Hoffman 2 Vents?

SteamCoffee · January 8

Anyone have a source for, or a suitable replacement for the #2 vacuum radiator vent? Seems that they are no longer made. Any one?

Jamie Hall · January 8

Do you really need a vacuum vent? Unless ALL your vents are vacuum vents, there's no point in having just one.

If you really need a replacement, you'll have to assemble it from a combination of a conventional vent attached to a very low cracking pressure check valve and then the radiator.

109A_5 · January 8

Hello @SteamCoffee,
Seems kind of sad to me, but is seems the HVAC industry has given up on vacuum with a one pipe system. Hoffman 76 is may be the only I know of and it is a main vent.

ethicalpaul · January 8

Yeah this is the vent I was thinking of in another thread where I thought it was a #75 or #76. As 109A_5 says, #76 is a main vent and it costs almost $400.

Forget looking for a check valve solution, unless you really have to know for yourself.

There is no check valve that opens at a low enough pressure to make sense for a radiator vent.

SteamCoffee · January 8

Darned depressing! I have a selection of main vents ready to put to work, I’ve gotta dig into their construction and see if the check valves can be installed? Who knows, maybe another solution will come from someone's garage. May have to go Paul..iirc the #3 vent is still available. Btw the Paul brochures of the day claim a 25% savings. Some real life numbers/experiences would great.

ethicalpaul · January 8

Honestly, there is no way you could save 25% just by adding vacuum. You would be pulling more heat out of the boiler at the end of a cycle, true, but then the boiler water is going to be cooler at the start of the next cycle.

You could argue that the heat would be lost to the basement between cycles anyway, and that's true, but it's so little BTUs to bring the boiler water from warm up to 212--the vast majority of BTUs in a call for heat are used to generate the steam.

PMJ · January 8

The argument the dead men make is that open vented all the steam must be delivered against atmospheric pressure so the boiler must generate something over 14.7 psi to get it to move to the radiators. With sub-atmospheric delivery that 14.7 at the header is not needed so obviously the delivery is accomplished with a lot less effort.

I don't have any figures for how much this saves. But I can say for sure it does save. Igor published numbers with a pumped system and the savings was very significant.

But I will say it one more time - the real benefit to vacuum operation is on the comfort side. Radiators stay very noticeably warmer longer between burns which evens things out considerably and natural balancing occurs because radiators in the colder areas pull more of the available steam from the mains between cycles. My upstairs/downstairs difference which was significant (and a pain) disappeared altogether with vacuum operation. Steam returns much faster to the radiators on the next burn because every burn starts with the system at the deepest vacuum. Remember, all this happens every cycle and that adds up to a lot of steam travelling against less resistance mostly to the coldest places (wherever they are today) in real time.

If you haven't experienced this first hand then you really don't know.

One other thing, as Hoffman explained, in a one pipe system just one vacuum vent on one radiator will cause that radiator to pull a greater share of the total system steam than without it. Why? Because at boiler shutdown all the other radiators will instantly cease to pull steam from the main while that one won't stop. It isn't that much each time.....but it is every damn time, and it adds up.

SteamCoffee · January 9

PMJ! Exactly! There may not be ONE spectacular money saver, but the combination of incremental improvements can. Our job is to provide dry steam in amounts that the radiation can efficiently put to work. So much of the early steam systems were focused on boiler control. Dampers made that tough, but today we have much more precise control, making many of the boiler mechanisms moot. With that solved, concentrating on the mains to radiation and back is the issue. 1 pipe seemed forgotten by the industry, but I’m intrigued by how much LESS pipe weight may have to be heated. Especially for those with counter flow systems. Gotta start somewhere.

Jamie Hall · January 9

Couple of minor comments, more on the nit-picking side. Can't help myself. First -- the pressure in any steam system will, upon burner shutdown, equalize throughout the system at more or less the speed of sound. One vacuum vent in an otherwise atmospheric system isn't going to have much effect. Second, a two pipe system has no more pipe to heat up than a one pipe system, since the dry returns never see steam (actually many one pipe systems have more, since the "dry returns" on such systems are actually steam main extensions, and do see steam)

And a comment on dampers in early coal fired systems. They actually were, in many cases, dismayingly simple if you don't mind mechanical gadgets, and provided very precise control -- including, on some systems, well into an overall vacuum. That wasn't the problem. The problem was that they only controlled air, not fuel, and at "part throttle" they were horribly inefficient!

ethicalpaul · January 9

First -- the pressure in any steam system will, upon burner shutdown, equalize throughout the system at more or less the speed of sound.

I have several gauges hooked to different parts of my system including radiators and I agree with you--it is instantaneous for all practical purposes.

And to agree with you on the amount of pipe, I would agree a one-pipe system may have more additionally because the pipe sizes of one-pipe systems tend to be larger since they have to have room for steam and returning condensate.

SteamCoffee · January 10

Well, if your system isn’t tight, of course it will equalize asap., the 1/1700 expansion ratio of water to steam is the same in the other direction. The collapse of steam creates a massive pressure drop and if the system is tight, will hold it for a while. 400lbs of cast iron won’t stop creating steam upon the end of a burner cycle in a vacuum, I’d think. I’m also confused about this reference to “1 vacuum vent in an otherwise atmospheric system” is raising its head. To be clear, I’m talking about a total vacuum system. As for draft control I’d imagine Boiler return traps were invented precisely for this reason, probably very common back in day. The Silent Steam Team video of the Hoffman #2 salesman demonstration device video is quite instructive.ymmv

Jamie Hall · January 10

The system willl equalize in any case, at approximately the speed of sound. The question is to what pressure will it equalize? A tight system may drop into a remarkably low absolute pressure. A leaky one -- or one with conventional vents - will drop to atmospheric.

Boiler return traps -- yes. But also a host of other patented gadgetry. Some to get the water back to the boiler, some to control the differential pressure. Ingenious folk. And many of them -- no moving parts, no electricity, no transistors, and going strong after a century plus.

PMJ · January 10

I attach again the Hoffman discussion of vacuum for one-pipe steam. On page 25 is where the suggestion is to put just one of their vacuum vents on just one radiator to see the effect. You could see the same effect by installing a valve on a radiator before the vent and just closing it when the boiler turns off, even though all the other radiators are still open vented. This is often dismissed here as can't possibly be much of an effect, and also that it somehow only applies to banked coal fires. I disagree and side with the dead men. There is nothing different about the physics when a fire is just reduced and increased or if it goes out completely temporarily and then turns back on.

Jamie Hall · January 11

I give up

ethicalpaul · January 11

Yes, see the effect, the placebo effect

109A_5 · January 11

Hello @SteamCoffee,
I have a small one pipe system. I kind of like the idea of vacuum, lower boiling point, less air in the system so less oxygen, less corrosion, and maybe the steam will move faster since it is not pushing against atmospheric pressure. However I understand there may be balancing issues if there is any leaks.

My system has a variety of vents Hoffman, Dole, Dole vacuum vent and it does drop into a slight vacuum when the burner stops that dissipates in a few minutes or so. One day I got the radiators good and hot, blocked off some but not all of the non-vacuum vents and shut off the boiler, the vacuum was deeper and lasted much longer. Some day I will block off all of them and see what happens. 2 of the vents are hard to get to.

I have not really noticed any greater heat output with the vacuum vents as compared to the other various vents, but never really focused on it either.

If my system seems to hold a vacuum between cycles I will probably build this valve and install it on all the vents.

The funny thing the old commercially made vacuum vents typically used a thin metal plate to trap the vacuum. I kind of thought with a mix of vents in the system it may take a bit more pressure to lift the metal plate so the non-vacuum vent vents may vent faster, just a theory of mine.

PMJ · January 11

@SteamCoffee and @109A_5 , I applaud your interest and efforts in this. As you already know you are on a lonely road.

More than 30 years ago I purchased a house with steam heat knowing nothing about it. Being a mechanical engineer and interested in stuff by nature I listened to the massive amounts of air going in and out of my steam pipes every time the boiler ran and asked myself a simple question. If all that air had to get out to let the steam get to the radiators, then why just let it all back in when the boiler went off? What advice I came across was and still is is that keeping the air out had benefits with coal fires but that vacuum was nothing but trouble in today's systems. I pursued it anyway as it seemed to me the system in my house was the same one of almost 100 years ago.

Along the way I read documents like the one I posted here, and my direct hands on experiences just kept confirming what the dead men had written. I confirmed what they said that air was an enemy working against the project of delivering steam. I confirmed that getting steam to where I wanted it when I wanted it was dramatically easier without all that air in the way. I confirmed that it was dramatically easier, especially the where I wanted it part, if the whole system pressure was sub-atmospheric.

Keeping most of the air out in a two pipe system without a pump turned out to be a no-brainer, costing next to nothing to do, and my system has been completely transformed. Yet you continue to read here comments suggesting if subtly that I am imagining the whole thing. Or at a minimum it is suggested that there can't possibly be enough benefit to justify any effort. I won't speculate here why that is.

I think the dead men are laughing at us poking holes in these systems and inviting in all the air. Or maybe they are crying.

dko · January 11

How easily can you replicate what you did to your system to every other system out there in whatever condition the pipes, fittings, and valves are in? Cannot remove any walls or floors. Do it all at a competitive price and be done in the same amount of time (1-2 days at most). Don't take business out of the equation either.

PMJ · January 11

dko said:
How easily can you replicate what you did to your system to every other system out there in whatever condition the pipes, fittings, and valves are in? Cannot remove any walls or floors. Do it all at a competitive price and be done in the same amount of time (1-2 days at most). Don't take business out of the equation either.

I hear you. For what it is worth it took next to nothing on my nearly 100 year old piping. I tightened stems on maybe 10 of the 100 year old radiator valves and the main culprit was the packing on the main 100 year old shutoff 4" valve over the boiler. It tightened fine too. No disassembly of anything. That is literally all I did for tightening. That said, If there are holes in joints in walls I get that is a show stopper. Don't know how unusual my system is. But I think there is also a misconception that you need a really tight system. You don't. My vacuum will last 4 hours. Even at one hour it would have major benefits.

Mark N · January 11

I enjoy the yearly theoretical discussions about 1pipe naturally induced vacuum systems. I consider it purely theoretical because the radiator vents aren't available and haven't been manufactured for a long time. From what I've read in TLAOSH when the change over from coal to oil was made in the 1930's there were lots of issues with systems that had vacuum vents installed. The oil burner would turn off and a vacuum would form before all of the air had been removed from the radiators. The air would expand to fill the void caused by the condensing steam and this caused problems with balance. I have no experience with vacuum vents and can only go on what I've read. They probably stopped making them because of economics, no one was buying them anymore. I think the diagram in Hoffman literature showing a 14.7lb weight on the air vent to be just a little marketing. At sea level 14.7lbs in 0 PSIG. Steam moves on pressure differential, and it will move quite efficiently with just a fraction of an ounce difference between the boiler and vents. In 2024 if you want economical operation of your 1 pipe steam heating system it best to work on the venting of the mains and rads to achieve balance and economical operation.

Mark

SteamCoffee · January 12

I think the biggest isssues is lack of scholarship. The interest in 100 year old steam systems is small, but a pamphlet here, an old textbook there and a wives tale or 2 over there make it hard to sort out! One thing for sure is that selling 1 pipe vac venting do dads wasn’t as profitable as Air Eliminators, Return traps etc. soooo, we need to fiddle around. The big companies moved on. I’ll head where my hunches are and give it a go. None of these systems will get better, more efficient or user more user without interest. The physics are always the same but how and when they’re applied is the key.

ChrisJ · January 12

PMJ said:
I attach again the Hoffman discussion of vacuum for one-pipe steam. On page 25 is where the suggestion is to put just one of their vacuum vents on just one radiator to see the effect. You could see the same effect by installing a valve on a radiator before the vent and just closing it when the boiler turns off, even though all the other radiators are still open vented. This is often dismissed here as can't possibly be much of an effect, and also that it somehow only applies to banked coal fires. I disagree and side with the dead men. There is nothing different about the physics when a fire is just reduced and increased or if it goes out completely temporarily and then turns back on.

Here's my response to Hoffman's claims.

It's advertising and old advertising isn't in any way better or more honest than current stuff. If anything I'd say it's worse.

Long Beach Ed · January 13

PJM mentions the ease in tightening up his system. I've tightened several and my experience is the same as his. I find the hardest part is in locating the leaks. Plug the vent tappings. I bush down a fitting to a 1/4" air compressor fitting and pressurize the system. At about 10 lbs the leaks will whistle like teapots.

Usually every radiator valve packing nut needs to be tightened a half turn and the sight glass washers replaced. Sometimes there's a bad joint somewhere, maybe a saddle tee with a rubber gasket or some junk. In an hour the system is as tight as new.

Jamie Hall · January 13

Some of those solutions will work on some systems. Some won't (tightening a packless vapour valve, for instance, is an interesting exercise in futility -- and may fatally damage the valve). Also be gentle with that air pressure -- if you really want to go to 10 psi, make sure that anything which might be damaged is removed or valved off.

PMJ · January 14

Long Beach Ed said:
PJM mentions the ease in tightening up his system. I've tightened several and my experience is the same as his. I find the hardest part is in locating the leaks. Plug the vent tappings. I bush down a fitting to a 1/4" air compressor fitting and pressurize the system. At about 10 lbs the leaks will whistle like teapots.

Usually every radiator valve packing nut needs to be tightened a half turn and the sight glass washers replaced. Sometimes there's a bad joint somewhere, maybe a saddle tee with a rubber gasket or some junk. In an hour the system is as tight as new.

Thanks much for this @Long Beach Ed . And I admire your courage. The only approved narrative here is that such tightening requires an effort, chance of success, and risk profile on a par with climbing Mount Everest.

Mark N · January 14

@PMJ it's always worth the effort to find and eliminate steam leaks in a 1 pipe steam heating system to minimize the amount make up water the boiler needs which will prolong the life of the boiler for many years. That will save lots of money for the homeowner.

PMJ · January 14

Mark N said:
@PMJ it's always worth the effort to find and eliminate steam leaks in a 1 pipe steam heating system to minimize the amount make up water the boiler needs which will prolong the life of the boiler for many years. That will save lots of money for the homeowner.

Certainly does. Two pipe too obviously. The tightening we were referring to was focused on getting tight enough to hold vacuum. I'm regularly advised that effort is not worth it. But it would appear it's all the same thing.

Also consider that vacuum operation helps in the same way. With all that air going in and out - the air leaving has more water in it than the air that just came in.......24/7 it does add up to water consumption that everyone would rather not have. Well maybe not everyone. It would appear that some have convinced themselves that air is a plus and George Hoffman was a con man.

ChrisJ · January 14

It definitely adds to water consumption. A lot.

Jamie Hall · January 14

For what it's worth -- if anything -- the system Cedric powers uses NO water except for the necessary LWCO blowdown. I mean... NO water. Unfortunately, it no longer has the Hoffman 76 vent. That got replaced by a Gorton #2 many many years ago...

And no, I have not convinced myself that air is a plus. I just don't have the need for, not see the economic justification for, a Hoffman 76. Sorry.

Mark N · January 14

A 1 pipe steam system is open to the atmosphere, so some water loss is inevitable through the main vents and the radiator vents. My boiler uses between 1 to 1 1/2 gallons of water per year. I have a probe type LWCO so no reason for blow downs. I find this amount of water usage to be acceptable. A 1 pipe system needs to have main vents and vents on the rads. Depending on the number of mains and the number of rads this adds up to a lot of vents. Vacuum main vents are available but the rad vents are not. This fact makes it impossible to test if naturally induced vacuum will work without the issues reported in TLAOSH.

Mark N · January 14

@PMJ and @SteamCoffee I found this article, https://www.heatinghelp.com/assets/documents/112.pdf
The article is from 1941, read the sections about one-pipe vapor and one-pipe intermittent vapor.

ethicalpaul · January 14

I only think he was a bit of a con man by saying that you could try a single one of his vents to experience the benefits of vacuum.

oh and he was a minor con man if he said you could save 25% with a vacuum system.

But if he believed those things himself I would just say he was mistaken

PMJ · January 14

Mark N said:
A 1 pipe steam system is open to the atmosphere, so some water loss is inevitable through the main vents and the radiator vents. My boiler uses between 1 to 1 1/2 gallons of water per year. I have a probe type LWCO so no reason for blow downs. I find this amount of water usage to be acceptable. A 1 pipe system needs to have main vents and vents on the rads. Depending on the number of mains and the number of rads this adds up to a lot of vents. Vacuum main vents are available but the rad vents are not. This fact makes it impossible to test if naturally induced vacuum will work without the issues reported in TLAOSH.

@Mark N , people are pretty aggressively steered away from vacuum here and have been for years based on the same narrative you outlined. I have a copy of a post from 2003 from a guy who had a vacuum one-pipe system with all #2 vents. They had started to fail and he was looking where he might get them saying it was "imperative" that the vacuum be restored. When asked why "imperative" he said because without them the radiators cooled down 30 minutes faster when the boiler went off and air followed the steam all the way back to the boiler. He was told that vacuum was "problematic at best" (I guess he couldn't be seeing what he was seeing in his own house) and that because "all" the air doesn't get out of the system it expands and blocks steam flow. He was advised to open up his system to the air with regular vents. His third post was his last......

Um, "all" the air never gets out of even pumped systems. Not even 1/2 of it ever gets out of mine. Hmmmm. The possibility that this ever worked except somehow with a coal fire has never been allowed around here. And some of the most distinguished names in steam heat with long lists of patents get labeled as con men here for having published literature promoting it, stuff that says exactly what that poor OP described how his system worked.

Anyway I thought that post was pretty decent evidence - someone actually operating a one pipe system with all #2 valves and intermittent fire who loved it....in fact, it was one of the reasons I kept on with it. I didn't see what was fundamentally different in two pipe except that it would be a whole lot easier to do. I was right, and I love it too. I am enjoying the best comfort and the lowest gas consumption of my more than 30 years in this place. If I said we were going back to the days of mains vents, vaporstat and T87 I'd find my bags packed and out on the front stoop.

Jamie Hall · January 14

Remember: each person has their own reasons for doing, or not doing, what they do. Most of the time they are valid. Respect them.

PMJ · January 15

ethicalpaul said:
I only think he was a bit of a con man by saying that you could try a single one of his vents to experience the benefits of vacuum.

oh and he was a minor con man if he said you could save 25% with a vacuum system.

But if he believed those things himself I would just say he was mistaken

If you don't let air back into even one radiator in a one pipe system it will in fact stay warmer longer than all the others. It has no choice. Please think about this. The steam is collapsing in that radiator dropping the pressure fast, faster than it is dropping in the main. There is still steam in the main feeding it. Steam will continue to flow from the main into it. All the other radiators also are condensing and dropping their pressure. However, all those voids will be filled by air from their rooms, not steam from the main, because the room has the highest pressure and will be the supply. In the case of the radiator with the vacuum vent the highest pressure is still the main. Hoffman is correct, you can see the effect this way.

People really can't seem to grasp what a big deal this is when every radiator in the system is doing it. They apparently can't appreciate the difference between running radiators that stop getting steam from the mains INSTANTLY when the boiler goes off vs radiators that NEVER stop getting steam from the mains. They also can't appreciate how fast the boiler starts steaming again when the header pressure is even 2-3 psi below atmospheric and how fast it returns to the radiators on the next burn. Several burn minutes are saved each and every cycle.

ChrisJ · January 15

@PMJ

I think the issue is 25% is substantial.
If there would be a 25% savings on my system where is that 25% currently going?

PMJ · January 15

Jamie Hall said:
Remember: each person has their own reasons for doing, or not doing, what they do. Most of the time they are valid. Respect them.

I'm not telling anyone what to do. I am responding to the attempts by others to discourage interest in this by DIYers like the OP on this thread. That is the only reason I commented - to support his interest. Please note the discouragement that showed up as always and now disparagement of George Hoffman too.

PMJ · January 15

ChrisJ said:
@PMJ

I think the issue is 25% is substantial.
If there would be a 25% savings on my system where is that 25% currently going?

I don't have a number. It is impossible to run tests where conditions are exactly the same. I know my consumption is down from where it used to be a significant amount.

Where is it going? Not where you want it. I have risers in all my uninsulated outside walls. Open vented when the boiler goes off steam flow to radiators stops instantly so all the heat from the steam in those risers is lost in the outside walls. In a vacuum system the boiler keeps making some steam, and steam in the mains keeps flowing into the radiators that otherwise wouldn't have and so heat from it gets into the rooms that otherwise would not have.

I think maybe people can't appreciate this because cast iron radiators feel warm after the boiler goes off for a long time even though they get not one bit of new steam. I published thermal images of the difference vacuum and open vented not long ago. It took 5 or so minutes longer for the radiators to cool to the refire temperature in vacuum than not in the same conditions. I can repost if you want.

Jamie Hall · January 15

Ok, I'll say it a little more plainly. What works and gave large apparent savings for you, @PMJ , I have no doubt about. You would be a good deal more convincing, however, if first you could point to why it works for you, and discount any other variables -- but more important, it would help if you stopped writing your experiences and advice in such a way that it implies that you regard the rest of us to be idiots, which I assure you we are not.

reggi · January 15

ChrisJ said:

@PMJ

I think the issue is 25% is substantial.
If there would be a 25% savings on my system where is that 25% currently going?

It's right on page 23 , now thats with coal..very popular when the article was written

Mark N · January 15

@PMJ you posted,

"people are pretty aggressively steered away from vacuum here and have been for years based on the same narrative you outlined. I have a copy of a post from 2003 from a guy who had a vacuum one-pipe system with all #2 vents. They had started to fail and he was looking where he might get them saying it was "imperative" that the vacuum be restored. When asked why "imperative" he said because without them the radiators cooled down 30 minutes faster when the boiler went off and air followed the steam all the way back to the boiler. He was told that vacuum was "problematic at best" (I guess he couldn't be seeing what he was seeing in his own house) and that because "all" the air doesn't get out of the system it expands and blocks steam flow. He was advised to open up his system to the air with regular vents. His third post was his last......"

I do not doubt that the poster was seeing what they were seeing, but what advice should have been given? The vents they needed to maintain the vacuum operation weren't available. @109A_5 posted further up in this thread that they still have some Dole vacuum vents on their rads. This is what they posted,

"I have not really noticed any greater heat output with the vacuum vents as compared to the other various vents, but never really focused on it either."

Maybe @SteamCoffee and 109A_5 will have some success with replicating 1 pipe vacuum operation and report back with their results.

Hoffman 2 Vents?

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