Efficiency v. Cost

Mark Eatherton

More like a minimum of $270.00 per year. And, if you are in need of a boiler replacement, don't try and amortize the WHOLE cost of the high efficiency replacement, only amortize the cost differential between a conventional boiler and a high efficiency boiler.

One thing for sure, although the cost of energy may be low at this time, it will NOT stay low, and the cost of installation will not be coming down soon. If you're thinking about doing it, I'd recommend you go ahead and pull the trigger now.

But, that's just my opinion.

ME

[Deleted User]

Through previous discussion here it appears that I have a boiler with an efficiency of about 82%.

I'm trying to decide if it makes sense to replace it.

I use 8-900 therms/year at $1 ea.

If I buy a 95% boiler I figure I'll save ~$125/year on gas. [900-((82/95)*900)=$124]

Do I have that right?

If I buy good modulating-condensing boiler how long will it last?

tim smith

I would say not. I don't see any real benefit to changing it

at this time. Maybe as gas rises the economics will make better sense. Tim

D107

comparing efficiences

Mark what goes into your calc for savings gained from going from 82% to 95% boiler? It's obviously not just 13%. (on near design days a mod/con isn't doing 95% so I gather.) Is it the outdoor reset, upgraded near-boiler piping......?

Thanks,

David

Darrell_4

Don't overlook some of the costs that aren't in the brochure.

The typical mod-con will have a higher maintenance cost per year...not alot, but more.

There will probably be some piping changes required to upgrade.

To maximize the benefits of the mod-con there may need to be significant changes to the delivery system of your home. If your installer wants to just stick a mod-con in without addressing the delivery system...get another opinion.

The efficiency comparison isn't a linear graph. The mod-con is more efficient at different loads. The atmospheric boiler is pretty much always the same.

As energy costs go up, and they will, so will maintenance costs.

All considered, if your boiler is working fine you may not ever pay for the upgrade with fuel savings. But, it still may make sense to do it. You may get points if you sell. You will probably get points, or credits, for having a higher efficiency appliance if Mr. Obama has his way. You may even get demerits for keeping the atmospheric boiler. There may be a state of federal program to help you pay for the upgrade.

You will have new equipment.

If your installer is sharp, you will save much more than the brochure says.

Just a servicemans perspective.

Mark Eatherton

10 years worth of field experience in applying the technology...

The MINIMUM reduction in energy consumption we saw was 30%. We saw as high as 60% in certain commercial apartment house situations.

I think the majority of the savings comes from the fact that the appliance can modulate its burner to match the real time load.

ME

Steven Eayrs

not 95% on design day????

And why not?? Look at it another way..... Most mod/cons have fully modulating burners, and almost any older burner does not.
With outdoor reset, and mon/con type, you can set up the boiler to match the load, to get 95%, most of the time its running, regardless if its running at 20% or 100%.
Not something you could do with the ol' on/off 100% hot running boiler, regardless of heat load.
So its not just 13% difference. the ol'boiler is 13% less yes, but it only has one speed...which is 100%. What if you could run this thing at 30%, and still provide all the heat you need?
So your really comparing a 13% more efficient unit, that may be able to provide all you need at say 30 or 50% of the units top output, verses a 13% less efficient unit, that always has to run at 100%.
Did that make sense?
So you need to realize you could possibly cut yor bill in half. Other factors of course play into this, but this is the basis of the difference.
Anyone on here whos telling you its not worth it, evidently has not stepped into this century yet.
Is there a payback? yes! And as long as thats true, really who cares how long it takes!! You got anything else you know of on this earth, that you get a payback in $$$ on? Definitely not the 30K truck you drive. Can't trust the stock market, or the property you own.
And whatever you calculate for savings now, is only going to increase with higher fuel costs.

disclaimer......this offer excludes the return on investments in family, friends and of course spiritual freedom. They will always be there.

Darrell_4

I like the way you explained it...

But, I have family I've invested in and there is not going to be any payback...ever!

You will note that I have modified my position on mod-con boilers abit. I just inherited six abused and neglected munchkins...I think I can save 'em! I have not opened them up yet.

Steven Eayrs

theres always a few bad apples...........

and there plentiful on the yellow brick road.

Robert O'Brien

What about

the $1500 tax credit?That helps narrow the differential between CI and Mod/Con!

Unknown

Replacement?

The question I have is whether or not the existing boiler is bad and needs replacement? How is the system presently configured and what type of radiation is used? What can be done to increase the efficiency of the present system?

If a new boiler is required anyway then a modcon with system upgrade is probably the way to go. If the existing boiler is relatively new, then the decision is not so clear cut.

No one has addressed the other question asked, which is how long the new modcon may last. The answer is no one really knows. A cast iron boiler can reliably last decades. Some inexpensive modcons with poor maintenance have lasted less than ten years.

Reliability is an other issue. A modcon is necessarily technologically more complicated than a simple cast iron boiler and will require more frequent maintenance. Repairs may be more frequent and expensive than for what you have now.

Just some factors to consider when making a decision.

tim smith

The intitial question was he has a 82 % efficient boiler

currently, should he keep it or should he upgrade to a 95%. That is why I posted not really worth it.

[Deleted User]

More data

Lots of interesting info here. Thanks to all who have contributed.

Does any of the following modify any opinions?

The house is 1100 sq. ft. and the heat load, calculated at -17°outside and 70° inside with several methods is about 35-37,000 Btu/Hr.

It is presently heated with a Midco natural gas Economite conversion unit in a Crane-line Midget boiler. I believe the boiler is 50+ years old and seems to be OK at present.

The Midco has an input of about 143,000 BTU/Hr determined by measuring ccf/hr.

The heat emitters are cast baseboard in a single pipe single zone configuation that works quite well. I don't plan to change them.

On days when the low is -20° and the high is -5° the burner runs 6-6.5 hours out of 24 hours. I measured this, it's not a guess.

More info:
I drive a 1991 Cavalier with 280,000 miles, not a $30K truck.
I am retired and get a SS check. I don't pay taxes, so no tax credit or deduction advantages.

[Deleted User]

> The question I have is whether or not the

> existing boiler is bad and needs replacement?



Other than leaking (mine isn't), what are the signs of a bad boiler.

Mark Eatherton

Combustion analysis required...

Fred, the cast iron vessel may very well outlive everyone on this thread. What is more important is what the combustion efficiency of the appliance is. Even though it is rated for 82% thermal efficiency, if the burners have degraded, the combustion efficiency may be suffering. The only way to determine that would be to contact a qualified combustion testing company and let them diagnose the combustion efficiency of the appliance.

And don't let the analyst buffalo you with the "% efficiency number" reading from his analyzer. There are no less than 100 combinations that can get you to a certain number. Pay attention to the oxygen, carbon monoxide, excess air numbers, breeching draft, over fire draft (if applicable) and report back here with those numbers so we can give you an idea of your appliances health.

Your cast iron radiant system is conducive to the use of a modulating/condensing boiler for what its worth.

The life expectancy of these new boilers is unknown under ideal conditions. They've been around for at least 10 years, and will be around for ever...


ME

Andrew Hagen_2

Boiler Replacement

My view is that if you are replacing the boiler anyway, a Triangle Tube Prestige Solo 60 would be a good choice. However, with your current fuel use, it is difficult to justify the cost of replacement based on payback. That is the catch with low heat load homes.

At some point, conservation begins to trump the additional cost of efficiency. I believe your heat load is very near that point.

MIke_Jonas

Yeah, but.....

You can throw combustion efficiency numbers around, that's fine. I have no problem with that.

What no one ever discusses, (maybe I'm just ignrrnt and have never stumbled across this) but I have never seen the comfort issue addressed as it applies to a high efficiency boiler getting it's combustion air from outside, as opposed to using indoor air already heated for combustion then venting it out the chimney.

To me, this is a pretty big comfort issue. One that can not be measured and be listed in any brochure.

The ability of a high efficiency boiler to produce domestic hot water more efficiently than a standard water heater adds to the long list of benefits as well.

I prefer a homeowner find a contractor they are comfortable with, and use whatever boiler they sell, instead of telling homeowners to look for a particular brand.

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

tim smith

Fred, now that it is known that you do not have an 82% boiler

and we kind of know your economics. Your boiler may only be 65 to 70% efficient. With that said, say you save 25% on your fuel bill?? At today's dollars that would be 250.00 savings a year, knowing that a replacment boiler could be 8-10,000 give or take some. I would worry that you are putting dollars out that you could use elsewhere more prudent for your situation. With that said, rates are not going down so your fuel bill could go quite a ways up in future but my crystal ball is a bit cloudy right now and so I can't see the future. If your boiler is in decent condition and tuned up, save your money for now and use it for some fun in life. Good luck, Tim

[Deleted User]

> and we kind of know your economics. Your boiler

> may only be 65 to 70% efficient. With that said,

> say you save 25% on your fuel bill?? At today's

> dollars that would be 250.00 savings a year,

> knowing that a replacment boiler could be

> 8-10,000 give or take some. I would worry that

> you are putting dollars out that you could use

> elsewhere more prudent for your situation. With

> that said, rates are not going down so your fuel

> bill could go quite a ways up in future but my

> crystal ball is a bit cloudy right now and so I

> can't see the future. If your boiler is in decent

> condition and tuned up, save your money for now

> and use it for some fun in life. Good luck, Tim

[Deleted User]

82%


How do we know that it isn't 82%?

I'm not questioning your veracity, I'm just interested in how it is figured.

Mark Eatherton

Because...

50 years ago, 82% was unheard of. More like 75% thermal efficiency was the norm back then. Not to say that your appliance isn't 82% efficient thermally, but with it being oversized as much as it is, thermal efficiency is not what's eating your savings account up. Seasonal efficiency is what is killing you, and I'd guess it to be less than 50% or less.

On your boiler, there should be a tag showing input and output. Output divided by input will give you the appliances basic thermal efficiency. None of this really means much without having a combustion analysis performed. That will show what the steady state thermal efficiency of the appliance is. That is the proof of where the rubber meets the road.

ME

[Deleted User]

OK I'm going to have to get smart on this

I feel that I need a pretty good understanding of the test and test procedure before I have a test done.

> Pay attention to the oxygen, carbon

> monoxide, excess air numbers, breeching draft,

> over fire draft (if applicable) and report back


Are these numbers that would normally be in a report for a combustion efficiency test?

I did a quick Google search and it looks like I'll have to dig deeper. There wasn't a lot of info offered.

I didn't find anyone offering this service on the web or in my phone book.

Darrell_4

He's got a conversion burner on that thing, as well, so the numbers on the tag won't give him the real scoop. The conversion burner will be less efficient than the original oil burner.

[Deleted User]

Seasonal efficiency is

> what is killing you, and I'd guess it to be less

> than 50% or less.

>

> On your boiler, there should

> be a tag showing input and output. Output divided


I did a little reading on seasonal efficiency. I see what you mean, especially given that I'm running a 26% duty cycle on the coldest days.

Since I have a fair idea of the heat loss I may be able to calculate seasonal eff. if I can get the temp data. I'll look into that.

The Boiler says 127,000 BTU/hr with a 1.5 gpm input. I assume that's fuel oil. If so that's not a very pretty number.

I don't know if that gets better or worse with the gas conversion burner with it's 143,000 BTU/hr input.

Unknown

Does the boiler maintain constant temperature throughout the heating season, or does it operate "cold start" and only fire when the thermostat calls for heat? Your seasonal efficiency will be much lower if it maintains a 180F constant temp regardless of the need for heat.

The DOE tests for seasonal efficency assume constant temp operation, and is a significant factor for lower efficiency at low duty cycles. If your boiler only fires for a long period to heat up the mass of the cast iron radiation and then shuts down and remains cold for a long period, the loss of efficiency is not nearly so great. Duty cycle modulation in itself is not the real enemy. It is the standby loss of a boiler sitting there at temperature, rapidly cycling on and off, while delivering little or no useable heat to the living areas that mainly contributes to low seasonal efficiency.

Jim_64

73% by math on my '83 burnham

brushed, vacuumed, tested and adjusted the gas a couple years ago. i don't use it much, but it still burns a perfect flame. and an unmentioned value of a ci boiler, when operating in an an in-ground, 'uninsulated' basement or garage, the space get's heated. a mod will never heat it's own space. they're closet boilers

[Deleted User]

> Does the boiler maintain constant temperature

> throughout the heating season, or does it operate

> "cold start" and only fire when the thermostat

> calls for heat?

I don't know if I've seen it get up to 180, rarely to 160. It doesn't run unless there is a call for heat and the water is not warm enough. Many times only the circulator runs.

On warmer, say 40°, days the water temp may drop to 80° or less in the several hours between firings.

Doug_7

Seasonal Efficiency vs. Steady State Efficiency Graph

As others have pointed out, the rated efficiency of an atmospheric boiler is only achieved at 100% firing rate, on a new, clean, finely tuned boiler, running at optimum conditions. This is the Steady State Efficiency.

When the heat load is reduced, the boiler goes into ON-OFF control mode and the boiler efficiency drops sharply at heat loads below 50%. When OFF - the boiler turns into a radiator, wasting heat up the flue. Also boiler heatup / cooldown losses.

The attached NBS chart illustrates the measured difference between Seasonal Efficiency and Steady State Efficiency of an atmospheric boiler, as a function of firing rate.

At 100% firing rate these two efficiencies are the same.

Lets assume at 100% firing rate that your Steady State Efficiency is 70%. (Not new, not clean, not finely tuned and not at optimum conditions.)

At 20% of heat load, the seasonal efficiency will be about 85% of 70% which is about 60% efficient.

At 10% of heat load, the seasonal efficiency will be about 72% of 70% which is about 50% efficient.

With a Modcon boiler the boiler efficiency actually increases slightly as heat load is reduced and the boiler modulates down to match the heat load.

This large drop in seasonal efficiency of an atmospheric boiler is why you will get a much larger gain in efficiency and much larger cost savings than the simple difference between 82% and 95% would seem to indicate. I got a well documented 32% increase in efficiency and a 32% cost savings going from a finely tuned atmospheric boiler to a Modcon.

Basically, the 82% efficiency number of an atmospheric boiler is very misleading with respect to the actual seasonal efficiency and actual performance. There is not just one efficiency number for an atmospheric boiler - you need to follow the heat load / efficiency curve.

Doug

Unknown

It sounds like you are operating as efficiently as possible with the type of equipment you have. The several hour long periods between firings assures that steady state efficiency is reached during firings and cycling losses are minimized. The fact that your water temperature varies as a function of heat loss is a plus factor in increased efficiency. This is the type of performance that is accomplished with outdoor reset in modern systems. Another plus is that your circulator operates without firing the boiler, thereby utilizing the stored heat of the boiler when needed, instead of losing it up the flue or radiating it into the basement. Your standby losses will be lower and seasonal efficiency will be higher than a typical system which maintains a constant 180F as assumed in the DOE calculations.

The newest government efficiency regulations will require new boilers to have the same energy saving strategies as your system has been utilizing for the last 50 years!

Mark Eatherton

Thank you for taking the time to get educated...

There is a company called National COmfort Institute.

http://www.stopcarbonmonoxide.com/

You can go there and put your zip code in and find a local contractor who is qualified to analyze your flue products. I forgot one critical parameter, that being flue gas temperature.

If that doesn't work, as an alternative, the is a Find A Professional link in the Resources button at the top of this web site.

It would also help if you could give us the make and model of the appliance. All of my recommendations are based on a natural gas, natural draft appliance. It sounds as if possibly you have a power burner on your boiler. In which case, some of the things I have said would not be applicable.

ME

[Deleted User]

> It would also help if

> you could give us the make and model of the

> appliance. All of my recommendations are based on

> a natural gas, natural draft appliance.




Does this change anything?

The house is 1100 sq. ft. and the heat load, calculated at -17°outside and 70° inside with several methods is about 35-37,000 Btu/Hr.

It is presently heated with a Midco natural gas Economite E20 conversion unit in a Crane-line Midget boiler. I believe the boiler is 50+ years old and seems to be OK at present.

The Midco has an input of about 143,000 BTU/Hr determined by measuring ccf/hr.

The heat emitters are cast baseboard in a single pipe single zone configuation that works quite well. I don't plan to change them.

On days when the low is -20° and the high is -5° the burner runs 6-6.5 hours out of 24 hours. I measured this, it's not a guess.

Steamhead (in transit)

The E-20 in that Crane-Line

was not a flame-retention burner IIRC. A newer flame-retention burner like the HeatWise SU, Carlin EZ-Gas or Midco EC-200 would do better.

But that still wouldn't get around the fact that the boiler is way oversized.

Time to replace it.

"Steamhead"

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Doug_7

Documented Savings - Boiler Replacement

For some good documented information on the improvement in heating efficiency achieved by switching from an atmospheric boiler to a ModCon go to:

www.aceee.org/energy/state/durkin_ashrae_journal.pdf

This will download a July 2006 ASHRAE article titled Boiler System Efficiency.

Atmospheric boilers in 20 schools (10 were steam boilers and 10 were hot-water boilers) were replaced by ModCons and the natural gas use before and after (corrected for degree days) was compared.

Table 1 show an average 68% cost savings for the 10 schools in which steam boilers were replaced with ModCons.

Table 2 shows an average 49% cost savings for the 10 schools in which hot-water boilers were replaced with ModCons.

I also believe the cost of crude oil and natural gas will rebound to high levels as soon as the economy recovers.

Doug

Steven Eayrs

great facts Doug!!!

You would think that would be enough to convince the sceptics, but my guess is it won't. Some will still try to convince themsleves that theres no real savings to technology, and the old gray mare is faster than the car.

[Deleted User]

Combustion analysis

I finally found a couple of guys that could do this for me.

The cost was $80. Does that seem reasonable?

As an aside, in one case I spoke with the business owner who was ready to come up today and do it. Good business.

In the other case I spoke to the tech who would do the work and he asked what system I had and what was my usage etc. He then said that he was familiar with my equipment and that he expected that he would see an efficiency of 80-82% steady state. He also said given what I told him if it was his money he'd not do the test. Hmmmm.

See my next post on seasonal efficiency.

[Deleted User]

I look at Seasonal Efficiency

I looked at last year.

I know what my gas usage was so input is easy.

945 ccf/$982/97335 MBtu

I've calculated heat load a couple of ways and it comes out 35-37000 btu/hr for my 1100 sq.ft. house. See house info below.

I obtained hourly temp readings for the year and subtracted them from 70° then multiplied the result by 427 BTU/hr-°F (for 35000 Btu/hr). These totalled 98007 MBtu. OOPS, 101% seasonal efficiency.

I re-checked the latest HL calculation and decided maybe the infiltration was ¾ change/hr instead of 1 change/hr. This changed the heat load to 30000 and the total output to 81009 MBtu or 83%.

Since it's easy with a spreadsheet, I looked at heat loads of 28000 (78%) and 20000 (55%).

Does this seem reasonable?

I'm used to having my work questioned (I hang around with some engineers) so have at it.

The house has some insulation in the walls, redwood siding, fanfold insulation and vinyl siding on top. 231 sq.ft. of single pane windows with alum combo storms and steel insulated doors. All doors and window are recently caulked. 12+ in. of attic insulation.

Doug_7

Btu / HDD / SqFt / year

Suggest you benchmark the overall energy efficiency of your house:

Calculate your your Annual Heating Btu Use per Heating Degree Day per Sq Ft of floor area. Using Heating Degree Days from your weather office takes into account your local climate.

The Annual Btu used includes both building heating and domestic water heating.

If it is under 5 Btu / HDD / SqFt / year you are in good shape. If it is over 10 you are below average.

This considers both heating system efficiency and building envelope efficiency. Both are important.

My Btu / HDD / SqFt / year is 3.8

A super-insulated house with high-efficiency heating will be less than 1 Btu / HDD / SqFt / year.

See attached.

Doug

Unknown

Actual heat loss

Your calculations seem reasonable, but your actual heat loss is really the question. Since you know your actual fuel usage and duty cycle on a near design temp day, why not work backward from there?

Assuming boiler fires for 6 hours out of 24, you are at 25% duty cycle. Assume 100% boiler efficiency for now. Total heat input = 143 KBTU/Hr x .25 = 35.75 KBTU/Hr which at constant indoor temperature equals your heat loss. This would be your worst case heat loss since you know your system is not 100% efficient. So it seems your calculated heat loss is a bit high.

If we assume 75% efficiency, your actual heat loss would come out to be 26.8 KBTU/Hr which seems more reasonable.

Stephanie Custis (yes, Mark's wife)

Tax credits

and retirees. Although I am certainly not a tax accountant, I think that you may still be eligible for a "tax" credit under the current program. Check with an accountant, but I think its like the earned income credit.

[Deleted User]

Status Report

First, thanks to all that responded to my questions.

I have decided that if or when I need a new furnace it will be a Mod/Con boiler.

To help decide the if/when question I've arranged for a combustion anaysis combined with a leak test for the house.

When I get the data I'll ask here for help interpreting it.

[Deleted User]

NEW DATA

OK, I had the furnace measured and looked at leaks in the house.

Furnace measurements.

Used Bacharach Fyrite calibrated 02/09
Stack temp 390°
CO 170-206 ppm
Oxygen 1.4%
CO2 11
Combustion efficiency 82.4%
Excess air 6.3
Free air 221

Would someone interpret these result for me?