Goin' Up the Country: Milvaco Vapor/MegaSteam Rescue

izhadano

Jamie Hall Member Posts: 13,379
4:12PM edited 4:13PM
For reference: the residual heat in a modern steam boiler, assuming that it's cooling to room temperature, is around 60,000 BTU. However, if we assume a reasonable level of vacuum (- 5 psi relative, 10 psi absolute pressure), there will be no more evaporation at 200 F, giving us only about 15 degrees -- or about 6,000 BTU.

Um... is this worth it? That's 10 cents worth of oil at the price I pay.

Jamie,
I've converted single pipe steam heating system on second floor of my house into vacuum heating system. It's 2 family house with original single pipe steam heating system on 1st floor. When vacuum heating system started for the 1st floor, it took more then an hour till steam get into nearest radiator (original old boiler still in place). For the second floor it took ~1.5 hours with .original old boiler just because of longer piping and poor insulation inside walls. This time dropped to 35-40 minutes when 2nd floor system was converted into vacuum system with auxiliary vacuum pump, and to 15-20 minutes after boiler upgrade. Beside fuel savings - Table 2, it's significant difference in comfort - much less room temperature oscillation, soft heat. less noise.
No persuasion, just personal experience.

izhadano

another clarification:
vacuum pump is controlled by vacuum switch to keep 18 -12" Hg vacuum in a system. Independent temperature controller switch vacuum pump on (and open vacuum pump shutoff valve) when boiler exhaust flue gas temperature more then 80 - 100 deg. C (to make vacuum when boiler starts and to keep vacuum in cooling system). I've tried 100 deg. C and dropped to 80 deg. C in order to reduce vacuum pump load; if your system is leak tight 100 deg. C might be a better choice. And 3rd independent temperature controller shuts off vacuum pump (and closes vacuum pump shutoff valve) when temperature at the vacuum pump separator exceeds 40 deg. C - to prevent vacuum pump from hot water vapor.

Steamhead

Sounds like you've made a lot of progress since this last came up!

Jamie Hall

Please people -- be aware that I'm not saying that adding mechanical vacuum to a system won't work. It will. I'm not saying that utilizing natural vacuum won't work. It will. What I started off trying to explain is that "vapor system" and "vacuum system (assisted or not)" are not the same thing at all.

Also, I'm wondering if the additional complexity, even minor, is worth the effort.

And for @izhadano -- in my humble opinion even 20 minutes -- while it's surely an improvement on an hour -- for steam to arrive at the end of a steam main, unless it is a very very long one, is outrageous. 10 feet per minute is slow.

ChrisJ

Jamie Hall said:

Please people -- be aware that I'm not saying that adding mechanical vacuum to a system won't work. It will. I'm not saying that utilizing natural vacuum won't work. It will. What I started off trying to explain is that "vapor system" and "vacuum system (assisted or not)" are not the same thing at all. Also, I'm wondering if the additional complexity, even minor, is worth the effort. And for @izhadano -- in my humble opinion even 20 minutes -- while it's surely an improvement on an hour -- for steam to arrive at the end of a steam main, unless it is a very very long one, is outrageous. 10 feet per minute is slow.

On a really cold day my system can get steam to every one of the 10 radiators within 90 seconds of the thermostat calling for heat.

It does it repeatedly without vacuum.

PMJ

Jamie Hall said:

5,000 cycles, @PMJ ? Great days. No wonder you're working on squeezing every drop out of your system. I just went and checked Cedric's controller. 2248 burner starts since the new controller was installed, 2 years ago (the old one suffered a very rare failure -- the final relay contacts welded. How often does that happen?)

So @Jamie Hall , great way to put it. 5000 opportunities to squeeze out something that isn't there at all open vented. There were zero opportunities to squeeze anything in your 1124 cycles last year. Using your numbers what if it was only $.05 a time or even $.025? My whole season gas bill was under $1000 last year on a 1000 EDR system in Cleveland Ohio with no insulation.

Remember, I started all this to get even heat not to save money. I concluded logically that really even heat could not be achieved by letting a boiler making steam at multiples of the rate of actual demand run straight to tstat satisfaction. That results in radiators filling way fuller than they ever need to be followed by long off periods when they return to room temperature and the system again fills totally full of air. So I started breaking up the burns and closing up the system. Low and behold, the better I got at the even heat part the more my gas bills went down. So I continued tweaking, even though the conventional wisdom here was that long runs( which by definition meant long offs) were best and vacuum was bad for intermittently fired systems and only for the coal days. The facts just kept coming in saying that neither of those things were true. Whatever folks chasing hurry up tstat satisfaction from call are after, it ain't even heat.

First I spread the burns out in timed even cycles with a total burn rate I knew would satisfy design day conditions. This was pretty good. But then 2 years ago I came up with the idea of putting a temp switch on my most remote rad's feed pipe in the garage and using it to determine when enough steam had gone out there on a new firing and when it had stopped flowing enough in the vacuum stage that I should fire again. These switch points of course would change with the conditions so the cycles would adjust themselves.

The remote temp switch idea was a real step forward. The system just really likes 2-2.5 burns per hour. The colder it gets, the longer the calls go on and the system just hangs there firing 2 times an hour burning for 8 minutes +/- squeezing some extra on the back side of every firing and then sitting in prime conditions of low pressure, warm piping, and no air to remove to make and deliver steam on every new fire. It is the waits between firings that get shorter in the cold because obviously the steam is condensing faster. Radiators stay 1/2-3/4 full(in the cold) and warm all the time. It is truly a beautiful thing, and it really is not complicated to do in 2 pipe.

Oh but OMG, no one will go here because those cycles are so terrible and will destroy the equipment say the experts. Sorry, one gas valve at least 40 years old, the other 25 years old, my damper 25 years old. This isn't all about luck. I would gladly have bought any of these during this time for the results I am getting.

ChrisJ

@PMJ

Regarding how long equipment lasts I'm sorry but your sample size is incredibly small.

izhadano

Jamie Hall said:

And for @izhadano -- in my humble opinion even 20 minutes -- while it's surely an improvement on an hour -- for steam to arrive at the end of a steam main, unless it is a very very long one, is outrageous. 10 feet per minute is slow.

Jamie,
It seems to me (may be wrong though), that 20 minutes is a good timing for modern gas steam boiler to start producing steam from cold start. Old boilers are much heavier and requires more time. For second floor steam system, I stuck with original 100 years old plumbing buried in walls, not insulated (BTW, it's a reason why boiler upgrade alone does not produce significant fuel savings in large buildings). Replacement would require gut rehab of the whole house, including 1st floor in my situation. Not worth the potential gains/savings. "IMHO", conversion into vacuum heating is less cost and efforts, so gains in savings and comfort are justified.
I'm not changing original steam system on 1st floor to have comparison base for 2nd floor improvements. Also, it's a pilot based controller/electricity independent system, so no concerns about power shortage which became more frequent in last years. Have gas shortage for couple hours only once in 20 years.
Just clarification...

PMJ

ChrisJ said:

@PMJ

Regarding how long equipment lasts I'm sorry but your sample size is incredibly small.

@ChrisJ ,

And therefore what?

PMJ

@izhadano ,

Please correct me if I am wrong but I don't think vacuum will help steam travel any faster down a cold pipe. Doesn't that pipe need to heat up first anyway? Moving air out as fast as a cold pipe will warm up is a very simple venting task that can be achieved easily through one very small hole. Once the pipes are warmed up vacuum helps delivery a lot.

This is also a reason I have found a real advantage with really long calls and spaced firings. All the starts then are warm ones. It challenges the theory of long runs long offs where all the starts (though fewer) are much colder. I have found that the steam delivery as related to the coldness of the piping (which is relative obviously to the time off) is not a linear relationship but an exponential one. I have found more warmer start cycles to be a significant advantage over fewer colder ones.

neilc

I don't know,
1 1/2 hrs, 2 hrs, for steam ?
even at 20 minutes,
anything more than 20min and you have to ask where are the main vents? and why aren't they working? and then that the rad vents are dead slow also,
maybe I missed it but unless you are reestablishing some old vacuum system, I would chase venting before retrofitting a mechanical vac system

Jamie Hall

There are some things I am a bit fanatical about ("Credo in unum Deum..."). Others, not so much. How one sets up one's steam -- or any -- heating system is in the not so much category...

ChrisJ

PMJ said:

@PMJ

Regarding how long equipment lasts I'm sorry but your sample size is incredibly small.

@ChrisJ , And therefore what?

You honestly don't know?

If you don't, there's no point in us discussing any further.

PMJ

ChrisJ said:

PMJ said:

@PMJ

Regarding how long equipment lasts I'm sorry but your sample size is incredibly small.

@ChrisJ , And therefore what?

You honestly don't know?

If you don't, there's no point in us discussing any further.

Your actual statement that I represent a sample size of one didn't need stating at all as was plainly obvious and known by all who read my post.

So I am assuming you meant to imply or infer something else. Not knowing specifically what that is, the thing you didn't write down, apparently makes me unfit for further conversation.

Ok.

Your view that your system already does all that vacuum could ever hope to do is well known. That works for me just fine. I do respect your position of total disinterest in this. What I'm not following is why you venture in at all to these totally worthless conversations. 

Steamhead

Jamie Hall said:

There are some things I am a bit fanatical about ("Credo in unum Deum..."). Others, not so much. How one sets up one's steam -- or any -- heating system is in the not so much category...

This one?

https://www.youtube.com/watch?v=ErJ3u_ePnuI

Steamhead

neilc said:

I don't know,
1 1/2 hrs, 2 hrs, for steam ?
even at 20 minutes,
anything more than 20min and you have to ask where are the main vents? and why aren't they working? and then that the rad vents are dead slow also,
maybe I missed it but unless you are reestablishing some old vacuum system, I would chase venting before retrofitting a mechanical vac system

Agreed. The system in our Find a Contractor ad distributes steam over some 200 feet from the boiler, on a few ounces pressure, in less than 10 minutes- down from an average of 2-1/2 hours before we did the vent upgrade. This not only evened it out, but cut its fuel consumption by a third.

I'm sure the faster-moving steam makes condensate much more quickly now, but as long as it drains back to the boiler quickly that should not be a problem.

We purposely don't use extremely long cycles, since the system heats up faster if the pipes are still warm.

The Steam Whisperer

Most of the of the 2- pipe naturally induced systems that we have worked on worked quite well with vacuum once we fitted them up with a 3/4 inch Apollo teflon ball check valve, with no spring, and a big mouth or two mounted above as a safety measure. We did have one that heated better after we removed the vacuum check ball that was still in place. This system wasn't in the best of shape. I never did get the concept of why these systems wouldn't work well with vacuum with a modern boiler. The vacuum just reduces the density of the air in the system, so it should still heat the same in a vacuum with the same distribution as if the air density were higher, except quicker. I could see, however, if there were big leaks, that the distribution could get effected by air venting out the leaks and the steam favoring those areas, or if the air leaks back in more densely in some areas than others. I suspect this variation in density would not last long......nature abhors these types of things. If the system is that leaky it probably wouldn't hold much of a vacuum for very long anyway. We usually see about 5 to 6inches of vacuum on our systems at shut down and it will slowly drop over time. The system still has at least 3 to 4 inches vacuum when the boiler fires again using a thermostat set for 1 CPH ( honeywell). On our systems with vacuum pumps we will see the system hold vacuum for many hours with no pump operation.

ChrisJ

PMJ said:

ChrisJ said:

PMJ said:

@PMJ

Regarding how long equipment lasts I'm sorry but your sample size is incredibly small.

@ChrisJ , And therefore what?

You honestly don't know?

If you don't, there's no point in us discussing any further.

Your actual statement that I represent a sample size of one didn't need stating at all as was plainly obvious and known by all who read my post.

So I am assuming you meant to imply or infer something else. Not knowing specifically what that is, the thing you didn't write down, apparently makes me unfit for further conversation.

Ok.

Your view that your system already does all that vacuum could ever hope to do is well known. That works for me just fine. I do respect your position of total disinterest in this. What I'm not following is why you venture in at all to these totally worthless conversations. 

To be honest I don't like how you're talking to me, or others on this thread.  Steamhead sure as hell deserves a lot more respect.

I have never said my system does what a vacuum system does.  I've said over and over that vacuum even if it did work would not allow the control I have on single pipe.


You saying your gas valve, damper and boiler have lasted many cycles suggests they all will and that's far from true.  It's that simple.


If I've come across as disrespectful to anyone I apologise.

PMJ

ChrisJ said:

PMJ said:

ChrisJ said:

PMJ said:

ChrisJ said:

@PMJ

Regarding how long equipment lasts I'm sorry but your sample size is incredibly small.

@ChrisJ ,

And therefore what?

You honestly don't know?

If you don't, there's no point in us discussing any further.

Your actual statement that I represent a sample size of one didn't need stating at all as was plainly obvious and known by all who read my post.

So I am assuming you meant to imply or infer something else. Not knowing specifically what that is, the thing you didn't write down, apparently makes me unfit for further conversation.

Ok.

Your view that your system already does all that vacuum could ever hope to do is well known. That works for me just fine. I do respect your position of total disinterest in this. What I'm not following is why you venture in at all to these totally worthless conversations. 

To be honest I don't like how you're talking to me, or others on this thread.  Steamhead sure as hell deserves a lot more respect.

I have never said my system does what a vacuum system does.  I've said over and over that vacuum even if it did work would not allow the control I have on single pipe.


You saying your gas valve, damper and boiler have lasted many cycles suggests they all will and that's far from true.  It's that simple.


If I've come across as disrespectful to anyone I apologise.



I was talking to you.

Thanks for the clarifications.

As long as we are clarifying...

Your position that you have control needs that prevent any consideration of the use of vacuum in your system is a perfectly good reason to have no interest in it. I have no interest whatsoever in trying to convince you to be interested in it. What is curious though is that you seem to rarely miss an opportunity to deny the existence of or minimize the benefits stated by others who are interested in it and feel qualified to do so with no first hand experience of your own. Maybe it is just about what someone else posted here recently that you like to stir the pot.

I do have great respect for @Steamhead as he knows way more about 99% of what is needed around here than I do. You will note I very rarely but in on any of that. But here in the one thing I do think I actually have more first hand experience in I will openly take issue with what I think is misinformation. I am happy to be proven wrong about any of it.

I'm not sure why anyone would take my life comment as that I intended it to be an expectation for everyone. It was however intended to pushback against the standard party line here that any control scheme that significantly increases cycles should be dismissed out of hand because it will damage the equipment.

jumper

If there are no traps, as is the case in one pipe systems, then why does it matter where one evacuates air from? So seal all vents; evacuate air before boiler fires; and experience warmth.

AMservices

jumper said:

If there are no traps, as is the case in one pipe systems, then why does it matter where one evacuates air from? So seal all vents; evacuate air before boiler fires; and experience warmth.

Unfortunately its not that simple. 
If you can't get all the air out (or enough air out) and keep it out, the remaining air will be compressed into the radiators.  
At 15 hg there's still 50% air in the system. And if the air can't get out, steam can't get in.
You would need to sustain 27 hg to fill 90% of the piping. 
Good luck trying to get a 100 year old system that tight. 

PMJ

jumper said:

If there are no traps, as is the case in one pipe systems, then why does it matter where one evacuates air from? So seal all vents; evacuate air before boiler fires; and experience warmth.

In two pipe anywhere on the dry return will work for an air vent/check valve location to let air out. I put mine in the garage so there is literally no exchange of air between the inside of the system and the living space. 

jumper

AMservices said:

Unfortunately its not that simple. 
If you can't get all the air out (or enough air out) and keep it out, the remaining air will be compressed into the radiators.  
At 15 hg there's still 50% air in the system. And if the air can't get out, steam can't get in.
You would need to sustain 27 hg to fill 90% of the piping. 
Good luck trying to get a 100 year old system that tight. 




How much air does 2 psig steam push out through radiator vent? What is in a radiator below its vent?

AMservices

jumper said:

If there are no traps, as is the case in one pipe systems, then why does it matter where one evacuates air from? So seal all vents; evacuate air before boiler fires; and experience warmth.

you said to seal all the vents. so 2 psi or 100 psi isn't pushing any air, its compressing it, into the radiators.

AMservices

In the LAOSH Companion, the Moline system is my personal favorite. no traps, steam ejector, orifice supply valves, 1 vent.
really everything you want in a vapor vacuum system.
Every time i hear someone suggest, just plug the vents and pull a vacuum from anywhere, it makes me think of what it says in Molines sales brochure.
"If the fire is allowed to remain too long without attention, air will , of course, be finally admitted through minute leaks in pipes, fittings, etc,; as it is practically impossible to provide an airtight heating plant, nor would the cost justify the attempt."

If it was possible to charge a steam system with a strong enough vacuum and heat reliably every cycle, some dead guy would have put his name on it.

ChrisJ

AMservices said:

In the LAOSH Companion, the Moline system is my personal favorite. no traps, steam ejector, orifice supply valves, 1 vent. really everything you want in a vapor vacuum system. Every time i hear someone suggest, just plug the vents and pull a vacuum from anywhere, it makes me think of what it says in Molines sales brochure. "If the fire is allowed to remain too long without attention, air will , of course, be finally admitted through minute leaks in pipes, fittings, etc,; as it is practically impossible to provide an airtight heating plant, nor would the cost justify the attempt." If it was possible to charge a steam system with a strong enough vacuum and heat reliably every cycle, some dead guy would have put his name on it.

Have you ever worked on a hermetically sealed refrigeration system?  They're kind of air tight.

And there's no reason you could not build a steam system in the same manner.

AMservices

Have you ever worked on a hermetically sealed refrigeration system?  They're kind of air tight.

And there's no reason you could not build a steam system in the same manner

Building a system from scratch with what we have available today is more plausible then trying it with a 100 year old piping.

ChrisJ

AMservices said:

Have you ever worked on a hermetically sealed refrigeration system?  They're kind of air tight.

And there's no reason you could not build a steam system in the same manner

Building a system from scratch with what we have available today is more plausible then trying it with a 100 year old piping.

I can only speak for my system, but in my case the supply valves are the main issue I see. Get rid of them, and my chances of holding a vacuum go way up.

Jamie Hall

It's the old question, @ChrisJ and @AMservices -- how much do you want to spend? What will the money get you?

And regarding @Steamhead 's comment a few posts back -- yes, that one!

AMservices

How much money do people spend replacing steam with something else to try and save 10%?
If @ChrisJ wants to prove his system can hold a vacuum indefinitely, im not going to try and talk him out of it.

ChrisJ

AMservices said:

How much money do people spend replacing steam with something else to try and save 10%?
If @ChrisJ wants to prove his system can hold a vacuum indefinitely, im not going to try and talk him out of it.

With all due rexspect, I never made such a claim.
I originally responded to your comment : "If it was possible to charge a steam system with a strong enough vacuum and heat reliably every cycle, some dead guy would have put his name on it."

The fact is, it's very possible. You never mentioned a 100+ year old system, in fact you mentioned dead people so I assume you mean when the system was built.

I have zero plans of changing anything on my single pipe system as it performs more than good enough for the task at hand.

Please read through my comments above in the thread.

jumper

My experience is with multiple unit residences. Only periodically did super have to pull vacuum. Usually in those days with an eductor. That may be too much for a homeowner?

Another factor was that those buildings used overhead distribution and two connections to terminals. So maybe we'd classify system as two pipe? In one building designer tried single connection. I believe there were problems but the reason may have been knuckle heading.

The big issue I think was gravity condensate return. Boiler room had very high ceiling and there were loopydedoops that I could not understand.

The purpose of these systems was minimizing original cost, not fuel. Low pressure makes for smaller risers which makes insulation easier.

jumper

AMservices said:

In the LAOSH the Moline system is my personal favorite. no traps, steam ejector, orifice supply valves, 1 vent.
really everything you want in a vapor vacuum system.
Every time i hear someone suggest, just plug the vents and pull a vacuum from anywhere, it makes me think of what it says in Molines sales brochure.
"If the fire is allowed to remain too long without attention, air will , of course, be finally admitted through minute leaks in pipes, fittings, etc,; as it is practically impossible to provide an airtight heating plant, nor would the cost justify the attempt."

If it was possible to charge a steam system with a strong enough vacuum and heat reliably every cycle, some dead guy would have put his name on it.

The vent/air eliminator was key to all those vapor systems. Also the weakness. A cheapo vacuum generator is simple and relatively foolproof. Can say something similar about make up water supply.

Jamie Hall

Just keep in mind in all this, folks, that a vapour system is not necessarily a vacuum system. A vapour system is distinguished by being designed for a very small pressure differential between the steam mains and the dry returns, with radiator flow primarily controlled by calibrated orifices and valves (and, usually, traps -- though not necessarily), crossover traps, and one main venting location at or very near the boiler. In some systems this was just an open pipe to the chimney. In others, which had various devices to ensure that that very small pressure difference was never exceeded, sometimes the vent held against a vacuum, and sometimes not.

Imposing a vacuum on a vapour system will upset the balance and operation of the system, unless the vacuum is applied to both the steam mains and the dry returns so as to maintain the very small pressure difference.

ChrisJ

Jamie Hall said:

Just keep in mind in all this, folks, that a vapour system is not necessarily a vacuum system. A vapour system is distinguished by being designed for a very small pressure differential between the steam mains and the dry returns, with radiator flow primarily controlled by calibrated orifices and valves (and, usually, traps -- though not necessarily), crossover traps, and one main venting location at or very near the boiler. In some systems this was just an open pipe to the chimney. In others, which had various devices to ensure that that very small pressure difference was never exceeded, sometimes the vent held against a vacuum, and sometimes not. Imposing a vacuum on a vapour system will upset the balance and operation of the system, unless the vacuum is applied to both the steam mains and the dry returns so as to maintain the very small pressure difference.

So.... What's my system?

Jamie Hall

Dunno, @ChrisJ . Or, more accurately perhaps, I forget...

ChrisJ

Jamie Hall said:

Dunno, @ChrisJ . Or, more accurately perhaps, I forget...

Single pipe that never exceeds 1oz and most of the time runs at 1/4 to 1/2 an oz.

Jamie Hall

Single pipe? Then one pipe steam. The fact that it never exceeds a very low pressure is great -- boiler nicely matched to the system. Indeed, that would be the case in any system which had the boiler well matched to the system.

If you had a mechanism -- such as, perhaps, a Paul system, where you could pull a vacuum on all of the vents, then you could call it a one pipe vacuum system -- and, while you were at it, run the radiation at a lower temperature, potentially saving fuel on warmer days (although now the boiler would be oversized... oops... modulating steam boiler? Hmm...). In fact, you could control the vacuum level with an outdoor reset

The question then becomes how do you create and control the vacuum? In principle, such a system is no different -- in terms of the thermodynamics in the system -- than a heat pump, except that it uses a different heat transfer/phase change medium In both, you would have an evaporating heat source, a condensing heat sink, and a device of some sort to create the necessary pressure differences. As well as various necessary -- more or less -- control devices.

ChrisJ

Jamie Hall said:

Single pipe? Then one pipe steam. The fact that it never exceeds a very low pressure is great -- boiler nicely matched to the system. Indeed, that would be the case in any system which had the boiler well matched to the system. If you had a mechanism -- such as, perhaps, a Paul system, where you could pull a vacuum on all of the vents, then you could call it a one pipe vacuum system -- and, while you were at it, run the radiation at a lower temperature, potentially saving fuel on warmer days (although now the boiler would be oversized... oops... modulating steam boiler? Hmm...). In fact, you could control the vacuum level with an outdoor reset The question then becomes how do you create and control the vacuum? In principle, such a system is no different -- in terms of the thermodynamics in the system -- than a heat pump, except that it uses a different heat transfer/phase change medium In both, you would have an evaporating heat source, a condensing heat sink, and a device of some sort to create the necessary pressure differences. As well as various necessary -- more or less -- control devices.

So what makes a vapor system a vapor system of mine runs lower pressure but isn't a vapor system?

Jamie Hall

The distinctive thing is the very low and maintained design pressure differential between the steam mains and the dry returns. Ideally one will work quite happily with no traps, and returns open to the atmosphere. Most of the gadgetry we associate with them was there to make sure that low pressure differential was controlled within a rather narrow range -- or, in the case of traps (other than the crossover traps, which are required) to compensate for fiddly fingers on otherwise properly set radiator valves (it's took several years for me to get Cedric's radiator valves properly set... ).