To modulate or not!!

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  #1  
Old 01-01-08, 06:19 AM
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To modulate or not!!

What does modulation save you? The condensation part makes sense if it is condensing. What percentage of the time does the boiler condense? The amount of time the boiler condenses is application dependent. Whereís the savings proof? Savings from old boiler to new mod/con is not enough info. Whatís your opinion? I have mine but I want to hear yours. Why is the European market still about 72% cast iron when condensing has been out so long over there. Donít take this post the wrong way, not bashing just looking for opions. I like condensing boilers but feel they have there place which is not everyplace.
We have different codes and regulations in the states.
 
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Old 01-01-08, 10:46 AM
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Tough question...
I'd bring it to a boiler rep.

I guess it would depend on how inefficient is the system that rou're replacing.

The June-2007 edition of HPAC-magazine has a very interesting article just on this subject. I've used Photo-Bucket by first converting a PDF into a JPG. Hope it works.





I have other informative articles as well.
 
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Old 01-01-08, 04:34 PM
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I guess someone could always check their gas meter daily along with their HDD and run for a couple of weeks. Run it with modulation as one test and for the other run it with the minimum fan speed set the same as the maximum fan speed to test it is a bang bang. I would think their should be some savings if \I had to guess but like you there isn't much in the way of proof in claims out there.

I wouldn't be able to test that easily because my boiler's minimum modulation is effectively very close to my true heat load so it has to be under 10įF before my boiler starts modulating fan speed rather than the time interval between firing cycles. I wish boilers were smaller. Some of the efficiencies are lost with fixed speed pumps. Only the Vitodens has a VS pump although I think the MCBA controlled boilers could handle a VS pump as well.

Interesting question though...
 
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Old 01-01-08, 06:21 PM
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Unfortunately I usually row a different direction then others. I donít do it because I am afraid of change or I need big time proof. I do it as I see what happens with jobs, fuel bills and trying to look at all the parameters. I ask you do not fall for what people say or do without putting some thought in to it with open minds. I am of belief there is not much savings between mod/cons and non-chimney vented cast iron boilers. I know there are forums, which would burn me at the stake for saying that. Here are some facts and thoughts I have come up with.
I have been involved in two jobs this year, which I followed closely so far. One is a mod/com the other a direct vent CI boiler.
The facts are as follows. 1. Proper boiler sizing saves fuel. 2. Near boiler piping can assist in fuel savings. 3. Condensing saves money due to higher efficiency. 4. When 95% condensing boilers are not condensing they are not 95%. They could be in the mid 80ís. 5. There is stored energy (heat) in cast iron and water volume. 6. Cast iron takes longer to heat up due to higher water volume and cast iron. 7. Mod/con is higher maintenance.
My thoughts. 1. Modulation does not save much fuel. Right or wrong I have thought this for a few years now. Btu input per hour is btu input per hour. The mod/con runs longer cycles with less input. The cast iron runs shorter cycles with more input but stays off longer before it comes back on. 2. Iíve heard the argument of higher standby loss on the CI boiler. The standby loss is in the structure. If the circulator is running it also cuts standby loss as hot water is moving to the system. Sidewall vented boilers lose very little through the vent. 3. With the use of 2 stage ODR which the cast iron boiler uses starts the circulator as stage one utilizing the circulator first. Stage 2 fires the boiler if the primary loop does not get warm enough.
Jobsite 1. Existing boiler 240k about 25 yrs old. Heatloss 87K. Chose 120k mod/con as next size smaller was 70K. Utilizing ODR. Mix of cast iron, copper tube, cabinet convector radiation.
Jobsite 2. existing 210k CI boiler about 24 yrs old. Heatloss 160k. Installed 88% direct vent CI boiler. Radiation is Radiant on first floor, cast iron on second floor and indirect.
Both piped primary/secondary
Savings per month after determining btu per DD. Jobsite one. Mod/con - 48% savings Jobsite 2, cast iron - 52% savings
I will follow these for the winter.
Sorry for a very lengthy post.
 
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Old 01-01-08, 06:39 PM
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Opinions? OK. Hang on....

To me, modulation is a bigger selling/efficiency point than condensing. Modulation saves fuel, period. Take a 5:1 turndown. Why run at 80k in the fall/spring (and winter warm spells) when you only need 16k? If the boiler runs continuously from October to April, that's less cycling, wear and tear. Slow and steady wins the race. Match the heat input to the heat loss. It would be fascinating to run a modcon and a CI boiler in identical homes for a season to see what happens. The Canadian energy houses test bed leaps to mind as a good one for this.

In my view, condensing is a bonus. I would also distinguish (as Carol Fey did in a recent article), between condensing in the hx where the latent heat released gets you the added percentage efficiency, and condensing in the flue, which may "look" efficient because the condensate production is high, but it's not doing anything for your efficiency. So you want return temps sufficiently low to condense in the hx. That's pretty low. I think Fey said well under the standard 130F.

However, I've also recently come to think that for many homes, you can condense a heck of a lot more of the time than you might think. My own home is a case in point. I don't have a modcon, but I do know what my supply and return temps are.

I have a Revolution RV-4 serving two zones of fin-tube and a 40 gal indirect, controlled by a tekmar 260. Installed Oct 2006. My initial reset curve had a low limit of 110F supply, and 170F at design (5F outdoors). Heat loss at 5F is ~47k. Heat loss at 50F is ~14k.

We spent a fair bit of the shoulder seasons last year at supply temps <130F (outdoor temps in the mid-30s and warmer), which in a modcon would have meant condensing. Last week, however, I added a tekmar indoor sensor. Now the control knows the outdoor temp, indoor temp, and boiler supply temp. The zone stats are set to hold a few degrees above the tekmar setpoint, so they generate a continuous call for heat. It's continuous circulation, and the supply temp is constantly tuned to hold space temp at the indoor sensor. In that same outdoor temp range (30s-low 40s), I have yet to see supply temps >110,and most of the time, it's 98F or lower (in the upper 70s with lots of solar gain). This includes days with lots and little solar gain, wide variations in wind speed and direction, etc.

Point being that it's entirely likely that a typical 2100sf house full of fin-tube -- sized in 1979 for 180F supply at design -- might usefully condense about 75% of the heating season. Maybe more! And if you're condensing, chances are you're well under the max firing rate, so you're modulating, as well. In two days I'll know how we do at temps in the teens. I'm betting supply temps still don't see sustained periods >130F, so there'll be <115F coming back to the boiler.

Savings proof? IMHO, there hasn't yet been a decent quantitative test. I think the modcon raves on some other sites (e.g., "we replaced the 1953 Arcoliner with a Vitodens and fuel consumption dropped 50%!") are well-intentioned, but hopelessly misleading and quantitatively useless. Brookhaven, the Canadians, or somebody needs to do a real set of tests.

While not a modcon, I think I have a pretty good couple-year test underway. Prior to the RV-4 I had a Series 2 206 installed in 2003 (bang-bang, no controls). It's obviously outta here (long story!). My shoulder season savings last year with the RV-4 were ~23%, and depth of winter 9-11% over the Series 2. (Everything normalized for degree days, hot water use, etc. etc.) That was without indoor feedback. With indoor feedback, I'm betting 23% will be the minimum now that water temps have dropped 30-50F across the board, and hugely reduced the cycling. If you'd like to give me a CHG, I'd be happy to plug it in next year and let you know how it compares to the Series 2 and the RV-4....

Why is Europe still 72% CI? I don't know. I live here and don't follow European HVAC market dynamics.

I am increasingly convinced that a modcon is a much better choice in a much larger percentage of typical American homes than anyone realizes.

So what's the "penalty" for going modcon? Some things off the top of the head:

1) Annual service is a requirement, not an option. Sad to say that most people would/will blow this off and their equipment will die prematurely. They will blame the boiler and modcons will get a bad rap.

2) Installation requires knowledge and skill. The knucklehead installers who don't know a modcon from a toaster far outnumber the competent professionals who do. Piping, pumping, controls, etc. are more sophisticated. Improper installation means the equipment will die prematurely. Homeowners will blame the boiler not the lowballer who installed it, and modcons will get a bad rap.

3) The heat exchangers are more sensitive to water chemistry. Add the cost of a bunch of Rhomar products to the annual maintenance. Don't monitor the water, and/or don't do the annual maintenance, and the boiler will die prematurely. Homeowners will blame the boiler, not their own inattention to having good service done, and modcons will get a bad rap.

4) This is not your father's boiler. This is a high-tech piece of equipment that requires skilled installation and annual attention. I think the jury is very much out on how long these things will last, and what the total life cycle cost will be under normal American use/abuse patterns.

It would be the height of irony if an 80% CI boiler that lasted 25 years with minimal maintenance had a lower life cycle cost than one or more 96% modcons needed to cover the same 25 years. And that's not even getting into the total materials flow and environmental impact of producing modcons, producing and shipping their parts, the water treatment chemicals, the environmental impact of annual service calls, etc. etc. etc. etc. etc.

5) Increasing and parasitic electrical use. We need way more efficient circulators. Some modcon hx's require big pumps that suck electricity. That's increasing use. Parasitic use refers to using circs on every zone, when a better piping/layout/control design might use far fewer, use VS or dP circs internally and externally, etc. In a continuous circulation modcon system, a 3-5 zone circ system really racks up the dollars. It would be nice to save electricity along with all that gas.

Whew. My fingers hurt!
 
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Old 01-01-08, 06:55 PM
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rbeck, your response posted while I was doing my manifesto. Suffice it to say I find your thoughts and rationale on direct-vent CI vs. modcon very interesting. Some of what you describe are reasons I went with CI and not a modcon. I might not be in your boat, but our courses are not terribly different.
 
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Old 01-01-08, 07:24 PM
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Originally Posted by rbeck View Post
Jobsite 1. Existing boiler 240k about 25 yrs old. Heatloss 87K. Chose 120k mod/con as next size smaller was 70K. Utilizing ODR. Mix of cast iron, copper tube, cabinet convector radiation.
Jobsite 2. existing 210k CI boiler about 24 yrs old. Heatloss 160k. Installed 88% direct vent CI boiler. Radiation is Radiant on first floor, cast iron on second floor and indirect.
Both piped primary/secondary
Savings per month after determining btu per DD. Jobsite one. Mod/con - 48% savings Jobsite 2, cast iron - 52% savings
I'd have to think about comparability for a while, but in the meantime, a somewhat better metric to compare these two sites might be BTU/dd/sf.
 
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Old 01-01-08, 09:55 PM
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rbeck, unless you can swap the boilers at those 2 closely monitored sites with each other for a while the comparison numbers are moot. Each is being compared to what was there before and I would doubt that both of the original boilers were identical in efficiency.

I think modulation saves but only to the point where the additional electrical load (which tends to be fixed) offsets the added gains in efficiencies and yes I do believe that modulating does save for the very same reason that correctly sized boilers save money. The whole idea of modulating is so that the boiler can perfectly match the varying heat load of the building so that the return temps and flue temp can be the absolute minimum possible.
 
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Old 01-02-08, 01:39 PM
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I appreciate all your responses.
The CI boiler replaced a more efficient boiler than the mod/con did. The mod/con install replaced a boiler more oversized than the CI did. That should have been a larger savings. The Mod/con was Ĺ the size of what was taken out. We saved less than 50%. If modulation is such a great fuel saver, the boiler Ĺ the size why wouldnít the saving be more than 50%?
The CI boiler was 25% oversized and the boiler was less efficient. Why more fuel savings?
 
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Old 01-02-08, 02:36 PM
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Originally Posted by rbeck View Post
If modulation is such a great fuel saver, the boiler Ĺ the size why wouldnít the saving be more than 50%?
The CI boiler was 25% oversized and the boiler was less efficient. Why more fuel savings?
Three reasons leap to mind (and there are likely more):

1) 48% and 52% are not statistically different, given the number of, and poor control on, the variables involved.

2) Unknown/unknowable and/or poorly modeled variables preclude identification of real differences, including everything from the heat loss to the emitter output to the boiler input/output, the uncertainties associated with the variables, etc. etc.

3) These buildings and systems are sufficiently different that direct comparison is not appropriate.

These are absolutely not criticisms directed at you. They are illustrative of the difficulty in trying to evaluate real-world boiler/system performance in general. What's needed is a scientifically-based experiment where the key variables are controlled, the uncertainties are estimated, etc.

Brookhaven did a study with a condensing and a CI boiler in the same house, plugged into the same radiation. I'll post a link later when I can find it. It's the closest I've seen to a scientific comparison.
 
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Old 01-02-08, 02:43 PM
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I've seen that and I think there were too many loop holes in it. If it is the one I saw they used an oil fired ci boiler and a gas fired mod/con. That is also not a fair apples to apples test. If you post it I will re-read.
Thanks
 
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Old 01-02-08, 04:56 PM
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Can we flip this around?

Modulation is a control technology that tries to exactly match the boiler's firing rate with the current heat load. Therefore, if modulation has no impact on overall system efficiency then why should a correctly sized boiler be any more efficient than an oversized boiler?

Does sizing matter? I believe that it does and that modulation means that the sizing is based on the current actual load, not just some educated guess (manual J) of what the house should need for what might be the coldest 5 hours of the year (design day).

Besides gas consumption, the electrical consumption for the fan motor is lower when modulated back (too bad cheaper VS pumps aren't part of the equation) and this should be factored into any efficiency numbers so that it is a combined number.

There are also a couple of comfort factors at play as well and ultimately heating systems are about comfort. At low loads the boiler is quieter and the temperature swings are minimized.
 
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Old 01-02-08, 05:01 PM
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xiphias, is the study mentioned at the bottom of this article what you are referring to?

http://www.nora-oilheat.org/site20/u...olicy%20r7.pdf



edited... maybe this

http://www.bnl.gov/est/files/pdf/ButcherAachenPaper.pdf
 
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Old 01-02-08, 05:11 PM
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I think the ability of Ci and water volume play an important part of cycling. We are not just talking about modulation and efficiency. We are also looking at fuel usuage. When we talk about CI boilers most people think about the old systems. Let's update to today with P/S and two stage outdoor reset. I would not install a cast iron boiler without reset and in my opinion should alsways be 2 stage. The idea of proper sizing you discuss makes a lot of sense. Every boiler removed (98%)should be larger than what is put back in. I am not saying the Ci is as efficient but I don't think it makes that much of a difference. I have asked many contractors what the savings is with a cast iron change out and m0d/con change out. The numbers are usually 25-50% for both if ODR is used on Ci boilers.
 
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Old 01-02-08, 07:44 PM
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No, this...

http://www.pubs.bnl.gov/documents/28709.pdf

I stand somewhat corrected. It was two oil-fired steel boilers. Monitor FCX (condensing) and Thermodynamics LM 75 (cold start bang-bang). No modulation.

It might have some weak spots -- I haven't read it thoroughly in a couple years -- but my point is that they approached the problem rather scientifically. They controlled a number of variables to the extent possible, measured a bunch of parameters, described the weaknesses of the approach, results, etc.

As I sit here enjoying the benefits of indoor feedback, I am wondering how much more efficient any boiler would be if given the right inputs. Today had temps (and therefore HDD) and solar gain the same as a couple days ago, but infiltration from a 20+ knot breeze was about triple what it has been. Surprise! The indoor feedback sees this in the building response and the average water temps are up a bit. My ODR curve wouldn't see that, and if dialed down all the way to theoretical heat loss, I might be cold tonight. As Who said, it's also about comfort.

I agree that modcons are not a silver bullet, and that the efficiency/savings potential of high mass/water volume CI direct vent is probably underestimated.

I would really, really like to see a rigorous comparison of a few different kinds of boiler and control configurations someday.
 
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Old 01-02-08, 07:58 PM
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Originally Posted by xiphias View Post
I would really, really like to see a rigorous comparison of a few different kinds of boiler and control configurations someday.
I hereby offer my domicile as a 'test bed' ... you guys can bring any boiler you want, install it, tell me what data you want, and I promise, you'll get all the data you want. I'll even buy the beer !



I confess I didn't click the links and read the articles again, but is that the one where they had two identical homes, side by side ?
 
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Old 01-02-08, 08:05 PM
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{edit: I'd like to put a note here that I mis-understood what a modulating burner was. So in my text I stated it incorrectly as something similar to an ODR. I just found out that it is a method of changing the heat output of the burner. This brings the complexity of a modulating burner to a new level. }

rbeck, interesting subject, and at a good time. Being an old boiler I had to do a little research along with what research into new boilers that I have been doing. Some good points have been raised that I can atest to. Along with other items that factor into what it really costs to heat a home.

Condensing boilers are interesting, but appear to me to be expensive and a bit complicated. When engineering something the first 98% is easy, the last 2% takes the other 90% of the effort. This is the way I see a condensing boiler. It is trying to tweak that last bit of efficency out of a drop of oil.

Need a different flue which may or may not be easy/costly. The boiler itself needs to be made of a decent grade of stainless steel to prevent corrosion (expensive). A pump may be required to remove the condensate. With the other byproducts of combustion this drain off will also be corrosive (are sewage treatment plants ready for this?). And clogging of the lines, pumps and drains will occur.

Modulating, just to be sure I believe this is where the boiler temperature is controlled according to the volume of heat required. You mention an ODR, which from I've experienced, works.

Over the years I've come to notice that on cool Fall nights the boiler will run for an hour or two. The boiler temperature would go to the upper limit of 175F. As dawn arrived the day would warm up and all that energy in the boiler would waste away. Windows in the house would actually get opened since it was so nice and warm outside.

Then that night the same couple hours of run time would happen, with the open windows later the next day. The oil tank level would drop like rock. I'd been better off pouring the oil on the ground and lighting it.

This past Fall I started to change the aquastat. It was set to a max of 130F. The burner would run a little then shut off, but the circ's would keep running for a bit longer. House was comfortable, and the oil level, well, it barely moved. As the average outside temperature fell I turned up the boiler temperature (140, 150, . . .). As it is going into the teens tonight (with wind) I now have the max at 165 F.

Talk about a poor mans ODR. thing is, it made a huge difference. System: hot water, oil fired, CI baseboard, CI boiler, all about 50 years old. In decent condition, tuned.

Another area that I've noticed is the electric bill. Easy to see $100 a month added from the boiler running 18 hours a day. The burner itself draws 5.5 A at 120 volts. A new Riello is rated at 2.2 A (measured the current one, just the rating on the Riello). Plus the circ's and thermostat controllers.

Being a CI boiler it can hold some heat. However, I do believe that combined with CI radiators this is the best way to go. A circulator can turn on and draw heat from the boiler without having the burner running. About 10-12 years ago I was researching for a new boiler and basically the only thing I could find had aluminum cores.

I didn't feel it was a good match for an all CI radiator system. Electrolytic action, corrosion, too rapid of a heat rise. So what was there is still there, CI. (Lately I haven't run across aluminum ones, did they go away?).

Where can a large CI system be inefficient? Heating the water temperature too high for the overall heat demand. ODR is #1 in preventing this.

Flue losses. Auto dampers are now a no-no on oil burners. They scare me anyway, had one on there when we bought the house. Not there anymore.

Looking at oil burners, can get an optional air shutter damper. Not sure why it's optional. Between good tight/sealing boiler doors and a shutter damper standby flue losses drop considerably. I can easily feel the draft into the shutter on the current burner.

More insulation inside of the boiler cabinet will also reduce standby losses. However, with an ODR, boiler temperature is already reduced.

Why isn't the burner draft pulled directly from the outside? I have a vent on the other side of the basement to feed the burner draft. So the burner turns on and pulls air in from the basement, this air is replenished from an opening 20 feet away. The warm basement air being used for the burn is now replaced by cold outside air.

Not sure what to do about the barometric damper. It does allow basement heat to go up the flue even when the burner is off.

Everything above goes back to an efficiency rating of a boiler. They can measure this and that and say "it's 90% efficient." Heck, I can do better then that by putting a strip heater in it and only counting the oil it burns (sorry, my cynicism is showing).

I am looking to replace the burner. Going from a 50 year old design to a nice new flame retention setup should increase the efficiency by 7%, 10%, 15%?? At 7% it pays for itself in 2 years. That is a good return on investment.

Not sure if that would be the case if the whole boiler is replaced with a mod/con. Shoot, the darn thing has already lasted 50 years. The last 20 with no replacement parts other then filters and nozzles (the baffle I am still working on).

High tech and the latest and greatest is nice. But I like to see an item first prove it's worth. Like the auto damper and the 'heat recovery' devices that used to be put on the oil burner smoke pipe.

-My last closing thoughts- (did I hear a sigh of relief? <g>)

It is the whole boiler/burning system that needs work. I see too many other areas that waste fuel other then squeezing the last btu out of a drop of oil. If a new house is built and a new mod/con boiler is used, then rest of the system can be built into the house as it too is being built.

Trying to retro-fit a mod/con is not going to be nearly as cost effective. And, even with a new build, it really needs to be worked into the house as a system. Items such as eliminating the condensate pump by proper drain placement. Flue design & placement, oil tank placement with no pump required, burner air drawn from the outside, access for maintenance.

But at the same time, that mod/can should have a shutter damper, and an outside air draw. Along with low energy useage motors and controllers (circ's, oil pump, blower, zone valves, thermostat controllers, etc.).

Al.
 

Last edited by OldBoiler; 01-02-08 at 08:27 PM.
  #18  
Old 01-02-08, 08:14 PM
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Xiphias,

After reading through this thread I went looking for additional info on Tekmar controllers and ODR in general. I saw a post that suggested that complicated boiler controls don't pay for themselves in a reasonable amount of time. Seems your experience with the Tekmar 260 + indoor temp is different. Can you comment further?

Also, Stein Heurtey (an industrial reheat furnace manufacturer) has a furnace they call the digital furnace. When the burners operate, they do so at full fire. They cycle the burners on/off as opposed to modulating the firing rate. They claim this gives them very high turndown and allows the burner to operate at their optimal design condition. Many of the burners in these systems degrade in performance as they firing rate is decreased. While this is in a steel reheat furnace and not a boiler, the concept seems similar to the on/off of a conventional cast iron boiler vs. that of a modulating unit.

The parallel I see is that the conventional unit with ODR allows for optimizing the required firing rate and will squeeze out a little more efficiency as the return water temperature will be lower than a conventional cast iron unit without ODR. Is this consistent with your thoughts/opinions?

A link to the digital furnace is below if you are interested.

http://www.stein-heurtey.com/steel-f.../digitalf.html
 
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Old 01-03-08, 04:04 AM
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Originally Posted by manonano View Post
After reading through this thread I went looking for additional info on Tekmar controllers and ODR in general. I saw a post that suggested that complicated boiler controls don't pay for themselves in a reasonable amount of time. Seems your experience with the Tekmar 260 + indoor temp is different. Can you comment further?
I think the answer on payback is "it depends." It depends on things like the thermal performance of the house, the kind and amount of radiation, the piping of and type of boiler, full or partial reset, the controls, etc. Some buildings/systems will benefit more than others.

In retrofit applications, like a marginally-piped 80% CI boiler, you'd be constrained to partial reset and/or require a bunch of repiping. The initial cost would be high and the payback might be unreasonably long or even non-existent over the remaining life of the boiler. But if you're replacing the boiler, then options abound and the added expense may well be worth it. In my particular situation, I figured that the payback on the added controls is a couple years. Less than four, for sure. I plan to be in the house for a long time, so it's worth it.

In either case, a good thing to do is spend some serious time doing homework and running the numbers.

In another couple months I should have a good comparison between two different boilers and three different control strategies. Will post results and try to see how the costs shake out. (Of course, the biggest cost was hiring an incompentent, lowballing hack to do the first boiler, which had to be ripped out and replaced due to code violations, safety hazards, and whatnot. We'll be paying for that mistake for years....)

Stein Heurtey. Will have to read sometime. If furd is following this thread, I'd be very interested in his thoughts. Industrial-scale stuff is right up his alley.
 
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Old 01-04-08, 11:07 AM
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I have absolutely no experience with steel mill reheating furnaces but I can tell you that ALL commercial and industrial size boilers have modulating burners. ON / OFF control of such burners would be an impossibility along with being an extreme safety hazard.
 
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Old 01-04-08, 05:49 PM
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All the cast iron comm. boilers still offer on/off, L/H/O, L/H/L, and full mod burner applications
 
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Old 01-06-08, 03:56 AM
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I just read and pondered the BNL test comparing condensing and non-condensing boilers that was posted above. Is this a joke or what? Letís prove the condensing boilers are better but letís slant the thing as far as we can to prove a point. There are more slants to this report than the leaning tower of Pisa.
They took a condensing boiler with outdoor reset and modified it to improve the operation from a fixed temperature valve to an auto valve operator. Than they proceeded to compare it to a low water volume steel chimney vented boiler with no ODR.
The comments to have better condensation we should either add baseboard, reduce flow to increase delta T, intermittent flow reversal to reduce uneven heating with larger delta T, Oversize duct coils or two speed circulators. The only one, which makes any sense at all, is the last one. If I am going to quote a boiler and tell the home owner not only are they getting a more expensive boiler with less warranty, requires more maintenance, more expensive parts. I have to add baseboard or make them less comfortable to save an extra 5%. After all this it still will not get me my 95% all the time. Who gets laughed off the playing field?
I can sell them a CI product, add 2-stage ODR connect to their existing system, less maintenance and a lifetime warranty and they will recover the price way before the other option. Which one makes more sense?
If this is a new install instead of a retrofit it makes sense to design with mod/con and oversize the coils or baseboard. Use radiant as much as we can to help reduce water temp. All this makes sense on new jobs. On existing jobs mod/cons make sense on old gravity jobs or steam conversions. I am not too sure they make sense on all CI radiator jobs or baseboard. I usually look at the heat loss at various OD designing temps compared to the amount of radiation to determine a condensing point. Compare this to the average OD reported temps and determine how much the boiler will be condensing.
I wonder who paid for the above tests. Maybe the check written had a few more numbers on it if the results were artificially improved.
If we are going to compare products letís compare apples to apples. If the comparison is a mod/con lets use a sealed combustion CI or steel boiler. If the mod/con has ODR (which most do) lets put ODR on the other product.
This is my opinion on the report for all itís worth. The sweet thing about the forums we get lots of opinions. We should all be open minded enough too not only listen to the opinion of others but listen with an open mind. As much as it may sound I am against mod/cons I am not! I just think not all applications require one. Looking at a fuel savings at the end of the day there are other options, which will save just about as much or more fuel dollars. What ever happened to constant circulation or two stage thermostats? Either one of them can save up to 25% dependent on water volume of the system and boiler.
 
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