Goin' Up the Country: Milvaco Vapor/MegaSteam Rescue

Steamhead

This job took me back to my old stomping grounds- Harford County, MD. It's located in the far northern part of the county, which is still very agricultural- developers haven't had free rein in this area as they have further south. The high school up here was built on the site of a farm where they raised ducks. I'm told that North Harford students are still known as "Duck Farmers" by their various rivals.

There are a few indications that time has visited this area- there is now a roundabout where two state highways intersect, there is a convenience store at the roundabout and a little restaurant/carryout near the school, and there are now traffic lights at the school entrances. That's about it.

So we got a call from someone who wanted us to look at a steam system. When he told me the radiators have a pipe connecting at the top of one end with a valve, and another connecting at the bottom of the other end, I knew we were in for a treat. Here's the house- the gutter guy had a scaffold up:



and a radiator, with an outboard trap:

Steamhead

The Vapor hardware was made by the Milwaukee Valve Co., using the name "MILVACO". I had encountered the name before- @Noel used to manage a whole campus full of MILVACO gear. This installation is pretty typical of later Vapor systems, using a Return Trap, crossover traps (outboard) and a vacuum-type air vent:



But that wasn't what caught my eye at first. Someone wasted no time reading the boiler's I&O manual:

Steamhead

So we got to work:





Turned out the old king valve was stuck halfway open. We didn't put another one in- this house is on well water so it would likely fail too:

Steamhead

All done. We also upgraded the crossover traps to Big Mouth Crossovers and used a Gorton #2 as the main vent:



The oil tanks and some of the radiators are not hooked up due to ongoing work in other parts of the house. We'll be back to service the burner and test everything later.

@Gordo also made some video of this job- go here to see the list:

https://www.youtube.com/channel/UCA_ZKNA-k-nA4eH5qNb3jXA

Larry Weingarten

Hi, Looks like you've got some work to do! What was the system not doing or doing?

Yours, Larry

Steamhead

He'd called us to check it out. I pointed out the improper piping and we got the repiping job.

Jamie Hall

That's the sort of place I like to be -- and the sort of work that makes me very happy, first thing in the morning!

ted_p

Beautiful work, as always!

Steamhead said:

The Vapor hardware was made by the Milwaukee Valve Co., using the name "MILVACO". I had encountered the name before- @Noel used to manage a whole campus full of MILVACO gear. This installation is pretty typical of later Vapor systems, using a Return Trap, crossover traps (outboard) and a vacuum-type air vent:
.....

Steamhead said:

All done. We also upgraded the crossover traps to Big Mouth Crossovers and used a Gorton #2 as the main vent:
.....

Does switching from the vacuum-type air vent, to the conventional (Gorton #2) air vent (which allows air to be drawn back in) change the way the system operates?

EBEBRATT-Ed

The angle grinder did a good job getting the valve off and saving the threads.

Jamie Hall

I'll be interested in @Steamhead 's reply to this one. But just on the basis of thinking about it, I would expect -- "not really". Maintaining a vacuum in a vapour system would, in the days of coal, have been very beneficial, as the system would continue to make steam -- and thus heat the radiators, although at a lower temperature -- for a long time as the fire died down. I would think that it would have made it much easier for the poor soul stoking the boiler to maintain a nice steady even heat! But with modern, low mass, fuel fired boilers I'm not at all sure that there would be any advantage, as the amount of residual heat available in the boiler is small, and, of course, there's no input from the burner.

Steamhead

@Jamie Hall , the problem with vacuum induced this way on a modern steam boiler is that the boiler shuts down before all the air is out. This can lead to poor performance.

A small vacuum pump would cure this. This is why we stuck with crossover traps- only one connection between the system and the atmosphere makes vacuum easy to add, if someone ever comes up with a suitable small pump package that contractors can buy and install.

PMJ

Steamhead said:

@Jamie Hall , the problem with vacuum induced this way on a modern steam boiler is that the boiler shuts down before all the air is out. This can lead to poor performance.

A small vacuum pump would cure this. This is why we stuck with crossover traps- only one connection between the system and the atmosphere makes vacuum easy to add, if someone ever comes up with a suitable small pump package that contractors can buy and install.

Just for the record there is no such thing as getting "all the air out". Pumps can remove more and further enhance performance, but even they do not remove all the air. So there is always air in a vacuum system....just more or less of it. There is no breaking point at which enough air has been removed for vacuum to begin to work. So even a little vacuum is good and enhances performance, and more is better.

Vacuum is simply the condition of having the entire system pressure (the remaining air and the steam) below atmospheric pressure.

Natural vacuum is still free for the taking just as in the coal days and can still provide many performance enhancements. In two pipe steam I have yet to encounter one negative thing about it, only a significant number of positives.

Unfortunately a significant part of what is really great about steam heat is misunderstood and now apparently has been completely lost.

Steamhead

@PMJ , @DanHolohan discusses this at length in "The Lost Art of Steam Heating". My experiments with vacuum vents produced much the same results.

Basically, unless you get all (or "enough" of) the air out, when the system goes into vacuum the air will expand in volume. This can actually block steam circulation since with the vents closed there is no way to eliminate the air.

I'd love to see vacuum come back into the steam-heating business, but natural vacuum production just doesn't work that well.

PMJ

Steamhead said:

@PMJ , @DanHolohan discusses this at length in "The Lost Art of Steam Heating". My experiments with vacuum vents produced much the same results. Basically, unless you get all (or "enough" of) the air out, when the system goes into vacuum the air will expand in volume. This can actually block steam circulation since with the vents closed there is no way to eliminate the air. I'd love to see vacuum come back into the steam-heating business, but natural vacuum production just doesn't work that well.

I've read all @DanHolohan's stuff on this, that it is only for when coal fires burn down. I'm not making this stuff up. I have run my Mouat 2 pipe system closed up sinking into natural vacuum every cycle for nearly 20 years. The vacuum does the same thing as it did in the coal days - it pulls more steam out of the boiler as the pressure falls and delivers it to the rads each and every cycle. It steams and delivers faster on each new burn because the new burns start in very low pressure. We are talking minutes of steam delivery every cycle with the burner off that does not occur open vented. Open vented delivers air from the room into the rads and mains each time the burner goes off which then requires pressure to remove again every darn cycle. We are talking minutes of delivery difference here each and every cycle. I've done it both ways. This really isn't close. The heat is dramatically more even than open vented and more efficient.

So I'm really not sure what to say. I don't wish to offend anyone but what is being said and written about it just ain't so. Natural vacuum in a 2 pipe system is easy and will dramatically outperform open vented in comfort and efficiency. I've done both and I am a mechanical engineer living in the structure paying the gas bills. I'm well past the theory stage.

One thing is for sure - vacuum sure won't come back when the experts default conclusion is that it doesn't work very well like they do on these pages. That is really unfortunate. I guarantee if the systems around me ran like mine does they wouldn't be ripping them out like they are.

Steamhead

@PMJ , apparently you got lucky.

ted_p

Steamhead said:

@PMJ , apparently you got lucky.

@PMJ: I trust that @Steamhead knows what he's talking about when he say that passive vacuum systems very seldom work these days, and have a theory that might account for your success: You have "made your own luck".

Let me ask you: Are your radiator inlet-valves still original; and if not, what have they been replaced with?

PMJ

ted_p said:

Steamhead said:

@PMJ , apparently you got lucky.

@PMJ: While I trust that @Steamhead knows what he's talking about when he say that passive vacuum systems very seldom work these days, I have a theory that might account for your success: You have "made your own luck".

Let me ask you: Are your radiator inlet-valves still original; and if not, what have they been replaced with?

Careful @ted_p,

Don't work and can't work are two very different things.

@Steamhead is saying it can't work in theory because bad things happen - expanding air and such. Or if he isn't he should clarify. That he sees many systems not working well with vacuum vents on them is guaranteed. That customers won't pay for the time required to tighten them up to return to vacuum operation is highly likely. But those things have nothing to do with the physics involved and are not grounds for a "can't" work position. Nor are they grounds to deny that working passive vacuum is in fact better - especially if he never actually experienced it. Perhaps he will clarify.

I have no need to trust anyone about this. I have run this way for many years and I know in 2 pipe steam passive vacuum is a major improvement. It is turning out that in this one area apparently I am the expert. It seems I have runaway the most personal experience anyway. Perhaps in another thread I will list all the positives and really upset folks.

Radiator valves - all original 1926. I have 23. I'd say about 1/2 of them leaked(not steam but wouldn't hold vacuum well). All stems tightened successfully and easily years ago and I have never had to return for any more tightening.

izhadano

Hi gentlemen,
unfortunately I can't participate in discussion on steam system particular valves, air vents, boilers, etc. - just don't have proper training and experience. Fortunately, don't have all the biases and trade habits associated with such experience. My background in Chemical and Petroleum Engineering was helpful, though.
I've been tinkering with vacuum heating system for quite a while.
Luckily met Ed Infantino - A&M SERVICES . Ed was "nut and bolts" wizard behind 3 accomplished residential retrofits of steam heating systems into vacuum heating in MA, Main and PA.
Here is a results of 7 years study and synopsis of steam heating systems conversion into vacuum heating systems.
Feel free to comment and ask questions.
Igor

PMJ

izhadano said:

Hi gentlemen,
unfortunately I can't participate in discussion on steam system particular valves, air vents, boilers, etc. - just don't have proper training and experience. Fortunately, don't have all the biases and trade habits associated with such experience. My background in Chemical and Petroleum Engineering was helpful, though.
I've been tinkering with vacuum heating system for quite a while.
Luckily met Ed Infantino - A&M SERVICES . Ed was "nut and bolts" wizard behind 3 accomplished residential retrofits of steam heating systems into vacuum heating in MA, Main and PA.
Here is a results of 7 years study and synopsis of steam heating systems conversion into vacuum heating systems.
Feel free to comment and ask questions.
Igor

I refrain from speaking about 1 pipe now as I got a real beating here when I suggested vacuum would work with those systems too without first hand experience. So I will leave that to you guys. I will say that from what I know about vacuum if I did own a 1 pipe system I would be fishing those plastic venting lines to all the radiators for sure. Really cool system. Ultimately much finer control possible than with 2 pipe.

Jamie Hall

You know, I sort of thought about writing a longish commentary on all this, but... since some folks have far more experience than I, and others have all the answers, I decided it wasn't worth it. Suffice it to say that the actual physics of both mechanically induced vacuum operation and natural vacuum (sealed system) operation are very interesting.

ChrisJ

Steamhead

@izhadano , have you all gotten to the point where the upgrade- at least the vacuum pump portion- can use standardized parts?

mattmia2

It seems you could achieve vacuum on one pipe steam with vents with check valves although it would let you know very quickly where you have pitch problems.

motoguy128

mattmia2 said:

It seems you could achieve vacuum on one pipe steam with vents with check valves although it would let you know very quickly where you have pitch problems.

I looked in to this extensively, and couldn’t come up with a cost effective way to do this (off the shelf fittings and parts). The other challenge is that a system tat might not leak steam at 1 oz, or 8oz may leak with 2, 3, 5 psi vacuum. That means air gets sucked in through leaking valve stem seals and your balance will be all out of whack. I have tons of red stains on my valve stems when my system was previously run above 1psi with an oversized boiler and slow main venting. But now It’s perfectly balanced and runs under 1oz with just barely enough capacity to fill all the radiators evenly and can’t heat all of them fully. But I save energy by leveraging that opportunity and using TRV’s instead.

If they still made Hoffman 2 vents, it might be workable.

JUst a side note, once you are running on very low vapor pressure, the system tends ot partially balance itself as the steam gets drawn towards bigger radiators and larger laterals. So a 50EDR radiator on a 1-1/2” line will get more steam than a 30EDR on a 1-1/4” with the same vent setting. I believe this is a because the leading edge of the steam is creating a vacuum and it progresses. The larger pipe And radiator has more surface area absorbs more heat, pulling more steam forward.

So even if you don’t have a vacuum, a vacuum is being created as it progresses.

Jamie Hall

I said I wouldn't talk physics, but @motoguy128 brings up a point which seems to have been lost in the weeds in several of these discussions.

There is a very very critical difference between "conventional" steam systems -- running at perhaps 1.5 to 2 psi boiler pressure -- vacuum systems, running at perhaps 2 to 3 psi vacuum, and vapour systems.

Pressure differential. Not pressure, pressure differential. Both conventional steam systems and vacuum systems (mechanically induced or natural) run at a significant pressure differential between the boiler and the outlet from the radiation (whether it is a vent, a small vacuum pipe, the dry returns, whatever). From the standpoint of fluid flow and the evaporation/condensation cycle in the system, the source of the pressure differential is completely irrelevant. The only thing it affects is the temperature at which evaporation takes place and, correspondingly, the temperature at which condensation takes place.

A vapour system, on the other hand, whether it is Milvaco or Hoffman Equipped or Trane or whatever, is intended to operate on a very small pressure differential -- on the order of a few ounces -- between the boiler and the outlet from the radiation. As long as that pressure difference is kept small, again the absolute pressure at which the system is operating is completely irrelevant, except as it affects the temperatures.

It is vapour systems which are the odd ducks, not vacuum systems, and they must be treated and operated with that in mind.

motoguy128

What I’d point out however is that in 1 pipe, the only thing that makes a system able to operate on vapor is the relationship, or ratio if you will, of the pipe size, total EDR/load including pickup and boiler size.

I just salvaged a system near me, that at first glance appears ot be conventional 1 pipe Based on lateral and main sizes, but happily operates under 2oz of pressure now that I installed Adequate main venting. With more venting I suspect it will run even lower. It was pretty remarkable to fire it up after changing the vents and see it run with a stable water line (despite improper header) And needle lightly bound just under 2 oz on a 8 oz gauge. I’m sure it will peg the gauge once it starts closing vents and fully heats the system. It really needs 2 size smaller boiler based on the installed radiation I counted.

I sometimes wonder if the only think making a system, “conventional” is that the boiler is a little big and the main venting too slow.

But there’s a push to make systems fully heat the radiators and then cycle on pressure switches.

Similarly, we seem to size Atmospheric cast iron hot water Boiler the same. Add plenty of pickup then just have them cycle on the temp limit. Rather than size them run out of capacity at 180F or less with more rational pickup factor.

PMJ

Jamie Hall said:

I said I wouldn't talk physics, but @motoguy128 brings up a point which seems to have been lost in the weeds in several of these discussions.

There is a very very critical difference between "conventional" steam systems -- running at perhaps 1.5 to 2 psi boiler pressure -- vacuum systems, running at perhaps 2 to 3 psi vacuum, and vapour systems.

Pressure differential. Not pressure, pressure differential. Both conventional steam systems and vacuum systems (mechanically induced or natural) run at a significant pressure differential between the boiler and the outlet from the radiation (whether it is a vent, a small vacuum pipe, the dry returns, whatever). From the standpoint of fluid flow and the evaporation/condensation cycle in the system, the source of the pressure differential is completely irrelevant. The only thing it affects is the temperature at which evaporation takes place and, correspondingly, the temperature at which condensation takes place.

A vapour system, on the other hand, whether it is Milvaco or Hoffman Equipped or Trane or whatever, is intended to operate on a very small pressure differential -- on the order of a few ounces -- between the boiler and the outlet from the radiation. As long as that pressure difference is kept small, again the absolute pressure at which the system is operating is completely irrelevant, except as it affects the temperatures.

It is vapour systems which are the odd ducks, not vacuum systems, and they must be treated and operated with that in mind.

This is an important point I think not well understood. When you take a system below atmospheric pressure the whole system shifts down and the pressure relationships inside (the differentials) all stay the same. A 2 pipe system is all wide open inside. There are no areas that suddenly become very different relative to others just because the whole thing has gone sub-atmospheric. The behavior inside is still the same. Balancing is better closed up and sub-atmospheric but these are subtle differences which accumulate over time.

Question though @Jamie Hall - when you say "conventional" are you saying there are two pipe systems(or 1 pipe for that matter) designed with the delivery piping so small that you literally cannot flow the volume of steam required to heat at capacity with partially filled radiators unless the pressure differential between header and rads is 1.5 psi or above?

ChrisJ

@PMJ

Seems like you would need an awfully long pipe to create enough resistance to need 1+ psi at the boiler.

I think I had calculated my longest run needed just under 0.25" wc which just happens to be where the system runs on cooler days.

Obviously my system is small, but just how long would piping need to be to get up to 1 psi worth of friction?  Doesn't seem plausible in a home.

PMJ

ChrisJ said:

@PMJ

Seems like you would need an awfully long pipe to create enough resistance to need 1+ psi at the boiler.

I think I had calculated my longest run needed just under 0.25" wc which just happens to be where the system runs on cooler days.

Obviously my system is small, but just how long would piping need to be to get up to 1 psi worth of friction?  Doesn't seem plausible in a home.

Agreed. Therefore my question. What residential system is designed to run at 1.5 to 2 psi or ever needs to.

ChrisJ

PMJ said:

@PMJ

Seems like you would need an awfully long pipe to create enough resistance to need 1+ psi at the boiler.

I think I had calculated my longest run needed just under 0.25" wc which just happens to be where the system runs on cooler days.

Obviously my system is small, but just how long would piping need to be to get up to 1 psi worth of friction?  Doesn't seem plausible in a home.

Agreed. Therefore my question. What residential system is designed to run at 1.5 to 2 psi or ever needs to.

I do not know where that came from and a smoldering coal fire certainly wasn't doing it.

I suspect it was an arbitrary number thrown out as a upper limit rather than a minimum 

I would expect any residential system to run at 100% at 1/4 psi or less.  

PMJ

ChrisJ said:

PMJ said:

ChrisJ said:

@PMJ

Seems like you would need an awfully long pipe to create enough resistance to need 1+ psi at the boiler.

I think I had calculated my longest run needed just under 0.25" wc which just happens to be where the system runs on cooler days.

Obviously my system is small, but just how long would piping need to be to get up to 1 psi worth of friction?  Doesn't seem plausible in a home.

Agreed. Therefore my question. What residential system is designed to run at 1.5 to 2 psi or ever needs to.

I do not know where that came from and a smoldering coal fire certainly wasn't doing it.

I suspect it was an arbitrary number thrown out as a upper limit rather than a minimum 

I would expect any residential system to run at 100% at 1/4 psi or less.  





In which case then aren't we all then able to operate at vapor system pressure differentials between header and radiators? I certainly am.

AMservices

A good thing about using a vacuum pump is you can fill more of the radiators, faster with lower temperature steam. That way at the end of the cycle whatever steam is still being produced by the hot boiler will still work its way to the radiators. Furthermore using the vacuum pump to maintain a steady vacuum while the burner is off, ensures the steam and whatever expanding air remains will still be moving in the intended direction through the system.
Ether way, naturally induced or mechanical vacuum, i don't see the remaining air as the culprit.
The infiltrated air is the problem. Air leaking back into a radiator, especially right at the valve stem is how steam will be cut off. Air that's already in the space isn't a concern because steam is still the denser gas. Steam pushes air around so as long as more air isn't getting back in, steam should be able to get any where it was before the burner turned off.
I've restored a couple large steam system that were still using a ball check as the main vent. Works great! Does exactly what you would want it to do. But the ball check is the exception. They don't break and vent quickly. @Steamhead is right replacing the vacuum vent because it does vent as fast as the gorton 2 and it probably dosen't work anyway so it could only hurt the operation.
Modern day steam systems absolutely can be restored to benefit from a vacuum. But you have to repair the leaks.
@motoguy128 I just want to say about your large radiator with 1.5" supply, steam could be favoring that radiator over the one with the 1.25" valve because it has a lower pressure drop. It might also have to do with the leaking valve stems. Steam might go to that 1.5" valve fast then 1.25" valve if the stem is venting faster. The temperature of the air surrounding a radiator is a factor as well. A colder radiator will condense steam faster making a lower pressure, drawing in more steam. Thats how and why a vacuum system is self balancing.

The best way to make a single pipe system work with the benefit of a vacuum is.... ready for this?
Another pipe.
Running air lines to a common vent makes a simple, less expensive 2 pipe steam system.
I know its more expensive then replacing air vents. But after its done you only have to worry about 1 vent And you have a system thats self balancing.
Put a small vacuum pump on it and decrease your startup time and pickup loses.

Thank you @izhadano for the compliment.

ChrisJ

The beef I have with that is the amount of energy left after the burner shuts down is very little on a modern boiler.

It's not the same as a fire dying down but keeps burning.  The burners are off and the block + water doesn't have that much mass.


All of the other things aside, that part I feel is moot.

Jamie Hall

Oh dear. No, of course most residential systems will -- and do -- and should -- run very sweetly at relatively small pressure differentials.

The difference between vapour and most other systems is that not only do vapour systems run at very small differentials, they are designed from the ground up to do so, and they will not run properly, if at all, at any differential much over half a pound, if that. Many of them -- I'd venture to say all of them, now -- do have a main vent or vents -- but most of them, if they are operating correctly, don't need one. Not that a vent to somewhere isn't needed, of course it is, but that the "vent" never sees steam, if all is well, and never closes. If the system is controlled properly, it never needs to. The entire return side is open to the atmosphere at all times.

Note that you could do the same sort of thing on a one pipe system, if you used orifices or vapour type metering valves on the radiators. Jand ust a jolly old open hole to the atmosphere at the other end of the radiator!

You still need to vent the mains, and this was -- and is -- done with crossover traps; steam traps arranged to let keep steam from entering the returns -- which returns are basically open to the atmosphere (if all is going well).

Now where things get confusing is that many brands of vapour systems employed a belt and suspenders approach to the radiator controls, and put a steam trap on the outlet to the radiators. Is it needed? Not if the inlet valves are properly adjusted. They often aren't -- and may never have been (the dead men weren't much more perfect than we are). One can operate such a system on a higher ultimate pressure differential and, other than throwing the balance off, nothing really evil happens.

Further, some -- not all -- vapour system installations from the days of coal had various interesting arrangements -- all patented again, and of varying complexities -- to automatically adjust the draught on the coal fire to maintain the correct pressure differential. Most of the time these worked remarkably well, although the efficiency was horrid and stack emissions were worse. But at least you didn't have to go down to the boiler, squint at the pressure gauge, and throw on more coal or adjust the draught -- or not -- as the situation demanded!

Things get further confused in that many vapour systems had additional appliances, all patented, some with more moving parts than a clock and some with no moving parts at all, which were designed to keep the pressure differential low. They all do this in much the same ultimate way: they close the vent from the dry returns to the atmosphere and switch steam pressure from the boiler into the dry returns, thus reducing or eliminating the pressure differential across the system. This was done so that water wouldn't back out of the boiler into the steam mains if the pressure go too high, creating a dangerous low water situation. Remember, we're still talking about coal fired boilers here, and coal fires, then and now, occasionally get out of hand -- and you can't just flip a pressuretrol or a switch and expect them to go away.

Again, some, but not all, vapour systems had main vents arranged to close on a vacuum. The purpose here was to allow water vapour to continue to be produced at the boiler and condensed in the radiators at lower temperatures, as the fire in the firebox died down -- both hopefully slightly increasing the overall cycle efficiency of the system (still atrocious, but not quite as atrocious, perhaps) and to keep some warmth coming from the radiators. If the system was tight enough to hold a vacuum for a long time, so much the better -- as soon as someone stoked the fire again, you would get more vapour to the radiators. In my view, however, it was not the intention to create a sealed system, however. It certainly was not the same concept as a mechanically induced vacuum on the returns (or on the vents in some types of one pipe radiator systems) where the objective is to remove the air from the radiators and returns by increasing the pressure differential between the mains and the radiators on the one hand and the returns on the other faster than would happen naturally.

But this shouldn't detract from the essential characteristic of vapour steam systems: designed from the ground up to have a small pressure differential between the steam mains and the dry returns, and to regulate steam entry into the radiators so as to never more than supply just enough steam at that pressure differential for the radiator to condense, and no more.

PMJ

ChrisJ said:

The beef I have with that is the amount of energy left after the burner shuts down is very little on a modern boiler.

It's not the same as a fire dying down but keeps burning.  The burners are off and the block + water doesn't have that much mass.


All of the other things aside, that part I feel is moot.

This really has to be experienced to appreciate the difference. The effect is greater with a big older boiler like mine which is still making some steam 4-5 minutes after the burner goes off. But the real benefit of the vacuum condition is more about the fact that steam flow to the radiators is not interrupted instantly when the burner goes off like it is in open vented systems but continues a long time after. The system just sits there drawing every possible wisp of steam out of that boiler and continues sending it to the rads. I keep a differential pressure gage comparing the header to the far corner of my main loop at all times. It will still be showing 1"WC differential 30-45 minutes after the flame goes out. So a good portion of this time is spent still delivering steam to the radiators. Open vented systems spend this same time filling radiators and mains with air that then needs some steam pressure to remove it. The system sitting in vacuum instead for the next fire will start making steam minutes earlier due to the low pressure and deliver it faster because there is no air to remove. These are not small differences.

I have said for some time that efficiency is really about net steam delivered at the radiators per burn minute though I don't think it has really registered with anyone. When you think about this considering what I have said above I think it is pretty obvious we are talking a very significant percentage advantage in this for the vacuum system.

hvacfreak2

Nice job on the header piping Frank and Gordon. I'm anxious to hear how it does when you get it online , neat old system.

Hey just an fyi , I noticed a tremendous performance increase when I insulated the header on mine. It may be worthwhile on a repipe job like this to really show a difference.

Jamie Hall

I said I didn't have any answers.

Jamie Hall

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.

ChrisJ

Jamie Hall said:

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.

I would argue that in most cases you won't even lose that 10 cents.  

PMJ

ChrisJ said:

Jamie Hall said:

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.

I would argue that in most cases you won't even lose that 10 cents.  

Is it worth what? In 2 pipe there is literally no investment required to do it. In fact you save the cost of real vents which are not needed. If you add a less than $100 timer you don't need traps either so that maintenance goes away. Sounds like the math is real complicated. Anyway, I guess you guys aren't interested but at $.10/cycle I'll take it. I did 5000 cycles last year. Gee, maybe a few more cycles isn't so terrible after all. If 3000 btus got all the way to the rads with the burner off every cycle that doesn't open vented that is a big deal.

Secondly, you guys did see the part where I said the residual heat in the boiler is not the important part anyway right? It is the delivery . You can rationalize it all away if you wish to try but in so doing you have to say Igor's numbers aren't so. Slippery slope there.

Oh, and I haven't even mentioned the improved comfort performance which would be worth the effort with no $$ gas savings.

Sorry @Jamie Hall , I know, too many answers. I should be apologizing for being the only one with actual experience with natural vacuum instead.

Jamie Hall

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?)