High Efficiency Paybacks

Tony_23

You must be joking. That last post of yours merely stated what most professionals on this site knew long before you ever came here.

You may think you have a bully pulpit talking down to the other consumers here on this site, but try and remember you are just that, a consumer. You may be an electrical plant engineer, but you are NOT a heating professional. Not a contractor, not a heating engineer. You're simply a man with time on your hands, an internet connection, knowledge of metals and an assumption of understanding all there is to know about the heating business. You bloviate to HO's and DIYers as if you've got 40 years EXPERIENCE in this field. You've got ONE mod/con under your belt and you think you're an expert. Then you feel the need to be the authority on whether they are worth it or not.

Give me a break.

john_230

High Efficiency Paybacks

I am looking to replace a boiler (baseboard heat), 3300 sq ft house above ground. Small amount of finished space in the basement. Indirect 40 gallon water.

Estimates on heat loss are 100,000 +/- for above grade. (190 linear ft of baseboard, 170 excl basement)

Most firms are pitching high efficiency boilers; Bedaras, Burnham, System 2000 and others. I have been considering sing pass cast iron boilers based on pricing (Peerless, McClain, Smith, etc).

Does anyone have a good sense of payback periods for the high efficiency boilers, as efficiency figures are not very useful in determining comparative oil consumption

Uni R_2

Not really...

AFUE is a joke (manufacturers submit their own numbers on how their own boilers do under ideal circumstances) and in fact much of your actual efficiency will come from how it is configured (piped and controlled) rather than the absolute efficiency of any particular boiler. This industry is lucky in that it can pretty well say anything since there is so little research done.

john_230

re: your remarks - high effficeiency paybacks

thanks. i had a hard time justifying the expense myself.

From broad brush looks like paybacks between 10 and 20 years, depending on the consumption savings, of which figures are not published and hard to pin down.

Everyone wants to reference the efficiency data but no one will verify that it translates to consumption gallons.

They also want to sell the outdoor thermostate to accompany the high efficiency boiler, but give no data on its effect on operating cost (with or without)

Uni R_2

Get the outdoor reset controller...

It is worth it just for the comfort alone.

Brad White_191

\"AFUE is a joke\"...

Ok, so this AFUE rated boiler walks into a bar...

Sorry Uni, there is nothing funny about AFUE... I tried..

Mark Eatherton

And boiler sez...

I'm HOT, got anything cold to drink?

Bartender sez, "Sorry we don't serve boilers here."

Boiler sez, "It;s just a name, a misnomer if you will. I really only heat water."

Barkeep sez "Are you sweating, or are you one of them new condensing boilers??"

Sorry... Carry on

ME

mark ransley

If AFUE is a joke than what is real. AFUE is all I can go by. Figure energy is going up every year as it always has and pay back will be less as costs increase, so go for the best. England banned non condensing heat when they still exported energy. Here we do nada, how dumb. No wonder we consume 25% of worlds energy, how utterly dumb we are.

Perry_5

A better explaination of AFUE - and the differences in boilers.

It is not true that AFUE is a joke. It is very real and very important.

What is true is the very few people understand boiler efficiency - and especially boiler efficiency at partial loads.

What is worse is how boilers are sized to houses. Does anyone actually put in a boiler that is the correct size.... or do we put in boilers that are 25 - 50% oversized (if not 100% - 200% oversized). If you don't understand the boiler efficiency curve - it will really appear that AFUE is a total myth...

For a non condensing boiler the classic boiler efficiency cure is a fairly rounded curve (think of the shape of the top half of an "O". Now it is not exactly round - and the shape can vary by boiler box and burner design - but it will be a well rounded curve.

Back in the 60's most boilers were designed so that the peak efficiency - the top point of that rounded curve - was often in the 85%-90% firing range. That allowed for dirty burners, etc. to not severely effect the boiler operation (i.e: a home type fixed firing rate boiler would age and wear into its most efficient point of operation).

These days, I suspect that most non-condensing boilers are designed so that the top of the curve is at or near 100% firing rate (with a pristine boiler). I note that I'm not sure that I've seen an efficiency curve on a modern home heating boiler.

So if you can run your boiler at or very near 100% firing rate constantly you will have a very efficient home heating boiler.

Of course, if the boiler has to cycle on and off because you cannot maintain full fire rate there are a number of other losses and inefficiencies that come into play - with often severe penalties.

If you have a modulating burner - then the question is how fast is the drop in the efficiency curve for the reduction in firing rate. With a single burner and/or no other controls on air flow the drop off can be severe. You could have a 85% efficient boiler at 97% firing rate, and a 50% efficient boiler at 75% firing rate. It is possible to design for higher efficiencies at partial firing rates (a shallow dropping curve) - but I'm not sure how that translates into the modern smaller boiler designs.

Thus, if installing a new non-condensing boiler you will find a range of how well it works based on proper sizing to the actual heat load and how often it has to cycle. Some installations can be reasonably highly efficient; others are atrocious and need a steady stream of lots of dollar bills.

The efficiency curve world changes substantially for a mod/con boiler.

Properely designed a mod/con boiler is least efficient at 100% firing rate - and the efficiency improves as the firing rate goes down to a reasonable level. Thus you may see a mod/con efficiency curve showing 87% efficiency at 100% firing - rising to 96% at 1/3 firing rate. The efficiency does drop off below some minimum firing rate - and it can be severe.

So, if you can properly size a mod/con to a building; and keep it at or above a reasonable minimum firing rate; it will be more efficient than any non-condensing boiler.

But, given the "standard" sizes available and the tendency to oversize a mod/con can spend considerable time cycling on and off. Many of the same inefficiencies that plague a non-condensing boiler when it cycles on and off also plague the mod/cons.

To give a very relent example: I have a Vitodens 200 6-24, with a rated output from 22 - 81 MBtu/Hr.

On a design day my house needs about 60 Mbtu/Hr. Thus the boiler is inherently 25% oversized - and it was the smallest Vitodens made. However, if you look at how the sizing numbers are done - that method is conservative as well. Perhaps I only need 50 MBH on a Design day....

From a practical matter: My Vitodens cycles on and off whenever the outside temperature is above about 20 F. I've never figured the break point (and it depends on wind as well); but I just don't get to steady firing unless it drops into the teens... This is not the most efficient boiler possible; but it was the best bet overall when considering all other issues.

The other option looked at was the TT 110 - which would have been massively oversize. Would it every have gotten out of cycling off and on for my house? Note that I rejected the Muchkin due to what appears to me to be some basic design flaws. I have no regrets about eliminating it from consideration.

I sure wish someone would come out with a decently constructed 30 MBH mod/con boiler. Gang two or three of those and you would have truly wondrous efficiency for almost all houses (not to mention inherent reliability).

Back to the original question about the relationship of AFUE to actual efficiency. It all depends on how well the system matches the house. A poorly sized mod/con will be less efficient than a properly sized non-condensing boiler. But, in general; a modestly oversized mod/con is usually more efficient than a modestly oversized non-condensing boiler - and it is noticeable.

Now as to your question about high efficiency paybacks. A month or so I started a thread concerning could a practical mod/con boiler be built. My proposal was that the higher cost of a mod/con boiler would only be worth it if the boiler had a reasonable long life (well in excess of 10 years). The problem being that many of the mod/cons do not seem to have been designed to last that long based on my experience with HX materials and the service conditions. It is a long thread and you might wish to find and read it.

Also, for the record: I have a Vitodens 200, with a Vitocell 300 water heater; was one of those whom the gas company changed the meter because they thought it was broken, and do expect that it will last 15 - 20 years+ and will pay for itself. I note that I will also start building my own personal stockpile of parts so that it can be quickly repaired as there are not many of these around in my area. Overall - when I'm done I suspect I will have tied up over $1000 in parts; which will extend the payback if the parts are never used.

Perry

Bob Bona_4

how can they?

mileage WILL vary. Nobody has the exact same living habits, comfort zones, house envelope tightness at any given time. Some people like it at 60, some at 74. Some like 5 minute showers, some like 40 minute showers.

All that can be done is averages, and realistic expectations. AFUE to the techie may be a hard number to pin down, but take it for what it's worth.

Tim_41

eff

Efficency on boilers are refering to the flame. How eff is it burning. I had a friend use a wohler combustion analyzer on a wood stove. It was 81% eff. Does it make it really eff?? No. It all depends on how you use the heat that you produced. Is putting 450 to 500 degrees up your stack with a single pass system eff? Or, how about 300 to 400 with a 3 pass boiler. Much less temps with a mod/com. I would prefer using all of the heat that I produced to heat the home. As many here have said, its the control strategy and piping. Don't forget your pumping eff. Is 8 circs easier on the power bill or one VSC circ better. ODR is a must. I could go on but there are many here who will forget more than I will ever know on this and they most likely explain it in better terms.

Wayne_29

Perry your boiler is oversized

As are your posts

Everybody else, you are welcome

(Shout out to my elite peeps)

Mark Eatherton

That's OK Tim...

Perry's last post made me forget everything I thought I ever knew about boilers, combustion, efficiency etc. In fact, I fell fast asleep half way through, but that's probably due to sleep apnea... How confusing can we get?

As it pertains to over-sizing and modulation, the balance point of any structure is dependent upon how much internal gain is occurring at any given point in time, and THAT TOO is a variable, so don't bother trying to find it unless you're looking for it in a dark cold house.

However, it has been my EXPERIENCE that an atmospheric appliance of any style/make/composition, that cannot modulate the air flow through the appliance as it modulates flame strength, will have so much dilution air going through the combustion process during low burn that its net efficiency will be terrible, like less than 50%. Unfortunately, most atmospheric modulating (2:1 turn down) appliances spend the majority of their run times in the low flame mode.

THose few appliances with an infinite modulation capability in the atmospheric range (RayPak) have a tendency to crystalize their aluminized burners due to the flame being impinged on the burner face, causing the burner slots to enlarge, causing fuel waste and eventual burner failure, but that's a topic for a WHOLE nuther thread...

A modulating burner CAN modulate the air flow commensurate with fuel flow, and eliminates the wasted BTU's associated with the combustion process. In fact, there is technology coming out that mimics the automobile, watching the exiting flue gas oxygen content to fine tune the combustion process even more. Also, its thermal efficiency is highest at low burn with low return temperatures (below 140), so theoretically, it would be more efficient if it WERE oversized, which no one in their RIGHT mind would do, but it does happen.

The biggest problems with AFUE is that it rates ALL boilers with an entering water temperature of 140 degrees F, which would VOID the warranty of most atmospheric appliances. AFUE was originally conceived so that Joe and Jane Six Pack, the great American consumer, could compare the efficiency of a Train Furnasty to a Burntham Boiler. They (US Gubernmint) were trying to mimic the M.P.G. standards used on the automobile, as it were.

The biggest fallacy of AFUE is that when comparing like appliances (boilers), to the consumer, it would appear that they will use only 15% less fuel by going to the higher efficiency mod-con appliance, and that is hard to justify, based on cost installed.

The truth of the matter is, when displacing an atmospheric appliance with a modulating appliance, the MINIMUM reduction in fuel consumption that I have SEEN, is 30%, and as high as 60% depending upon the existing conditions.

As an interesting aside, Buderus and Viessmann still make atmospheric cast iron boilers, but they are not allowed to sell them on the European market. Guess where they unload them.. You guessed right, the good ol' US of A.

One day soon, we too will not be allowed to sell those dinosaurs. Why do you think that most all the North American boiler manufacturers have aligned themselves with a high efficiency boiler manufacturer that they can put in their own box? They can see what coming as well...

Get ready for the rush.

ME

Unknown

Pay Back.

How old is your existing system? What type of fuel? How much for the 80% vs. the 95%? Is the cost difference going to payback?
Have you looked at what it cost for each system, the 80% vs. the 95% and see how long it will take to pay back the cost difference between the two? If you need a boiler you are going to pay install no matter what system you get.

Why do we always have to push the payback? I understand making a sound investment, but what is the payback on the $2800 flat screen TV or, the $35,000.00 fuel guzzling car that we keep for 5 yrs or less?

We need to start looking at other issues beside payback. Fuel increases and that payback you figured today might end up being much bigger that you ever figured.

We balk at cost of heating equipment but in the grand scheme of things the cost is so small compared to the crap we waste our money on.

Payback factor should be part of a decision but not the whole. Payback numbers are a guess. Most time the changes I make to a system when installing a new boiler will increase the payback.

The whole system and house should be looked at as a whole.

It comes down to do you want a Hugo, BMW, Honda or a Ford?

I have no idea what you are being sold or for how much. But you should always get multiple quotes and compare like systems. I find that there is only a couple of thousand dollars between my 83% CI and a 95% Mod/Con quotes.
Is a more efficient system worth an extra couple of thousand, payback or not?

Perry_5

Combustion efficiency is not equal to boiler efficiency...

In a well designed boiler - operating within its designed firing rate; combustion efficiency has a high correlation to boiler efficiency; but they are not one and the same.

I will also admit that you cannot get efficient boiler operation unless you have efficient combustion.

Combustion efficiency is determining how much energy in the fuel gets converted to exhaust gases that can be used as a heat source.

Boiler efficiency is how much effective energy does the boiler transfer to its working fluid based on how much energy is in the fuel.

All boilers have losses, and the losses can even outweigh the fuel input at the extreme. The old fashioned constant pilot light is a common example where you can have very good combustion efficiency - and zero boiler efficiency (the pilot light is not supplying any usable heat to the heating system).

Just improving combustion controls (even with O2 sensors, etc) will not change the basic dynamics on the boiler efficiency curve versus firing rate. Note that I am not against trying to improve combustion efficiency. That is a piece of the puzzle.

Sorry if that seems a bit over your heads.

Perry

J.C.A._3

Not so much over our heads....

Why do you feel it takes a dissertation to answer a simple question?

Get over yourself...and keep it short.

Most folks see a response that is going to take a flipping hour to decipher...and just move on.

You're not impressing anyone and take a mile round way to answer a simple question.

KISS big guy...Chris

Unknown

My sentimates exactly,

Chris & Fred!
I was just sitting-back waiting for someone to say that!

Dave

Perry_5

Fred - you have it partially right

Agreed. I appreciate the honest critique.

Many heating professionals do in fact know the basics of boiler efficiency vs combustion efficiency; and probabably know the basic shape of the efficiency curves.

Yet, I can point out post that occur where contractors on this site do in fact confuse the two - or maybe don't know the difference; and I often have not seen anyone else from the contractor side jumping in to correct them. Why not?

OK, maybe my efforts aren't the best; and maybe I miss the point of some post (don't we all), and sometimes I'm tired and not thinking the best (havn't we all done that). If other people were jumping in to explain this when needed I wouldn't try.

Not all contractors are truly educated professionals. I know you know that.

So OK; I'll try to stay away from the obvious. But I will be looking for you and some others to step in when someone post that a boiler efficiency is good because of the combustion efficiency they got on their analyzer, and other things.

Do have a nice day,

Edited to add: You are right in that I am not a HVAC engineer (a heating engineer). But I am a an actual degreed engineer who deals with many of the same issues involved with HVAC; and I have decades of very real operating, maintenance, and even engineering of boilers, piping, pumps, controls, etc - with developed specialty in heat exchangers. What's the hot project of the moment I am involved with at work - improving the performance of an air handling cooling coil system.

Perry

Wayne_29

Brad is THE ONLY ENGINEER ON THIS SITE

The rest of you just play one, on the internet

Wayne_16

Don;t give up Perry

A lot of us techs, the diy's and others have learned alot from the posts from people like you, (all the Mark's, Hot Rod, Brad White,Mad Dog and others) have unselfishly given/presented there works, & time. Many have freely answered questions in the hydronics, combustion, proper installs etc. to name a few, to the rest of us that want to learn and understand the equipment we own, and or service. One would have to wonder how many times the same question has been asked and a personal reply is given by a member of this forum freely each time. The information gained here has been invaluable, even if I have learned something, that I will not use in the future, I still consider it a valuable leason.

One of the main reason's I frequent and lurk on the site, is I consider the information presented on this site CORRECT. Something to take to the bank so to speak. When information is presented that may be of a questionable nature, other members ask for more information/facts from the original post to substantuate the statement prior to rebuking the fact(s).

Dan Holahan and others have encouraged the professional service person, the business owner, and the homeowner to feel free to post topics, and ask questions with the same honesty and integrity.

All readers of this site have the same rights and responsibilties to post and present information important to them.

Back to the original topic long winded explanations, I personally accept them, and am grateful someone is willing to take the time to fully explain the topic from their view point.

Enough of the long thread, Wayne

Gordy

Wow

Tough crowd today. Is our favorite team not in the Super Bowl?

Gordy