Move on or not?

noran01

I have an older colonial style house in downstate NY and have an original (to me) single pipe steam heating system. The current boiler is an older Peerless and grossly over-spec'd...



I currently have an unfinished basement so the horrendous layout of the single pipe system hasn't been an issue (about 2 ft off the foundation all and about the same down from an already low ceiling), but that is changing as I am looking to finish the basement. To top it off, the gas water heater is also past its prime (~13 years old). I have been thinking of ripping the entire system out and doing retro radiant on the first floor (since the basement ceiling is open) and then running baseboards on the second. Obviously this is a bit of work and the wife isn't exactly on-board

Is it worth getting a new, more efficient boiler, and tightening up the piping layout in the basement? The system has been working just fine (aside from the sometimes high natural gas bills) and I had the radiators blasted and powder coated prior to moving in so not only are they functional, but aesthetically pleasing to look at too.

Thanks!

SlamDunk

I'll bet a properly sized and piped boiler would be more inexpensive to operate than your current boiler and more comfortable than a retro floor radiant system or baseboards.

EBEBRATT-Ed

Depends on how many $$ you want to spend. You need a new boiler anyhow. So the choice is repipe the basement steam or go all hot water. Fixing the steam will be less $$ and you already powder coated the rads

GW

It will bite the dust some day, may as well get it over with if you have the dough. If you sell the place someday you’ll have buyers wanting a newer system anyway

noran01

Thanks for the comments so far.

My biggest concern staying with the steam setup is wall space and soffits in the basement - which I am not a fan of as I am fairly limited (especially with height) as it is (7' from slab to bottom of joist)

Obligatory pic of one of the radiators for reference

Steamhead

Nice looking radiator.

And it a subsequent owner wants to rip everything out, let them pay for it.

Keep the steam.

gerry gill

Keep the steam

noran01

Just for clarity sake I plan on being buried in the backyard and have no intentions of selling, etc... hence why I want to ensure I make the right call.

Danny Scully

Where downstate or you located @noran01? I operate Scully’s Plumbing in the Nassau County area of Long Island. I’ve repiped many a steam system to allow for a finished basement, and I’d love to help if I can.

noran01

@Danny Scully I am in Wantagh and would love some assistance as that was my next question - a recommendation for someone local! I'll send you a message

John Ruhnke

You can cut your fuel bills by 68% on average switching from steam to water as described in this attached paper. You can keep the radiators. You just need to add another pipe and get that down to the basement. You could also do radiant or baseboard. A mod/con boiler, competent installer and quality outdoor reset controller would be needed to hit those numbers in the study.

Steamhead

Here we go again. That "study" has been floating around for years, and is extremely easy to debunk.

In order for such a "study" to have any meaning, it would have to compare a steam system operating at the best efficiency it possibly can, to a hot-water system also operating as best it can.

Buried in the article is a telling remark regarding the steam systems, which gives us a clue as to their poor condition:

On page 55 it said:

Most were high/low fire units started and stopped manually.

Manually. With no automatic control whatsoever. How can any system run efficiently under manual control?

You're gonna have to do better than that. And it won't be easy- AFAIK no such comparison study, with both systems in peak condition, has ever been done.

STEVEusaPA

John Ruhnke said:

You can cut your fuel bills by 68% on average switching from steam to water as described in this attached paper. You can keep the radiators. You just need to add another pipe and get that down to the basement. You could also do radiant or baseboard. A mod/con boiler, competent installer and quality outdoor reset controller would be needed to hit those numbers in the study.

Are you guaranteeing the 68%?
Didn’t know it was that easy, just run a return pipe.
Of course switching from 16 ozs to 20 psi, nothing could possibly leak, right?

To the OP, there are many examples on this site from the steam gurus de-knuckleheading these steam systems and providing customers with superior comfort and very nice savings in operating costs.
That would be my 2 cents.

Alan (California Radiant) Forbes

If I had your money and your tendency to radiant, I'd make the switch. Radiant floors are second to none.

The biggest hurdle may be your wife. : )

gerry gill

When I switched my house from forced air to steam, the gas company sent a guy out cause they wanted to know why my usage dropped so much.

John Ruhnke

I have converted radiators from steam to hot water on a few jobs before. A couple miner leaks , not in the radiator, some where else. Yes a radiator might leak. We usually had extra radiators as the clients usually did some radiant in a room or two.

Nothing is that easy like I said you need a competent installer.

I found the 68% to be pretty accurate. The savings were very good in the houses we did it in.

Though I would admit just replacing rundown existing equipment with new well designed equipment alone will save you 10 to 30% without the mod/con boilers. You could hit that staying with steam. So you are right in complaining about the poor condition of existing equipment found in the study. But most existing equipment people want to replace, that we find in boiler rooms is in bad condition

One of the important secrets to efficiency in a hydronic heating system is low water temps. Steam has the highest water temps so it loses in that area. A steam boiler also has a lot of mass. Post purge techniques are impossible. So pulling the heat out of the boiler and into something else like the system 2000 does so well is impossible.

What you can do with a steam boiler to reduce co2 is limited.

noran01

Yikes, this derailed a bit. Just for the record I wouldn't convert from steam to water simply for the fact of work and cost involved to be at the same position. I'd rather go baseboard (low temp) and radiant for my first floor with two condensing water heaters.

@Alan (California Radiant) Forbes I am in total agreement there. Two things could backfire on me; one being the fact my wife would kill me after opening up finished walls on the first floor. Second, assuming that didn't happen, she would then say how come we didn't do heated floors upstairs It would result in a no-win situation!

woobagooba

Thank you for the reference John. I realize the paper is more than 10 years old, but I wonder what the gurus here think re: Total Cost of Ownership of the condensing boilers?

From the paper ... Will condensing boilers enjoy the same 40- or 50-year life expectancies that engineers and owners have come to anticipate from the “old standards?” It is too soon to tell, but the initial results are encouraging.

John Ruhnke

@woobagooba

That paper was written in 2006. I would say that mod/cons are better and more reliable now a days. Though a cast iron boiler is still going to last twice as long in my opinion.

I think the average for a mod/con is 15 years.
A cast iron boiler is 30 years.

So for a good cast iron boiler hooked to a steam system done by a real pro and maintained properly would last about 30 years. I have replaced some steam boilers and not one of my installations has failed yet that I know of.

I had a couple of leaky defective hot water cast iron boilers fail upon first start up but none that survived my guarantee. Both boilers were replaced for free by me. They survived after that.

I would say steam can be reliable. Though it does need maintenance.

The Steam Whisperer

Yes, we recently converted a two pipe steam system and saved about 40% on fuel. It was converted from non operative vacuum pump system to supply valve orifice system running at a maximum of 3 psi., the power burner boiler firing rate was reduced closer to load and the boiler and burner were fully serviced. Return water temps are about 70F nearly year round ( they climb a bit during the 4 or 5 days a winter during extreme cold).
Before this past winter we replaced the current burner with a smaller modulating model, fixed some bad main traps, and set up the burner with a new control to run outdoor reset. I expect we saved at least another 10% to 20% from these improvements.
So we save about 50 % to 60% on the fuel bills "converting' the inefficient steam to a modern, properly functioning steam system. Oh, and our electrical use is still only about 600 watts for heating about 31,000 sq ft of 1928 construction.

So how much more efficient is a hot water conversion?

In your case, you may want to upgrade the system to a version of the minitube system. You can probably supply most or all of your radiators through the vent hole with a small steam supply tube and then the current piping can be used for a return. You can then eliminate the big piping in the basement and install a small 3/4 inch or 1 inch return to collect the condensate and bring it back the condensate pump at the boiler.

Jamie Hall

To - OP -- @noran01 , we've all been around this rodeo a number of times here on the Wall in the years I've been on it.

First, on efficiency. The maximum efficiency of a modulating/condensing hot water boiler, properly installed, tuned and controlled, is around 96%. The maximum efficiency of a modern steam boiler, equally properly installed, tuned, and controlled is around 86%. The difference comes from being able to operate the mod/con at low enough return temperatures to condense the water vapour in the exhaust; it is simply not possible to do that year round, unless the radiation in the building is sized for it -- which means very large.

You'd have to give up the radiators to get anywhere near the efficiency, and also have a very well designed radiant system (which may or may not do the job, depending on how well the building is insulated).

In most -- not all -- cases, steam piping can be rearranged so that it is no more than a few inches below the joists in a basement , and usually it can be routed to be only around the perimeter (again, not always); rearranging the steam piping does add to the cost of installing a new boiler, but not that much.

As @Steamhead noted, we have yet to see a fully documented cost or efficiency comparison of a steam system relative to a hot water system in identical buildings, both equally well setup. The comparison studies which turn up are almost invariably comparing older -- sometimes very old -- steam systems with full dress modern mod/con systems -- which is almost as invalid as comparing the efficiency of a Model T Ford with the latest full hybrid vehicle. That said, based more on theory than on such a study, it would be my opinion that the maximum practical energy savings would be on the order of 5%.

Balanced against that should be the additional cost and complexity of fully modulating/condensing equipment, both in terms of first cost (capital investment) and maintenance.

The bottom line is that if the existing steam system is quiet and heats the house well, I could not and would not recommend tearing it out for any other system, I could -- and would -- recommend a new boiler, installed by someone who is really good at steam (and @Danny Scully , who has been mentioned is very very good indeed) and, at the same time, rerouting the steam pipes as needed to facilitate your remodeling. I might add, on the side, that it is perfectly possible to add separately controlled heat to the basement area with a steam boiler, if that were desirable.

John Ruhnke

@Jamie Hall

You said "The maximum efficiency of a modulating/condensing hot water boiler, properly installed, tuned and controlled, is around 96%. The maximum efficiency of a modern steam boiler, equally properly installed, tuned, and controlled is around 86%."

That is according to afue. Which is measuring all equipment at the same water temperature 180 degrees. AFUE is doing a huge injustice to the mod/con and overstating the efficiency of the steam boiler. The rule of thumb is that for every two degrees you drop in water temps you save 1% in energy costs. So the mod/con is about 30% better at a average water temp of 120 degrees as found in radiant heating. than what afue states. The steam boiler is going to run 15% less efficient than its stated afue number. The Europeans have completed a new energy efficiency study about 15 years ago and got into this all with great detail. They showed the Mod/con to cut fuel bills in half over a average atmospheric boiler. This is in line with and confirmed the Durkin study. A steam boiler is going to perform worse than a average atmospheric boiler.

Check out the link. That study was very involved that was used to develop the euro standards. The link is to a paper that summarizes the work they did.

Steamhead

woobagooba said:

Thank you for the reference John. I realize the paper is more than 10 years old, but I wonder what the gurus here think re: Total Cost of Ownership of the condensing boilers?

From the paper ... Will condensing boilers enjoy the same 40- or 50-year life expectancies that engineers and owners have come to anticipate from the “old standards?” It is too soon to tell, but the initial results are encouraging.

Maybe I'm missing something, @woobagooba , but where do you fit into this? Did you write the paper?

Although I haven't seen any figures- or how said figures were arrived at, which is most critical- I would think the additional maintenance involved with a mod-con would count heavily against it relative to a cast-iron hot-water boiler. Coupled with the increased cost of such a unit, the increased cost of installation (can't exhaust into a standard chimney) and the fact that these units' service life is shorter than a cast-iron boiler's (especially those early Gianonni-based units) , the advantage is probably less than expected.

And if a mod-con is not maintained, its efficiency drops. This goes against customers' perception, based on decades of gas-company propaganda, that gas-fired equipment doesn't need periodic maintenance. @Mark Eatherton , one of our premier Wallies, did an experiment some years ago where he skipped maintenance on his own mod-con and the efficiency drop was astounding. I don't recall the details so I'll let him fill us in if he so chooses.

John Ruhnke

The mod/con is 50% better for other reasons than lower water temps. Low water content and the modulating burner that can provide a closed and pressurized combustion process that can modulate the incoming fuel and air mixture. As the fuel increases the fan speed and air increases too for a perfect mix.

The atmospheric boiler has a unpressurized and uncontrollable air mixture. The only thing you can do is adjust the fuel mixture to the air flowing by gravity through the boiler and up the chimney. Very limited in ability.

ChrisJ

Do guys like @John Ruhnke honestly believe a properly working steam system with a boiler that's rated 80-85% AFUE is somehow actually running at 28% efficiency?

Think about that........ Did I do my math correctly? The best HW boiler pulls off 96% so in order to save 68% with that you must be starting with 28% no?


28% efficiency. 72% of the input is wasted.

So with my system I put in 125,000 btu/h and somehow manage to heat a house that needs 74,000 with only 35,000 actual output into the living space and the system still cycles via the thermostat. That's a neat trick.


Just out of curiosity can someone tell me the flue temps on a boiler running 28% efficiency? I know, combustion, AFUE and system efficiency are totally different but I'm curious. That sounds like one toasty flue.

Steamhead

John Ruhnke said:

@Jamie Hall

You said "The maximum efficiency of a modulating/condensing hot water boiler, properly installed, tuned and controlled, is around 96%. The maximum efficiency of a modern steam boiler, equally properly installed, tuned, and controlled is around 86%."

That is according to afue. Which is measuring all equipment at the same water temperature 180 degrees. AFUE is doing a huge injustice to the mod/con and overstating the efficiency of the steam boiler. The rule of thumb is that for every two degrees you drop in water temps you save 1% in energy costs. So the mod/con is about 30% better at a average water temp of 120 degrees as found in radiant heating. than what afue states. The steam boiler is going to run 15% less efficient than its stated afue number. The Europeans have completed a new energy efficiency study about 15 years ago and got into this all with great detail. They showed the Mod/con to cut fuel bills in half over a average atmospheric boiler. This is in line with and confirmed the Durkin study. A steam boiler is going to perform worse than a average atmospheric boiler.

Check out the link. That study was very involved that was used to develop the euro standards. The link is to a paper that summarizes the work they did.

AFUE was designed for scorched-air furnasties. It doesn't work so well for any water-based system. What it DOES do, is allow us to compare equipment in similar categories, since everything in a category was tested the same way.

And don't forget, steam has two other advantages:

1- There is far less water to be heated in a steam system, offsetting any perceived lower boiler efficiency. This is also one reason steam can be so quick if it's vented properly, and

2- Since a quantity of water expands 1700 times when boiled, no pump is needed to fill the system with steam. Again, the system must expel the air quickly at ounce pressures to facilitate the process.

Some systems do use return tanks and pumps, but they don't run all the time as in a hot-water system. Only a vacuum pump would run all or most of the time on a steam system.

Speaking of European practice- I recall reading somewhere that when a European boiler reaches five years old, parts start getting hard to find. Planned obsolescence. I don't know what experiences the rest of you have had, but our customers would never accept that. If they are going to replace a boiler, they don't want to ever replace it again.

John Ruhnke

I am not having any of the mod/cons I installed fail and need to be replaced yet. Though I don't have many over 15 years old because my first one was most likely in the early 2000's. I have a lot around ten years old though. All going strong.

A study I read gave the mod/cons a average life of 15 years.
Cast Iron is 30 years.
Even though a lot of you may comment on 50 year old cast iron boilers they were built better back then. Thicker and heavier. Don't think your modern boiler is going to last as long.

John Ruhnke

@Chrisj

This is the whole reason I developed my own efficiency formula. I got a patent on it.

When you consider all the losses through out the entire heating system you will find systems out there running at about 5% efficient. I am not joking. Its real bad out there. The difference in efficiency between homes is enormous. Consider insulation in houses and well add it all up. Overall efficiency differences in overall efficiency of the entire home are even bigger than just comparing heating systems.

Some baseboard heating or radiators attached to the outside wall are losing 50% of there energy to the outside wall. This was confirmed in a study I read that showed how electric baseboard heat was costing twice as much as a electric radiant heated ceiling in the same home. Since electricity is 100% efficient than 50% or half of the energy had to be lost by the baseboard through the outside wall.
Consider the time I was with a Energy Auditor who showed me some thermal imaging scans of a lot of fiberglass insulated homes where the average insulating contractor was stopping about a foot short at the bottom on the insulation and this all makes sense. The baseboard in a lot of cases is going where the insulation contractor likes to skimp on insulation.

woobagooba

@Steamhead

Steamhead said:

Maybe I'm missing something, @woobagooba , but where do you fit into this? Did you write the paper?

I do not understand your question and no my name is not Dunkirk.

John Ruhnke

@ChrisJ

The worst offender award goes out to the duct guys who often should be happy if they achieve 5% efficiency when they stick there entire heating and cooling system in a uninsulated attic. Those ducts are huge and give off energy at a rate 15 times that of any hydronic pipes. On top of that they leak and sometimes leak badly all over the attic. They should call those hvac systems, attic heating systems because that's what they really are. They dump more heat and cooling energy in the attic then they do in the house.

On top of that the general contractor comes along and says you need to ventilate the attic. So now as if the attic heating guys aren't dumping as much energy into the attic as they possibly can. The general contractor comes along and dumps all that energy outside the house. Its almost like they designed the system to waste energy.

ChrisJ

John Ruhnke said:

@ChrisJ

The worst offender award goes out to the duct guys who often should be happy if they achieve 5% efficiency when they stick there entire heating and cooling system in a uninsulated attic. Those ducts are huge and give off energy at a rate 15 times that of any hydronic pipes. On top of that they leak and sometimes leak badly all over the attic. They should call those hvac systems, attic heating systems because that's what they really are. They dump more heat and cooling energy in the attic then they do in the house.

Here's the problem........

Let's take the example of the house with the walls not insulated at the bottom.

If that's a steam system and you convert it to HW and leave the envelope alone and charge the customer for this service, your efficiency isn't changing enough to matter. You may gain a little, but not enough to matter or ever pay for the work.,

You are never going to gain 68% by converting from steam to hot water. Ever. As @Jamie Hall pointed out, that would be typically a 10% increase, often less. That's not including the electric needed to run the pump(s) etc. Also increased cost of equipment.

Fixing broken systems is another subject because you could fix the broken steam system and make it an efficient steam system. You could of course also fix the broken house and tighten it up and insulate it. That's completely separate from converting to HW.


I am a little confused by how you can convert heatloss to efficiency though. 100% of the heat you put in, will be lost through the envelope.

retiredguy

Wow, everyone has his/her opinion on the conversion of a steam system to a hot water system, it's benefits and cost-savings. I learn new stuff every day from reading your posts. I started in the HVAC business as a service tech during the 1968/69 heating system. I just got out of the navy and then tech school and knew everything there was to know about heating systems until I got to my first service call. It has been a learning experience ever since. After 6 years I was hired by a company that serviced and installed commercial and industrial steam systems in schools, hospitals and businesses. Western Pa. was their normal business area however we would go anywhere that the customer would pay for. My opinion is that there is a cost savings when converting from steam to hot water. Most of the savings comes during the milder days when radiation temps can be lower and pick-up loads are greatly reduced. The amount of actual savings from the "steam to water conversion" is almost impossible to compute since most conversions are accompanied with system and building up grades. The big question for me is "is it all worth the cost" and what is the ":pay back". I did not enjoy seeing a conversion since steam was my love and life after my family. Go right ahead and post your opinions since today is another day and there is still much to learn.

Jamie Hall

Unfortunately there seems to be a good deal of misunderstanding, if not flat wrong, information in this thread, particularly regarding fuel efficiency. At least one of the contributors seems to have a very odd understanding of efficiency...

@ChrisJ , I follow your calculations using Mr. Rhunke's number, and come up with the same numbers you do, which is absurd on the face of it.

I stand by my initial comments on relative efficiency of heat sources. I have a suspicion that some others may be confounding the overall "efficiency" of the building with that of the heat sources, and I will happily grant that a poorly insulated or sealed building will take more energy to maintain a given temperature in the interior than a well insulated one -- the most extreme example, of course, being a tent.

Sad.

ChrisJ

Jamie Hall said:

Unfortunately there seems to be a good deal of misunderstanding, if not flat wrong, information in this thread, particularly regarding fuel efficiency. At least one of the contributors seems to have a very odd understanding of efficiency...

@ChrisJ , I follow your calculations using Mr. Rhunke's number, and come up with the same numbers you do, which is absurd on the face of it.

I stand by my initial comments on relative efficiency of heat sources. I have a suspicion that some others may be confounding the overall "efficiency" of the building with that of the heat sources, and I will happily grant that a poorly insulated or sealed building will take more energy to maintain a given temperature in the interior than a well insulated one -- the most extreme example, of course, being a tent.

Sad.

Like I added in my last post.
How can one convert heatloss into an efficiency percentage?

100% of what you put in will be lost, in theory. Probably a little less due to people, electronics etc. But overall, 99% will.

So how can someone take that and claim it's a less efficient system because it's X%?

JakeCK

Not offering any opinions just some raw data I've collected over the years. It is 3 years out of date now since I have a toddler who keeps me busy but I still do keep all the bills so I could update it. Use this as you wish when considering ROI on heating equipment upgrades. Of course every house is different.

The house is a 1928 Sears kit home. 1470 sq. ft. mostly original. Very little insulation in the walls, 6" in the attic floor joists. Original wood windows with aluminum storms save two that are vinyl(pukes). 30+ yr old hot water boiler with cast iron rads. The actual kit home was the Sears Barrington.

The Steam Whisperer

The problem of pick up loads in steam systems was long ago largely solved by using supply valve orifices on conventional systems. Mr. Gifford in New York uses only 10% pick up factors. I use about 15% pick up factors of the peak heat loss ( not connected radiation) for orificed steam systems to allow some extra capacity for setbacks. Pick up load is nearly eliminated with minitube steam systems. Resetting the water temp/steam temp in a steam system was also addressed long ago with vacuum reset, though not as great as with hot water. Outdoor reset of the radiators is also accomplished through the use of supply valve orifices and/ or vacuum reset.
I do agree that commercial atmospheric boilers run about 15% less efficient that a sealed combustion boiler. In fact most of the commercial atmospherics I see are generally closer to 55% seasonal efficiency due to excessive radiation ( typically about 60% oversized if installed from about 1905 to WWII) and boilers about 60% oversized for the radiation load These boilers are usually running at about 40% capacity or less on design day. However, this sizing issue can be addressed on most larger systems by first downsizing the radiation to current heat loss using orifices and then downsizing the boiler to heat loss. We have a number of systems were the upgraded system only uses 1/6 the capacity of the original heating plant on all but the most extreme winter days. The previous example of a 1928, 31,000 sq ft masonry building with almost no thermal upgrades was only running about 1.1 million btu input into the original 2.8 million btu input boiler on design day.
The importance of proper sizing for atmospheric is not nearly stressed enough. I had the opportunity to replace a modern 140,000 input boiler with stack damper with an equivalently AFUE rated 63,000 input boiler and saved about 12% on the fuel bills. This was despite the fact that the 140,000 input boiler was running at very low temps in a converted gravity system and the new boiler was running at higher temps due to bypass piping in the same system.

Let's stop basing savings from conversions of broken down, out of date oversized steam systems using oversized on/off atmospheric heating plants and start looking at up to date steam systems using modulating sealed combustion boilers, properly sized systems and boilers with outdoor reset.

John Ruhnke

@ChrisJ

68% is the average savings on a steam conversion to hot water with mod/con and outdoor reset. I presented the facts. Now go back and do your research. Critical analysis and thought is missing in America.

When a person is confronted by something he doesn't understand that goes against his beliefs he digs his heals in and resists harder. He refuses to look at the evidence shown.

If you need further evidence call Prisco Panza of Shelton Winnelson. He sells steam to hotwater conversions all the time to many contractors. The savings are always huge and always noticeable.

ChrisJ

John Ruhnke said:

@ChrisJ

68% is the average savings on a steam conversion to hot water with mod/con and outdoor reset. I presented the facts. Now go back and do your research. Critical analysis and thought is missing in America.

When a person is confronted by something he doesn't understand that goes against his beliefs he digs his heals in and resists harder. He refuses to look at the evidence shown.

If you need further evidence call Prisco Panza of Shelton Winnelson. He sells steam to hotwater conversions all the time to many contractors. The savings are always huge and always noticeable.

I don't know that I'd say you're digging your heals in deeper, but you certainly aren't going about it easy.

The Steam Whisperer

ChrisJ. If you do the math of comparing a typical 60% oversized ( based on standing radiation) 30 year old atmospheric steam boiler with no stack damper operating in a system with uninsulated basement piping that the radiators are also 60% oversized with no outdoor reset and then install a boiler that is properly sized with radiation properly sized, insulated piping, with outdoor reset and can condense at least part of the heating season, 68 % is possible. When looking at seasonal efficiencies ( which much more accurately predict overall fuel usage), it makes sense.
The steam boiler operating in that system is probably only 55% seasonally efficient when it was new ( based on national board of standards testing of atmospheric hot water boilers from long ago) Add sludge and lime build up to increase stack losses, I could see the seasonal efficiency drop to 50% or below. The new system is probably operating the boiler at about 90% seasonal efficiency. Doing the math for this factor alone is about a 45% reduction in fuel use.
Modulation with outdoorreset, whether steam or hot water, is often agreed upon to save about another 12%. Add these all up and you get 57%. Add in insulated piping, some additional reduction in distribution losses, and that 68% makes sense.
However, if you start with a sealed combustion power burner steam boiler that is sized to heat loss with radiation downsized to heat loss using orifices and/or maybe even better running vacuum, set up the burner to modulate based on outdoor reset and then insulate the piping, things change dramatically. You now have a boiler running about 80% seasonal efficiency or higher( Old Kewanees and Pacifics have combustion efficiencies of 86% with stack temps around 300F), building heat loss is reduced because of outdoor reset to nearly the same extent as hot water reset, off cycles losses are also reduced due to burner modulation like hot water, and the distribution losses greatly reduced to eliminate this waste. The only thing left is the 6% condensing gain, which could also be reduced if using a condensing steam boiler since the return temps off this type of system are around room temperature nearly all winter.
I'd say the hot water system has a slight advantage in outdoor reset since distribution losses will be lower and there will be a little less stratification induced heat loss and some gains due to condensing. And now you are in that 10% possible reduction in fuel usage.

However, you have now added pumps that must run nearly all winter long, since you are running outdoor reset, so your electrical use climbs dramatically compared to the steam system. We only need 600 watts to heat 31,000 sq ft with steam, wheras you probably need about 4 times that amount or more for hot water panels, and double that again for radiant floor.
This reduces the saving of hot water several percent.

I believe John, since the system conversions are likely out of date and beaten up steam system, but also agree with you ChrisJ, since your system is likely to be in much better shape and properly insulated.

Again, lets compare an up to date steam system with an up to date hot water system.

ChrisJ

@The Steam Whisperer What about the little thing mentioned about the average life of a modcon being 15 years vs 30 for a CI steam boiler? Shouldn't we factor in the cost of two boilers and installation for both? That's not exactly pennies.

John Ruhnke

@ The Steam Whisperer

Most of what you are talking about is only available in the commercial space. Do they make a residential power burner? or residential steam outdoor reset? It sounds like you have some good solutions to make steam more efficient. That is great. Keep up the good work. You have some solutions I am not aware of and sound like they work well.

The big point I would like to make sure sticks in everyone's head is how drastically different real word efficiencies are. There is lots of room for improvement. This should be good news to everyone in this forum because we are the ones that can profit from these improvements. Also the average person believes AFUE. So they think there isn't much that can be done. When you tell somebody that a piece of equipment has a afue of 85% they think at most they can gain is 10% if they go with the absolute best. When you think of real world seasonal efficiencies you can easily cut someone's fuel bills in half. Real world seasonal efficiencies are much more drastically different. 5% efficiency for that uninsulated hvac system in the uninsulated and ventilated attic is not a unrealistic number. And yes if Durkin is saving 80% a year in fuel on one of his steam to hot water conversions than the old system is less than 20% efficient. When you account for losses Durkin didn't or cant address in the boiler room that real world efficiency number is even lower because Durkin's project isn't 100% efficient either.

So go look at my past comments in this thread at the quoted efficiency and fuels savings from real world studies. Use this as a baseline to fix or improve existing buildings and heating systems. Go out there save our planet and make some money!!!