Another Look at Vapor Vacuum

Dave in QCA

I had originally written this post on another thread on hoffman #2 vents.  However, there seems to be quite a lot of confersation on vacuum systems in the last few days and I thought I'd repost this as it might have gotten lost.



<strong>Thoughts on the Subject of Vapor Vacuum Heating



Is Vapor Vacuum Only For Coal Firing?</strong>



I think part of the mystery of vapor / vacuum has to do with coal firing, how it worked and how it was regulated. Coal burning in a boiler or a furnace with reasonable good quality draft and check dampers did not burn uncontrolled like wood or coal in a fireplace. While some of us are familiar with how wood can be controlled in an airtight stove, coal is much more easy to regulate, especially after the initial gassing period when all that is left is a glowing pile of carbon. The draft can be shut down and the burning coal will nearly extinguish, producing little usable heat at all. It may appear as if the fire has gone out, but a small core of burning coal will remain in the center. A fire can be held like this for quite a period of time, 30 minutes to several hours. When the draft is thrown open, within a few minutes, the entire mound of coals will again glowing bright red with red - blue flames licking up out of it. A coal furnace, stove, or boiler can essentially be turned off and on by the movement of the draft.



Dunham actually shows diagrams of electrical control of coal-fired steam boilers where a room thermostat operated a damper motor, connected to the both the draft and check dampers by little chains. This would allow completely automatic control of the firing of the boiler and would produce steam cycles not unlike what we see today on gas or oil fired boilers.



On most other vapor systems, I see special controls that operate off of very low pressures, say 8 ounces or below. Some of these systems describe that steam is maintained in the mains at all time and the regulation of heat in the building is via the proportional radiator valves. Thus, if it were mild outside, the rad valves would be mostly closed, or perhaps all closed. This would cause the boiler firing to adjust down to a very low point, that held a few ounces of steam pressure in a static condition.



Even in these types of automatic damper control, there is the ability for manual adjustment that would turn down the draft and let pressures drop.



<strong>Steam vs Hot Water vs Vapor/Vacuum</strong>



In the time around 1890 - 1900, the options for quality heating were pretty much between steam and hot-water. Steam had the reputation of being noisy, hard to regulate, annoying vents, and in many cases, the heat was on too much of the time. When the steam went down, the radiators cooled quickly, resulting in the feeling that the heat was off, and a phenomenon known as "cold 70". Thus, the on/off character of steam was seen as undesirable. Hot water was mild and even. But the downfall of water was that it was slow. If you let the space cool down, it took a long time to get the system warmed up and even longer to get the space warmed up. The radiators were also out of necessity, quite large, and the initial cost of installation was high. And so, the battles between cheap hard to control steam and expensive comfortable hot water waged on.



Then, around 1905, someone realized that if you let a steam system fall into vacuum, you could boil water at a lower temperature, the steam would not be as hot and the same for the radiators. With the ability to modulate the temperature of steam, a vapor / vacuum system could mimic the operation of a hot water system, with its inherent ability to produce modulating radiator temperatures. Also, since many vapor systems operated with a separate return line, there was no need to have a hissing vent in your bedroom or living room. Since the temperature of steam could be reduced, the piping losses to unheated spaces were reduced as well. Most importantly, it seems that vapor/vacuum operation provided a much better ability to control the delivery of heat to the space and thereby prevent overheating and wasted fuel. The ability to improve distribution meant the the heated space was much more balanced, and this too prevented overheating of individual rooms and the waste of fuel. And, in addition, unlike slow hot water systems, vacuum/vapor could be up to temperature and steaming in a matter of minutes.



Many Vapor Vacuum systems and components were invented by numerous engineering companies and they flooded the market. It must have seemed like a modern miracle, that steam heat, which had the public misconception of high pressures and danger could actually operate under a vacuum and cooler than the temperature of boiling water! WOW! A Modern Miracle!



Now, 60 years after most coal boilers were taken out of service or converted to natural gas and oil, we find ourselves in a time where we wonder about the knowledge of the dead men. Dan Holohan has done an amazing job of learning what the dead men knew and of compiling about every piece of published information on the subject of steam heat that ever existed. He has put it all together into a packaged form that makes it easy to understand, and it's organized at our fingertips. Absolutely Amazing! I cannot begin to explain the importance of his work,not only in the present, but even more so in the future.



But, there is something that gnaws at my curiosity, and it will continue to do so until I am able to experiment on my own, make observations and tabulate findings. This is on the subject of Vapor Vacuum. I know that Dan does not make stuff up, and neither to the knowledgeable pros, who contribute so much to this site. But here is the reason that I am skeptical about the accuracy of the statement, Vapor/vacuum is for coal only". It seems to be an accepted truth. But, Dunham very clearly stated that their vapor vacuum systems were good for any kind of firing, whether coal, oil, or gas. A number of other vapor/vacuum equipment producers said the same thing. Were they wrong? Were they lying? I doubt it. Was the idea that vacuum operation would save money, just an elaborate marketing hoax? I don't think so, it sounds to logical.



So, where did "vacuum is for coal" come from? I know that Dan doesn't make stuff up because I have accidentally found a number of his citations and specific information in other old and hard to find publications. Some of them I found in the Heating Help library and others in Google Books or other places. The thing that is missing, or at least that I have been unable to find, is factual justification of the statement "vapor vacuum is only for coal." But, I have found one statement to this effect. It is not substantiated, and no explanation is given as to why. But, in the Hoffman Specialty vent selection guidelines it states,

"Determine if the vent is to be installed in a vacuum system. The Model 76 Main Vent is for vacuum service.

It should be used on systems with a vacuum pump or a vapor system with a coal or wood fired boiler.

Systems converted from coal or wood fired to oil or gas should use non-vacuum vents such as the Model 75."

Perhaps this is the source of the commonly accepted truism? I don't really know, but it's the only source I have been able to find.



So, if this is the source of this directive, why would they say it? Perhaps, they thought that with very precise thermostatic controls that were now available, combined with the use of the #75 main vent and #40 radiator vent, that they felt that very even delivery of steam throughout the system was now possible, even on a very short steam cycle in moderate weather where only one or two sections of a 15 section radiator would heat. Perhaps, because they were so confident in their vents combined with good thermostatic controls, that they thought temperature control would be perfectly acceptable. If that is what they were thinking, they were pretty much correct. And since fuel was so cheap back in those days when the conversions were taking place, the added economy of keeping the vapor vacuum system in good operation seemed unimportant, and things could be simplified by forgetting about vacuum altogether.



Am I right? I don't know. Maybe? Maybe not! But, over the next year or two, I'm going to give it a good try, and I'm going to get my 1909 Dunham system to operate in a vacuum and see how it works.



Assuming that my guesses as to why Hoffman made the statements that Vacuum doesn't run on gas or oil unless there is a vacuum pump are right. I have to remember that much of the savings produced by vapor/vacuum operation were because of good control of the heat and the elimination of waste. But, there are a few other factors that are left on the table.



When steam operates at 212, every time steam comes up, it has to raise the distribution piping to 212F. Even on insulated piping, the losses of pipes at 212 are going to higher than losses at 180F. The efficiency of the boiler, boiling water at 212 is going to be very slightly less than boiling water at 180F. And then, there is the whole venting thing. So much effort goes into getting the air out of the system as fast as possible to that the steam can travel around unimpeded. Then when the boiler shuts off, we want to relieve the vacuum as fast as possible and get that air back in there... and we do it as fast as possible. Every time the air comes in, we just have to take it out again. Every time that atmosphere comes in contact with water, it oxygenates it and causes corrosion. The CO2 in the air also forms a very week dilute amounts of carbonic acid, that causes corrosion in the wet piping. Why are we so eager for this to occur? Why not have vapor vacuum with gas and oil?



<strong>Greening Steam</strong>



It seems to me, that we may wait along time for the boiler companies to give us what we want in the form of 3 pass gas fired boilers with all heating surfaces below the water line, and so many other improvements that would improve the economies of steam heat. These things should be done, and will be done, but when, is the major question. In the mean time, it appears to me that vapor/vacuum is worth another look. We know we're not going to find 45% savings like some of the old brochures stated. We have probably got most of that just by having better controls. But, we don't have all of the savings that vacuum operation can provide, and it seems to me like it would make good sense to go after it.



We've got some pretty darned smart pros on this site, and of course Dan ain't chopped liver either! These people are the leading minds in American steam heat today. Look at what has been accomplished in new advancements such as dropped headers, steam mini-tube, maximized venting, actual tabulated flow capacities of dozens of vents, main vents, and traps. etc.



I accept that my thinking on this subject may be all wrong, and there is not one penny to be gained. I also accept the possibility that more study and thinking on the subject is in order. And who better to do it than all of the people who contribute to this site and work on steam heat.

Rod

Vapor Vacuuum

Hi Dave- Thanks for taking the time to outline the vacuum steam situation.   The statement that vapor vacuum is only good for coal firing is correct as only wood/coal through control of the draft is the only firing method at the residential level that is capable (at this moment) of being modulated. At the present time gas and oil burners for the most part are similar to military flamethrowers, that is ,either fully  ON  or OFF. To replicate the coal wood burner what is needed is a fully modulating burner in both oil and gas along with a control system that works on both temperature and pressure. You would also need a control system that would use both steam pressure and temperature and outdoor reset.

Due to the small steam market , the complexity of setting up the controls and the fact that you are trying to incorporate this into present systems, a lot of which are old enough to collect social security,  I’m afraid I don’t see this happening.



From what I can see vacuum has two distinct benefits. One is the rapid distribution of steam and two is  using vacuum’s lower temperature advantages to produce steam.  At this moment  using vacuum for quicker steam distribution is probably the most doable/ practical application.  Developing a vacuum /variable low temperature steam system might be more practical if it was applied to  Gerry Gill’s wonderful mini tube system though it seems to work well enough just as it is.  Gerry, If you are reading this,  have you ever considered incorporating vacuum into your system?



Long Beach Ed recently mentioned using a taco pump and a venturi to create a vacuum. I hadn’t heard of this before and I think it has great possibilities. It’s quiet , relatively cheap and other than the pump, has few moving parts. Using a variable or two speed pump you could raise and lower the vacuum as desired.

Carlin  was supposed to be working on a 2 stage burner that could be used in smaller residential but I haven’t heard anything on that in a while. Maybe with the cost of fuel beginning to rise again we will see something develop.

- Rod

twopipe

vapor on gas system

I have a 1908 Webster two-pipe system in my house and over the last year I restored it to operate as a vapor-vacuum system as it was originally designed.  The system was originally coal, then oil, and now it has a modern Burnham gas boiler.  This was actually gainst the advice of my heating guy but I'm an engineer and based on discussion on this board last year I couldn't figure out why the recommendation to avoid vacuum made sense.  And I had to replace the traps and fix leaks anyway, so as long as it was being restored why not give it a try?

So last winter it mostly ran at atmosphere as is the conventional recommendation, and this year it is being run as a vapor-vacuum system.  Had to replace some leaky return lines (these were mostly okay under atmosphere operation but they had noticable leaks under vacuum) and replace the small vacuum ball valve- there is no vacuum pump. 

As a vapor-vacuum system it runs very quietly and evenly.  When firing it builds up an ounce or two of pressure, and then when the boiler stops firing it drops down about 16-20oz of vacuum (if my gauge is accurate).   The system maintains vacuum from cycle to cycle, and therefore the venting is typically quite short- just a few seconds.  Steam also seems to come up faster, probably because the water starts boiling faster under vacuum and there is less resistance to its movement in the pipe.  The only thing I noticed is that I have time my weekly cleanout of the LWCO to be during a firing cycle, otherwise the vacuum just pulls air into the system.

I really see no negatives to operating this way- the system runs great and my house is very comfortable.  As for positives- I'll have to wait until the end of the season to see how the heating bills compare with last year.

Dave in QCA

Modulating Burners

Rod, Modulating burners would be a great advancement.  I think that Powerflame has a high turn-down model, but it may be a bit large for most residential applications.  It seems to me that Carlin has a modulation gas burner as well. 



In my understanding of vapor / vacuum systems, (which may be flawed) a modulating burner would bring great advantage, but is not necessarily required.  Dunham described their system as working perfectly well with on/off firing of oil and gas burners, and that the benefits of the manner in which the system operated would reduce the on/off heating characteristics of the system to which it (vapor/vacuum) was applied.



One description of the operation of a Vapor Vacuum system, written by Alfred King, goes as follows. First, the system is brought up to full temperature at which point all of the mains and radiators are fully charged with steam and all of the air has been exhausted.  At this point, all vents are closed and steam is moving throughout the system, from the boiler to the radiators where it is being condensed.  The pressure of the boiler and piping is say, as an example, 8 oz., the system is in equilibrium with steam flowing throughout and condensate flowing back to the boiler.  Then the fire is cut off.  Boiling slows, but does not cease, as the radiators are still condensing, drawing steam from the boiler.  The 8oz pressure drops into the vacuum range and even though no heat is being applied to the boiler, it continues to boil and vapor is produced. (Because the pressure has dropped)  Vacuum essentially links the radiators to the boiler, through the link of the vapor in a sealed system.  As the temperature falls because heat is given off at the radiators, they draw more vapor to them, deepening the vacuum and further lowering the boiling point of the water in the boiler.   Thus, the temperature of the radiators, the vapor, and the water in the boiler continue to cool at the same rate, with mild boiling in the boiler and flow of vapor all the while.   (Remember, this is all happening with NO fire.)  King further describes that at a temperature of around 150F, flow of vapor will cease.  ( This no doubt corresponds to the completeness of the vacuum drawn.) 

After a period of time, if the boiler fires again, vapor will begin to flow throughout the system almost immediately.  If some amount of time has elapsed, the temperature of the boiler must first be raised to the point where vapor production ceased, (150F was the example)  Now, with vapor flowing at a vacuum condition, heat is again being delivered to the radiators.  As the temperature of the radiators and the rest of the system is slowly increased, the strength of the vacuum is decreased, i.e.,( pressure increases), and as this occurs the boiling temperature of the water in the boiler increases. 



Thus, when heat is applied to the boiler setting in vacuum, vapor begins to flow and the temperature of the entire system climbs at the same time.    The boiling temperature in the boiler is dependent on the pressure or vacuum.  The only way you can raise the boiling point is to reduce the vacuum.  The only way you can reduce the vacuum is the increase the temperature of the entire system. 



So, it seems quite likely that in a mild weather condition, a boiler setting in 22 in Hg vacuum, when fire is applied will begin to boil at about 150F and vapor will flow throughout the system.  As the temperature of the system climbs, vacuum decreases, etc., etc., the firing cycle, it is plausible to think that the system may come up to a temperature of 180 or 190 in 15 minutes, at which time the thermostat may be satisfied.  The fire shuts off, and the cycle repeats, all running at temperatures much lower than conventional steam. 



Now, if we had a fully modulating burner, it could be possible to modulate that firing rate down to more closely match the heating load of the building and thus allow continuous, or nearly continuous firing of the boiler and and flow of sub-atmospheric vapor.  However, constant state operation is not necessary according to the "Vacuum" Dead Men.



I have paraphrased quite a bit, but this my understanding of the operating of vapor/vacuum heat as King described it ca. 1905-1908.

Dave in QCA

U Hah!

I knew it!  I suspected that there were others out there, secretly operating vapor - vacuum systems, in spite all advice to the contrary.



Your observation of having to blow down your LWCO while the system is operating at pressure is to be expected, and it is also a good double check because it lets you confirm that the device actually shut the burner down as it's supposed to.



I'd like to know more about your system.  Have you experimented with running up a higher cycle of steam... fully heating up all of the radiators, etc., and seeing if that produce a greater vacuum?  Maybe that is the way your system operates anyway.

Enreynolds

I think

that we are not comparing apples to apple here.  Vacuum on a one pipe steam system is totally different than on a two pipe system, and need to be considered separately

Consider, if you will, a two pipe system complete with vacuum air vents, and of course, a tight system.  On the first firing of the system, all of the air is purged from the steam carrying pipes and radiators.  The returns will still have some air in them as is normal.  Now the boiler shuts down, and vacuum begins to form as the steam condenses, causing the boiling point of the water in the boiler to lower.  Thus the boiler continues to create steam, even though the burner is now off.  This steam continues to create the pressure differential to move the steam to the lower pressure areas of the system, namely the radiators.  Once the system creates an equilibrium temp/vacuum pressure, steam creation ceases, and stays in a vacuum state. End of first cycle.

Now we move on to the next cycle.  Burner starts, and boiler water begins to heat.  Steam begins to form earlier because of the vacuum and starts to move toward the lower pressure  radiators.  Steam moves faster now, because it does not have to push the air out of the way, out of the vents. The system will cycle up to its normal operating pressure, meet the thermostats call for heat and repeat.  Cycle after cycle.

Changing the system pressure in a two pipe system should not vary the distribution characteristics of the system, but might uncover some flaws.

I am planning on replacing the crossover traps in our Webster system, and experimenting with returning it to its original vapor/vacuum glory, and hopefully enjoying some reduced heating costs.  We will see.

Dave in QCA

Exactly where I am

En, you successfully described what I was also trying to describe, but somehow you used about 1/10th of the words that I used.  



I too am just getting ready to remove my main vents and install crossover traps to the return piping.  Next, I'll remove the condensate return pump and reconnect for a gravity return.  I plan on venting everything through a main vent point on the return piping.  Since I am controlling with a vaporstat, an air eliminator or return trap is not necessary and they were removed from the system and discarded long ago.  I Just need a check device and am planning on simly using a 1/2" or 3/4" swing check valve.   Dunham showed this configuration in one of their drawings.   Also, Dunham showed an equalizer between the steam main and the return piping, with a check valve allowing flow from the returns to the steam main.  This would have allowed a fast transfer of the vacuum to the return piping alleviating any tendancy for condensate to be pulled backwards as the steam mains and rads pull a vacuum.



Keep us informated of your progress and results.

Enreynolds

Just ordered

Four Watson McDaniel F&T traps for the crossovers, should be here by the 20th.  I am looking at a little more high tech check valve for the system from [u][size=8][color=#0066cc]www.fcgilbert.com[/size][/color][/u].  Their Series 200 has a cracking pressure of 1.6 oz (.1 PSI), and boasts 0 leakage.  Waiting for a call right now as to pricing.

Dave in QCA

Using Mepco 1E

I happen to have 3 Mepco 1E straight configured traps that I am going to use.  I actaully removed one antler of 2 Gorton #2 and intalled one 1E venting to the room.  It is actually venting much better than the Gortons were because of the fact that my mains retain enough warmth so that the Gorton does not fully open on any cycle except a cold start.  



Let me know how you make out with that super check. 

Enreynolds

So It looks like

There  may be a glut of Gorton #2 s on the barter page soon?!?

twopipe

vaporstat with vapor-steam

I've thought about using a vaporstat with my vapor-vacuum system but I can't quite figure if it would work.  What do I set the cut-in and cutout pressures to be?  Will the vaporstat cut in if the system is pulling vacuum?  The pressure drops pretty fast when the boiler stops firing, so not sure if it would just be cycling on and off very quickly. 

twopipe

vaporstat with vapor-steam

I've thought about using a vaporstat with my vapor-vacuum system but I can't quite figure if it would work.  What do I set the cut-in and cutout pressures to be?  Will the vaporstat cut in if the system is pulling vacuum?  The pressure drops pretty fast when the boiler stops firing, so not sure if it would just be cycling on and off very quickly. 

twopipe

vaporstat with vapor-steam

I've thought about using a vaporstat with my vapor-vacuum system but I can't quite figure if it would work.  What do I set the cut-in and cutout pressures to be?  Will the vaporstat cut in if the system is pulling vacuum?  The pressure drops pretty fast when the boiler stops firing, so not sure if it would just be cycling on and off very quickly. 

Dave in QCA

vapor stat

Remember, a vapor stat is a limit device.  It won't make your boiler do anything by itself.  Just like a pressure stat shut the fire off if the pressure exceeds the cut out pressure, the same is true for a vapor stat.  The only difference is that the vapor stat is intended for a much lower pressure range.



I set my vapor stat at 10 oz.  I sized my inlet orifices that I installed on all of the radiators for 8 oz operation.  My boiler is down-fired, but still greatly over sized, so I let the pressure climb up to 10 oz.  If the pressure exceeds 10 oz, it will cut out the burner until it drops to 6 oz. (the cut-in) and the vapor stat allows the boiler to fire.  If the thermostat had ended its call for heat, the vapor-stat will not make the boiler fire.  If the boiler falls into a vacuum after firing, the vapor-stat is not effected and has not effect on the boiler.  Vacuum does not hurt the vapor stat and the vapor stat will not "make" the boiler fire.



It is similar in operation to any other limit device.  For example, think of a low water cut out.  If the water level goes to low, it will shut off the boiler if it is firing and/or prevent the boiler from firing until the water level is bought back to normal.  However, the LWCO does not force the boiler to fire just because the water level is correct.

Dave in QCA

Two steps forward, one step back.

Yes, I hate to undo "improvements" that I have already made and that have cost good money, but....    I will have 4 spare Gortons, 2 Hoffman 75s and a handful of Heattimer varivales that I had installed as riser vents.  They won't do me much good setting on the shelf!      I'd like to get something out of them.  Ebay can be a good place for such items as well.

ttekushan_3

Vacuum experiments

The only setting I had at my disposal in the past for experimenting with vacuum was in an old building with store fronts and 2 floors of apartments above.  The boiler room was in a sub basement on one side of the building, feeding a long main with three drip stations, each station being at a transition in the elevation of the main.  I rented a store in the middle of the line and had one of the drips in my basement.  I had access to the boiler room and to my own basement only, so anything done had to be in one of those spaces.  Anyway, it was a basic two-pipe system with traps at the drip stations with one dry return, gravity return.  [We took the system back to gravity when the boiler feed pump failed]



So it was a long, linear system with a significant time delay between heating of the tail end versus the beginning.  The room temp diff from one end to the other was about 7 or 8 degrees F if I recall correctly.  Noteworthy was the delay in the steam getting past the "hump" at the drip station in my basement.



The purpose of the experiment was to see if I could even out the steam distribution and speed the pick-up time given that the boiler was slightly undersized.



Enter SHOP VAC and hoffman 76's vacuum main vents.  Now, this system was NOT tight by any means (valve packings mostly) but I couldn't control that.  Therefore, the vac did not run all the time the boiler was running, but only triggered by a thermal switch somewhere along the main and operated on an adjustable time delay relay.



The thermal switch was located in my basement on an uninsulated radiator riser.  The boiler would fire, begin producing steam, and when the steam made its way part way down the main, the shop vac (attached below the return vent through a swing check) would turn on.  The boiling at the boiler became audibly vigorous, and the steam would now charge its way down the rest of the main and up the risers.  The timer was adjusted to allow the vac to run long enough for a section or two of each radiator to heat. 



This was quite instructive as it proved that the balance of the system was maintained in the absence of vacuum, so long as each radiator started condensing at the same time.  I think this is the key to the Paul system as it both does some of the "pick up" work and gets all the radiators on equal footing early in the cycle.



Once the boiler shut off, a mild vacuum (maybe 2" Hg)  would develop for long enough to cool the boiler some.  A further evening out of the room temps would occur at this time.  The temperature differential from coolest to warmest dropped to 1.5 to 2 degrees F.



The experiment proved three things:  1)  That vacuum return evens out temperatures, 2) Vacuum return shortens the "pick up" time required and total boiler run time, 3) The building temp could be dropped a bit since no one was cold anymore, and 4) I wanted to learn a lot more about vacuum (including both naturally induced and subatmospheric) operation of steam systems.



===



In the absence of a vacuum pump, it seems to me that the system would have to be pretty tight for naturally induced vacuum to produce even temperatures as running the system to saturation (all rads filled with steam) to get the vacuum initiated.



So this brings me to an idea that I had regarding Gerry Gill's mini tube steam system (I'll cross post this to that thread when I get a chance):  What if we introduce a pressure vessel akin to a reservoir tank whose sole function is not to collect condensate but to be an air/vacuum moderating chamber, say, large enough to limit the depth of the naturally induced vacuum created by the system without readmitting any air.  At this point we may be able to achieve a system with hermetic characteristics and the benefits thereof.  I would really like to not have to blow down a boiler anymore!

Dave in QCA

AMAZING!

It is absolutely amazing that you were able to achieve such amazing results with a relatively low level of vacuum, produced by a shop vac no less!

WOW

Thanks for posting this!

twopipe

Some more on my system

I have been running this way all winter so, yes, it has run on days where the boiler fires for a long cycle. The vacuum never goes above 2lbs- not sure why or what it is supposed to get to on the system. The ball valve that is used as a check valve is probably not perfect, and the sytem probably has small leaks somewhere.



But i am not sure it matters, the objective is to keep the steam from condensing a little while longer so that the latent heat in the steam gets to the radiators inatead of the pipes. Dropping the boiling point by a couple of degrees gives it quite a while at the speeds the steam is moving. So not sure that a higher vacuum would really bring much more benefit.





One thing i did do was change the setting on my thermostat from "gravity return" to "hot water" which increases the allowable cycles per hour. By allowing more frequent cycling the vacuum is maintained.

Dave in QCA

And the dead men said ?

I recall many descriptions of vapor vacuum claiming that it had all of the benefits of hot water and all of the benefits of steam, combined together.  So, since even at a mild vacuum, you are able to distribute steam very quickly when the boiler starts to fire, a hot water setting seems reasonable.

Abracadabra

shop vac

uhm.. wow... just wow..











This is making me itch to throw a vacuum pump/shop vac on a building with a cold stack of 3 apartments.  I think if I could get steam there quicker, I'd make a bunch of people happy.

jumper

stuff

>>Many Vapor Vacuum systems and components were invented by numerous engineering companies and they flooded the market. It must have seemed like a modern miracle, that steam heat, which had the public misconception of high pressures and danger could actually operate under a vacuum and cooler than the temperature of boiling water! WOW! A Modern Miracle!

PMJ

Vapor/Vacuum

Not just for coal.

I have been running my 1926 2 pipe gas system with vacuum for about 10 years. It fires on and off from one main wall thermostat like any residential system. I removed all the radiator vents and have only a 1oz check valve vent on the main return line. Water boils for about 4 minutes after the burner goes off and the vacuum works up to about 20-30"H20 between cycles as the steam collapses. Of course boiling starts much more quickly when the burner fires again because of the vacuum. There was really no change to the steam distribution throughout the house except that it gets there faster. All radiators heat just as evenly as before if not more so.

 I have been in the house 20 years and my experience has been that the biggest problem with steam is the time lag from the call for heat to the satisfaction at the thermostat  and that causes too much overshooting. I smoothed this out by installing a simple PLC that spreads out the boiler run/off times and gives the warming radiators time to put heat in the room. In other words even though there is a continuous call for heat the PLC is cycling the boiler and will not let it run flat out. The PLC monitors the total call time and gradually increases the %on vs %off time of the cycles until temperature is reached. It also monitors total time off with no call and runs the burner longer on 1st start up when necessary. I do not ever remember walking by the thermostat and not seeing it exactly on target.   Love this system. You couldn't convince me to go back to letting all that air back in every cycle.

vaporvac

Trand VaporVac for Gas

Hello everyone,

First time back for this heating season and thought I'd pipe in with my 2 cents.  My house has a Trane vacuum system that was originally installed for GAS in 1914.  There was a coal furnace, but this was installed as a back-up as apparently gas was not always reliably available back then.  I have the original specs to the house which called for a gas furnace and states that the coal was for back-up and to be installed at the owner's extra expense, and have spoken with the owner's sons many years ago, and they verified that gas was original.  It also states in the original manual that it was good for both gas and coal. So it seems apparent that this was the case for at least The Trane system.

Although my furnace needs replacing, (see post to come), it still holds a vacuum of a few inches.  I hope this will improve with a new non-leaky boiler and a little TLC

BTW, the old coal burner (The Behemoth) still has the "Iron Fireman" that kept it automatically filled and stoked as described by Dave. There's even an on/off switch that glowed red when turned on.  It was years before we figured out that mystery switch!

Hopes this helps move this thread forward.  Thanks for everyone's help last year.  Unfortunately, I don't think there's any chance to make it completely through this season.  Oh, well.

Cheers,

Colleen

jumper

intelligent control

Any intelligent controller like PMJ's with variable (modulating) input will improve any heating or cooling system.



>>Many Vapor Vacuum systems and components were invented by numerous engineering companies and they flooded the market.

jumper

intelligent control

Any intelligent controller like PMJ's with variable (modulating) input will improve any heating or cooling system.



"Many Vapor Vacuum systems and components were invented by numerous engineering companies and they flooded the market."



Salesmen pushed too many "steam heat improving" components. Expensive to maintain and kills the cost and simplicity advantage of steam over hot water.

elfie

vacuum pump needed?

in an low pressure trapless/ventless radiator system with only a condensate receiver vent (ie. the only air vent in the system), it seems that installing a check valve on the vent pipe would at least eliminate the reentry of air back into system



consequently, it becomes a closed system (assuming no pipe joint leaks, etc)



and addition of a vacuum pump increases rate of air elimination in the system which may be of benefit (and would depend on effectiveness of the checked condensate receiver air vent)



a fascinating thread

PMJ

Vapor/vacuum

Just  couple other items for those interested:



In addition to the very low cracking pressure check valve on the main return I added an  electric solenoid valve which the PLC opens after a preset time (to make sure the benefit of the vacuum is gone) so that the return is wide open to the atmosphere dropping back pressure in the main to a minimum. This valve closes when the burner cycles off to build the vacuum again. I am planning to add one of these valves at the other far end of the system as I am sure there is some back pressure there as far away from the current main relief as it is.



Even though this system is now 85 years old I had no trouble making it tight enough. The only leaks I found were at the radiator valves and all are still original (you know the ones with the wood handles) and I could hear the air going in on the leaky ones. A little tightening did the trick. I am sure new ones would be even tighter but the max benefit of the vacuum is during the cold periods with more frequent cycles anyway and I will see at least -20" H20 hold through 10 minute off cycles.



It is really cool right after the burner fires and there is a full boil going (like one minute in) but still significant vacuum in the system to open a valve somewhere on the return and hear the boiling stop completely in an instant. The Dead Men really knew what they were doing.



In my opinion the natural vacuum system is significantly more efficient and quieter with dramatically better temperature control.

Dave in QCA

clarification

I thought I would ask for some clarification of your vacuum terms.  Did you mean inches of H2O?  Vacuum is usually measured in inches of Hg  (inches of Mercury).  Most compound boiler gauges read from minus 30' Hg to plus 30 psi.   I was wondering because pulling 20" Hg is a pretty strong vacuum, but 20" H2O -- not so much. 

PMJ

Vacuum terms

Dave,



Yes, I mean inches of water and you are right it is not so much. At most I see -40inches between cycles on the coldest days. I think to get really tight all those old valves would have to go. Even at these relatively low vacuum levels the effect is rather dramatic.

Dave in QCA

very interesting

So you have a little less than 2" Hg. A pretty mild vacuum.  It is interesting to know that your observations are that it greatly improves the operation of your system.



I suspect that tightening your valve packing will to as much as anything, even as much as putting in new valves.  I have experienced new valves on hot water systems that become leaking in a couple of years.  Tightening the valve packing or adding a little bit more packing is an ongoing maintenance issue 

jumper

sealing

Air can diffuse through a water tight pipe joint. Any one you can get at should be gooped.

Same with valve stems. Instead of cranking down on packing nut.



If you can keep out air any condensate that doesn't drain will evaporate. So ideally no vent at all. If your radiators require traps, orifice is simplest.

vaporvac

Upping the vacuum

Wow! If I'm reading this correctly, I should really see some major improvement in my vacuum when I get a new boiler that doesn't leak like a sieve. I'm currently getting at least 2" of mercury.  What other measures might one take to improve it further.  I don't have traps, mbut never found any evidence of orifices either.  I'd appreciate any input.

Colleen

vaporvac

Upping the vacuum

Wow! If I'm reading this correctly, I should really see some major improvement in my vacuum when I get a new boiler that doesn't leak like a sieve. I'm currently getting at least 2" of mercury.  What other measures might one take to improve it further.  I don't have traps, mbut never found any evidence of orifices either.  I'd appreciate any input.

Colleen

twopipe

Finding leaks

The best way to find out where your system leaks is to hook up to ain air compressor (when boiler not running of course) and pump the system up to 15psi or so. You'll hear and see where it leaks. That was hot i got my system fixed to run under vacuum.



Some leaks are acceptable. You really just need the system to hold a reasonable vacuum between cycles on a typical cold day- it doesnt need to be perfect. If it can hold 10-15psi for 20 min under pressure you are probably fine Under vacuum.

nicholas bonham-carter

Green with envy

Now I wish I had 2-pipes instead of 1-pipe!

Colleen, how about reposting in another thread. You must have some sort of limit on your rads to admit only a portion of the steam into the rad--pictures?

Dan what about a subcategory here for vacuum steam. Maybe if the steam only were at the top, we would not have so many steam postings on the Wall.--NBC

jumper

one pipe vacuum

You can make a one pipe system work under negative pressure as well.

See the recent threat on Paul conversion.

nz

How to convert...

So...assuming I wanted to convert my two-pipe Dunham Vapor system to vapor/vacuum in the future...I should:



1. Fix my leaky packless valves (see my latest post regarding repair/replace)

2. Fix all my traps (I'm about 50% of the way through this project)

3. Replace my boiler room return vents (the only ones in the house) with Hoffman 76s?

4. Add a vacuum gauge



Is it really this easy?

Dave in QCA

That is pretty much it

Nick, you pretty much got it.

1., yes your valves have to be totally tight.  If you hear or see any seepage, you won't hold a vacuum more than a few minutes.

2.  yes, traps need to be working for any operation.

3.  Yes, replace the vent on the return line with something that does not let air back in.  Hoffman used a combination air eliminator and air check.  The air eliminator had a float in it that closed the vent port if the water level got up to the height of the air eliminator in the return line.  The air check let air go out, but not back in.  Hoffman did not protect against the possibility of escaping steam from the return lines.  It was assumed that the traps in the system would be maintained.   In lieu of the Air Eliminator which protects against rising water in the return lines, which is caused by rising pressure int he boiler, you can control with a vaporstat on the boiler so that pressure is limited at a lower pressure.  The so called Dimension B states that you must have 30" of height between the water line in the boiler and your vent port, for every 1 pound of pressure in the boiler.  If you limit at 8 -12 oz, that is plenty, then you can see that you are fine with 15-22".   I would install the vent device a little bit different than you have the G2 installed.  I would put in a loop between the existing low connection that you are using and the upper connection on the horizontal line.  In the top part of that loop, I would install a Tee, and vent from that point.  It would get you a little more height.

Also, dunham shows an option on one of their drawings whereinsteadt of an air check, they pipe from the air eliminator to a location near a floor drain and simply use a swing check at that point.  Therefor, you could simply use a swing check for the vent.  It would have to be VERY tightly seating.  And, as long as you control your boiler pressure so that you do not have water coming up the return line, and maintain your traps so that you do not have steam, it will work fine.

4.  As far as the vacuum gauge, your code gauge may already show vacuum.  Most do.  It is typical to see 0 in the middle, 30 psi on one side, and 30" Hg on the other side for vacuum.



One Additional Thing.......

One other thing that Dunham usually did was use a return line equalizer.  It was basically a 3/4" pipe that ran between the steam lines, in the area coming off of the boiler, and connected to the return lines, near the air eliminator.  In that line there would be a shutoff for servicing, and a swing check valve installed in the direction to allow flow from the return lines to the steam lines.  The purpose is to transfer the vacuum to the return lines quickly.  When the boiler shuts off, the steam carrying pipes will go into vacuum fairly quickly and the vacuum will travel throughout the system on its own.  Without the equalizer, there will be a flow of air, in a backward direction between the return lines and the steam lines and radiators.  This means the the remaining air in the return lines will be sucked up through the radiator traps and into radiators and steam lines.  This causes a slowdown of condensate flow and also an audible bubbling sound.   Look on your steam lines in the area near where your vent station is on your return line and see if you find a 3/4 or 1/2 pipe stub that is capped off.

nz

Vents

Dave,



Do you mean like this (see pic below)? I repiped this about 6 weeks ago...I guess I would just throw two or three Hoffman 76s in lieu of the Gorton #2 and the Hoffman 75 I have there now...



My code gauge has markings for vacuum, but it never moves - one way or another. The Wika 0-3 PSI goes into the negative during the condensing phase after the burner shuts off, and then goes back to (around) zero. I was thinking I should get a second, vacuum gauge and add it to my pigtail here (in addition to a vaporstat, which is also on the list of things to do.)



I will look for the return line equalizer.

Dave in QCA

Perfect Piping!

Yes, this is exactly what I meant.  Have you posted this picture before?  If not, I imagined it in my head but thought it was too hard to verbally describe.  You have it exactly correct!

Yes, a couple of Hoffman 76 would add the vacuum capability.  If you wanted to check how tight your system is, you could try a 1/2" swing check valve and see what happens.

The Hoffmans have a float in them, but from evidenc I have seen, they don't totally seal and tend to drip a bit.  The Gorton also has a float, but from what I have heard, they may not seat and will squirt out water, but I have not tested one myself.  

But, like I said, the vaporstat would give you a control that would prevent water from rising to the vent level.  I plan on using a swing check valve myself, after I get my vents all repiped with crossovers, remove the condensate tank and pump, etc etc.

vaporvac

What equalizer?

Hi again,

I'm just wondering if the equalizer on the return line is the same as the equalizer that's supposed to go from the header to the boiler.  I have a weird equalizer  that looks very differnt from most specs and am now wondering if this is actually the kind you're talking about.  It does clang alot when the boiler heats up after a cold start.

I'm very interested in maintaining and vastly improving the vacuum in my system and had considered REMOVING that equalizer as I thought it was wrong.  I'd like to get this sorted out before putting in the new boiler. Thanks.

Teresa