“Vacuum Boost” for steam heating system

BobC

Increased efficiency is very good but at what point does complexity and the increased maintenance / repair negate the gains?

When I was on oil I had the boiler cleaned out every year and outside of occasional air vent replacements (done by me) and the replacement of an ignition transformer (also done by me) I've had ONE service call in 35 years for my one pipe steam system. How much would I have paid in those 35 years if I had a high efficiency (and probably complex) system.

In my view reliability and total cost of ownership count for a lot.

Bob

izhadano

I'd like to suggest separating the discussion into three topics.

1. Steam system retrofit into vacuum
- smaller diameter tubes (less time for heating, less heat loss)
- high speed of vapor
- enable even heat distribution through building
- higher boiler efficiency
That saved ~35% fuel in old times. The main obstacle was maintenance due to steam traps failures. So when hot water circulators were introduced in 1930th the competition was lost.
With new vacuum heating development it's possible to eliminate steam traps, use modern plumbing technology and new plastic materials for heat distribution system, better control heat distribution, reduce size and load of vacuum pump and run system at higher vacuum level. It would be reasonable to expect to achieve at least the same level of fuel savings as in old times and my pilot tests confirmed it.
Please, note that that I'm not comparing to hot water heating system here.
Agreed on this?

2. Condensing boilers
Correct me if I'm wrong, but improvement of hot water heating is close to it's limits. Condensing boilers are claimed of higher efficiency, - 95 versus 85-87% but their work in condensing mode counts for only 30-35% of the seasonal heating load. Does 4% efficiency ((95-85)x0.35) worth higher boiler cost, maintenance, condensing section repairs/replacement, higher cost of low temperature heat distribution section?
Besides, I'm skeptical on condensing boilers 95% efficiency - http://homeenergypros.lbl.gov/profiles/blogs/scrutinizing-condensing-boilers-with-the-second-law-of
So, it's better not consider hot water heating with condensing boilers as a top performer over regular hot water heating. I'd suggest comparing vacuum heating to regular hot water heating system.

3, Vacuum heating benefits versus hot water heating system:- Vacuum system can work at similar lower low limit of heating temperature and at higher temperatures - up to 218 versus 180oF - to heat up space quicker
- higher speed of heat delivery, practically no limit on building height and size
- simple installation (similar to 2-pipe steam system versus circuit base)
- single low capacity vacuum pump employed for a short periods of time (or very occasionally for leak tight new systems) versus multiple circulators employed for duration of heating cycles
- safety - no hot water spillover and expensive repairs for leaking system
- no mechanical floors, pressure reducing valves, etc for high rise buildings
Did I missed anything? Would you suggest any aspect of operation where hot water heating system has advantage over vacuum heating system?
Please, note that I'm not discussing here the heating system efficiency based on heating balance, boiler efficiency, etc. Just using common sense for comparison. It would be great to run both systems side by side in similar buildings or in portions of the same building.
Thanks.

Gordy

The addition of the vacuum pump in a steam system parallels the addition of a circulator in a HW based system done long ago.

Both systems reap the benefits of smaller pipe diameters, longer horizontal run outs, and faster btu delivery which all increases system efficiency, and decreases capital costs.

ttekushan_3

As I understand it though, the vacuum pump has very little to do. It is not responsible for circulation in this system. It just maintains a maximum baseline vacuum. Intermittent operation at best. Igor's earlier experiments if I'm not mistaken invoke no vacuum pump at all. It's just formed after the initial heating/purging of air. The vac pump is a response to the real world problem of maintaining deep vacuum, short of developing a fully hermetic system.

Other than that, all the kinetic energy, turbulence, and proportioning etc. is provided by the generation and condensation processes.

A side note that I find interesting is that combustion analyser readings of the same boiler are the same with either a pumped HW configuration at 212F or with steam generation at 212F. All that that energy of distribution and proportioning, in addition to the significant work done by the vacuum of condensation appear to be unaccounted for. What is all of that worth? Maybe just enough to bring actual fuel usage of a well tuned steam system in line with systems of higher stated efficiencies. Something to consider.

BobC

@Gordy i agree with your categories, vacuum assisted steam has great possibilities. There are hundreds of modest 70 to 100 year old homes in my neighborhood that were built with single pipe steam heat. Most of them have had insulation installed so the original system has more radiation than they need now. A vacuum system would be a good match for them if it can be done without bankrupting the owners of these homes.

We need small boilers that can be fired at different levels and that may mean using atmospheric rather than wet based boilers (lowest I see is about 285,000 for standard wet based boiler firing) to keep the firing scheme simple and affordable. Testing should be done to determine exactly what the efficiency difference is between those two boiler configurations

Bob

Larry Weingarten

Hmmm: After reading Dan's article, I wonder if it isn't the perfect fix for the problems ElizabethinSF was having?

Yours, Larry

SWEI

BobC said:

We need small boilers that can be fired at different levels and that may mean using atmospheric rather than wet based boilers (lowest I see is about 285,000 for standard wet based boiler firing)

It's far easier to get good combustion numbers when downfiring (modulating) a power burner than an atmospheric. Slant/Fin Intrepid TR-20, W-M SGO-3, and Crown KSZ-065 all look like good candidates. The MegaSteam (Crown KSZ) would be ideal (once a certain maker extracts its head from its nether regions and we get a gas option there.)

We'd also need affordable options for small modulation-capable burners. Powerflame X400M and the Midco LNB are both interesting.

Assuming Igor is successful, it may come down to buying the castings and rebadging the entire thing as a packaged system.

jumper

Here's an exergy analysis. Venting sucks big time. Boil water to desorb air in the water. Exergy destruction. Use steam to push air through vents without a piston. Exergy destruction. When boiler rests,air re-enters and desolves in condensate. Exergy destruction. Then boiler fires again to boil the condensate and desorb that dissolved water again. And that's one reason why venting sucks exergywise.

We remove all air from refrigeration machinery down to millimetres of mercury air pressure. Why not fraction of an inch for steam?

Now First Law trouble as well. If atmospheric pressure is the same inside as outside,then First Law states that internal energy of air in cold house is the same as in a warm house. So maybe heat loss calculations are suspect too?

jumper

Hatterasguy said:

jumper said:

Now First Law trouble as well. If atmospheric pressure is the same inside as outside,then First Law states that internal energy of air in cold house is the same as in a warm house. So maybe heat loss calculations are suspect too?

Why?

The temperatures can vary at the same pressure.

Elementary First Law plus Perfect Gas law calculation.Internal energy per pound of air increases with temperature as does specific volume. So internal energy of air in your house stays constant. Your heating system makes your home warmer rather than makes the house contain more energy.

ChrisJ

jumper said:

Hatterasguy said:

jumper said:

Now First Law trouble as well. If atmospheric pressure is the same inside as outside,then First Law states that internal energy of air in cold house is the same as in a warm house. So maybe heat loss calculations are suspect too?

Why?

The temperatures can vary at the same pressure.

Elementary First Law plus Perfect Gas law calculation.Internal energy per pound of air increases with temperature as does specific volume. So internal energy of air in your house stays constant. Your heating system makes your home warmer rather than makes the house contain more energy.

You've lost me.
Warmer is more energy, so... ??

ttekushan_3

Just have to remember that warmer air takes more space so at the same pressure there's just fewer molecules of air in the house, that's all. A house isn't hermetic. Mine isn't that's for sure.

ChrisJ

ttekushan said:

Just have to remember that warmer air takes more space so at the same pressure there's just fewer molecules of air in the house, that's all. A house isn't hermetic. Mine isn't that's for sure.

Hmmm.

ttekushan_3

@Hatterasguy said
"If you want the pinnacle of perfection with the vacuum system, it requires controls that will vary the vacuum based upon OAR and a modulating burner that is also controlled electronically based upon the heatloss."

All the old electromechanical controls that can control vapor pressure differential have long disappeared from catalogs. Most of these were proprietary to a specific system's manufacturer anyway.
But with today's inexpensive PID controllers and sensors, it's not particularly difficult to control firing rates based on the system pressure differential and control overall minimum vacuum with respect to atmospheric pressure controlled by ODR.

Interestingly, Fraccaro Vaporad system from Italy, which is a ceiling radiant system, has no steam traps like Igor's and has an active vent head. The vent head has a vacuum pump and also pressure and temp sensors that control the vacuum pump. Apparently, it runs the vacuum pump as long as the temp is less than the temp of saturated steam at that pressure. In this way, it determines whether it is measuring air pressure or steam pressure. It pumps air from the system irrespective of pressure.

It's an interesting approach. I have no idea if it retains vacuum while idle or if it even operates sub-atmospherically by design.

http://www.fraccaro.it/?q=en/dettagli-prodotto/98/industriale/vaporad#/0

ttekushan_3

ChrisJ said:

ttekushan said:

Just have to remember that warmer air takes more space so at the same pressure there's just fewer molecules of air in the house, that's all. A house isn't hermetic. Mine isn't that's for sure.

Hmmm.

Just say'in I don't think any laws of thermodynamics are being broken every time the heat comes on. Very bad karma when you break thermodynamic laws.

jumper

here are some links for thermodynamics enthusiasts.
The second link is to Emden's original article published in 1938.
The first link is to an article copyrighted by Association of Physics Teachers in 2011 discussing Emden's 1938 article.
I include here an abstract of Emden and the beginning of the 2011 article. It says that physicists tend to make the same mistake that Hatterasguy keeps defending.

http://www.stat.physik.uni-potsdam.de/~pikovsky/teaching/stud_seminar/Heating_room.pdf

http://www.nature.com/nature/journal/v141/n3577/abs/141908a0.html


Research Article
Nature 141, 908-909 (21 May 1938) | doi:10.1038/141908a0

Why do we have Winter Heating?

R. EMDEN's 1938 Abstract
THE layman will answer: “ To make the room warmer”.The student of thermodynamics will perhaps so express it: “To import the lacking (inner, thermal) energy.” If so, then the layman’s answer is right, the scientist’s wrong.

Thermodynamics of heating a room©1911
H. J. Kreuzera

jumper

Hatterasguy said:

Real simple:

If you want to believe the energy in the room is constant, where did the energy that the boiler utilized disappear to?

Figure that out while respecting the First Law.

Energy was utilized into increasing the temperature.Not into increasing the energy. Maybe you've confused the two.

Here is a translation of Emden's short 1938 article.Courtesy of R.Kubo. By permission of me.

Why do we have winter heating?
Divertissement 2 From Thermodynamics (North Holland, 1976)
Ryogo Kubo
University of Tokyo
The layman will answer: "To make the room warmer." The student of thermodynamics will perhaps so express it: "To import the lacking (inner, thermal) energy." If so, then the lay- man’s answer is right, the scientist’s is wrong.
We suppose, to correspond to the actual state of affairs, that the pressure of the air in the room always equals that of the external air. In the usual notation, the (inner, thermal) energy is, per unit mass,*
u = cvT. (An additive constant may be neglected.) Then the energy content is, per unit of volume,
u = cvρT, or, taking into account the equation of state, we have
we have For air at atmospheric pressure,
Pρ =RT, u = cvP/R.
u = 0. 0604cal/cm3.
The energy content of the room is thus independent of the temperature, solely determined by the state of the barometer. The whole of the energy imported by the heating escapes through the pores of the walls of the room to the outside air.
I fetch a bottle of claret from the cold cellar and put it to be tempered in the warm room. It becomes warmer, but the increased energy content is not borrowed from the air of the room but is brought in from outside. Then why do we have heating? For the same reason that life on the earth needs the radiation of the sun. But this does not exist on the incident energy, for the latter apart from a negligible amount is re-radiated, just as a man, in spite of continual absorption of
nourishment, maintains a constant body-weight. Our conditions of existence require a determi- nate degree of temperature, and for the maintenance of this there is needed not addition of energy but addition of entropy.
As a student, I read with advantage a small book by F. Wald entitled "The Mistress of the World and her Shadow". These meant energy and entropy. In the course of advancing knowledge the two seem to me to have exchanged places. In the huge manufactory of natural processes, the principle of entropy occupies the position of manager, for it dictates the manner and method of the whole business, whilst the principle of energy merely does the bookkeeping, balancing cred- its and debits.
R. EMDEN
Kempterstrasse 5, Zurich.
* The author has assumed that the specific heat of the gas is independent of temperature; a rea-sonable approximation for the oxygen and nitrogen around room temperature.

hvacfreak2

The energy is the sensible and latent heat in the room ? It started out in the fuel , transfered to the water , and rejected to the room. That is my guess.

ChrisJ

Yes,
Warming the room does not add any energy to it.
That's why it tries so hard to get out side to where it's colder...........because there's no difference.

Sigh.

Gordy

A little help ?

http://www.scientificamerican.com/article/energy-can-neither-be-created-nor-destroyed/

izhadano

Have comments on Hatterasguy@May 28
///////////////////////////////////////////////
My personal opinion is that the Paul system was successful at a time period where nobody vented the mains properly and the one pipe steam system was terribly inefficient because of it. So, enter the Paul system and there was a dramatic fuel efficiency increase with limited air in the mains.
All they had to do was put a few #2's in place and they could have had the same efficiency for a fraction of the cost of the vacuum system.
/////////////////////////////////////////////////////////////////////
A NYSERDA 1994 report
http://www.osti.gov/scitech/biblio/10191625
on high-capacity air vents usage for one-pipe steam heating system concluded that “there was a reduction in the maximum spread of apartment temperatures, however there was no difference in energy consumption between "vents on" and "vents off" periods.”

U.S. Department of Energy Building America team, conducted a 2011 -12 study
http://www.gastechnology.org/Solutions/Documents/BAPARR-Reports/Case-Study-Steam-System-Balancing-and-Tuning-for-Multi-family-Residential-Buildings.pdf
to identify best practices, costs, and savings associated with balancing steam distribution systems. Results of increased main line air venting, radiator vent replacement, and boiler control system upgrades measures led to increased tenant comfort and an average savings of 10.2% of the natural gas heating load. Probably, these savings should be attributed more to the boiler control system upgrades rather than to increased main line air venting and radiator vent replacement.

Paul48

“there was a reduction in the maximum spread of apartment temperatures, however there was no difference in energy consumption between "vents on" and "vents off" periods"

Someone has to explain that to me. Can you fix that?

Paul48

"Results of these measures included a more even distribution of heat throughout the buildings. This led to increased tenant comfort and an average savings of 10.2% of the natural gas heating load".

Which of these highly sophisticated studies should you believe?

izhadano

Hatterasguy to Steamhead on May 28, 2016
//////////////////////////////////////////////////////////
And, finally, before I leave this discussion, weren't you the one who disputes the 95% efficiency claims from the mod-con and claim that your steam systems are just about on par for efficiency?
///////////////////////////////////////////////////////////////
Actually, it was me disputing 95% efficiency of mod-con boilers.
Please, check the Brookhaven National Lab study http://energykinetics.com/wp-content/uploads/2015/10/afueSummaryReport.pdf
“Lab and field studies show you can cut your fuel bill over 30%, even if your heating system is rated at over 80% efficiency.”
“Cold start and cold finish operation of Energy Kinetics’ System 2000 has the lowest overall idle loss and the best seasonal efficiency performance among all home heating systems tested, including highly rated condensing gas and oil systems”.
Hope, you consider BNL “base line” trustworthy, not "highly sophisticated study".
This reference may resolve your doubts of 30% improvement for the heating system of 65-75% efficiency.
Also, what’s interesting, is that vacuum heating system naturally mimic the Thermal Purge and Hybrid Energy Recovery concept of System2000. When the steam boiler stops, vacuum formed in radiators continue purging heat from boiler. Somehow did not mention this when lists benefits of vacuum heating.

Paul48

Vacuum systems of the variety you created would purge, with the vacuum source at the radiators.

Steamhead

Hatterasguy said:

It would be excellent to know the baseline so some wild claims as you have posted above won't be taken incorrectly by those who don't understand any of it.

The baseline in my statements, as I have stated many times in this thread, is the performance of the system before we started working on it. It's not "wild" to cite this baseline when describing performance improvements resulting from our work- au contraire, this puts it in terms that a building owner can grasp easily.

JUGHNE

I'm thinking there could be a variable factor involved for building heat loss.
It would be when any improvements are made to balance steam delivery. The overheated rooms with the windows open on cold days would perhaps close them and less heat would be lost to the outdoors.
The BTUs lost thru the previously open window would then be available for the building envelopment thereby lowering the heat loss......just an idea.

ChrisJ

Hatterasguy said:

JUGHNE said:

I'm thinking there could be a variable factor involved for building heat loss.
It would be when any improvements are made to balance steam delivery. The overheated rooms with the windows open on cold days would perhaps close them and less heat would be lost to the outdoors.
The BTUs lost thru the previously open window would then be available for the building envelopment thereby lowering the heat loss......just an idea.

This would seriously improve the system efficiency.

All the more reason to know what it is prior to, and subsequent to, the vacuum install.

If the system efficiency is suffering significantly due to massive room unbalance, despite the improved main venting, we ought to know about it prior to the test.

Otherwise, I can already see it coming:

"We got a 30% improvement when we added vacuum to the system".

Fundamentally, this implies that the system was never properly installed and balanced and the original efficiency was in the toilet (55%).

Fantastic job. Pat everybody on the back!!

What's the efficiency of your steam system?

ChrisJ

Hatterasguy said:

ChrisJ said:

What's the efficiency of your steam system?

For the heating season '15-'16:

DD: 3173
Base temperature: 63
Boiler size: 262K input
Total boiler hours: 800 (Tekmar 279)
Calculated heatloss: 120,000 BTUH @6F

Total fuel: 209.6M BTU
'
Calculated heatloss in BTU: 160.3M BTU


System efficiency: 76%


Sure, I could be off by 15% on the heatloss. This would give a system efficiency of 65% if the actual heatloss is 102,000 BTUH.

It is a three story apartment building with no insulation and a flat roof with a footprint of 1600 square feet.



So, what I can conclude, (which will not be possible by others), is that a vacuum system could possibly increase the system efficiency from 65% (if my heatloss is less than calculated) to a maximum of about 77%. The result is an 18% decrease in fuel consumption. Any greater than 18% would be a physical impossibility. And, this fuel benefit would only be possible if the current heatloss is 102,000 BTUH (and not the calculated 120K).


I also have a check on the heatloss using the Tekmar 279. On the design day, the boiler will run at a percentage of 58%.

So, it will deliver 115,500 BTUH to the rads at a system efficiency of 76%. If the efficiency is 65%, the the system will deliver 98,700 BTUH. I am quite sure that the building needs more than 98,700 on the design day.

The system is somewhere between 65 and 76% efficient based on the boiler manufacturer's specifications which several members on this forum say are wrong. They have also said the combustion efficiency rating analyzers give is wrong as well.

Combine that with your guessed heatloss which according to you may be off by as much as 15%.


Hmmm.

Steamhead

Hatterasguy said:

Steamhead said:

Hatterasguy said:

It would be excellent to know the baseline so some wild claims as you have posted above won't be taken incorrectly by those who don't understand any of it.

The baseline in my statements, as I have stated many times in this thread, is the performance of the system before we started working on it. It's not "wild" to cite this baseline when describing performance improvements resulting from our work- au contraire, this puts it in terms that a building owner can grasp easily.

The baseline in my statements, as I have stated many times in this thread, and for which you still do not understand, is the system efficiency before you put any vacuum devices onto it.

If you were to obtain this baseline, it would prevent any wild claims of efficiency that violate all physical laws.

If you want to read the wild claims of efficiency that violate physical laws, just read the documents cited above that claim to show a 30% fuel improvement on a 75% system.

What I understand is that you're making this a lot more complicated than it needs to be. When dealing with a building owner, they want to know how much improvement they can expect over what they now have. We tell them what we've achieved on previous jobs, as stated many times before. It really is that simple.

When you include factors such as building heat loss that have nothing to do with the efficiency of the heating system itself, you create a whole different discussion. I repeat, this thread is about improvements to the heating system, not the building envelope or anything else.

JUGHNE

I too agree that heat loss of the building doesn't seem to come into play on the efficiency of the heating system.

I mention the occupant induced heat loss (open windows) which is not actually the building envelope loss. But just closing the windows and redistribution of excess heat will improve overall efficiency.
The size of the building and its heat loss need not be in the equation, IMHO.

The bottom line is literally the bottom line of the monthly gas bill.

SWEI

Hatterasguy said:

Calculated heatloss: 120,000 BTUH @6F

There's your problem. We know that number is really a rough estimate, and we know it's overstated.

jumper

Hatterasguy,where do you think the energy comes from to push air through vents? At what temperature do you think the waste heat from that energy ends up at? Did you read the article I cited? Do you understand it?
http://www.stat.physik.uni-potsdam.de/~pikovsky/teaching/stud_seminar/Heating_room.pdf

SWEI

If we accept that we don't know the actual heat loss, and if we are using the same estimated heat loss for all the comparisons, doesn't it cancel out?

Steamhead

Hatterasguy said:

Heatloss is absolutely required to determine the system efficiency of a heating system, whether you wish to believe it or not.

No, they are two completely different things. The efficiency of a heating system is determined by how well it transfers the heat from the boiler to the rooms. Once the heat has reached the rooms, the heating system's job is done.

What happens to the heat after it reaches the rooms is a completely different issue. This is where the building's heat loss comes into play. Both of these factors figure into a building's overall fuel consumption.

Again, this thread is about improvements to the heating system, not the building envelope or anything else

SWEI

Hatterasguy said:

SWEI said:

If we accept that we don't know the actual heat loss, and if we are using the same estimated heat loss for all the comparisons, doesn't it cancel out?

it does not cancel out. If the calculated heatloss changes, the overall system efficiency changes.

Didn't we just stipulate that the heat loss is the same?

ChrisJ

And yet, we've had guys disagree with combustion efficiency ratings as well.

So, if you only know your boiler's output within 10-20%, and your heatloss is off 10-20%, where are we? What is the boiler actually delivering into the system?

Tim said my boiler was running at 78% if I recall, and Jim said 69% and that these numbers were typical in real life.

I have no idea who to believe and I've yet to come up with a way to measure the actual steam delivered.

Gordy

The envelope efficiency can effect the heating systems efficiency.

Example: if a boiler is matched to an existing envelope perfectly it never cycles. If the envelope is upgraded. The boiler is now oversized, and cycles. This would effect part of the heating systems efficiency.

Of course this would be an example where a change of an envelope system has affected the performance of the heating system.

We usually try to think of total efficiency of all sub systems together.

In my mind the envelope does affect the efficiency of the heating system.

There are several sub systems though . The boiler efficiency, the btu delivery infrastructure efficiency, the emitter efficiency, and envelope efficiency. Like it or not they do effect each other some more than others.

ChrisJ

Hatterasguy said:

ChrisJ said:

So, if you only know your boiler's output within 10-20%, and your heatloss is off 10-20%, where are we? What is the boiler actually delivering into the system?

Tim said my boiler was running at 78% if I recall, and Jim said 69% and that these numbers were typical in real life.

I have no idea who to believe and I've yet to come up with a way to measure the actual steam delivered.

You know your boiler's output (combustion efficiency) within 1%. There is nothing really to guess about that parameter.

Now, certain people have no idea what they are doing so YMMV.

I do?
How do I know that? I only know what the manufacturer claimed, but Shopvac also told me my 1/2HP vacuum is 5.5HP so......


Are you saying Tim and Jim don't know what they're doing?

Steamhead

I was thinking the same thing, Chris.................

jumper

>>The pressure is unreadable on the gauge. The "energy" is insignificant.<<

Then what difference does it make if you vent only the rads? Why bother venting mains?

>>Everyone is still waiting for your explanation of where the energy goes when the boiler adds "heat" to a room held at a constant 70F.<<

Obviously you haven't read,or you don't understand, "Thermodynamics of heating a room". I urge you to study it. It will profit you more than insisting here that permanent air removal is pointless.

I used to think like you,Hatterasguy,but eventually I came around.