000 BTU, this means that either the program you used overexaggerated by 247%, information was entered incorrectly into the heat loss calc, or you weren't really at design conditions.

jp was asking this question (I assume) to try to narrow down how much heat loss calcs acutally overexaggerate their numbers - as this is information that would really be interesting.

Michael

[Deleted User]

A wet heads dream...

It is currently zero degrees F outside. Design conditions. I'm getting prepared to replace my current Munchkin T-50 wall hung boiler with its newest contender and wanted to do one last thermal analysis prior to removing it and thought I would share the data with you all. Bear in mind, that by design, I have done NO maintenance on the fire side of this system. Just run the wheels off of it, like we Americans are prone to do...

At present, the flow rate is 3 GPM (verified with 99% accurate flow meter). System delta T is 10.8 degrees F.

So, the math, 8.33 X 10.8 X 60 = 16,193 BTUH OUTput.

I clocked the gas meter sitting next to my boiler at 183 seconds per cubic foot. Last known caloric value of the gas (utility bill) was 831 btu/cu foot, so more math,

3600/183 = 19.67 cubic feet/hour. 19.67 times 831 = 16,347 btuh INput.

So, output (16193) divided by input (16,347) = .9905 %

No??

Attached is a graphic from the steady state, and I do mean STEADY state operation.

BTW, this almost exactly reflects the results I saw when the system was new 5 years ago...

Also, FWIW, the reason the graphic shows such a low OSA temp is because I have the OSA sensor disconnected to force the unit to maintain a fixed temperature of discharge at 150 degreees F as a part of my ongoing study of set backs and resets and their applicability to mod con boilers. Don't let that confuse the issue. The only thing I want you to focus on is the steady state thermal efficiency of this appliance...

I will be testing the unit at high fire for DHW production soon and will also share those results with you.

ME

kevin coppinger_4

love this stuff....

very neat....where does the old unit go? HfH?

To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"

Paul Rohrs_5

Dr.Eatherton to ER STAT!

We have got a Flat-Line Dr.....

Nice Mark. Good to see that boiler dialed in and performing.

J.C.A._3

Much like the.....

Racontoors...Steady as she goes.

Flatline indeed! Thanks Mark. Chris

DanHolohan

What a fine way

to spend a Saturday!

Uni R_3

Over how long?

The horizontal axis goes 0-100. What are the units?

[Deleted User]

Seconds...

But it has been doing the SAME thing all day long...

ME

[Deleted User]

The old unit...

will be recycled into my retirement home and converted into LP provided that the factory that lent it to me agrees...;=)

ME

Uni R_3

And...

What will be hung in its place?

[Deleted User]

Here's a picture of my wife taking a bath...

Now you know why I married the woman...

Her math is as follows;

42 seconds elapsed time for one cubic foot of natural gas.

3600/42 X 831 = 71,228 buth INput.

Flow rate during DHW production = 3.5 GPM

Delta T during DHW production = 36.4

3.5 X 8.33 X 36.4 X 60 = 63,674 btuH OUTput.

Output divided by input = 89% thermal efficiency.

That is slightly better than it was when it was new...

Enjoy the view!

ME

[Deleted User]

Another high efficiency heat source...

of course. To be honest with you, I am not allowed to tell you exactly what I'm putting it..yet.

I'm sure the manufacturer will allow me to tell you eventually, but thats not my call.

But I can tell you this much. It is supposed to be even MORE efficient than the one I'm taking out. That's why I'm putting the other one in. To test it at 1 mile high.

When I build my second home, soon, it will be dubbed as a high altitude testing laboratory (8,000' ASL) with the ability to test all gas fired equipment at that altitide.

Bear with me.

ME

Paul Rohrs_5

Thumbing through

http://www.engineeringtoolbox.com/water-density-specific-weight-d_595.html

This shows the weight of a gallon of water at 140F at 8.2048 lbs. I think this will change you efficiency slightly, but I think you are after accuracy.

To plug in the values of the original post:

8.2048 x 10.8 x 60 x 3gpm = 15,950.13

15,950.13 divided by 16,347 input = 97.57% efficiency

I still would be thrilled with this number.

Regards,

PR

realolman

"Here's a picture of my wife taking a bath...


You got a wierd lookin' wife

[Deleted User]

You are correct Paul...

I was just trying to keep the math simple. I think Siggy mentioned the water density issue the last round too. I also don't think that this is exclusive to the product I am testing. I think that it is the technology in general, and a person could expect nearly the same results regardless of brand name, provided that the conversion from gaseous energy to heated water energy is essentially the same, that being MODULATION/CONDENSING.

These are some exciting times to be in the energy conversion/conservation field. If someone had tried to tell me where we as an industry would be today 10 or 15 years ago, I'd say "Yeah, right... (winkie wink)"

ME

[Deleted User]

You should see my kids...

The one without the sun glasses is my son...

ME

Paul Rohrs_5

Mark,

Is there any way for you to monitor gas usage soley for space heat and DHW? I would love to be able to keep the numbers separate for true efficiency readings.

A NO solenoid that monitors gas usage for space heating, then as the DHW contacts energises, the gas gets routed through another NC solenoid. Seems extreme, but then the gas meter you have only measures space heating mode.

I agree, exciting times.

Lets devise a new little "Black Box" that has a USB port that has sensors for inlet temp, outlet temp, outdoor sensor that factors degree days, and therms per degree days, a gas meter with digital or LCD readout that can feed into a Windows driven program.

Now we can get efficiency readings on demand, track therms and therms per degree day and chart it (with history) in Real Time.

Time for me to get out the Lincoln Logs, Erector Set, and Lego's.

Paul

[Deleted User]

It could be done Paul...

Except I only have one "EVENT" data logger, and it would take three to acheive your data logging goal. One to monitor the run time of the DHW pump, one to monitor the run time of the space heaiting pump and one to log the gas meter points contact closure per cubic foot.

If I had the three event loggers, I would be able to corelate the gas used during the given pump "ON" times to the minute because all events are universally coordinated to the PC's clock.

As it is, I can tell the hours of burner run times above and below 50%, but it does not have enough discreet resolution to acheive your goal.

While we are on the subject of control relevancy, I see absolutely no reason why these mod con manufacturers can't design a control logic around their equipment that would limit the amount of burner input based on relative thermal efficiency. In other words, when the clutch starts slipping (rising flue gas tempratures in relation to fluid supply temperatures and differentials), back off on the gas and let the load catch up to the heat exchangers heat transfer ability. Don't attempt to over drive it. Just because we think it should be ULTRA hot temperatures doesn't mean it really HAS to be ultra hot. I know this because I've watched the Buderus 2107 logic "coast" right to the required DHW tank temperature without hitting the 180 degree F water temperatures I'm used to seeing in these applications (side arm heaters), so I know the algorithyms exist to drive the controls to make it work. Target versus rate of rise versus deviation.

Maybe a new bent on logic, called PIDIL, proportional, integral, deriviative intelligent logic.

Sounds a lot more attractive than FUZZY, (Friggin' Unreliable Zippity Zap Young'ns....)

ME (King of Acronyms)

Mike T., Swampeast MO

Mark:

I couldn't agree more that some serious opportunities for control improvements of mod-cons exist.

Flue temp rising faster than supply temp indicating excessive output compared to emitter ability is just one indicator of inefficient operation. Other indicators exist in the supply and return temps as well as the difference between internal and externally sensed supply temps.

Not only can you identify when the emitters are falling short of output ability but you can also identify when the emitters are being over-supplied.

Your season of operation without outdoor reset and daily room temperature setback [seems] to have demonstrated what I've long suspected:

Condensing operation alone can only increase boiler efficiency--it takes modulation to increase system efficiency. This is why AFUE number are so utterly bogus when it comes to comparing non-modulating boiler with modulating boilers. The modulating boiler actually perform to (or even above) their efficiency rating virtually regardless of load. The non-modulating boilers only perform to their efficiency rating in the laboratory under constant load.

Mike T., Swampeast MO

Mark:

I'd try to do a similar experiment (operating the boiler to a fixed temperature regardless of outside temp) but I have a problem.

Even though 135°F supply is sufficient for design conditions, my bathroom radiant floors are simply connected to the mains with no form of control other than the reset curve. Remove the reset and my bath floors would overheat severely in even "average" weather. While I could shut them down completely for a test I'm spoiled and don't want to do without them for any long period of time...

Unknown

Mark, am I reading this right? You're doing this with a 140 return water temp?

Shouldn't even be condensing at that temp, should it?

Mike T., Swampeast MO

Mark:

Must ask.

Are you using primary/secondary?

If not, are you now fully TRVd?

If so 3 gpm the secondary flow rate?

(Please excuse original error regarding "if not" and "if so". It's that weird backwards thing in my head again...)

Maine Doug_52

To my

boiler room to run against the twins.....

[Deleted User]

Yup...140 return...

One of them thangs that'll make you go "HMMMmmmm..."

ME

[Deleted User]

Nope, intentionally mispiped Mike...

My house is a one pipe system. I intentionally did not pipe it per the manufacturers recommendations because I wanted to "test" the system as a whole to see how it would adapt to a less than ideal condition. The control adapted quite well. As an example, on a call for DHW, it recognizes the fact that I am not pushing 8 GPM through it, so it limits the water temperature. I don't think I've EVER seen it go any hotter than 167 degrees F even on a DHW call, when its is supposed to go to 180 degrees F... But then again, I've NEVER run out of hot water, so 180 degrees F is not necessary in the first place.

I piped the space heating side in series with the boiler, and the DHW side is parallel to that, except it goes through my reverse indirect and has a valve that cross ties the two loops to bring the indirect into the flow stream of the space heating system whenever the OSA is above 35 degrees F. When it is below 35 degrees F outside, the cross connection is eliminated.

ME

Please understand that I would NEVER do this in a customers house, but then again, I try NOT to do experimentation at the customers expense. My house, my laboratory:-)

ME

Mike E_2

This chart from Viessmann may answer why you are getting high efficiency with high temperatures.

Mike E_2

Possible explanation

This chart from Viessmann may answer why you are getting high efficiency with higher temperatures. When you were in space heating mode, you were running at 16,347 BTU. That's between 20% and 30% depending on how you figure in the DHW boost of the T-50.

So looking at the vitodens chart (which should basically apply to all coiled stainless-steel mod-cons) you can see that while operating at minimum fire, the heat exchanger is very "oversized" for the load. This allows the flue gasses alot of contact time with the water. So even with high water temperatures, you still get high efficiency. However, if the water temperature is even lower, the efficiency will be still higher - especially at greater loads.

You can also see that while in DHW mode, you had lower return water temperature compared to space heating, but the efficiency was actually lower. This is because the heat exchanger is "maxed out" with the full(almost full) burner output.

Mike T., Swampeast MO commented on this characteristic in this thread from early December http://forums.invision.net/Thread.cfm?CFApp=2&&Message_ID=294380&_#Message294629

He will hopefully be able to give some more information about this, as I personally don't have a mod-con yet (coming this summer).

Mark E - while you were at low fire in space heating mode, were you producing any condensate?

Now watch this undo all the effort to "right size" the boiler and go back to oversizing.

Michael

[Deleted User]

Michael...

This thing condenses ALL the time, just at a lesser rate.

But I find the same thing with all the different mod cons I work on. They ALL condense, even at higher temperatures.

(Here come the nay sayers...;-)

ME

jp_2

calc'd heatloss?

so, the big question, what is the calculated heatloss of the house?

[Deleted User]

I think it came in around 40 K....

What relevance does that have to steady state thermal efficiency of the appliance? Other than the fact that I have the ability to circle the wagons, slowly, around the load.

If I didn't have modulating capabilities, the boiler would be short cycling like a Banshee, which is the norm...

Mine runs coninuously at design condition.

ME

jp_2

heatloss calcs

yes, i am wondering why ME's calcs are so far off from what ME has measured? kind of goes back to the old "rules of thumbs" are good enough...(thats a joke, please)

also the numbers suggest that AFUE numbers are not far off.

tim M has stated that gas meters are only within 2%, jack Davis has said that gas values can vary by 10% within any given day, so I'd say ME stuff agrees with AFUE.

Mainemike

Picture

I was thinking the same thing but didn't want to be the first to mention it. Great data Mark, keep us up to date.

Mike E_2

AFUE

Rated AFUE for mod/con boilers is pretty accurate (some calculations have shown that the rated AFUE is lower than what the equipment acutally runs at.) This is because the boiler will run constantly and not encounter any off cycle losses. And mod/con boilers will see even higher efficiencies at lower firing rates as the chart from Viessmann shows.

However, the rated AFUE for bang bang boilers is way off - much more so if the boiler is oversized. This is because of all the off-cycle losses that aren't adaquetly accounted for in the rating process.

Michael

jp_2

But,

you can't blame AFUE for an oversized boiler! if you overisze a mod/con it would become less efficient too due to short cycling.

Mike T., Swampeast MO

\"Intentionally Mis-Piped\"

Given your confirmed system operation, I'd say PROPERLY PIPED!!!!

Don't tell me that you didn't give serious thought on how to pipe your system even if it didn't conform to "conventional" instructions...

Surely you'll use what you've learned when it comes to systems you install for others.

[Deleted User]

Its not so much a matter of the question you DID ask...

as it is a matter of what you DIDN'T ask, and to be quite honest, I am GLAD you didn't ask the other question, because it would have caused me ALL kinds of work. That question being, "What other gains is the house seeing?"

I can list them by type, but can't account for them individually.

1. Solar gains
2. Body gains (humans and dogs and how much heat does a cockatiel generate...)
3. Appliance gains (2 refrig's. 1 freezer, washer/dryer, range, stove, TV, stereo, 2 PC's and other standby transformer types of loads.

And as Paul Harvey says, Now you know the REST of the story...Well, almost all of it.

I believe the loss calc program (Wirsbo) I used to be fairly accurate.

I challenge ANYONE who has ever done a loss calc, AND sized their equipment properly, to go out to that home at design condition and tell me their heat source (other than MOD CON) is running at 100 %. I know this, because the closest I've seen under those very same scenarios is 50% duty cycle. If the boiler is running at capacity, I guarantee you that it is due to excessive infiltration, that one key element that NONE of us has ANY control over, that will KILL the comfort levels of our systems...

Hence, the reason I stated in the original thread that I wanted eveyone to focus on the net thermal efficiency numbers, not the condensation production or non production, not the operating temperatures, not the BTUH demand, just the net thermal efficiency numbers. :-)

Simply stated, I don't have all the answers...


ME

[Deleted User]

We do it by the book Mike...

The thought has crossed my mind, but in order to retain warranty, we do not deviate from the manufacturers instructions, unless it has to do with a possible life threatening situation, like CO spillling from an appliance due to their fixed, open relief hoods, and the need for a barometric damper.

Then and only then do we deviate. And even that is a last ditch effort to correct a dangerous situation.

ME

Mike T., Swampeast MO

Mark:

Together, I believe that you and I have given CONCLUSIVE evidence that modulation ROCKS!!!!

The difference between yours and mine:

My home is not yet truly occupied. Me working in the daytime, a big computer system, a cube refrigerator, a cat and whatever heat comes from my woodworking tools. Yet I still find actual loss around 50% of Manual-J when space temperature is constantly maintained

jp_2

missing ALL the fun,

you are missing all the fun here.

for estimates, 2,000 Kalories diet, est 330 btu's/hr/person

dog: est 35 lbs, 500Kal diet, 85 Btu's/hr. appliciances i would just take their watt loads and convert to btu's. frig just dumps heat back that re-enters later on.

those little transformers are just radiant surfaces, take there temp & surface area and there you go!same goes for the washer/dryer.

sun load? big guess, big load. estimate by elimination.

do your test during the day, then at 11pm. this gives approx 5 hrs of pure nighttime radiation to do its thing.

which brings up your night time radiation experiements, what you should have tried is to re-create what you saw in the desert, not a insulated box but something like a plate of steel, bar-b-q lid?

edit:
so, i think the night time test will show you why the error is so large in the calc compared to the actual usage. I don' t see people/dogs and appliciance making up the difference. unless you have 8 kids, cook and clean constantly and like lots of 75watt light burning.

jp_2

numbers don't JIVE

is the little clock in the corner of your attachment correct?

It reads around 9am.

so, I do not see many lights contributing to gain, sun would not have had much time to heat, so I have to say something is way off?

16,000 btu from boiler - 40,000 house load leaves way too much error(24,000 btu), unless you make the hotest chili north of mexico!

i would rather have seen 6-8 hours of operation opposed to 1 minute 40 seconds, but i think you would agree.

jp_2

Nay sayer?

I would agree 'they' all condense, more importantly, are they condensing in the condensor/HX where the boiler gains efficiency or just at the last foot of vent pipe where no gain is picked up?

other threads talk about much high stack temp oil boilers condensing causing problems up stream.