Give U.S. smaller Mod-Cons!

Constantin

.... perhaps you're misreading the Viessmann literature, but the firing rate of the 6-24 is considerably lower than 200MBH... (<a href="http://www.viessmann-us.com/web/canada/ca_publish.nsf/Content/Vitodens200-DataChart_ca_english">see Viessmann</a>). 6-24's modulate roughly 22-81MBH (DoE output), which still makes them much too large for a towel warmer.

I like your electric approach... and agree that it's a better one. One thing I would like to see is a easy-to-install option where bathroom occupancy
<ul><li>starts the bathroom fan (or remote fan)
<li>recircs water as needed
<li>heats towels, if needed</ul>

No one seems to offer such a solution as yet, one has to assemble them using a number of different components, mfgrs, etc. It could be a pretty simple solution, where one board has a number of relay contacts to start recirc, etc.

Mike T., Swampeast MO

I'm currently spending HOURS dealing with three different and VERY well informed homeowners all of whom have REALISTIC maximum heat loss in the 40-60 mbh range.

Mike C_3

Buderus

On the GB142 you can actually set the amount of BTU you need. You can change the percentage so that it dosn't operate at 100%

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Brad White_110

I am with you, Mike-

My heat loss and that of my Susan's is similar, about 1500-1800 SF of floor space, older homes as tight as we can make them. Heat losses of 47,000 to 55,000 at a 0 degree design. Our boiler inputs (actual and going in) range from 94,500 (my Monitor MZ) to Susan's Vitodens at 91,000.

So long as a "boost" can be had for DHW production, (HTP's strategy), or a clearly delineated storage strategy, a 60 MBH input would seem ideal, with modulation down to 12-15 MBH (5:1 or 4:1 turndown.).

Mike C.'s point about the GB-142- does setting that back allow for modulation to the same overall ratio? Or does it just lessen the range and put you closer to the minimum?

Good call, glad you posted this.

Perry_2

To a point - but not low enough; What about...

The GB124 has a minimum firing rate of 22,700 BTU/Hr boiler output (and a maximum of 75,200).

You can adjust it to anything above that - up to 75,200; but cannot get below 22,700 BTU/Hr - which means cycling boiler operation for about 5 months in my application.

What would be almost ideal for many small houses and appartments would be a boiler with a range of 12,000 to 48,000 BTU/Hr.

I know that 4 to 1 turndown can be expensive to achive efficiently. But, even a 3 to 1 turndown line would work well; immagine the usefullness of a line that was set up like this; and set up so that two boilers could be tied together.

10,000 BTU - 30,000 BTU

15,000 BTU - 45,000 BTU

Can't you just see a 2 boiler circuit operating continuously at very high efficiencis from 10,000 - 60,000 BTU/Hr (or 15,000 - 90,000).

Perry

ScottMP

I'll add my name

to that list. I nice little mod-con would suit alot of applications.


Scott

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Darin Cook_5

Consider This

Even the best heatloss program out there is only an "educated guess" so there is alot of "protection" built in to any program for some CYA security. So most boilers even "properly" sized are too big. Most people out there have way too much boiler. If we could get the turndown ratios available in Europe we could fine tune our systems to stay properly sized right up into the WWSD stage. Most guys don't care about this because no customers complain if they are warm.

Think about how even the smallest oil boilers out there can be way oversized. Everyday blasting away at full output. Think we need clean oil and modulating oil. More food for thought.








Darin

hr

Another way to skin that cat

I too would like to see a mod con run 5K to maybe 40K.

Sounds like HTP will offer a modulating Voyager tank style soon. Now that may be better yet as the 50 gallon buffer would allow some real small micro load the ability to sip for an hour or more before firing.

Either match the output exactly to the smallest load, or buffer the correct volume to handle a small draw for a period of time.

Properly built and insulated a sealed combustion tank style should have a very small standby loss. It may be the better of the two options.

I fear keeping a 5K flame safe, clean, and rectifiable could be a challange. Seems like the blower would be spinning some very low rpms to burn that low? Nothing worse than intermitent lockouts caused by wind influences, low flame prove-ability, etc

hot rod

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Tony_23

common problem

For small loads, I use the Ultra 80 which modulates down to 16K, program the max firing rate to match load at DTD and let it roll for DHW on high fire. The bottom end can be programmed higher but not lower.

Currently, I'm experimenting with my own 105 and have lowered the max outlet temp and firing rate for DHW in an attempt to save a little fuel. The "natives" haven't complained yet.

My real problem is when the heatloss rings in at 25-30K at DTD.

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joel_19

HR

i agree with hot Rod a buffer tank may be better. Howevere i wish we could get smaller on oil . I'd like to see oil go to really high pressure or something like a car fuel injector to get reliable low flow rates

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Perry_2

Small boilers.... Where & Sizing of a buffer tank

Actually, keeping a 5K flame stable would not be that hard, and the pump would be running at a normal spead - with a boiler designe for it. an 8:1 turndown would be very hard to do though. Several companies have demonstared 4:1; and it seems everyone can do a 3:1 ratio.

Power plant boilers (20 stories tall) have spent 10's of millions so that they can achieve 5:1 turndown ratios from the original 3:1 turndown ratio (an area I have a background with - as I've seen the retrofit work and dealt with the limitations involved).

So a 5 - 20K boiler would be reasonable. Probably handle a boiler flow of about 2 GPM (give or take) and you may need something like the Viessmann Low Loss Header to connect to the system (unless you had a very small heating need and 1.5 - 2.5 gpm would work). The burner assembly would also be tiny so that it would run on normal oil or gas pressuers. Perhaps a 1" exhaust vent line...

To get an 8:1 turndown would take a 2 boiler combo working together.

My real question is where would you put the buffer tank and how would you size it?

In my case I have a single pipe monoflo T systym. I would think that the buffer tank would be on the system return (the LLH boiler inlet) so that the system could run a while without the boiler seeing a call for more hot water.

How would you size it? 15 minutes of secondary system flow, 30, 60 etc (assuming my secondary system runs at 10 GPM a 1 hour tank would hold 600 GPM).

Or would you completely separate the systems and have a large "hot water heater" for a buffer tank?

Keep in mind that I'm planning on a Vitodens 200 at this stage (Model 6-24).

Perry

Wayco Wayne_2

I've had

good success with the Munchkin T50. It even has a boost on the indirect side of things. I also know that ACV, the company that makes the Prestige MOd Con is looking at smaller boiler capacitys because of super insulation of buildings that is coming to the European market. They are also into electric boilers for smaller loads. WW

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Weezbo

The British have them*~/:)

for what its worth i would like to mention they also have condensing oil fired equipment in the 2K-40KW range.

maybe some WTO trade restrictions need to be lifted by public outcry.
sorry folks that's the instigator in me. got in a group of trouble in high school for that...it is not quite shouting fire in a crowded theater however i have had it flawlessly expounded to me for hours that it is quite similar...:)

Paul Pollets

So???

The 6/24 would work fine. Are you trying to say the minimum modulation of these units should be lower?

There's probably a reason why they don't go lower than 20K.

I'll ask my Viessmann buddies when I have the chance.

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Constantin

Is it that easy?

Perry, what is your background? Have you developed home heating appliances? I guess I am not yet convinced that a 5kBTU/hr input rating is as easy to achieve as you seem to. Also, you can already buy a NTI 400 that has a 16:1 turndown ratio... but like all other boilers, the lowest output so far on the US market is around 12-15kBTU/hr.

Granted, Viessmann and other manufacturers do offer lower-output mod-con heaters elsewhere, but in the US market, the selection seems to be limited.

Anyway, coming back to your question, Siggys program has a nifty module that helps you size buffer tanks. Cheers!

Perry_2

High turndown ratios

While I have not been involve in home appliance size units the issues are the same from a flame stability, air supply, waste gas exhaust, and boiler efficiency standpoint.

It is quite possible to have a burner with a very high turndown ratio (and combinations of burners streach things a lot farther). How efficent can that burner heat a boiler large enough to handle the maximum firing rate is an issue.

How do you properely control air/fuel mixture for a high turndown when all the air supply must be sized for the maximum firing rate.

How do you effectively size exhaust gas piping for a high turndown boiler?

While you can always add a lot of extra mass to the boiler - and have air supplies and gas outlets that can be partially turned off as needed - that is a very large and complex system that usually has poor reliability.

You also tend to loose a lot of efficiency by running a small heat source in a large boiler. Other losses start accumulating.

Pick your size: 10,000 Btu or 10 Million Lb/Steam per hour. Same issues.

To build a small mod-con all that has to occur is for them to downsize the existing burner, HX, and other components approprite to the scale needed - the controls stay the same.

The science field has a number of precission controlled small heat source burners available if the boiler Mfr's are looking for something that is proven to work (down to very small heat outputs).

The question is do the Mfr's see that there is a big enough need to develop and market the product.

I too had noticed that in Euorpe that smaller Mod-Cons were available (but not down to 5K). Why not here in the US? Good question.

Perry

Perry_2

The minimum should go lower

Yes, we are saying that there is a market for boilers with a mimimum firing rate that is lower.


A 6/24 has a minimum boiler output rate of 22,000 Btu/Hr.

That boiler will probably have to operate in cycling mode in my application for 5 to 6 months of the year.

A 3/12 (11,000 Btu/Hr - 40,000+ Btu/Hr would be a much better match). Only problem is - it doesn't exist here in the US.

1st rule of boiler sizing: Don't buy more boiler than you need... You loose efficiency due to boiler cycling. Modulating condensing boilers can have amazing efficiencies - if you can keep them running in their modulation range.

Lots of smaller houses in the US - or modern larger airtight/well insulated houses do not need a 6/24 for maximum efficiency. They need somthing smaller.

Why spend the extra $ for a modulating condensing boiler if it is usually going to work as just a normal boiler?

Perry

Constantin

I have a couple of guesses...

... based on my experiences developing a small outdoor gas boiler. We had no blower to help.... so creating a system with no ΔP no matter what the outdoor conditions (40+MPH winds, corners, etc.) was a challenge.

My guess is that flame stability even with the benefits of variable-speed blowers, high-turndown valves, etc. would be hard to maintain at very low input ratings considering all the different ways that vent terminals get installed. Never mind abusive installations...

hr

A 40K mod con might

dissuade a lot of folks from using cheap, dangerous, throw away water heaters for radiant

At least some of them. Many more as fuel prices continue to rise.

Properly priced a bank of 40K mod cons would be an excellent way to handle a load that varies a low of lets say 8K to 120K as now we would have a wide modulating range and be able to stage the units in and keep them in the best, lowest return tempersture condition.

Plus the redundancy of multiple units and the ability to get some big DHW loads handled quickly.

I would guess a unit that size would almost be palm sized Looking like the small engines used on model airplanes and cars.

Rumor indicate perhaps Lochinvar may have a mini size mod con in the works.

Wouldn't a 1" PVC vent pipe be sweet for retro fits! Jam a handful of those up and old B-vent sleeve Heck 1" PVC may even flex around a couple 45's in an old b vent system.

Maybe use that flexible PVC that is seen in the swimming pool industry. Don't get me started...

hot rod

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Paul Pollets

One of the reasons...

...is that a 40K btu output means very slow recovery rate for any indirect tank attached. No one wants to hear that their tank takes 30min to recover when it could be satisfied in 10. And...do you really think a slightly smaller min modulation will affect pricing?? I really doubt pricing will fall below the cost of a T50. If the boiler has an ASME rating. This type of system design (10-40K Btu's) is why water heaters predominate at the lower end of the market. Some clients would balk at the cost of a small modulating boiler with limited indirect tank recovery rates.

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hr

Aerco has 23-1 turn down

on their larger size. 45K to 909K. As I recall they use solonoids to stage in various modulating gas valve/ burner stages.

I'm not sure that would be cost effective for a 100K boiler. I thing ganging together small units would be a better options for residential sizes.

hot rod

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Gordy_2

Mini Mod Cons

Been observing this thread a while. I like the way you think Hot Rod. Instead of staging the mini mods, why not zone multiple heat sources. Have not put much thought into it, but would probably be talking a smaller heat source yet for each zone depending on loads, Micro Mod Cons. You are the expert. Just thinking out loud.


One other thought is, when does it become cost effective to use multiple boilers to achieve a turndown verses just bearing with what is out there as a single unit.

Gordy

Weezbo

let me ask you a question ,seeing as you are here

Have you had any experience with MIURA boilers?

Brad White_111

Miura

I have specified Miura but as steam generators for a hospital in Connecticut about ten years ago. Quick response but do not have any data, those being done with my former company. Do they make a line of condensing boilers too? I remember them as small-footprint and efficient on steam.

Perry_2

Brad: Question for Viessmann

Brad:

I understand that you at a Viessmann facility recently (and perhaps in Germany). Did anyone ask if Viessmann was going to come out with a smaller Vitoden 200. I note that Viessmann has another model out in Europe in the 4.5 - 16 Kw range (16,500 Btu/Hr to 58,000+ Btu/Hr). That would most likely work a lot better for the smaller houses.

If not, you seem to have some contact -- why don't you ask.

Perry

Brad White_111

Viessmann Warwick RI

I was at Viessmann US HQ the week before last for two days, different classes. It is in Warwick RI which is exactly like Germany, only different.



There is a Vitodens 100 in the works, like the 200 except no internal modulating pump and simpler controls. As I understand it, the objective is a more affordable price point to compete with the market mean for ModCons.

You may well be right about a lesser input version and yes, I can ask. Far more astute and connected minds than I do habit this site, so by all means I would think they would have chimed in by now.

The Vitodens 200 by the way is exactly the same boiler as sold in Europe. The only differences is that they provide a power module for this side of the pond to convert US 120/1/60 Hz. current to the European standard. They are that indentical, taken right off the shelves, and even have the 167 degree F. (75C) temperature limitation required of German boilers.

Perry_2

I figured as much

I had guessed that they were identical except for voltage/frequency and controls in the "F" scales. This is fairly common with a lot of other industrial equipment.

Larger equipment will also come with different motors to match the voltage/frequency of the destination company.

The smaller mod-con was I belive a 300 series. The point being that Viessmann already has a burner/boiler coil for that size. How hard would it be to pair that with the advanced controlls of a 200 series and extending the lower range of the 200 series?

Perry

Perry_2

167 F outlet Temp Limit of Vitodens ? ?

Brad:

Is that a fixed limit; or is it the limit of the outlet of a Low Loss Header if you are using one?

If the boiler has a fixed limit of 167 F, then the LLH outlet temp will have to be lower (and perhaps much lower).

On the other hand... If the limit can be transfered to the LLH outlet (and say a boiler limit of 180 F) - then the LLH is more usefull.

Perry

Cosmo_3

That can be changed Perry

There is a code that will change the limit to a higher value. It is frowned upon however!

I think that like anything else, the big-wigs have to hear the clamour of the masses outside the gate to ever want to change. If there are enough people complaining, and they think there is profit in it, we will get low output boilers....eventually


Cosmo

hr

Should not the goal be

to heat the building with the lowest possible temperature. Therein lies the besauty of radiant floors, walls and ceilings. Probably why panel rads are so common in Europe.

Of course with condensing equipment it's not the supply, but the return temperature that matters for condensing mode. Even a 160 supply with a 30- 40 delta t would keep them in a sweat, where they sing the sweetest.

I'm sure indirects could be reconfigured with more HX surface to supply DHW at lower boiler temperstures also. Isn't this a feature of the Viessmann tanks already?

And of course those lower temperture systems play nicely to solar assist, which should be required on all new residences in my opinion.

hot rod

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Ken_40

Paul

Hey my friend,how are things on the left coast?

The "indirect recovery rate" problem seems to be easily overcome by simply increasing the unit's size by a factor of one.

The increased storage overcomes the "undersized" boiler notion, resulting in far fewer short-cycles and mod-cons will be in the upper capabilities of efficiency with greater frequency.

A good rule of thumb: Size the boiler for the heat load only. Compensate for any potential D/H/W shortcomings with larger storage capacity. The results of this strategy are rather obvious and far too often, overlooked IMO.

Shalom

Ken_40

Actually,

They have one of the most beautiful modulating gas trains I ever saw. A plate with "stepped" notches deals with the entire modulation mechanics, the "harmonics" of air/fuel interlocking linkage - and the designer was none other than Ken Cohen. He did some stuff for Slant Fin and now works for Mestek I believe.

Last I heard, he told me he was messing with ceramic boilers...

Perry_2

You are right; but...

In my case; my existing baseboard cast iron radiators have a tough time keeping up when it gets below zero here.

It appears that I will also have to use a Low Loss Header with a higher secondary flow to match my existing setup.

Now the nice thing is that with the Vicoden there will be a curve that it can follow so that it raises the secondary loop inlet temperature on the coldest days. In order for it to do that it may need to exceed the 167 boiler outlet limit a few days a year.

Of course, I'll wait for it to happen before changing things - in the hopes that the retrofit system works better overall and this never happens.

But, it is nice to know that I could raise the boiler outlet to say 175 which might be all that is needed.

Oh, the "E" in me says the retrofit system will have thermoneters - and perhaps even flow-meters installed so I can tell what is happening.... (unless the Vitoden allows real time data output..).

Perry

ALH_4

167

I have heard of no way in the coding to get the Vitodens to run above 167F. There are possible ways, but it's not in the coding.

Why conserve on everything except hot water? Flow rate, particularly at shower heads, is important. Say it takes 68,750 btu/h to keep up with a 2.5gpm shower head. It then takes 137,500 btu/h to keep up with a 5gpm shower head. How about a series of shower heads and jets? This is a complete assumption on my part but this may be why the 6/24 is the smallest Vitodens available. A smaller model would have their phones ringing off the hook because of customer complaints. It seems to have been a difficult switch for individual contractors to move from traditional cast iron boilers to these modulating condensing boilers. How bad would it be if there were people trying to heat 50 gallon indirects with a 40 MBH condensing boiler? People confuse temperature with heat so often that it may be wise for the manufacturers to wait a while. What is the mandatory training for someone to install residential boilers in the US nationwide? I can only imagine the types of calls and botched installations they have to try to salvage. We've seen many examples here on the wall.

-Andrew

Josh_10

Actually he recently designed the KN10 which is a condensing cast iron sectional boiler for commercial use.

The Aerco KC-1000 is the boiler you are referring to Hot Rod. The air fuel valve as it is called uses a stepper motor with a shaft that turns both air and fuel at the same time. As Ken said their are characterized notches for the fuel side and a butterfly valve for the air side.

I love Aerco's. I had the distinct pleasure of working for the rep. I have probly started up over 100 of them. They are simply the finest commercial mod/con out there. I also love the new C-More control system. It will allow any control variation possible.

I second the notion of smaller mod/cons though. Here in Western Washington it is very common to have a heat loss of 15 BTU per square foot. Add that up and you have a really good use for a 40,000 BTU boiler with a decent 5:1 turndown. I could sell atleast 1 per month.

P.S. Not sure if this is top secret but Aerco recently purchased an italian mod/con line that produces smaller boilers. I don't think they go smaller than 100,000 on the high fire though.





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Ken_40

Boiler size

is interesting.

Indirect storage capacity - is everything.

With proper design, a 40,000 BTU boiler could bath a family of 50!

True, the indirect would have to the size of Manhattan, but in normal conditions, we should never size a boiler based on anything but the heat load.

Mike T., Swampeast MO

As far as I know that 167°F (75°C) is ABSOLUTE when it comes to weather-responsive operation as it is mandated by law in the country of origin. Use of the LLH might allow higher boiler temperatures--if so, it's certainly not documented.

Based on the information you provided you'll NEVER need temperatures above that level unless you let the place get really cool in exceptionally cold weather and expect it to heat to "normal" in a hour or so.

Do realize however that during such a recovery that return temperature will be significantly lower than if the system is merely maintaining space temperature.

Mike T., Swampeast MO

Perry:

With 99' of cast iron baseboard and a design loss of 30-40 mbh, I cannot believe that they have a "tough time keeping up" in any possible weather conditions.

Do you really mean that they have a tough time recovering from deep setback in below zero weather???

Perry_2

Perhaps its a limitation of my current circulator

No one really knows what the flow really is: It could be anything greater than 5 GPM to a lot.

If it is low, and I have reason to believe that it is at least 10 or below based on some modeling I've done - then perhaps the reason that the baseboard is not keeping up in the cold is the low flow. If it were at 7 GPM then the there would be about 34.5 KBtu/hr limit. According to the pump curve the series 100 pump deadheads at about 8 Ft. That is not much. I should try to build a model of piping and monoflo resistance (head) to see where it probably is.

Me thinks that perhaps I should try and put in a flowmeter into my existing system and see what the flow currently is; at the start of the change. It might answer a lot of questions.

That might be another reason to change secondary circulating pumps.

Perry

Tony_23

Could also be

your limit temp. Didn't you state before that you had your limit at 150 ?

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hr

But a typical hot water tank is 37K

input, both 40 and 50 gallon tanks. Wouldn't a 40K mod con perform better than that considering 75% efficiencies of tank type gas or LP heaters.

Standby loss would be a lot less, and if the manufactures followed the HTP method where their 50K mod con boosts to 80K for DHW mode, that should be plenty.

I think it's time we start training consumers to "get along" with 40- 50 gallons of DHW. Time was when a 50 gallon was a large domestic tank. Seems the more we provide the more folks will squander. Like cheap oil

hot rod

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