Mod-Con Boiler and system questions???

steamfitter

Just curious!
In general, what is the range of EWT and LWT on hot water system design using Mod-Con Boilers? If you have radiant heat, I'm thinking the temps should be much lower than, let's say fintube radiation. Does that mean that the Mod-Con Boiler is less efficient for a traditional one-pipe or two-pipe hot water heating system as compared to radiant heating?
What I'm getting to, is, at what point does a home owner, contractor or engineer determine that a Mod-Con boiler retrofit to an older piping system worth the expense of installation?

Does a proposed retrofit require extra fintube (BTU's) or larger fintube, in order to run an updated system that may operate at lower temps to maximize condensing in the secondary heat exchanger?

A number of years ago, I had worked in NYC on a couple of new hotels that used a small bank of Mod-Con boilers and a new piping system with fan coil units in hotel rooms and cabinet unit heaters in the hallways and stairwells, but I did not have the opportunity to spend much time in the boiler room.

I am intrigued by the whole Mod-Con Boiler movement, but am curious as to how commercial and home conversions are holding up. Are they successful? I'm certain that good, reputable contractors, who know what they're doing, have success in converting an old system and eventually saving the owner money on fuel costs, but at what expense to them. Are they frustrated with call backs and problems which they did not predict? I hope I'm not crossing the line here with our rule of not discussing pricing. It is only in a general sense regarding the use of fairly new technology and their costs and savings for which I am discussing. I realize that this stuff is not that new, as we in America tend to move very slowly with technological change in some industries. I understand the UK has a law that does not allow the manufacturing of any conventional, non-condensing boiler. That's very interesting!

On that note, does anyone know a little history about Mod-Con?, or specifically the condensing boiler idea? Where and when did this amazing idea of condensing flue gases to extract latent heat for the (entering) hot water return begin? Who had the light bulb go off? History is so great!

Much thanks and gratitude!
Manny

njtommy

Pandora's box has now been opened.

Older piping is a problem. It's old and nasty followed by its going to dirty up the new boiler especially if it's tankless. All those things have to be addressed and need to accounted for even if you install new CI boiler

hot_rod

Heating systems are very dynamic, or ideally they should be allowed to be.

We agree the load is constantly changing on the system, as weather, occupancy load, doors open and close etc. It happened second by second.

So the goal would by, or should be, to have the heating system adjust to those ever changing conditions.

The debate becomes how best to do that.

Modulating the temperature to the heat emitters is one part, out door reset would be one way. ODR with indoor input, even better as occupant loads, cooking, etc will change the load regardless of outdoor conditions.

Anticipate and adjusting based on incoming weather is another, new wi-fi stats can do that by monitoring weather channels.

Changing the flow rate is another way, but trickier to manage as you need certain flow rates to allow turbulent flow to work for you. Boilers may have minimun flow rates also. When flow drops too low heat transfer drops quickly the loop or circuit output plunges, and the end of the loops or zones will not do much or any work.

We know hot goes to cold, 2nd law of thermodynamics, we also know the wider the delta T between the two the greater the heat transfer. So take it from there.

We are all still searching for the perfect mix of the above, burner modulation, boiler pump modulation based on firing rate, matching the input to the system with distribution temperature and flow is also part of the challenge.

Always remember BTUs can and do jump off trains, even fast moving ones. Finding the best "speed" without sacrificing the best efficiency possible is what we want. Burner efficiency, distribution efficiency and overall system efficiency are all pieces.

Without trading occupant comfort, of course. Since we need to sell and service these systems.

Reminds me of this slide that Robert Bean showed in a training recently, thanks to AR&T architects, visit their website, great work.
I'd argue we are still build systems as shown in the middle example.

I suspect homeowners would view complicated systems the same way as the architects.

steamfitter

Thank you!
Insightful! I will check out that architect's website. Love that evolution of heating system.

steamfitter

Hattersaguy-
Your explanations and examples are great and help me to better understand the nature and challenges of mod-con boilers.
I guess the real benefits are mainly with radiant.

hot_rod

Certainly low temperature radiant would be ideal, but depending on your climate, even systems requiring 180° on design day may benefit from condensing equipment.

First a heat load for the building, room by room. Measure the heat emitters. Are they sized close to the load? If they are oversized, or the building envelop has been upgraded, better yet.

Find the weather data for your location. Online find the temperature history, see how many days are below condition and how the temperature looks throughout the heating season. Sometimes called "hours of occurrence". NOAA and other sites have this data as a free download. You may need to register to get deep data. Local weather stations may have it, google around.

Then plot the temperatures need at the various days. With ODR you may find you can operate in condensing mode for much of the heating season.

Here is an example for Boston with 160 and 180F design temperatures.

Run a wide ∆T, no need to run a 20° as long as you cover the load. The colder the return and the wider the ∆, the better for condensing. The colder the return the more condensing potential.

Not all boiler heat exchangers are created equal, follow the manufacturers direction for flow rates and operating deltas.

Counterflow HX designs are best, get the coldest return near the hottest point for best boiler efficiency.

Here is a link to a good webinar on applying mod cons properly.


https://www.youtube.com/watch?

v=6mNECDHgDrg&list=PLuuV0ELkYb5VE0I4evUZ30b5U78CRlRdg&index=10

Pete Caruso is who I give a lot of credit for bring condensing equipment to our attention. He introduced us to the Monitor MZ. While not a modulating boiler, per say, it did show us the advantages of condensing.

Dave Davis and team at HTP pioneered the mod con product with the early Munchkins, from what I remember. The Sermeta/ Gianomni (sp) from France, heat exchanger has been around probably 20 years not, still very popular here and abroad.
www.sermeta.com A good video there.

You think high 90% is good, this video claims 110%

jonny88

Once I get into winter and my boiler is looking for say 160 water the primary loop on my boiler is hot.160 coming out and the return actually matches it,that is the return on the primary loop.Now when a zone calls 160 leaves my tees and goes to zone returning at about 140.The return goes back into my primary loop where it mixes with 160 water and will therefore not condense.I have BB in house.My response is both a ? and an answer just to make sure I am getting this right.On a fully radiant system however I do believe you can get the efficiencies that are stated.

Gordy

Being a steam guy you probably do not see what happens mostly around here with the whole mod/con homeowner situation. View some threads. Much to pick up. The systems end up being much more than just installing a HE boiler to try to get the most efficiency it can give. As @Rich so elegantly put it. The industry is giving us turds with rags to polish them. It's an umbrella statement that has some merit.

Gordy

Gordy said:
The systems end up being much more than just installing a HE boiler to try to get the most efficiency it can give.

Instead of just a boiler.......you need a bunch of rags to TRY and keep it polished.

All though there are some ( very few) that would find the complex aethstetics pleasing see middle picture in above post.

Most homeowners would be afraid of such complexities.

jonny88

I am so close to getting a sawzall.............I am going to actually when I get a chance take a video of boiler in operation.The way I see it if you have radiant its a homerun or large CI rads.Baseboard and modcons should not be in the same sentence ?am I of the mark.
That is with the exception of the UFT

NYplumber

There is no short answer. Years ago people said stay away from the cars with computers.today we all drive them.

I have built both mod-con systems and cast iron systems that were extremely efficient and cut customers bills. Installed modcons in high temp applications and cast iron boilers in medium and low temp. How you deal with short cycling, how you deal with when the boiler turns on, how you set temperature is all relevant.

Mod cons save money with less thought. You dont have to worry about condensate on the hx. Less issues with run time because they modulate. They cost more to repair. Are more sensative to electric and gas inputs. There are more parts to go bad. Cast iron boilers have their pros and cons too.

It comes down to the application and the customer.
In a residential setting 3000sqft and under, non radiant system, I will tell you upfront, if your counting pennies over a 20 year span, the cast iron done right will most likely cost less after you factor in one big repair and the yearly maintenance. (Yes yes i know everything needs yearly maintenance however cast iron is more forgiving.) I service alot of equipment and always ask for the bills. Just my $0.02.

NYplumber

@jonny88 baseboard and nod cons work just fine. My buddy had a $45 gas bill last month running 70 degrees day and night (tt boiler set up correctly ). A local cuatomer within a 5min drive had a $200+ bill and they are only heating half the house. Same construction same sq ft.

Gordy

I'm always cautious on who, and how the savings are calculated. Most times the noted savings is more the old oversized boiler to a boiler of correct size..........if that even happens. Or cheaper fuel switch at time of install.

hot_rod

Gordy said:

I'm always cautious on who, and how the savings are calculated. Most times the noted savings is more the old oversized boiler to a boiler of correct size..........if that even happens. Or cheaper fuel switch at time of install.

Some of the questions and unknown will take time to answer and discover. Talk about ROI not just fuel savings. If the boiler requires expensive repairs, or the HX dissolves from condensate within 5 years or less, did the fuel savings and high efficiency even matter?

Gordy

Yes ROI can be quite lengthy.

Rich_49

Steamfitter .

There are no magic circs , no magic boilers , no magic components . There is only proper system design , and the proper understanding of heat and that force only needs be exerted when it is necessary .

There is a misconception that flows must be turbulent , water must be hot for baseboard , designed for Delta T is for the design day . This is all perpetuated by a certain few who have been and continue to take advantage of ignorance for their own financial gain . I am not quite sure they actually understand because if they did it would suggest devious or nefarious behavior . Ignorance is reparable , stupidity and greed are not .

Boilers that are efficient have long been a complicated thing that requires great attention . There are many things going on in a system , and there are many manufacturers who peddle their wares to address these things and train people on why they are needed , when to use them and how to select them . Unfortunately for many , some guys were paying close attention and do not just tow the party line because they have never received compensation and actually took the time to listen and understand what was being said .

In the past few years some products have been developed that exposed some very inconvenient facts about what we have been told in the past . These newer products will change the name of the game and allow us to compete while doing an even better job than we have been doing .

In short , flow needs to be what it needs to be , temp is similar , emitters of any kind can be used in design as long as attention is paid water temps , series stuff should disappear , mass should be used to our advantage . If we remember that most of the testing and rating of this stuff has been done to older standards and expectations we can make this stuff what they have been telling us it is . The only caveat to them is it will require much less of their wares , from here forward we can really start to grow .

Baseboard that is existing does very often lend itself well to using modulating / condensing technology , not always , but often . Teaching or shall I say unteaching will make this better understood industry wide . This re education or clarification of the common mis conceptions being highlighted will grow the industry .

I suggest watching the entire Coffee w/ Caleffi episode Hot Rod linked to , It is very interesting and although some may disagree , Jody did a fantastic job . Listen carefully to what he said throughout the entire presentation .

This is certainly gonna get interesting ! Can of worms at present but don't be surprised if it turns out to be a can of SNAKES .

hot_rod

I agree with most of what Rich noted .

except this:
There is a misconception that flows must be turbulent , water must be hot for baseboard , designed for Delta T is for the design day . This is all perpetuated by a certain few who have been and continue to take advantage of ignorance for their own financial gain .

Flow does not NEED to be turbulent. But if you are chasing ultimate system and heat transfer efficiency, which it seems we all are, then turbulent flow is your friend and should be embraced, at the very least understood.

Rich_49

Efficiency should happen through all conditions Bob and sometimes turbulent flow is not necessary .
Amazingly , Bob said
" Run a wide ∆T, no need to run a 20° as long as you cover the load. The colder the return and the wider the ∆, the better for condensing. The colder the return the more condensing potential. "
Seems it changes from day to day . Check out the 2 slabs , simple question was , " which delivered more heat ?"

Let's just call it what it is . Many have no idea what is going on in their systems from one moment to the next and then there's the few dozen of us that do . Look at the big boy stuff from the other thread , A Taco question , Main Wall .
Sorry no pictures , only for those who know how to read and comprehend .

jonny88

When I did my conversion I got savings up to 70per cent.Thats great.My new boiler has had zero maintenance done to it but is running great.A ? which a few might be stuck on.When a mod con is condensing it is reaching close to optimum efficiency?Please explain in non engineer talk as Dan does how important this is.Just because it is running on 30kbtu does not mean you are getting the 95% eff which manufacturers are stating.Last week my boiler condensed about 12 gallons but I put that down to Odr .Thanks.

jonny88

Again I will take a short vid so it can be seen through your own eyes

Rich_49

This is interesting also . Same room , same condition , same EWT , different Deltas . Heat loss is included so we know that they are alike .

Gordy

Rich said:

Efficiency should happen through all conditions Bob and sometimes turbulent flow is not necessary .
Amazingly , Bob said
" Run a wide ∆T, no need to run a 20° as long as you cover the load. The colder the return and the wider the ∆, the better for condensing. The colder the return the more condensing potential. "
Seems it changes from day to day . Check out the 2 slabs , simple question was , " which delivered more heat ?"

Let's just call it what it is . Many have no idea what is going on in their systems from one moment to the next and then there's the few dozen of us that do . Look at the big boy stuff from the other thread , A Taco question , Main Wall .
Sorry no pictures , only for those who know how to read and comprehend .

Maybe Bob is talking P/S.
System side must be equal to or greater than boiler side. Pretty hard to achieve in all conditions some where an efficiency suffers depends. We are learning quite different.

jonny88

@JohnNY ,@Maddog and all other designers what is your take.So far only a handful will give input.The brightest in the business and there is no answer everyone can agree on.Is it s case of it depends or my way I'd better than your way.IfEurope is 20 yrs ahead should the kinks not be ironed out already

hot_rod

Rich said:

Efficiency should happen through all conditions Bob and sometimes turbulent flow is not necessary .
Amazingly , Bob said
" Run a wide ∆T, no need to run a 20° as long as you cover the load. The colder the return and the wider the ∆, the better for condensing. The colder the return the more condensing potential. "
Seems it changes from day to day . Check out the 2 slabs , simple question was , " which delivered more heat ?"

Let's just call it what it is . Many have no idea what is going on in their systems from one moment to the next and then there's the few dozen of us that do . Look at the big boy stuff from the other thread , A Taco question , Main Wall .
Sorry no pictures , only for those who know how to read and comprehend .

Efficiency should happen through all conditions Bob and sometimes turbulent flow is not necessary .

Turbulent flow and efficient heat transfer go hand in hand. Examine the workings of flat plate HXers, surface area and very turbulent flow through all those passages are why they are such good HX transfer devices. Same with a well designed boiler HX.
Same reasons turbulators are added inside pipes and heat exchangers to increase heat transfer. The word turbulator comes from turbulence, by the way.

Delta T to the boiler and delta T in the slab, different numbers Richard. Comfortable radiant slabs that provide the best comfort run 10°∆T. doesn't mean boilers like 10° ∆T operation.

The smaller delta t slab (higher average surface temperature, more btus jumped off the fast moving train transfers more heat to the space because the ∆T between room and surface is wider.
Hot goes to cold
wider ∆, more heat exchange.
Hotter surfaces transfer more energy than cooler

About 2 btu/ sq. ft output for every degree difference.
85F slab surface in a home, 70 ambient @ 30 btu/ft delivered.

For snowmelt 30F outdoor slab, 80 surface= 100 btu/sq delivered. Tough to melt snow with a 30 btu slab.

Paul48

Pump it fast...pump it slow. The only thing that matters, is, can the emitters shed the heat before it returns to the boiler. Most fin-tube system are not over-radiated to an extent to allow low supply temps. Cast-iron radiator system from the early part of the last century were over-radiated, in a lot of cases, because of the fear of Influenza. They could heat a room with the window open, and no insulation in the walls. Those houses are good candidates for a mod/con. Unfortunately, the farther we got into the last century, the more poorly suited the structures became for mod/cons.

NYplumber

HR thanks for the post. The wheels are always turning here, but when i read a good post like that i get into overdrive.
Enjoy your day.

Back to the subject, much of the savings on mod cons is the modulation. Take a look at big steel boilers with power burners that modulate with high/low settings. How do i know this translates to mod cons? Because 85% of the mod cons i see have no odr sensor and are set to 186*f from the factory, yet bills are routinely fifty percent of the non modcon counter parts.

Paul48

Some would say, Mod/cons are "ideally" suited for low temp applications. This leads to confusion. The more accurate statement says, Mod/cons are "only" suited to low temp applications.

hot_rod

Paul48 said:

Pump it fast...pump it slow. The only thing that matters, is, can the emitters shed the heat before it returns to the boiler. Most fin-tube system are not over-radiated to an extent to allow low supply temps. Cast-iron radiator system from the early part of the last century were over-radiated, in a lot of cases, because of the fear of Influenza. They could heat a room with the window open, and no insulation in the walls. Those houses are good candidates for a mod/con. Unfortunately, the farther we got into the last century, the more poorly suited the structures became for mod/cons.

Show me a fin tube, air handler, radiant loop, panel radiator, all things being equal as far as temperature supplied, that give more output at lower flows?

The fin tube does not need to be over radiated if the building load is a fraction of design for most of the year. The numbers will tell when, where and how the heat emitter will perform at lower flow and or lower temperatures. That is all I'm promoting is knowing how to use the numbers.

Some installers install mod cons running high temperatures JUST because they like the modulation. Is that a bad thing?
Maybe it is a micro zoned system and the modulation alone eliminates short cycles and high energy costs due to that.
Or a mod con used just for high temperature DHW production.

Rich_49

Bob, Give us all the Reynolds numbers for the 2 slabs above .

Of course the Deltas are 2 different ones Bob , But without the Delta from the radiant panel the Delta for the boiler will be much higher . You are very circuitous and obfuscate Bob .

Guess you just have a problem understanding how one can flow 70% of the fluid at almost half the head and still deliver the same BTUs while maintaining the same surface temp but deliver 3* cooler water back to the boiler . I say to you , that in your examples from the other thread , I was wrong , both slabs delivered the same BTUs , the wider Delta slab just did it using much less mechanical energy .

Just as a comment also , I don't know why you picked those specific Deltas unless it was to make the statement above about the accepted 10* Delta for radiant floors which are of the embedded installation type . Someday maybe we'll all laugh about this , but I sincerely doubt it .

DanHolohan

Rich said:

Bob, Give us all the Reynolds numbers for the 2 slabs above .

Of course the Deltas are 2 different ones Bob , But without the Delta from the radiant panel the Delta for the boiler will be much higher . You are very circuitous and obfuscate Bob .

Guess you just have a problem understanding how one can flow 70% of the fluid at almost half the head and still deliver the same BTUs while maintaining the same surface temp but deliver 3* cooler water back to the boiler . I say to you , that in your examples from the other thread , I was wrong , both slabs delivered the same BTUs , the wider Delta slab just did it using much less mechanical energy .

Just as a comment also , I don't know why you picked those specific Deltas unless it was to make the statement above about the accepted 10* Delta for radiant floors which are of the embedded installation type . Someday maybe we'll all laugh about this , but I sincerely doubt it .

Getting a little testy, Rich. You and H.R. are both smart guys. Be nice.

Paul48

hot rod....I'll grant you that, but show me any of those emitters, that when pumped faster does not send higher temperatures back to the boiler. This is the unacceptable conundrum you're presented with.

Paul48

"The fin tube does not need to be over radiated if the building load is a fraction of design for most of the year"


Then as a matter of fact, the building has to be over-radiated, by design

Rich_49

Not testy Dan just spirited . I do admit , it is inconvenient for some though . I apologize but there is only one me and everyone is experiencing the diplomatic Rich . PC gets nothing accomplished , this industry has had ample time to accomplish something but has failed us . This is the eleventh hour and time for lies or lack of understanding to cease .
maybe Bob could answer the questions of those he intends to corrupt and be either right or wrong .

DanHolohan

Rich said:

Not testy Dan just spirited . I do admit , it is inconvenient for some though . I apologize but there is only one me and everyone is experiencing the diplomatic Rich . PC gets nothing accomplished , this industry has had ample time to accomplish something but has failed us . This is the eleventh hour and time for lies or lack of understanding to cease .
maybe Bob could answer the questions of those he intends to corrupt and be either right or wrong .

This is The Wall, Rich, not the entire industry. It's a special place, filled with smart people who share what they know in a mature way. Can you make your points without getting nasty?

Rich_49

This is where the very best help folks and I thought that meant each other . I give what I receive Dan , always have , always will . Maybe you have communicated with Bob about his condescending tone and comments as if I require pictures . If you'd like me to not be here and help folks with real pertinent and helpful information to design / install better systems in more homes and be profitable just state that and I will leave the community which you started . I do what I do in the spirit of helping , not selling .

DanHolohan

Rich said:

This is where the very best help folks and I thought that meant each other . I give what I receive Dan , always have , always will . Maybe you have communicated with Bob about his condescending tone and comments as if I require pictures . If you'd like me to not be here and help folks with real pertinent and helpful information to design / install better systems in more homes and be profitable just state that and I will leave the community which you started . I do what I do in the spirit of helping , not selling .

I'm asking only that you make your points without being nasty, Rich. It's your tone that troubles me. Do you think you can make your case in a way that's not so combative?

njtommy

The problem is with baseboard is that it can only pick up so much heat and that's it. Your not forcing air acrossed it. Once those fins get hot your delta just drops off and your no longer running a 20 delta t. Is more like 5. Especially on mild days.

Does anyone make a ECM pump that goes down to 2 gpm?

Rich_49

Debate and differing opinions are inherently combative Dan . Nothing about my tone should trouble anyone , especially not you . It is not alright for some to talk down to others in a condescending , demeaning manner without expectation of recourse and like treatment . I and others have asked some important questions of the hydronic magician . He should answer them without skirting the issue .
This very issue needs discussing and my belief was that this forum provided that platform . If I need to be more PC I don't know that it would be possible for me to contribute . Maybe you could show me where I was combative so I can make an honest attempt to not offend , I cannot recognize at present what I may have said that you are referring to . If I place little Emojis after my offensive comments will that make it alright ?

I am not a writer like yourself and others Dan so am at a disadvantage in that way , but I do know about heating and cooling and would like to help others understand where they may be getting information that could make them less than they wish to be in the future .

hot_rod

Paul48 said:

hot rod....I'll grant you that, but show me any of those emitters, that when pumped faster does not send higher temperatures back to the boiler. This is the unacceptable conundrum you're presented with.

Correct, the example's intent is to show how nicely BTU's jump off fast moving trains, and how a 10∆ can make sense, and be highly desirable in portions of the system..

I like a separate buffer tank. Something to be said for high mass, also.
Chose the type of boiler you like, follow the manufacturers suggested operating conditions and flow requirements, and pipe the distribution via ODR off the tank.
Over the years I have tried 4 or 5 different boilers, the buffer makes it easy for me to switch equipment. The very first was actually a MZ boiler in my shop, almost 20 years ago. makes sense for my, probably not a very sellable system to the average homeowner.

My current backup is a HTP Solar Phoenix, running on just solar today with mild, sunny weather here.

I'm not convinced I want all my eggs in one basket for a heating device, I prefer the two piece approach..

My shop runs off a 100°∆ tank. My wood boiler likes high operating temperatures for gasification, I pull my radiant off that tank all the way down to 80°F. So 180-80= 100

I get most of the DHW from that tank, all the way down to 120F temperatures, without any legionella storage concerns by using an on demand DHW plate HX.

It also allows seamless integration of solar, wood, and backup LP for fuel choices. But it is not an everyman system.

There are many ways to use and leverage ∆T, just need to know and agree on some basic facts.

We all get to design and chose the system we feel is ideal for our home or customers buildings. Not everyone agrees on the method to get there.

njtommy

What if there's no room for a buffer tank in the same room as the tankless boiler? Can you hide it somewhere else?
How far away can your buffer tank be if you two piped it?

DanHolohan

Rich said:

Debate and differing opinions are inherently combative Dan . Nothing about my tone should trouble anyone , especially not you . It is not alright for some to talk down to others in a condescending , demeaning manner without expectation of recourse and like treatment . I and others have asked some important questions of the hydronic magician . He should answer them without skirting the issue .
This very issue needs discussing and my belief was that this forum provided that platform . If I need to be more PC I don't know that it would be possible for me to contribute . Maybe you could show me where I was combative so I can make an honest attempt to not offend , I cannot recognize at present what I may have said that you are referring to . If I place little Emojis after my offensive comments will that make it alright ?

I am not a writer like yourself and others Dan so am at a disadvantage in that way , but I do know about heating and cooling and would like to help others understand where they may be getting information that could make them less than they wish to be in the future .

There is diplomacy, polite conversation and kindness, Rich. It doesn't have to be constant combat. I've been running this site for 17 years and I've watched many people come and go. Some of them wrote and said the same things that you are now saying, but fighting never works here in the long run. It simply doesn't, which is why I am trying to reason with you. I love this place and I understand what makes for a strong community.

I don't want to drag this on. I hope I've gotten through. If you feel you need to leave, I understand.