Is modulating boiler really worth the extra $ ?

brucewo1b

I work wth propane but the therory is same basic thing, NG coming to the house is at street pressure, and the regulator at the meter drops to to working pressure usually and fed through what ever sized pipe will carry the BTU load of your house. Now sometimes you drop from street pressure to a lower pressure but not house pressure to another regulator that branches out to the appliances the higher pressure allows a smaller diamiter pipe to be used but has to be dropped again to working pressure at the branches. I hope this helps clarify the pipe sizes.

JIMBO_2

Is modulating boiler really Worth the extra $ ??

After planning to install an Ultra-80, I can't help but wonder if it is REALLY worth the extra $ compared to, say, a CGs-3. There doesn't seem to be a great deal of difference in efficiency between two, percentage-wise. Considering the 7 large radiators and cast-iron baseboard, as well as the 40 feet-or-so 2" black pipe headering off the boiler, all being fed with 180 degree water . . . I don't think the modulating boiler will have much chance to condensate very much. So I can't help but wonder if I'm not better off with the fixed-fire boiler with an outside air set-back. The ultra is roughly a thousand dollars more than the CGs. Do you think It wiser to go hi-tech or work-horse? Or am I driving myself crazy over-thinking this install????

tom_49

Jimbo,

Even w/o the boiler condensing it still is modulating, burning only whats needed. Pay no attention to the "rated"
efficiency, that number is very distorted ( to long to get into now ).

With all that cast iron, your going to be running much lower water temps than you think. Do constant circ w/ od reset. The extra $1000.00 will soon be forgotten.

Brad White_9

What you said

I agree, Tom. Absolutely. Well said.

Ron Schroeder

Work Horses I Love Work Horses

and I use a Peterbuilt work horse to pull a ten thousand gallon tank of fuel to deliver to my holding tanks at the office/shop, now I tend to use a International straight job to deliver fuel to my customers, now when I want to go pick up parts at the supplier I use my Dodge pickup, when I get home I jump in the wifes Aveo to go get a loaf of bread a quart of milk and pick the kids up from practice. Now on sunday I love taking a long drive through the mountains do I take the Peterbuilt?? Na I jump on the old Harley and take a tour why because I modulate down to save fuel depending on the task at hand no just think of the fuel you will save when ridding that Harley rather than that Peterbuilt through the mountains spring and fall each and every year.

Xc8p2dC_2

Green earth

It's not just the fuel savings that helps the enviorment, the higher efficiency, creates less pollution and cleaner air to breathe... You can brag to your friends your doing your part

JIMBO_2

I guess it's just \"old School\" thinking

I was thinking that the volumn of water that needed to keep moving to these large rads would work the butt off this lil' Ultra. I was also wondering just how long a life I could anticipate from the little darling? The WM in the basement has lived down there for 50 years now, granted it's a very hungry beast. But what is the average lifespan of an Ultra?

Plumdog_2

modulation

Good thinking. I would like to modulate all the way down to a Vespa with a basket on the back for loaves of bread. Remember Dumb and Dumber when they got that scooter and rode it all the way to Aspen? "This Hog gets 90 miles to the gallon"!

subcooler

Lifespan

Nobody will want to tell you 5 to 10 years if you lucky.
But 5 to 10 is probably about it.

Mike T., Swampeast MO

More like "mid-school" thinking. Cast iron rads don't need much flow volume. They worked just fine with nothing but gravity. Old-schoolers knew this.

joel_19

??

Why would you run the boiler at 180 all the time it should only run that hot when it's 0.

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

Ragu_5

Jimbo...

I'm a little slow. What's a CGs3? Thanks.

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

Ron Schroeder

Ragu

Its a W/M direct vent CI gas boiler

ABD

I don't understand the statement "even when it is not condensing it is modulating". The way my condensing/modulating boiler (with outdoor reset) works is, if the return is at least 20F colder than the supply, it runs full blast. Then when the return catches up and is less than 20F below the supply (which will happen when there is outdoor reset) then it throttles back.

So if the supply target temperature is 180F and the boiler is correctly sized, then it can never modulate. During ramp-up, of course it needs to run full blast. But when it hits 180F, it still needs to run full blast because otherwise it won't be able to hold 180F.

So the only non-reset non-condensing boilers than benefit from modulation are those that have been oversized. And the solution is simple, just don't oversize them! (But match them to the radiation, not to the heat loss, if there is excess radiation...otherwise it'll never get to 180F.)

J.C.A._3

D.Hastert,

2 words brother. CONTROL SRTADEGY.

Boilers are dumb, they need to be told what to do...If you don't tell them, they don't know.The magic lies therein.

What is this "Magic 180°" that you speak of? As far as I know, the radiation is USUALLY the oversized culprit. 180 isn't needed except on/in extreme conditions....especially with high and mid-mass radiation.

If a boiler don't have to run at 180°, why try to force it? Let the computer pick the right temp. for it...If it's either too high or too low, it will decide, and adjust accordingly.(the magic therein...if it's programed correctly.) Chris

Leo G_99

Jimbo

I'm still of the opinion, that a good cast/steel boiler with proper tekmar type controls, is almost as good as the mod/cons. Where they have them beat, is the longevity of the product. Don't forget, every time we replace one of these mod/cons, there has been a hell of a lot of pollution created in the mining, refining, building, shipping etc.

Do they save energy? Of course. But i have still to see a study comparing a mod/con with a properly ODR controlled, "old-fashioned" boiler. I tend to think that they don't save as much as the people pushing them would have you believe!

Leo G

D107

interesting question

From someone seriously looking at mod cons for my home:
Certainly Chris has to be correct about control strategy: I've heard it said that the highest water temp required might very well be 140-150 on a design day if someone programs the heating curve to do that.

But is there any truth to the other post about the boiler going at its highest firing rate once the Delta T hits 20 degrees? How many mod cons have sensors on the returns? How does the boiler (or control) choose the firing rate? The good mod cons can modulate in very small increments. Full firing rate is sometimes activated by a call for hot water. But if supply water is 140 let's say and return hits 120, if there's a call for heat and the control says the supply temp needs to be 145, why should it ramp up to full firing rate? Maybe after night setback but with constant circulation and not too big a setback, it's possible that the boiler would rarely fire at even near full firing rate. Yes?

David

Ron Schroeder

David

Basicly the boiler output is rated to the coldest day of the year that is the amout of BTUs you will need to heat the house on that day, the rest of the year, you will need fewer BTUs. An outdoor sensor is usually used too tell the burner how many BTUs are needed the rest of the time. As temps warm up outside the burner ramps down inside for the BTU load.

When its say 50 outside you do not need 180* water to heat with so you will have cooler water circulating with a small flme and if the return temps drop below 140* or so you start condensing and you will get more BTUs from the condencing process that will be put back into the heating system.
Now the mre excess radiation you have the cooler the water can be to heat the home so during the off season you get even more payback.

Its not just the heat curve but heat curve vs excess radiation to use cooler water. However worse case should be 180* design day and remember the coldest day of year only happens one time each year.

Dave Yates (GrandPAH)_1

It depends

First of all, you're ideally suited for a modcon with the cast iron rads and radiation.

Is a modcon a good or great fit? Depends.

You can't really make that determination unitil you've had an accurate heat loss calc performed. And that's just the first step and you still won't know.

The second and all important step will be a room-by-room comparison to the heat loss vs the heat emitter's capacity - in other words, is that cast iron oversized, marginally sized or slightly undersized. Chances are it's oversized and if you've done things like install newer windows or added insulation over the years, it's definately oversized. Thre key for operating a modcon at its best thermal operating efficiency will be knowing the numbers and setting the Ultra's operating perameters to run within the boundaries. The Ultra can achieve efficiencies of 99% (according to their local representative Ed Sanders from last night's meeting) and from my own personal experience with modcons and older systems with cast iron rads/BB is that you'll be operating in condensing mode for more than 70% of the year while enjoying greater comfort and much better fuel economy. No doubt more than enough to justify the added expense.

The Ultra comes with a 15-year warranty and costs one heck of a lot less than a car. Kind of like trading in a nash rambler for a hybrid. You'll be reducing pollution - even if you take into account the manufacturing process.

But, in the end, you must decide. Pay Weil and your installer a bit more just once or continue to fatten the wallets of the energy moguls - year after year after year after..........................

In my mind, it doesn't matter whose modcon gets installed so long as your contractor understands the technology and sets up the unit with a certified combustion analyzer. Just do it!

Example: I just finished another retrofit application quote in a three-story large row home with cast iron rads and BB. The ROI (return on investment) for this property for the additional costs came in at 23% and that was while using very conservative fuel savings between the modcon and standard boiler efficiencies. The owners will be receiving quotes for both types of boilers and will get the information behind my calculations to help them decide. It's their money & their decision to make once given the facts. We'll install whichever one they feel best fits their budget.

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

John Ketterman

> How many mod cons have sensors on the

> returns?


Most of them.

> if supply water is 140 let's say and return hits

> 120, if there's a call for heat and the control

> says the supply temp needs to be 145, why should

> it ramp up to full firing rate?


Every setup is different, but let's assume P/S piping with a boiler loop pump such that at full fire, delta-T across the boiler is 20F. In other words, say you have a 100,000BTU boiler, and a boiler loop pump that pushes 10gpm.

The boiler sees that the return water is now 120F (your example). Incidentally, if the boiler is off, there is no difference between supply and return at the boiler, the return is just going through the boiler and coming out at the supply. Anyway, if there is now a heat call, it has to run full blast just to heat the water to 140F. It cannot heat the water immediately to 145F (your example). So it has no reason not to run full blast; if it modulates, the water might never reach 145F. Only when the water starts coming back warmer than 125F, which might take a while, would it need to modulate.

Now Viessmans and other fancy boiler might have more complicated strategies, but that requires more sensors and more information. The basic strategy of "do not modulate until the return water is within x degrees of the target temperature" works well.

Mark Hunt

Also


most will fire off at a lower input and "wait and watch" the return water temp before modulating up.

If the lower firing rate is capable of reaching the design water temp, the boiler stays in low fire.

I spoke to a customer this week that is extremely pleased with the savings he has realized since we installed his mod/con boiler.(On a HWBB system I might add) The way he figures it, he is getting an 8.5% return on his investment. Where can you get a return like that?

Mark H

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

jp_2

j cricket,

the viesman measures temp on the supply not the return.

i wouldn't be surpirse if most modcons only measure supply.

boilers only real interest in supply temp.

if you measure return you must also measure supply. a lot simpler than mesuring return, then guess at flow rate, guess at pump gpm then calculate supply temp.

D107

choosing boiler:where in modulation range should heat loss fall?

So let's say the Buderus GB-142/24 modulation firing rate range is 84.8mbh and DOE gross output --varies depending on supply temps--somewhere between 22.7 and 75.2mbh, which net IBR probably somewhere between 20 - 65mbh. (temp range 176/140deg)

So assuming heat loss calc is correct, seems like best match ideally would be a house with heat loss of the highest net ibr. 65mbh so modulation could ramp down the most. 40mbh heat loss wouldn't be terrible either I guess. I see that the Knight and Ultra have lower firing rates available, as does the Munchkin. Wish Buderus could go a notch lower.

Thanks,

David

Mark Hunt

JP


The Munchkin, Prestige and Buderus GB measure both as does the Vitodens.

You are correct, you have to measure both.

The delta T determines what the boiler should do i.e. fire up or down.

Mark H

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

Mike T., Swampeast MO

I have certainly studied the difference between a condensing/modulating boiler (Vitodens 6-24) and an "old fashioned" boiler (Weil McLain CGM-6).

"Proper" for the W/M might be relative however... Boiler was typically oversized (not quite 2x by HVAC-Calc loss). 100 mbh loss; 168 mbh output for W/M, 81 mbh output for Vitodens. Both boilers driving a fully TRVd, gravity conversion system with standing iron radiators.

Reset for the W/M was mechanical. White-Rogers with both slope and offset adjustments. Did not concern myself with the possibility of condensation and used full reset. Did however "dial in" a significant amount of system bypass on the differential pressure valve. Warm-weather shutdown killed the system between 50°-55°F. Reset curve (0.8 slope) hit 141° @ 8° outside. No sign of condensation problems in the boiler or metal flue connection to old unlined brick chimney. System actually ran WARMER than before the TRVs, constant and constant circulation when the entire house was controlled by a single wall thermostat.

For first season with the Vitodens, I operated it at the same reset curve. Other than the ±10° firing of the W/M around the reset target, operation was virtually identical. Only other difference was warm-weather shutdown. With curve shift, I had to resort to devious measures to get the Vitodens to completely shut down in the same conditions (used the WWSD control to put the Vitodens into reduced temp mode and it was a few months before I figured out how...)

Fuel savings: About 43% (weather adjusted). Setback recovery: nearly identical.

For the 2nd season of the Vitodens I experimented with minimal space temperatures for the entire season and optimized the reset curve such that raising space temperature via the TRVs was nearly impossible. Another 7% savings (outdoor temp and space temp adjusted) compared to the first season with the Vitodens.

The fuel savings are VERY real!!!!!

J.C.A._3

But Mark...

"We've ALWAYS done things this way"...

I'm getting tired of hearing that crap. It DID work....but much harder than it ever had to!!!!

Modulating a fire is the best thing that ever happened to heating.We should embrace and accept the technology, but more importantly, we need to be EDUCATED in the ways.

BTW, subcooler...if these babies are only going to last 5 to 10 years, why are the companies warrantying them for up to 15 years? Get that bug out of your shorts and give in. This IS the future. If you refuse to LEARN anything about it, watch my dust because that's all you'll be seeing . BTW, coming soon,in OIL ! Chris

Mike T., Swampeast MO

If the Vitodens measures return temp, it's neither illustrated in the block schematic nor can I find any "extra" wires or any sensor. The Comfortol™ has an input for return temp, but it's always blank on my 6-24.

Mike T., Swampeast MO

Leo: Are you actually replacing mod-cons? If so, can you please detail the failures to include any problems with the installation?

They're certainly more complex. I also suspect that the high-grade materials used for the heat exchangers take significantly more energy to produce than basic cast iron. Of course the HXs in the mod-cons weigh a lots less...

While I've only used one mod-con (the Vitodens) I've carefully studied ALL literature available on the web for many. NONE I've studied seem particularly difficult to install. Depending on the system involved, they can actually be MUCH easier!

Old habits are however hard to change. Here in the US where hydronics have a small (and unfortunately diminishing) market share there [seems] to be a definite problem with engineers/installers truly competent to use these boilers.

For the life of me I can't understand why TRVs and FHVs are not standard equipment with new installations using mod-cons. I see BEAUTIFUL installations with many zones and many circulators with check valves and temperature gauges galore all controlled by a brain that tries to emulate TRVs/FHVs!!! TRVs and FHVs can eliminate near all of this added complexity while providing superior comfort.

Leo G_99

Mike

THANK-YOU for the real life comparison. I know it is only one experience where it was done in as much of a scientific way as possible with your conditions. But at least it is something. I have not replaced a mod/con yet, but they have only become very popular in my area in the last 2-3 years.

I agree, that in most cases they are not anymore difficult to install. It just seems in my experience, that I have more "service" issues with the ones I have installed (yes as per factory instructions), which I guess could be a good thing for my bottom line eventually! LOL!!

My biggest concern is not the technology or science of this product, but the length of time for service. I still feel that I am not representing my clients interest if I do not lay out the full story. And why do we have to get into a throw-away mindset with boilers? Are not cell phones damaging our enviroment enough as it is?

Leo G

Mike T., Swampeast MO

Yes, just one experince. And yes, I agonized about the VERY concerns you voice regarding reliability and "life cycle" costs.

But I refuse to believe that my experience is anywhere near unique. The only thing that makes it somewhat unusual is the TRVs.

Granted the TRVs certainly do contribute to efficiency, but NOTHING like the difference between the traditional boiler and the Vitodens!!!!!!!

The TRVs made it relatively easy for me to make reasonably valid comparisons regardless of indoor or outdoor conditions. Without them, I'd be in the dark and could NEVER calculate AND VERIFY these numbers via every check I can consider. If anything, I'm being conservative!!!!

Steve Ebels_3

Read this JIMBO

I posted this on another thread here but I'll throw it up here too in case you haven't seen it. It's a letter from a customer who had a Vitodens installed in his house (actually 6 apartments) and was originally sent to the installing contractor. I've blanked out the names of all involved to protect anonimity. Read it and see if this guy thinks a modern boiler with modern controls was worth his money. AFA life expectancy goes on a Vito, I wouldn't have a problem looking someone in the eye and telling them 20 years provided it's properly taken care of annually.


Dear /////

"I would like to take a moment to thank you for the fine work you did replacing the boiler system at my home. As you know, my house is 8500 SF and composes 6 apartment units and complex systems of piping. The Vitodens Boiler and indirect domestic hot water tank has been working excellent since you installed the system 1 year ago.

As I studied architecture and building performance at UC Berkeley, I was well aware of how inefficient and ill-installed my previous heating system was. I interviewed almost a dozen heating contractors before I chose your company, as I am very concerned with energy efficiency and long term lifecycle costs. Your knowledge about heating systems impressed me and you were given the contract.

You were able to replace not only the boiler and hot water tank, but improve the efficiency of the piping, pumps, and computerized controls as well. All together, the system you installed made my home much, much warmer than previous years, but also reduced my utility bills by HALF. And that includes the fact that the cost of natural gas was about 30-40% higher last year than previous years.

My home is an income producing apartment building and thus I have maintained accurate records of all expenses for tax purposes. In 2002-2003, my property spent $17,578 on utilities, most of which is always heating fuel. In 2003-2004, it cost $16,789 for utilities. In 2004-2005, after much added insulation and new storm windows, it cost $14,692 for utilities. In the past 12 months, since your work, I have spent only $7830 on utilities. I am simply amazed.

And now, as winter approaches again and many landlords will be worried about outrageous utility bills, I sit back relaxed, knowing that my house/income property will be toasty warm and extremely efficient to heat." Thank you ///!

The installation was in the Rochester NY area.

Mad Dog_2

You are correct on every point Mike.......................

But in most homes the folks don't want the extra expense and aesthetic changes that TRVs can generate...I know its silly. Mad Dog

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

Mad Dog_2

6 month CDs at Commerce Bank are only getting......

5%...........Mad Dog

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

JIMBO_2

Thanks

Thank you all, it has been very informative and educational. If all goes well, I will go with the Ultra-80 this week. However, I have encountered an issue with my gas line possibly being too small, at 3/4 inches. It runs about 30 feet from the meter, then it serves the hot water heater, the stove, and the clothes dryer . . . and now I am adding a conmod boiler. I guess I'll need to up-size the gas line to 1". What do you think?

S Ebels

My reference book says

(for natural gas) With gas @ .60 specific gravity, pressure of .5 PSIG and a pressure drop of .5 WC" you can carry 200,000 btu's. You have a dryer, 30K, stove up to 45K, water heater 35K and the boiler @ 80K for a rough total of 190K.

Put's you right about at maximum flow before you begin to seriously drop incoming pressure. In my book natural gas should be 1" minimum with 3/4" for LP.

PS: If you're on LP, which is delivered at a higher pressure, your 3/4" will carry a little over 300K btu which is plenty.

Tony_23

Careful

NG in my area is typically supplied at 7" wc. That's .25 PSI. I'd run the 1", then again I'd install a Gold Plus 30 also

JIMBO_2

It's getting complex, it is

This particular house is on Staten Island, NYC. It's a funny thing, though. There are new houses up the street from me, and the supply to the meter is only 3/4" From the meter into the houses seem to vary, some are 1-1/4" and a few look to be 1-1/2" The 3/4" coming off the street main, to the meter, is feeding the larger piping. It seems awfully odd, if the meter's supply is only 3/4" how would the owner adequately supply enough gas to today's fancy gas appliances?

Tony_23

Street PSI

Around here can run from 2 - 40 PSI. More pressure = smaller pipe. Appliances run at 5-14 inches of water column (wc). There are roughly 28" in a pound.

S Ebels

Around here

The ancient gas service from the street to my house is 3/8" type K tubing. Been in the ground about 45 years now and about once a summer you'll see the utility compnay trucks replacing one that corroded through. They do this with heavy wall PE pipe now. Usually 3/4" diameter. The street pressure here runs 40-50 PSI.

Just for comparison sake, 100' of 1" pipe will cary almost 9 MILLION btu's @ 50 PSI. Don't worry about the high pressure side of the system.

hot_rod

mod con failures

will be directly related to the installation, in my opinion.

Improperly piped without PS or adequate flow, to prevent hot spots in the hx, will be th issue.

But remember the failure of cast iron boilers, expansion tanks, sludged circ volutes, dissolved steel radiant headers, etc? All caused by the use of non barrier tube in ther late 80's and early 90's.

This, at first sighting, was blamed on the manufactures!

Properly installed and cared for I expect a 15 yeat + life.

hot rod

JIMBO_2

Thanks . . . I think indirect DHW will do it

After reading all the advice, I think I will opt for adding an indirect tank to the new Ultra to avoid repiping the gas line, that way I will save the BTUs that the 40-gal hot water heater pulled from the gas line. It will probably be more efficient that the stand alone heater anyway. This way, the 3/4" gas line "should" be able to handle the stove, clothes dries and Ultra-80. Yes? But, i wonder if the take-off placement of the tees that feed the other appliances makes a big difference? As it presently stands, the new boiler is last off the run. Perhaps it should be first?