99.97% Thermal Efficiency (ME)

Mark Eatherton1

Greetings Wallies,

It is currently 3.7 degress F above zero outside my house. Design condition for Denver is 5 above. This is when you get the chance to evaluate heating system performance at its' peak. It lets you know if your system is oversized or undersized and gives the chance to take a look at the thermal performance of the heat generation device.

I realize that not many people have a working hydronic labratory in their basement like I do, but I know that a good wet head spends a great deal of time near his boiler when it gets near design condition just to see how things are going. Me too.

I got up extra early (5:00 AM) this morning and came down stairs to see how things were going. I forgot to mention that yesterday I spent some quality time with the T50 and my combustion analyzer tuning it to peak performance.

So anyway, the first thing I do is to watch the system with the Service software to make sure that we are at steady state. Solid as a rock. The fan RPM's were stable as an oak table, and the delta T was rock solid as well. The appliance was holding a steady condition one step above it's minimum operating speed. I read the gas meter first to record how much gas this beaut was taking on. 42.69 seconds per 1/4 Cubic Foot. Here's the math for the input. 3600 (seconds in an hour) divided by 42.69 (elapsed time for 1/4 cu. ft. of gas to pass) =84.32 "units". The actual unit of measurement was 1/4 cu ft, so 84.32 times .25 = 21.08 Cubic Feet per Hour (CFH). The caloric content of natural gas for this locale is 830 btu/cubic foot so 21.08 times 830 = 17,496 btuH. Ya still wid me? Let me know if'n I'm losing you and I'll back up.

So, that in a nutshell is the input to the lil Muncher at this snap shot of steady state condition.

As most of you know, I have a flow meter on the hydronic side of my system so that I can see the actual flow rate for a given condition. This morning, with the space heating circulator running, it was at 2.5 GPM. Also, with the HTP software, I can see the actual delta T of the boiler for any given period of time that I record the data for. During this 45 minute period that I was evaluating the system, the temperature differential was 14 degrees F. Ready for some more simple math? OKay, 2.5 (GPM) times 8.33 (#'s per gallon)= 20.825 pounds per minute. 20.825 times 14 (Delta T) = 291.55 btu per minute. 291.55 times 60 (minutes in an hour) = 17,493 btuH output. So, this tells me that my homes actual thermal load for these conditions was 17,493 btuH. I must note that the wind was not blowing, so there was not a lot of infiltration loading during the evaluation...

So, we now know the output and the input of the system. If we divide the output of the system (17,493) by the input to the system (17,496) it comes out to .9998, or expressed as a fraction it would be 99.98 percent thermally efficient. I figure there has to be something thrown in for meter/sensor inaccuracy etc, so the final number is 99.97%

Not bad for a little Muncher.

Now, I just happened to have my Testo combustion analyzer sitting there, next to the boiler, not really doing anything, so I fired it up to see what it could tell me about the "steady state" conditions I was observing.

The CO was running 30 PPM, the flue temp was 147.6 (at the breaching of the appliance), the CO2 was at 10.4%, the O2 was at 2.4%, the excess air was at 12.9% and the computed combustion efficiency was calculated to be 88.4%.

See what I was telling you about the combustion analyzer lying to us?

In addition to all of this, I should note that the actual water temperatures for the 14 degree delta T were based on a supply temp of 151 and a return temp of 137 degrees F. Also, the flue gas exhaust system for my boiler is concentric for most of it's 15 foot vertical rise, and with it at 3 degrees above zero outside, the concentric vent was causing the incoming combustion air to be raised to 111 degrees F.

There was a steady stream of condensate pouring from the appliance, and I understand it has a caloric value of around 8,000 btus per gallon. I have yet to come up with a simple means of recording condensate production as it relates to real time.

Generally speaking, I am blown away with the technology behind this thermal beast of burden. My hat goes off to Dave Davis at HTP, along with Brian French, Jeff Cook and ALL the supportive folks at Heat Transfer Products. You folks are doing a wonderful job.

Comments? Questions? Observations?

Operators are standing by...

ME

Geo_2

t-50

Mark, this would be a good time to turn on your web-cam so we would all see you running around the basement in your jammies like a kid on christmas day, lol

Paul Rohrs

Yeah but....

> Mark, this would be a good time to turn on your

> web-cam so we would all see you running around

> the basement in your jammies like a kid on

> christmas day, lol

Paul Rohrs

Yeah but....

can I get fries with that and does she have a sister?

WOW!

PR

David Sutton_3

and the academy award for boilers goes to....

Mark !!! and the croud gos nuts, post a pic of that little laboratory you got down there love to see it!!....David

Mark Eatherton1

The lab...

here ya go.

ME

Mark Eatherton1

She has NUMEROUS sisters...

The T80, the M80, the M140, the M199 and soon, a big brother, the M399. To boot, they will be unveiling their new cascade control logic in the near future, the Vision 3 package.

ME

David Sutton_3

sweet job

what no operating table ????

J.C.A._3

Wouldn't it be nice ?

> The T80, the M80, the M140, the M199 and soon, a

> big brother, the M399. To boot, they will be

> unveiling their new cascade control logic in the

> near future, the Vision 3 package.

>

> ME

J.C.A._3

Wouldn't it be nice.....

(no I'm not quoting the Beach Boys)

If we all could have a way of measuring the gas meter, right next to the boiler? Talk about a time saver! I have occasionally had one I could see from a basement window, but to have it right there would be the bomb!

Maybe the local utilities could offer us a way to use the radio technology that they use for reading meters, to have in the basement for doing a good clocking , and not have to move like a runningback from the NFL. Chris

[Deleted User]

mark- question

im in northeast ohio which is predominently gravity hot water land..old, big, inefficient atmospheric boilers..could a system such as a gravity system thats being converted to pump, have a really efficient boiler such as munchie used even tho it would never be condensing? or is it just stick with a less efficient boiler for these old houses - thanks

Mark Eatherton1

I have heard...

from more than one source, that converting an old gravity system with atmospheric burner to the high efficiency condensing boilers will result in a minimum fuel savings of 50%.

Remember, the water supply tmeperature doesn't have to be at its maximum all the time. You could do a full reset with these puppies and stay in the condensing range for the majority of the time. Worse case scenario, these beauts are 90% thermaly efficient. Thats got to be light years ahead of the technology you're currently dealing with.

ME

Mark Eatherton1

The meter...

costs around $150.00. It's a MUST when you're dealing with propane at altitude. I don't know if you noticed, but there are wires coming out of the dial assembly that give a pulse closure for each cubic foot of gas that passes through the meter. With the use of a HOBO state recorder, I can tell to the minute how many btu's this baby is taking on.

Unfortunatley, my HOBO is at work on another project. Guess I'll have to pop for a personal model:-)

ME

Cliff Brady

Cheap wireless webcams received by your

wireless lan laptop are already out there from DLnk and others right at Best Buy/Circuit City.

[Deleted User]

thanks Mark

certainly would be something for customers to think about with gas prices rising as they are.

Unknown

Gerry Gill

Paul Lessard has installed a Munchkin up here in New England on an old gravity systems. It is working like a charm. He may be able to give you some figures on its performance. I was priviledged to work with him the day it was installed (TAKE THE TEACHER TO WORK ).

THE IMPORTANT THING IS SIZING PIPING TO THE UNIT.

My experience with the Munchkin's so far is that properly installed they can handle just about any situation.

[Deleted User]

cool, ive got to try one of these

ive been hearing so much about these that i'm really curious...

Eric Taylor_37

Comments

First off, WOW! When I first read your post I thought you were mistaken Mark, but I chewed on it for a while and I'm with you. The key is that concentric vent preheating your combustion air and cooling your exahust. I am thinking that your combustion analyzer is not lieing to you at all, it just assumes that you are loosing what it sees going up the stack while you are really reclaiming it after the measuring point. Sneaky sneaky

I would like to know what the combustion air flow rate is or the temp of your exahust at the top of your concentric vent. With that you can see how many BTUs you are reclaming from the stack. I'm guessing it accounts for roughly 11.5 efficiency points if you normally believe your combustion tester.

17,493 BTUH at 3 degrees?!?!?

What do you live in a Thermos bottle?

Sheesh!

Eric

Mark Eatherton1

Hi Eric...

I hear what you're saying about wasted heat recovery. I'm really in to that, and soon there will be heavy copper bands connecting the exhaust with the incoming combustion air further scrubbing additional waste heat out of the exhaust stream. Interesting that you should ask about the thermos bottle. My home is just your ordinary tract home built in 1952. It is 2X4 frame with double pane windows, and R15 walls and R30 ceilings. Nothing special.

The heat loss calcs I've performed on the house indicate a base load of around 40,000 btuH. When I yanked the original gas FA furnace, it was rated at 110 K input at this altitude. I replaced that with a 40 gallon water heater rated at an output of around 24,000 btuH.

Makes you wonder exactly how accurate the heat losses we perform really are eh...

To my limited knowledge, none of the current HL calc programs take into consideration the thermal mass flywheel affect, solar gains and other internal gains. Obviously, with the exception of two refrigerators and one freezers, there was no substantial internal gains coming from running lights, stoves etc at 5:00 AM. We do have two large dogs, one small dog and myself and the wife generating internal btus, but I don't think we make up the difference collectively.

I've said this before, and I'll keep saying it until someone with a higher power listens and gets the hint. Our current methodology for performing heat loss calcs needs to be upgraded. In many cases, we are still grossly oversizing our physical plants (ME included) and it's is not doing anyone any favors.

The nice thing about this new technology is that it has the ability to match the demand to its output.

I just got my current months utility bill, and with the new Muchkin on line, and relatively out of control, I reduced my energy consumption by 15% versus the old system, which was a 40 gallon water heater being fully reset with a Tekmar control. Before I adjusted the consumption to local weather conditions, the reduction "looked" more like 38%.

I didn't climb up on the roof to check the net waste heat recovery because there is snow on the roof, and its colder then heck outside, and at 99% thermal efficiency, I'm afraid that it might blow the combustion analyzers little brain to see what's really going on:-)

All of the latent heat of vaporization coming from the condensation is also being fully recovered and kept within the building envelope due to the condensate pump/neutralizer bucket located in the mechanical room. If I take its potential into consideration, I'm afraid the net thermal efficiency would be over the 100% mark, and even I would have a problem with that. Unless of course I could figure out wome way to spin the gas meter backwards...

Thanks for asking!

ME

Eric Taylor_37

Keep taking data!

Thanks for the info Mark.

Couple more points:

The input data is critical for an efficiency calc that is so close to 100%. You really need to get exact figures on the BTU content of the gas and its flow rate. How good is the gas meter? Even a small error would skew the results. That concentric vent may be absorbing some heat from the space to preheat the combustion air as well. Don't get up on your roof, but a temp and flow rate for the exhaust gas would give you a way to check calcs against each other. Maybe HT has data on fan speed versus flow rate or even a sensor for combustion air that you could tap?

Of course you can't get over 100%, or even 100%, but if you do it shows that something is wrong with the data. This is really fascinating.... Thanks for sharing.

Eric

Glen

Which flow meter are you using? I have thought about doing exactly what you have discribed re gas input related to heat requirments rather than a "straight" combustion analysis. Re other posts about the condensing values of the flue gases - it would be my thinking that only the gases condensing inside the boiler could be considered as useful - although environmentally more beneficial to neutralize and pipe to drain.

Greg Swob

Homeowner heat loss calc

Prior to a recent install, I showed the HO my heatloss calcs and explained why the equipment I selected was sized accordingly. As an engineer, he did his own calcs, using past four year's actual gas consumption. He rated the existing appliance as 80%, even though had we done a combustion analysis, it would have been much less no doubt. When we downrated the appliance to 70%, it appears our calcs were within a % or two of what he tabulated. I received four pages of color coded charts, graphs, and numbers from him - got to love engineers! We use Writesoft for our calcs. Greg

Dale

Gas meter

The btu content seemed pretty low but if that's what the therm factor says on your bill, that's figured per daily samples per month. The larger the test dial usually the more accurate, I would clock the meter on the largest test dial it has. And the local utility meter shop should be willing to drop yours on a prover to see what it actually is at low flow ( which is what you have) a normal meter can be off 3% each way and still be legal. Your measured stack temp leads me to think about 90 percent effeciency, will be interesting to see what it looks like long term. I agree with you completely about the heat loss calcs we use, still way too conservative. I see 120 K imputs being commonly replaced by 60k inputs ( 56K out) and they don't run constantly at design.

Mike T., Swampeast MO

One little change for the math?

Since you're getting numbers that might exceed 100%, here's something simple you neglected in the math that results in a TOUCH less heat loss and consequently, efficiency.

Water at 158° (your average temp) weighs 61.02 lb/cu.ft. There are 1,728 cubic inches in a cubic foot and 231 cubic inches in a gallon. So, this makes 7.48 gallons in a cubic foot. 61.02 (weight of cubic foot of water at 168°) divided by 7.48 (gallons per cubic foot) = 8.16#/gallon @ 158°.

When I plug that into the equations you used to compute output I get 17,136 btu/hr.

With 17,496 input I get 97.94%.

Still quite amazing, but I think it might be one of the tiny "errors" that you were looking for...

Brent_2

accuracy

I think you might want to look at the accuracy of your measuring devices. I'm not sure what brand of flow meter you are using but if your actual flow is even 2% off your efficiency has a decent change. At 2.45 gpm the efficiency would be 98%. If it was actually 2.55 gpm your efficiency would be 102%. Let me buy one right away!
I think the flow rate and btu content is critical to the calculations.

I'm not knocking you. You're doing more than I would.

heretic

AFUE

Very impressive laboratory.
Now why can't all boilers be tested under steady state conditions like this instead of sticking us with those silly AFUE ratings?

Unknown

I find it interesting

in a recent class I attended conducted by Hydronics Institute division of GAMA the instructor advised everyone in the class that after determining the heat loss from phamphlet H-22 to then add 5 to 10% to the calculated loss just to be safe. I expressed my feelings about this especially with high efficency equipment that the boiler sizing should be as close to calculated heat loss as possible. I feel that for many years sizing was done with a 25% added factor to "just be safe". I would hope that now days we can be much more accurate than that.

Unknown

Having a meter with some flex connectors

just for ease of clocking right at the equipment is a real good deal. Get one set for natural and one for LP. It will save a lot of running in and out. Local utilities will test it every so often for you at a minimal charge. I get mine done for free, hey I used to work for them.

Tony Conner

I Don't Think It's So Much...

... "steady state" that's required, as it's mass flow, and BTUs out divided by BTUs in. This could easily be done under standard lab conditions by manufacturers and regulating bodies, giving everybody an apples to apples comparison of steam, hot water, and forced air heating. And the method is dead simple to understand and verify. Very little room left for misunderstandings or "creative calculations".

Unknown

Gee, Tony,

> ... "steady state" that's required, as it's mass

> flow, and BTUs out divided by BTUs in. This could

> easily be done under standard lab conditions by

> manufacturers and regulating bodies, giving

> everybody an apples to apples comparison of

> steam, hot water, and forced air heating. And the

> method is dead simple to understand and verify.

> Very little room left for misunderstandings or

> "creative calculations".

Unknown

Gee, Tony,

That would be a GREAT solution.

What organizations would stand in the way of a change like that?

Noel

Tony Conner

This Is...

... THE test that should be performed by regulating bodies on steam, hot water and forced air heating air heating equipment. If one interested guy can DO THIS in his basement, WHY can't the manufacturers and regulating bodies do it?

And I don't think that you're combustion analyzers are lying to you. I think that they're giving you accurate info on COMBUSTION alone. The mistake people make is confusing combustion eff and boiler eff. They're related, but not nearly identical. Your 5AM heat in vs heat out is an actual, proper, BOILER efficiency calculation. Thanks for performing a proper test!

heretic

The Feds

"What organizations would stand in the way of a change like that?"

Apparently the clever folks at the DOE who came up with this AFUE insanity, for one...

AFUE has been very convenient for some marketeers.
I fear a certain amount of "designing for the test" is done as well, likely at the expense of real world design improvements.

Tony Conner

I Can...

...think of a couple right off the bat. I won't throw stones publicly, but they tend to be organizations that LOVE fantastically complex calculations, very often for no particular reason.

I visit and post on another board where there was a discussion on flow through a pipe, and how there was confusion because the previous guy hadn't actually recorded his method of calculation. One guy posted about how, if this calculation wasn't on a spreadsheet, it just essentially wasn't professional. I disagreed, and suggested that if somebody could solve my problem by figuring it out on the back of an envelope with a pencil, that would be fine with me. While spreadsheets could be valuable tools, just as often, they were used to deliberately make things as confusing as possible, because somebody was trying to hide something. The Romans successfully executed some of the greatest feats of engineering the world has ever seen, all without a single spreadsheet. And their numbering system didn't even have a zero in it.

Unknown

Of Course, Corey

You are absolutely correct.

Because boilers that don't pass the test can't go on the market, and because all new boiler ideas are tested, and because the ones that pass the test get marketed, you could say that they are "designed for the test"

This would be a great concept with a better testing method, too. I agree that new designs would be developed, but isn't that happening, regardless?

To me, the question is, "What test would be a better indicator?" Mark and Tony have great testing methods. How would a citizen communicate this with his government? Who wouldn't want this?

Pointing fingers at who ISN'T making any changes results in...., well, ...no changes.

If a manufacturer tries to get the testing changed, doesn't that look a little fishy?

Noel

Mike T., Swampeast MO

Market is dominated

by digital FORCED AIR however...

I know of no practical residential TRUE proportional forced air system and rather doubt that such is even possible.

It's that "magic" state of balance that I keep talking about with proportional control that allows these SIMPLE calculations to be made with [seemingly] reasonable accuracy.

Perhaps as modulating boilers become more common realistic tests of their MAINTENANCE efficiency will be developed.

Unfortunately there probably isn't much money available for such and ASHRAE doesn't seem in the least concerned because their money comes from the forced air industry. AFUE truly does seem skewed to giving the best possible numbers to new forced air equipment.

Tony Conner

But Even With...

... on/off burners, it is possible to perform exactly the same efficiency calculation Mark did. Steady state is not a requirement. You only need to have an accurate method to determine BTUs delivered to the load, and the BTU delivered to the unit in the form of fuel over the same time period. All losses due to partial loads or cycling will be captured in that "big picture" efficiency calculation. Then the other "smaller" efficiency calcs come in to play. The ones that let you identify specifically where improvements can be made - things like better burners, more effective heat transfer within the unit, lower skin losses, etc.

Tony Conner

I Agree...

... that the existing system doesn't stand in the way of new developments. I think that what it does, is generate a LOT of confusion - which I believe is one of it's intended functions. I know of an industrial plant near here that ripped out a perfectly good steam unit heater, and replaced it with a gas fired unit heater. This happened IN the boiler room, which has LOADS of capacity. The reason this was done? The sales brochure handed to the plant engineer by the rep showed a REALLY BIG eff number for the gas fired unit, and MUCH SMALLER eff number for the existing steam unit. The big number for the gas jobbie? It was the COMBUSTION eff - NOT the "BOILER" eff. Does the PE who is the plant engineer want to hear how he got snowed by the salesman? Nope - not on your life. He's very certainly not admitting anything like this to his bosses - that he, a professional engineer didn't understand something technical. I probably shouldn't be too hard on the gas fired unit heater guy. He likely doesn't understand the different "efficiencies" either.

Unknown

Aren't you in Canada, Tony?

Do you have the same testing methods as the DOE, here in the USA?

Who do you contact to effect a change, once you nail down the language of the change?

Noel

Mad Dog

you are out of your mind.................and I love it....

You are a Mad scientist.........Mad Dog

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

corey

RE: Innovation

"I agree that new designs would be developed, but isn't that happening, regardless?"

Perhaps innovation happens regardless, but can we really know? Perhaps brilliant designs never get out of the gates in the first place because it is determined the technology cannot be marketed effectively within the constraints of the almighty AFUE. Even good designs that do get to market will not meet their full market potential on the merits if they are hamstrung by AFUE comparisons. This is example of mandated government standards distorting a market.

Tony's specific example [above] shows us how this works.