Paul system

izhadano

According Dan’s info about efficiency of steam system conversion into two-pipe vapor Paul system from (“The lost art of steam heating”, 16th print, pp. 249 -251):

"Long absent, soon forgotten" solution on average saved 35% of fuel and paid off within first heating season. 



This was a good way for steam systems retrofits.  Does anybody has experience with Paul system? What’s the vacuum operating range?  I would appreciate greatly more

information.



Thanks.

Rod

Paul System

Hi - Can't help much. Hoffman still offers valves for the Paul system (See attached PDF) and for tubing, you might want to look into Polysulfone plastic tubing which will take high heat, up to 150 C.

- Rod

izhadano

Paul system

Thanks, for info. Still the question - what vacuum range did Paul system operated?

Actually, the question is  "What's the optimal vacuum range of operation in general for vacuum systems?"

Rod

Paul System

I'm not quite sure where you're going with your question about vacuum. My impression of the Paul System is that the major benefit was derived by getting the air out and the radiator filled with steam (and the rooms heated and the thermostat satisfied) in a minimum amount of time rather than about lowering the boiling point of water. You have to remember that this system was from the day where they had coal fired boilers and steam built slowly. If you haven't done so already, read Boiler Pro's excellent article

http://www.heatinghelp.com/article/11/Hot-Tech-Tips/1551/Taking-Another-Look-at-Steam-Boiler-Sizing-Methods-by-Dave-Boilerpro-Bunnell

and then consider the benefits of air evacuation by vacuum in that context. Of course with vacuum there is a small benefit of steam being produced for a longer period of time as the coal fire is slowly dying down.

As to how much vacuum is a practical operating range - 15 inches might be obtainable, but I think it's more likely to be around 5 inches.  Volume of vacuum maybe more important that high vacuum. Having a large vacuum storage tank (with a vacuum pump) so that instant vacuum could be produced ( like in the vacuum forming industry) rather than a vacuum pump slowly chugging away producing vacuum slowly maybe the way to go.

I gave the Paul System some thought and kept a few notes, but that was as far as I got. If you come across something interesting please share it with us.

- Rod

izhadano

Paul system

Thanks for the link to Boiler Pro's excellent article. Many

thoughtful explanations. Balancing main vents and radiators vents capacities is

an interesting approach described also in separate research of 1994:  http://www.osti.gov/bridge/servlets/purl/10191625-8qJZ5M/webviewable/.

“The project's objective was to determine if the installation of large-capacity air vents at the ends of steam mains and risers would economically reduce the temperature gradient between apartments and reduce the amount of space heating energy required.

The test was conducted by enabling and disabling air vents biweekly in 10 multifamily buildings in New York City between December 1992 to May 1993. The temperatures of selected apartments and total space heating energy were compared during each venting regime.

There was no difference in energy consumption between "vents on" and "vents

off" periods (see Tables 2 and 5); however, there was a reduction in the maximum spread of apartment temperatures.”





I put already on Wall basic info about “Vapor heating system with naturally induced

vacuum” - VHSNIV. As of today, retrofit of an old (~100 years) single pipe heating system into VHSNIV cost $150 (excluding labor on getting system reasonably

leak tight).  System consists of boiler, six radiators and is operated by existing controls, no additional equipment is required.  Vacuum formation in the retrofitted

steam heating system before leaks were fixed is shown in red lines – attached

graph. After getting system reasonably tight, the very first heating cycle created

24”_Hg vacuum (-12psig/ 2.7psia) – green line.   System was off till next morning; some air leaked in overnight. Next morning system started at -5 psig and vacuum -10_psig was reestablished – blue line. Ideally, leak free system can operate indefinitely under vacuum; needless to say that water makeup and corrosion are minimized.













The

reason why I’m so interested about Paul system: Dan’s  data on average 35% fuel economy and 1 year

pay back period  when steam system was

converted into Paul system. Should I know the operating parameters, might be a good

base for comparison.





















 

Rod

Paul System

It very basically comes down to getting a dwelling evenly heated to a set temperature using the minimum amount of fuel. This means achieving the goal in a shorter burn time and/ or reducing the fuel per hour burn rate.  `My feeling was with the standard burner setup (steady firing rate, on /off) the biggest benefit of vacuum was shortening the time it took for steam to distribute itself through the system. Until they get fully modulating burners for residential steam (I'm oil fired) I don't see where you can utilize the vacuum side all that much.

- Rod

izhadano

Paul system

From physic’s laws logic, it seems to me  that fuel saving on vapor systems come from the following:

- reduced heat loss from piping working at lower temperatures

- water start to evaporate at lower temperature, so preheating time is shorter (note that latent heat evaporation/condensation changes insignificantly)

- steam distributes evenly through all radiators (pressure drop from boiler to any radiator is usually ounces of water  or up to 2 psi; with  negative 8-10 psi vacuum in a system differences in pressure drop to each radiator become negligible)

- when boiler is stopped, and vapor condensation creates vacuum in a system, in addition more vapor is sucked from boiler into radiators



Probably, even heat distribution through the building is the most significant component. It was estimated for climate zone in MN  that for every 1oF increase of internal temperatures, the space heating cost increases by 3%  [http://www.mncee.org/pdf/tech_pubs/85-8.pdf]. So, ordinary building’s overheating of 14oF (average 7oF) corresponds to 21% more fuel spending.

Igor

ttekushan_3

boiler temp and other thoughts

I like the idea of building vacuum at the end of the cycle if for nothing else than lowering the boiler temperature to reduce stand-by losses.

Patrick_North

You mileage may vary....

When awful, unexpected, and expensive things stop going worng with our "we didn't know it was a fixer-upper" Victorian, I'll be tackling the Paul retrofit, too. That could be a while.

But I can tell you that my brief investigation suggests that the biggest benefit is quicker steam distribution, and that this can be gained with a very modest pressure differential. With an old one-pipe steam system it may be difficult to achieve much of a vacuum, anyway. It's also been suggested that a venturi-style setup is the way to go in crating your vacuum. A nice water pump could be cheaper to buy and operate, is nearly silent, and would never see live steam.

Good luck, and please keep us posted.

Patrick

izhadano

You mileage may vary....

Patrick, the reason of this post was to get more info about Paul system. What vacuum range was utilized? how leak tight the system was?etc.

To my surprise, -12 psig vacuum was created in reasonably tight ~100 years old single pipe system. It dropped to -6 psig after 24 hours due to minor leaks (please, see graph above). The weather is pretty mild in New England now, so system started only in the morning after cold nights. It will be more interesting to watch system on/off every 2-3 hours in the winter. I'll put more info later.

Igor   

Patrick_North

Sorry-

Sorry- I don’t think I understood the nature of your question.

I’m not a professional, but I’ve been told by pros here on the Wall that the Paul system was designed to work with just a few inches of vacuum. Given the nature of the vacuum source and the variability of individual systems (this was a retrofit option, after all) little more could be expected. And of course, they were also working with a "modulating" heat source- coal.

But you asked quite a different question also: "What's the optimal vacuum range of operation in general for vacuum systems?" This very much depends on the particulars of your system and what you are trying to optimize.

Good luck,

Patrick

Steamhead

Igor, was your gauge

showing vacuum in negative pounds, or in inches of mercury? The latter is the usual unit of measurement here..............

izhadano

gauge

Frank, I got very handy gauge - both positive (psi) and negative (psi + inch of mercury) - picture attached.

Steamhead

The vacuum part of the range

is inches of mercury, not "negative PSI". The negative part of the BAR scale appears to be still BAR though, maybe that's how it's done in that measurement system.



So your vacuum readings are in inches of mercury, not negative PSI. But they are still noteworthy!

izhadano

The vacuum part of the range

I modified  the graph to show Y-axis in psig, psia and inch Hg ...

sorry for confusions.

Dave in QCA

Interesting possibilities here

I find it interesting that vacuum operation of old vapor systems was set aside many years ago when systems were converted to gas or oil firing.  I trace the logic to rather simplistic information and language produced by Hoffman Specialty.  The reference to "getting all of the heat out of the coal" appears in their explanation of vacuum vapor systems.

However, when you look at the old literature written at the time the systems were invented and installed, the focus was on more accurate space control, of producing a heating medium with a variable temperature, just like hot water, but with the advantage of steam systems.  I.E., smaller radiators and quicker response.  The old literature didn't say anything about getting every last drop of heat out of the coal, because that coal fire was actually quite controllable.   I have heated with a coal burning stove, and it is amazing how a stove can be loaded with large bed of coal, and that fire can be turned up and down, from a barely warm coal that you think might be extinguished to a bed of bright red coals with licks of blue flames and tremendous amounts of heating coming out of it.  Once a stove, or boiler was loaded with coal, through the use of the damper the heat could be essentially turned on and off numerous times for a period of many hours.

So, the advantage really seems that you could produce vapor at a lower temperature than steam which would be a great benefit in mild weather.  Additionally, there are those side benefits of eliminating air from the system, which is the primary source of most corrosion and decay.

In the attached pdf file, the author describes how vapor will continue to flow in the system down to a temperature of 150F when the fire is reduced, or when it has gone out all together.  When the fire is restored, vapor will begin flowing again when the boiler reaches 150F, as long as the vacuum has been maintained. 

See Pg 79, 80, 81 in the attached file.

No one would question that fact that ODR (outdoor reset) on a hot water system would save money and provide a system with better control.  It seams the same logic would apply to steam / vapor. 

Anyway, it seems to me that the subject of vacuum vapor heating deserves some real serious consideration and experimentation.   Just like the steam mini-tube, there are probably some really good systems and setups that are being overlooked on the basis of, "it won't work with gas or oil - on/off firing".    

.

How come?

izhadano

Interesting possibilities here

Hi, Dave:

thanks for interesting book - attachment. Creating vacuum by bubbling air through mercury was an interesting concept, hardly applicable today though.

You pointed to very attractive feature of vacuum system versus steam system - boiler continue to supply vapor into radiator when burner is off.  In one radiator - one boiler lab model, I observed radiator staying hot for another 30 minute after boiler stop due to this phenomenon.

Also, starting system in vacuum is saving energy because heat is delivered to all radiators simultaneously and without air-pushing-out step.

Definitely, these are potential energy saving factors.

These benefits should be utilized in full scale for light weight copper conduit and panel radiators vapor vacuum system.

Thanks,

Igor



 . 

Dave in QCA

heats longer and sooner

If my understanding of this article is correct, not only does the vapor keep flowing until the boiler and vapor have cooled to 150F, but when the burner starts, as soon as the boiler temp reaches 150, the vapor starts flowing again.  Of course, the temperature of the boiler and vaport will continue to climb until the burner shuts off, but like a water system, the fluctuation could be minor, and the boiler and vapor could remain quite moderate in light load situations.

Patrick_North

False low limit

Dave, you said

"Of course, the temperature of the boiler and vaport will continue to climb until the burner shuts off, but like a water system"

But would this be the case? Once you've reached the boiling point, water's temperature does not continue to climb. It seems that you would need to be able to raise the operating pressure to atmospheric as the boiler came up to temp in order to get "full temp" steam, then lower it again to take advantage of sub-212 degree boiler water after the burner has shut off. Otherwise what you have is an oversized burner, and possibly undersized radiation.

Ideally, you'd also want to be able to modulate the burner so youre not limited to "free falling" boiler temps associated with on/off.

Getting better steam trasnmission via subatmospheric conditions seems pretty straighforward, but to create a modulating hot water type system sounds much more complex. Perhaps it's just a matter of finding the right controls?

I hope this conversation continues!

Patrick

Dave in QCA

Pressure and Temperature

I need to mention that I have not tried any of these theories, but am basing my comments on the writings by Alfred King about vapor and sub-atmospheric systems at the time they were invented, (a link to a publication appears earlier in this thread), and of my knowledge of basic physics.

In my previous comparison to a hot water system, I was speaking of a cast iron radiator hot water system in my home.  (I have a 2-pipe vapor system in an apartment building that I own.)  In my hot water system, in regular cycling, not recovery after a setback, it is common for the boiler to cycle on for 5 minutes in mild temperatures.  While the temperature of the radiators throughout the house increases as a result of this cycle, it is not a perceptible amount.  The radiator temperature is relatively constant, the heat being emitted matching the heat loss of the home, at the current weather conditions.

It seems to me, that when vapor heating systems are able to run in sub-atmospheric conditions, that the systems operating characteristics would be somewhat more like the character of a hot water system, and a little less like a normal steam/vapor system, where water boils at 212F and steam has one temperature, 212F, if it is operating at atmospheric pressure.

Remember, that if a steam system is operating at a pressure of 15 psi, the temperature of the boiling water and the vapor is 250F.  

If you take a vapor heating system containing boiler water with a temperature 100F and place it in a vacuum condition of 20.72 Inches of mercury, you will have removed almost all of the air in the system and you will have lowered the boiler temperature of the water to 158F.   If you start the burner and raise the temperature of the water, it will begin to boiler and vapor will flow throughout the system when the water reaches 158F.  As long as the input of heat from the burner matches the release of heat from the radiators and piping (which it probably won't), the system would remain at 158F.  Assuming that the input from the burner is greater than the amount of heat being emitted, the temperature of the boiler water will increase and the temperature of the vapor, the pipes, and the radiators will also increase. 

My comparison to sub-atmospheric vapor systems to hot water relates to the system as described above.  Lets assume that it begins to make vapor at 158F, gets the radiators and piping all up to that temperature, and continues to fire for another 10 minutes.  During that time, the pressure will increase (vacuum gets smaller) and the temperature will also increase proportionately.  Let's say the temperature of the boiler water rises to 176F, the vacuum (negative pressure) will now be 15.94 in Hg.  Let's assume at this point the burner shuts off.  The boiler will keep boiling and producing vapor, with the temperature of both falling, and the vacuum increasing until the temperature is back down to 158F at which point the boiling and the flow of vapor will cease.  But, if the burner were to cycle on again, let's say when the temperature had fallen to 160F, the temperature of the boiling water and the flowing vapor would start to increase again.  Assuming that the burner at sufficient firing rate, if it fired long enough, it would raise the temperature to 212 and the vacuum would be 0 in Hg

Thus, instead of a vapor system that has one temperature of boiling water and vapor, that being 212F, which is the way most systems are set up to operate today, when vacuum is applied, the temperature of the boiling water and of the vapor becomes a variable.

My comment comparing sub-atmospheric systems to hot water systems   was based on this variable temperature of the heating medium, and of the resulting evenness and constancy of radiator temperatures, as well as the resulting evenness and constancy of space temperatures.



And of course, in addition to the above, vacuum conditions also reduce the amount of corrosion caused by the air in the system, and allow for a much quicker and more even distribution of the vapor at the beginning of a cycle.



I leave open the possibility that this is all a bunch of Hooey and that I'm a bumbling idiot that doesn't know what he's talking about.   

izhadano

Pressure and Temperature

Dave,

I believe that your explanation of vapor vacuum system is correct. It's very similar to principles applied by ITC at Cooper Village project - http://www.green-buildings.com/certs/ITCSteamSystem.pdf. This approach should work regardless  of the vacuum creation method (vac. pump, steam ejector, naturally induced).

The benefits of vapor vacuum system can be utilized in full scale if combined with copper tubing and lightweight panel radiators. Especially attractive for high rise buildings - no heat exchangers,  high pressure pumps, valves, etc. and mechanical floor every 14-20th level up.

Even for Empire State Building steam heating system works at 3 psig, should work at 5-10 psia vacuum without problem. Ironically, current ESB green retrofit  is targeting 38% energy efficiency savings; meanwhile long ago retrofits of steam system into vapor Paul system on average saved 35% of fuel and paid off within first heating season. 

 

  

ttekushan_3

The efficiency of distribution increases

under vacuum as well. A small flame can develop quite the plume of steam under vacuum and heat is very effectively distributed throughout as the latent heat content of steam (and its speed) increases with lower pressures.



The heat output of a radiator in such a system will be lower as it has a lower surface temperature, and the number of pounds (mass) of steam in the system is lower under smaller flame/vacuum conditions even though the volume of steam will be the same as under conventional conditions. Nice steam trick, that.



Latent heat is steam's defining characteristic yet it is routinely overlooked by many a heating engineer/technician as if the temperature of the medium tells the whole story.

izhadano

The efficiency of distribution increases

Terry,

latent heat of water vapor is changing insignificantly depends on pressure in considered interval :

1001Btu/lb @ 5 psia (vacuum), saturated vapor - 162oF

967.6 Btu/lb @ 16 psig , saturated vapor - 216oF

But temperature of delivered heat is different (and controllable now !!!)

http://www.boilerroomservices.com/Facts/SteamTables.pdf

Thanks,

Igor

Dave in QCA

Confusing Terminology

Igor,

I had to pull up the chart that you posted to try to figure out what you are saying because the numbers did not make any sense to me.  By the way, the chart is very complete and comprehensive. 

However, if you are going to reference absolute pressure, where atmospheric pressure at sea level is 14.696 psi, and water boils at 212 F at 14.696 psi (absolute pressure), you need to reference that.  Otherwise, in an applied technology forum such as Strictly Steam on Heatinghelp.com, everyone assumes that you are speaking of gauge pressure, where  at 0 psi, the boiling temperature of water is 212 F.  Pressure is measured in psi above atmospheric pressure and vacuum is measured in Inches of Mercury, in Hg below atmospheric pressure.

This may help reduce some confusion.

Dave

izhadano

Confusing Terminology

Dave, sorry for confusion :

when psia is used, that's mean relative to absolute vacuum,

           psig - relative to atmospheric pressure,  so

                              Pressure,psig = Pressure,psia +14.7

similar in vacuum  5 psia = - 9.7 psig (14.7 - 5.0)

and I put this info on chart above all conversions to bars, inch Hg as well.

.

Dave in QCA

Ok, I think I've got it....

Ok, it's been a little too long since college physics classes.  So, psia is absolute pressure in pounds per square inch.  psig, is pressure in pounds per square inch, adjusted for atmospheric pressure of 14.696 pounds per square inch.  However, while negative psi is a valid vacuum measurement, I would point out that it is rarely used, and it is rare to find a gauge that is calibrated with this scale.  The norm in gauges for heating and pumping systems and  especially for steam / vapor systems, is that vacuum is expresses in inHg. 

Igor, you are not wrong, but I am only suggesting that if you speak in the language that the professionals in this trade use, you will probably have more ears that are able to hear and understand what you saying.

izhadano

Ok, I think I've got it....

thanks, another language to learn.

I'm a lab guy with basic knowledge of HVAC craft. Positive and negative psig were used to indicate clearly and transparently the status of the system - steam or vapor vacuum and operating parameters simultaneously.

Good intentions - wrong results, as usual.