99.97% Thermal Efficiency (ME)

Unknown

Corey

Check your e mail. I want to ask you something...

Noel

Tony Conner

Most Code & Regulatory...

...requirements are at least similar, and often pretty much identical. ASME is alive and well here, as is ASHRAE. I'll have to do a little digging. I suspect my experience will closely parallel my adventures with the requirement for double wall heat exchangers for domestic water service. What a merry-go-round that was. I got handed off to person after person, covering several different organizations. Apparently, NOBODY actually, y'know, MADE this rule. But yet, there it is on the books. In addition to nobody actually "making" the rule, nobody is quite sure WHY it came to be. Nobody can point to a specific incident, or group of incidents where somebody was poisoned or harmed in some way by the failure of a single wall heat exchanger heating their domestic hot water. In spite of claiming not to actually do anything, "Nobody" seems to have a huge influence on just what the rules are. It's maddening.

Mike T., Swampeast MO

Steady-state (maintenance) is needed, I believe

If you apply those simple calculations to an on-off system you only wind up with the efficiency at FULL output--something that occurs VERY rarely.

It would be VERY difficult to even measure this as it would require a completely different set of conditions for each appliance being measured; i.e. a space that nearly perfectly matched the output--for a protracted period of time.

Even if this is done, it would not produce a realistic efficiency number. I think that's what AFUE ratings attempt to do--make a reasonable comparison in real-world conditions based on DIGITAL control where output RARELY IF EVER is close to the actual loss.

Mark's observations are likely close to a "best case" scenario--even for a modulating heating appliance. Relatively steady and low outside temp; snow on the roof (remember it does insulate if the air is below freezing); and low wind. I'm NOT "KNOCKING" such by the way AT ALL--my own calculations/observations come from similar conditions.

AFUE ratings however assume that such NEVER occurs! The heating appliance is always working WAY too hard or not at all.

Mark has seen what happens when input nearly matches output. I've only "played with" such on individual radiators and floors under constant circulation, never the boiler itself. He seemed JUST as shocked as I was at the numbers coming out...

Dave Yates (PAH)

Gubbermint regs?

Try 1.6 GPF water closets, which will soon be required to operate on a 1.0 GPF!

No matter the regs governing how we arrive at AFUE's or the now more practical approaches being brought about as a result of condensing boiler technologies, the truth will out - and it will cause rules to be changed/altered. Slowly, very slowly - so slowly they seem to be standing still. Yet - progress will not be denied and will be driven by economics - both the greased palm as well as the consumer angst.

Mark, I love what you're doing. Reminds me of our ISH trip to Germany and how taken aback I was at their claims of efficiencies well in excess of 100%. We ARE on the right track and HTP is leading the charge. They've taken the bull by the horns and upset darn near everyone's apple cart! The Vision control has depth yet to be explored & we're bidding our first cascade boiler replacement in anticipation of this soon to be available technology.

In just a few years, we'll be exporting our technology to Europe. There has never been a more exciting time to be alive and involved in the hydronics trade.

As for rules, politics and slow-as-molasses-in-January changes? I've been re-examining my own frustrations regarding that very issue. After 3+ decades in the trades and 2+ decades in my own business, I'd become accoustomed to making changes whenever I saw an opportunity to improve myself or our operation - no questions asked - just do it. But committees move at a snail's pace & I have little patience for politics. Call it another learning curve, albeit a very frustrating one.



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Tony Conner

I Still Think...

...it can be done with on/off burner control. I suspect that you'd need to have the test cover a longer period of time, and would be representative of the normal load pattern. I know that for big industrial boilers, you can make an error on a meter reading that will affect the eff calc for a particular shift or even a day, either up or down. When the figures are looked at for an entire month, errors like that pretty much disappear.

If there was metering on the fan side of a hot air furnace, that measured the air flow, and temperature rise across the heat exchanger, the BTU delivered to the house could be measured. The fuel input would similarly measured. If you read the meters, and go back at the end of a given time period (week, month, or heating season), and read the meters again, you can run an efficiency calculation for that time period that would reflect all of the on/off's.

heretic

slow-as-molasses-in-January

Sounds about right.
Just imagine what this costs! How much wasted energy up the stack? Millions of heating appliance purchases influenced by this standard will be in service for decades to come.

Consumers believe in AFUE because there is nothing else.
You cannot translate AFUE into quantified fuel savings.
If you cannot quantify fuel savings, you cannot calculate an operating cost comparison or payback period for any equipment upgrade. In the absence of reason, there is chaos (and salesmanship).
How many customers come here and post the obvious logical questions;
"Should I upgrade my old boiler?"
"Should I buy boiler A or boiler B?"
"Why are air furnaces so much more efficient?"

They want hard (or at least rough) comparative numbers, and naturally assume that a calculation can be performed. With AFUE, the closer you look, the less meaningful it becomes. Sort of like a painting by Monet. Look too closely, and you may go insane...

Duncan_6

Closeup snapshot vs. the big picture

I couldn't agree more with you, Tony, about needing to expand the time frame to get an accurate picture of overall heating efficiency. Also acknowledge the differences between combustion eff vs. boiler eff or overall system efficiency. Points well taken.

Mark wanted to take advantage of a single design temperature day to get some usable info. I say good job, man, and interesting stuff. The heat loss estimate is startling. Thanks for the thought-provoking yummy brain food.

I know what you're talking about Tony, because in the late '80s, the company I worked for tried to dial in an accelerated monitoring program of energy useage. It was an attempt to determine actual savings of a weatherization and furnace tuneup program. The challenge was doing this measuring accurately, in a short time frame.

Houses were carefully selected: The furnace was the ONLY gas appliance. Pretty hard to find homes with electric stoves and water heaters and gas furnaces. Furnace run time, electricity usage, and number of occupants were some (but not all) of the factors considered.

Even with these constraints, the statistics were all over the map. Statistical normalization was needed to make sense of it all.

The smaller the sample time, the more magnified any other small measuring error becomes in time-sensitive measuring. And float-type flow meters and gas company gas meters aren't noted for two or three decimal accuracy, I don't think.

I was surprised to read in another post that gas meters are required to be within 3%, I had thought they were much more inaccurate.

In a quick search of AFUE testing (dogpile.com, using "AFUE testing" as keywords), I found a site that contained a little interesting info about AFUE testing parameters. They're selling boilers, but the AFUE testing strategy sounds about right.

http://www.qhtinc.com/analyzing.html

munchkin-man

Now thats what I am talking about, bingo

Cliff Brady

Please elaborate Jeff.

We don't know what you are talking about as this is your first reply in the thread, but we really want to know what you have been saying!

Mark Eatherton1

Meters...

The gas meter is an American AL 150 fitted with a special pulse output device to give contact closure for every cuboic foot of gas run through it.

The flow meter is a Letro flow meter. Letro was an industry standard for the solar industry back in its' hey days. I've check the accuracy of the flow meter before, and it appears to be dead nuts on. (Measured actual weight of water dispensed at a given flow rate for a given period of time, on both the top and bottom of its scale capability.)

I'm still waiting for Danfoss to bring out an inexpensive doppler metering device that would work with 1/2 and 3/4 inch pipes :-)

ME

Mark Eatherton1

Thanks Big Mike!!

I knew I could depend on you for a good mathematical once over!

Happy Thanksgiving!

ME

Mark Eatherton1

I fear...

that the manufacturers might not want us to know this information...

I have tested gas heating appliances this way before, and came up with some numbers that were WAY out in left field. The combustion analyzer fell within their printed data, but the actual thermal test proved they were WAY off...

Maybe they intentionally DON'T want us to know what's going on. If they want more of my business, they should publish true thermal efficiency.

ME

GW

Mark

What kind of flow meter are you using? I guess i'll be the doubting thomas here! If you haven't even measured the condensate into the equation, it seems to me like you're above 100%....

How are you measuring the gpm?

I'll be putting together a vitodens pretty soom and i;ll have pressure taps at the suc and discharge at each pump, then i'll do the math to see the head loss, then i'll plot it out on the pump curve chart.

Just curious!

Gary

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Mark Eatherton1

Gary

If you look at the photos you can see the flow meter for the hydronic side in the upper left of the photo.

The problem with gauges across the pump is gauge inaccuracy. If you're going to do that, may I suggest using one gauge and two valves. That way any inaccuracy is moot. That said, don't open both valves at the same time and expect to get an accurate differential across the circuit.

Open the discharge valve, read the gage, close that ball valve, open the suction ball valve, read the gage, do the math, close the ball valve when you're done.

ME

GW

yep

I see it, how is the accuracy?

gary

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