Simple 2 Pipe Vacuum Setup

PMJ

I got to thinking that some people might be thinking that my setup is complicated and expensive. It really is neither so I thought I would detail a possible simple starting place for any 2 piper interested in giving it a try.

You will need an delay on/off 24volt timer relay that has both the on time and the off time independently adjustable. I haven't looked in a while but I think you can do one of these for less than $100. By the way, the PLC I use is $129 which provides unlimited control options so this never gets very expensive. I don't have a model# handy at the moment for a timer relay but I will find that if needed. The output relay of this timer gets wired in series with the Tstat signal line going to the boiler. Once installed, it merely sets the actual burn time and off time (I call it wait time) to minutes of your choosing and keeps that regular pattern throughout the call for heat. With this being the only control device you will need to pick a cycle where the net total burn time % is enough that you know will heat the house on a really cold day. For me that is 50% so I would choose 10min on/ 10 min off which is 30 burn minutes per hour evenly spaced. You could make it 15 and 15 if you want only two cycles or 30/30 if you want only one. I ended up with 3 but nothing magic about that really. It doesn't have to fit evenly in hours either obviously. All up to you and kind of fun.

The above setup is where I started and ran several years. It merely spreads out the burn and cuts overshooting way down - especially if your boiler is oversized like mine. Its only real weakness is at startup where you really would like that first burn from room temperature piping to be a little longer. I have since installed a preheat sensor and my first burn is about 25 minutes. So the first hour with the above setup is a little slow but during times you actually need heat you don't need any preheats and the setup really improves everything after that. You also can just go to the device and easily change the on/off ratio anytime you like with the knobs on top. I highly recommend anyone interested in this at all spend $100 or probably less for one of these and start trying. It is too easy. Remember - these extra cycles are not bad and don't waste anything. Your system is not cycling on pressure because the boiler was never allowed to run long enough to build pressure or if it is something else is wrong.

Ok, on to vacuum. At this point I still had a vent on the end of the main at which I heard air going in and out of every cycle. As I thought about this I realized this air was just going in and out and wondered if that was really necessary. So I took it off one day just for the heck of it. Nothing changed really except that air now went in and out of the vent on the dry return. The rads seemed to heat just the same or maybe even a little better as air never actually got all the way back in the main anymore with the burner only off 10 minutes at a time. The startup cycle was still fine too. As I have pointed out there is plenty of time on that first warmup cycle for air to go out of the main through rads and out the dry return. At this point there were still a few vents on rads left around from previous contractors who didn't know what they were doing. By this time I had Dan's books and took them off. So then I had only one point where air was being allowed back in to the system when the burner went off and I wondered if that really needed to happen either. Well, I soon found that that didn't need to happen and the rest is history.

If you want to try this here is a simple start. I even have model numbers. You need one location on the dry return to install a 110V solenoid and an ultra low pressure switch. They need to be wired such that when the switch senses any pressure above atmospheric its contacts close and power the solenoid valve to open. This setup can be stand alone anywhere and does not need to be connected to anything at the boiler. When the burner goes off and the system begins to sink into vacuum, the switch contacts will open, the solenoid will close(obviously you need a normally closed one of these) and now your system is all closed up and air won't go back in. A vacuum gauge nearby to see the vacuum level will help. I use a Dwyer Cat# 1910-00 switch and an Alcon Valves Cat#UG86 solenoid. Both are a number of years old now - don't know current status. For whatever reason the 60" water vacuum this switch sees every cycle has never hurt it. Also, the solenoid valve must be put in with the flow arrow going out of the system. Won't seal against the vacuum the other way. Another thing, for safety I installed a simple check valve next to the solenoid in the event that the solenoid failed to open so no pressure could ever build in the system.

So there you have it. I probably missed something or have something backwards - just let me know. There really isn't a mountain to climb to give this a go. I have enhanced things quite a bit from here with PLC control but as I said before even that is not expensive nor is the programming complicated. Maybe there is no interest. That is ok too. I just wanted everyone to know that what I am doing is really simple actually. My steam is always going in forward motion to my rads during all calls for heat - always. No wasted effort chasing air back and forth. More even heating as mostly vacuum is pulling steam into rads more in response to what is needed rather than pressure pushing steam in based on vent location. I have found it to be a lot better and no vents to buy and maintain.

hvacfreak2

Shoot man , that is awesome . Have you noticed or documented fuel usage before and after ? It sounds like the comfort level was definitely noticed.

PMJ

hvacfreak2 said:

Shoot man , that is awesome . Have you noticed or documented fuel usage before and after ? It sounds like the comfort level was definitely noticed.

I'm thinking about digging that up. I have gas bills back to 1993 before I did anything. Just need to put that together with HDD data over a stretch now and then. A bit cumbersome but I'll try.

Again, I am sure it is more efficient but not crazy so. 10-20% wild guess. The real deal about this is comfort. Way more even and way more quiet. Even the doubling of vacuum this year from 30 to 60 inches has the family talking about that they don't hear a thing. Even the few expansion noises are down. Because air is not going back in the pipes cool less so less back and forth with those too. It is really cool.

Mad Dog_2

Fascinating. Keep goin. Mad Dog

PMJ

I took a quick look at some numbers. Maybe a little better than I thought.

Over a 14 week stretch in 1994 I used 190.9MCF and there were 3314HDD in that period according to data on Weatherunderground for my location. Over a 14 week stretch this year I used 120.1MCF and there were 2749HDD in the period. Looks to me like I am now using about 75% of the gas I was before for the same job if I am doing this right. Feel free to correct me as needed. Remember, in 1994 there was no vent damper either. Everything was as received.

I don't think there were any other factors involved but I should do more periods to confirm this. I am quite sure I am not doing worse and I think this easily pays for the equipment involved anyway. That said, I might even pay extra for the added comfort - though I am quite happy to win on both fronts.

EBEBRATT-Ed

Interesting. Wonder if you could do away with the pressure control and wire the solenoid in parallel with the gas burner using a relay. Burner on--vent, Burner off---vacuum.

PMJ

EBEBRATT-Ed said:

Interesting. Wonder if you could do away with the pressure control and wire the solenoid in parallel with the gas burner using a relay. Burner on--vent, Burner off---vacuum.

No pressure control now. Vaporstat is safety only.

You can't open the vent right when the burner comes on. You will still have vacuum nearly 4 minutes into each 10 minute burn. Need to stay in vacuum as much as possible. So solenoid needs to only open when system actually hits atmospheric pressure as determined by the pressure switch. It is only at that point that the small amount of air that leaked back in needs to be pushed back out or early in the call when you are still filling up a little more air needs to go out each time.

SteamCoffee

Cool stuff...any thoughts about vacuum pumps? Any more gains to be made by going sub-atmospheric a la Dunham Differential? Cost may outweigh the benefit for deeper/longer vacuum. Super interesting...

jumper

Primary goal is to eliminate air. Also to stop wasting exergy by using steam to pump air. Pressure is not important although cooler is always more efficient thermodynamically. In my opinion ideal is to maximize radiant relative to convection.

PMJ

SteamCoffee said:

Cool stuff...any thoughts about vacuum pumps? Any more gains to be made by going sub-atmospheric a la Dunham Differential? Cost may outweigh the benefit for deeper/longer vacuum. Super interesting...

Search @izhadano for info about pump driven systems. Igor has done a lot of work on this and has some pretty impressive numbers to show for what he can do with pumps staying sub atmospheric all the time. His thing with me was that my system would prove more able to hold vacuum than I was thinking at 90 years and he was right. I haven't spent 3 hours total working on leaks. Even at 1/3 the vacuum I have now the results were impressive. No one should let worries about that stop them from trying this.

I have stopped short of pumps for now. The appropriate ones are $500 or so and I'm not sure I can sell mission control here on any extra noise. Simplicity and fewest moving parts has been a goal of mine from the start and natural vacuum sure satisfies that requirement.

SteamCoffee

Ok, now how do we keep your "steam in motion" concept going in a mini tube system? Eliminating btu loss spent heating supply/return piping, pickup factor etc. seems like a very attractive area for gaining efficiency. A Minitube 1) under natural vacuum 2) gravity return, no $$ on condensate/vacuum pump 3) no steam traps, throttle at the rad inlet. 4) find a way to never trip on pressure... seems like the next step. Simple and very efficient.

Jamie Hall

The figures certainly look impressive. Being a bit on the suspicious side, though, I have to ask: did anything -- anything -- else change in the last 22 years about the building? The vent damper you mention. Windows? Any new insulation? Changes in outside building exposure (like more trees/less wind)? Change in interior setpoint (a two degree change in interior setpoint cut the fuel usage to 80% of what it had been)?

All that said, I have to wonder if simply using a good vacuum tight vent -- like the Hoffman 76 -- wouldn't accomplish much the same thing as using a pressure switch and a solenoid, both of which I'm wary of. As I understand it, that type of vent is closed on vacuum, and will only reopen if the pressure in the pipe is greater than the pressure outside -- which seems to me to be what I'm reading your pressure switch/solenoid setup does. I'll grant you that they aren't cheap -- no good big vent is -- but one of the real advantages in that regard of your system is that one doesn't need much venting.

Gsmith

Any thoughts on how this might be applied to 1 pipe systems? I could see putting simple check valves on my B&J big mouth main vents, but not sure how to handle the rad vents. And, maybe more importantliy, my system is balanced by the differing flow rates of the rad vents, and I'm not sure equal steam flow to all rads would work. Can't think of how to throttle the supply side like two pipe systems can, without causing water hammer in the rads. Maybe this should branch to a new thread, didn't mean to hijack this one.

Eastman

@SteamCoffee

SelectTemp mini-tube systems maintained steam in the main lines throughout the heating season. Each radiator utilized a TRV. Hence it makes sense that the installation manual for the system recommended sizing the boiler based on heat loss and not some other combination of EDR and piping and pickup factor.

I would think a vacuum version could only be an improvement in every respect.

Eastman

Nice video demonstrating a vacuum vent:
https://youtu.be/4ple0cVv6ow

Jamie Hall

OK I'm convinced. Now to convince the trustees...

AMservices

PMJ said:

SteamCoffee said:

Cool stuff...any thoughts about vacuum pumps? Any more gains to be made by going sub-atmospheric a la Dunham Differential? Cost may outweigh the benefit for deeper/longer vacuum. Super interesting...

Search @izhadano for info about pump driven systems. Igor has done a lot of work on this and has some pretty impressive numbers to show for what he can do with pumps staying sub atmospheric all the time. His thing with me was that my system would prove more able to hold vacuum than I was thinking at 90 years and he was right. I haven't spent 3 hours total working on leaks. Even at 1/3 the vacuum I have now the results were impressive. No one should let worries about that stop them from trying this.

I have stopped short of pumps for now. The appropriate ones are $500 or so and I'm not sure I can sell mission control here on any extra noise. Simplicity and fewest moving parts has been a goal of mine from the start and natural vacuum sure satisfies that requirement.

That pump and what I'm sure you could come up with to control it, would pay for itself within the first year I bet.
Having the ability to start the system under the vacuum, at the desired saturation temperature you need to heat the radiators to match the heat loss of your home, you would heat everything much faster never needing to build pressure.
I would expect you to lower your fuel bill another 25%.

PMJ

> @Jamie Hall said:
> The figures certainly look impressive. Being a bit on the suspicious side, though, I have to ask: did anything -- anything -- else change in the last 22 years about the building? The vent damper you mention. Windows? Any new insulation? Changes in outside building exposure (like more trees/less wind)? Change in interior setpoint (a two degree change in interior setpoint cut the fuel usage to 80% of what it had been)?
>
> All that said, I have to wonder if simply using a good vacuum tight vent -- like the Hoffman 76 -- wouldn't accomplish much the same thing as using a pressure switch and a solenoid, both of which I'm wary of. As I understand it, that type of vent is closed on vacuum, and will only reopen if the pressure in the pipe is greater than the pressure outside -- which seems to me to be what I'm reading your pressure switch/solenoid setup does. I'll grant you that they aren't cheap -- no good big vent is -- but one of the real advantages in that regard of your system is that one doesn't need much venting.

No Jamie, no changes to the building. It is 1926 brick construction with no isulation. Triple track storm windows installed in 1970's. I have not made any changes as slate roof very happy and heat bills acceptable and I don't want to upset anything. Unfinished 3rd floor - totally exposed tongue and groove roof decking in great condition. Last month gas bill $225. For 3500 sq ft and 1050 EDR. Heating set point always 69F and set back at midnight to 66 always. Recovery begins at 5:30 am and stepped through 12noon.

The improved numbers you see are really about this method of operation.

PMJ

> @AMservices said:
> Cool stuff...any thoughts about vacuum pumps? Any more gains to be made by going sub-atmospheric a la Dunham Differential? Cost may outweigh the benefit for deeper/longer vacuum. Super interesting...
>
> Search @izhadano for info about pump driven systems. Igor has done a lot of work on this and has some pretty impressive numbers to show for what he can do with pumps staying sub atmospheric all the time. His thing with me was that my system would prove more able to hold vacuum than I was thinking at 90 years and he was right. I haven't spent 3 hours total working on leaks. Even at 1/3 the vacuum I have now the results were impressive. No one should let worries about that stop them from trying this.
>
> I have stopped short of pumps for now. The appropriate ones are $500 or so and I'm not sure I can sell mission control here on any extra noise. Simplicity and fewest moving parts has been a goal of mine from the start and natural vacuum sure satisfies that requirement.
>
> That pump and what I'm sure you could come up with to control it, would pay for itself within the first year I bet.
> Having the ability to start the system under the vacuum, at the desired saturation temperature you need to heat the radiators to match the heat loss of your home, you would heat everything much faster never needing to build pressure.
> I would expect you to lower your fuel bill another 25%.

I think Igor would agree with you. Perhaps he will comment. I will make some sort of presentation to mission control. Wish me luck.

AMservices

Good luck! And steam speed

PMJ

> @Gary Smith said:
> Any thoughts on how this might be applied to 1 pipe systems? I could see putting simple check valves on my B&J big mouth main vents, but not sure how to handle the rad vents. And, maybe more importantliy, my system is balanced by the differing flow rates of the rad vents, and I'm not sure equal steam flow to all rads would work. Can't think of how to throttle the supply side like two pipe systems can, without causing water hammer in the rads. Maybe this should branch to a new thread, didn't mean to hijack this one.

My thoughts on one pipe: if possible run vent in 1/4 plastic tubing all the way back to boiler room to a mainifold where a PLC can control the venting of each and every rad. First warmup is in fact slow enough that air will leave ok through this small tube. Maybe has to be 3/8. Once evacuated one time you can learn how to vent each rad to balance things at will. Even totally shut off some rooms on some schedule. Based on my experience so far I would be pulling those tubes through my walls for sure. Would be much more control than I have now.

Gsmith

Very interesting, you have obviously given this some serious thought, I want to as well.

PMJ

> @Gary Smith said:
> Very interesting, you have obviously given this some serious thought, I want to as well.

Seems there are mostly one pipers out there. Much less expensive to install originally I suppose. I have been trying to think how to do those too but I confess it mostly makes make glad I have a 2 pipe system.

However, after what I have experienced there is no way I wouldn't be trying to keep air out of a one pipe system if I had one. Here is where I would start:

Think of what happens every time your boiler shuts down. Collapsing steam in each rad would create a void if it were not quickly filled by something. When boiler is on the void( let's call it space with lower pressure) that is trying to form is filled by more steam which sitting in the mains at slightly higher pressure than the air at the vent. With the boiler off in a vented system the void is quickly filled by air from the room. If you close off the vent on a rad when the boiler shuts off the collapsing steam in it I think it will pull more steam from the main which is insulated and not collapsing nearly as fast - even though all the other rads in the system are vented. I think I would try this on just one rad. I think it will end up condensing a slightly higher % of the total available steam in the system than it did before - a bigger share. I think so because it will pull some steam from the main when the boiler is off while all the other rads in the house are sucking air from their rooms. I think you will notice that the feed pipe stays warmer than all the other ones. This rad will put a little more heat into its room each and every cycle than it was before. Not much, but I think enough to notice if you are really paying attention. I notice all my feed pipes to rads stay warmer longer when the boiler shuts down when I run in vacuum because the rads are still pulling steam from the mains and not running backwards. In this way you could experience the effect of what I have been talking about here - the forward motion I call it.

My one caution to anyone trying this is in what to use as a checking device. It needs to be really open like all the other rads when the boiler comes on or it might quickly lose any advantage it gained in the off part of the cycle. That is why I ended up with a solenoid valve. Check valves have minimum cracking pressures that are too high. Even a few ounces is too high for this. Somebody said that steam checks are no longer manufactured. I don't know anything about them or if they have a cracking pressure. I'm just saying be careful about this. Very tiny changes in pressure affect this a lot. Anyone trying needs to give it a fair shot. It really took me a while and a lot of observation to appreciate some of the subtle aspects of this.

On other thing - the steam flow to the rads is not all equal in the vacuum phase. The available steam goes more where it is condensing the fastest and that changes from cycle to cycle and with changing building conditions. It is sort of self managing that way. The whole former maids quarters in back over the garage got noticeably warmer as I got more and more vacuum without any other changes just because it was colder there and grabbed a higher percentage of the available steam every off part of the cycle.

PMJ

Hatterasguy said:

PMJ said:

I took a quick look at some numbers. Maybe a little better than I thought.

Over a 14 week stretch in 1994 I used 190.9MCF and there were 3314HDD in that period according to data on Weatherunderground for my location. Over a 14 week stretch this year I used 120.1MCF and there were 2749HDD in the period. Looks to me like I am now using about 75% of the gas I was before for the same job if I am doing this right. Feel free to correct me as needed. Remember, in 1994 there was no vent damper either. Everything was as received.

You've clearly mastered that system over time. Well done.

Here's the thing that I need to resolve.............

What was the condition of the system back in 1994 when you had the data before all the mods to effect vacuum? Did it build pressure and were you paying for fuel to heat and pressurize the mains?

If one can achieve a system that runs on NO PRESSURE, being one pipe or two pipe, where can the fuel savings occur?

If I use the apartment building as an example (runs on less than 1 ounce) , it can send steam down to the end of the mains in about 2.5 minutes after a 32 minute shutdown. I envision reducing that time to about 1/2 that value if I followed your lead and ran the boiler every 15 minutes. Note that I am not at all convinced that that the time elapsed to obtain steam at the end of the main is all wasted fuel. The end of the main is the point where the last riser gets steam. Steam has already headed up the near risers and is well on its way to the rads that are closer to the boiler.

There seems to be a focus on reducing the time in the mains and a conclusion that this will result in significant fuel savings. I'm not convinced of this whatsoever, provided the system is operating without any measurable pressure.

If vacuum alone can result in 25% fuel savings (on a system that runs less than 1 oz), I'd sure like to know where the savings are obtained.

You are right it is not all vacuum. A lot of the difference from 1994 I believe was just the damper. There had to be some more pressure than now for sure but I don't think it was crazy. It always had a vaporstat control.

However, it is difficult for anyone to appreciate just how different things are in the boiler room running the way I do. Say I burn for 8 minutes. Significant boiling is still going on 3-4 minutes after shutdown. Upon restart a full boil is achieved in 15-20 seconds because the system is in the deepest part of the vacuum and the boiling point is at its lowest. So I am getting significant extra steam production with no burner, steam is always moving forward to the rads at all times, and no time or effort is wasted pushing air out. And in what I just posted above, in the burner off phase some self adjusting of steam to the colder places is clearly going on. These things really do add up to something. Exactly what the efficiency improvement is and whether it is worth any investment is up for discussion. I can tell you it is a much more pleasant way to run.

Very difficult I think though in an apartment situation. Just too tough to monitor what is going on. No access. I don't have a suggestion for that.

PMJ

Hatterasguy said:

Clearly, there must be savings by boiling at a lower temperature without any burner operation.

However, doesn't the boiling (with 1700X expansion), create an instantaneous loss of vacuum in the entire system?

Are the rads still condensing at a faster rate then the steam production at that point?

I'd try it on the one pipe apartment building if I didn't need the Hofmann 76 valves. Cannot easily run tubing to every rad to control the venting.

No, the loss of vacuum is not close to instantaneous. That is what is hard to imagine not experiencing standing next to the boiler. It takes 3-4 minutes from start of fire each cycle before my pressure switch opens the vent. Maybe I'll make a video of those gauges during the firing. So my system is only above atmospheric ( the most I ever see at the header is 2" water) for 4-5 minutes out of 20. This is a significant amount of time in vacuum at some reduced boiling point and really for free.

Still, your observations are valid. What is it really worth. I can't answer that. If you are really looking at just a straight up money thing I doubt you are really going to make a clear case to put more into the system you describe. It sounds like yours really runs well.

PMJ

I will look for a time to switch back and get the data. Unusually warm this year after record cold just 2 years ago. 60's again this week. We'll see if there is enough cold left this season to get worthwhile data. I get that it would be valuable data to others. However, I can already hear the lashing I will take back at mission control - "what did you do to the heat!". Seems I'm always screwing something up. Maybe someone can help me with the explanation.

I have never pushed this as an efficiency bonanza. I've just always been sure it is not a loser. I expect if I get the data it will leave everyone who needs to see a clear savings reason to do this in the iffy range. On the comfort side to me it is clearly a runaway winner.

PMJ

Oh boy, I was thinking just to open the dry return vent all the time and still cycle. I guess the test really needed is all the way back on the vaporstat. Believe it or not that really is a big difference in comfort. That will be boiling hot full rads compared to what I do now and really long off periods. Been many many years since I have been there. I know it seems difficult to believe but just the even cycling alone is a lot better.

I'll think about it some.

jumper

How expensive is an air powered venturi ejector? One can easily suck down to 28" Hg.

Paul48

They are very inefficient.

jumper

Paul48 said:

They are very inefficient.

More efficient than pushing air with 0.5 psi steam.

Unless your system leaks badly air compressor has to run minutes per day?

Paul48

Can you post a drawing of what you have in mind? What size venturi ?

jumper

Size of ejector depends on how big a compressor you'll use. For a house a few acfm should do it. Where you install it is where it's convenient for you. Just spring for more than one isolation valve for extra tightness. PumpGuy can probably help.

EBEBRATT-Ed

Understood. Very impressive! Your living with the system your working on and your work and your efforts are very impressive

PMJ

EBEBRATT-Ed said:

Understood. Very impressive! Your living with the system your working on and your work and your efforts are very impressive

Thanks much for the support.

Eastman

"Six Kinds of Steam Heat" from 1941 discusses the issue of maintaining balance in one pipe vacuum systems with automagically fired boilers:

https://heatinghelp.com/heating-museum/six-kinds-of-steam-heat/

In a nut shell, a valve of some sort was employed to reintroduce air periodically, thus restoring the systems ability to balance via cyclical venting.

butlermog

I don't want to be off topic, but I do want to share my experience.
PMJ has helped me greatly over the past few years as his system is very similar to mine (2-pipe Mouat). This year I finally installed the Teco SG2 PLC that PMJ turned me on to and got my boiler being controlled by PMJ's program instead of just the thermostat.
There was a small amount of efficiency gained by adding the PLC which is nice. However, the comfort of the house is completely different between this year and previous years.
Before the PLC and with the thermostat set always at 68 the temperature in the thermostat room would go between 67.5 and 70/71. Now with the PLC and the thermostat set the same the temperature of the room is steady between 67.5 and 68.5. This allows the entire house to be better balanced and comfortable as well.

It is my belief that the fuel savings would come with the addition of PMJ's vacuum setup which I would love to do for next heating season.

PMJ - Thanks for all of your help and your time.
Thanks to all of the community here as well.

PMJ

A little more food for thought:

My goal has always been just to even things out more than to try to save money. I observed that the original systems which could not turn the fire off were designed to closely match steam production with what was required to match heat loss continuously. In other words there was no on/off call for heat or the calls were infinitely long, whichever way you wish to say it. This would have resulted in radiators that were partially filled +/- all the time. So I figured if my goal was even heat then I would be succeeding if once initiated, my digital calls for heat went on a very long time - the longer the better. If I could put steam into the system at a rate that just kept the tstat in its deadband then rads would have to be partially warm all the time. That is when I came up with the pulsing or even cycling approach as the only way short of buying a modulating burner or a multi stage gas valve which would introduce possible combustion issues that I didn't know anything about.

That was where I started. The air thing just occurred to me along the way. But after I stopped letting air back in I realized how different the steam flow is when rads are empty with no condensation happening at all and when they are partially full. For instance, a radiator of the same size in the colder garage as one in the house will condense steam at a higher rate than the one inside obviously even at low positive system pressures. But when both are just full of air which needs to be pushed out the rate at which that happens is strictly about venting. The way I run pulsing with really long calls and rads always condensing something, a much larger part of where the steam flows is determined by which room is colder automatically and not by valves and vents. I have found that much of the balancing work then became entirely automatic and self adjusting. Obviously condensation rate is also a factor in the flow in systems above atmospheric pressure, but I observe that it is a bigger factor sub atmospheric with the burner off and when you add it all up I spend a lot of time that way.

So even though it seems like it is only a minute or two or whatever to push air out of rads to get going each and every cycle, I found that having the boiler off long enough for rads to totally fill with air was not helpful at all to the balancing process. And it doesn't take that many more cycles to accomplish this and I don't think it is that hard on gas valves and things designed for a few million cycles.

Is more even heat really required and is any of this effort worth it? Individual choice for sure. I have found this work immensely satisfying. I think most people would be very surprised by how nice the result is. My main reason for posting this was just to let anyone interested know how easy it is in 2 pipe.

PMJ

@butlermog ,

Fantastic! Thank you very much for sharing that.

jumper

PMJ said:

A little more food for thought:
...... For instance, a radiator of the same size in the colder garage as one in the house will condense steam at a higher rate than the one inside obviously even at low positive system pressures. But when both are just full of air which needs to be pushed out the rate at which that happens is strictly about venting...... I think most people would be very surprised by how nice the result is. My main reason for posting this was just to let anyone interested know how easy it is in 2 pipe.

No surprise after reading the above. Removing air improves any steam heating system. Improves HWH systems too.

izhadano

Hello Peter,
thanks for shearing your results - saying the truth they are better then I would expect.
Let me add couple cents to discussion...
At the beginning of my endeavor I tinkered with single pipe system with naturally induced vacuum - please, see slides from presentation at ASHRAE conference in Montreal.
The vacuum was naturally induced via air vent/check valve combo on each radiator. This setup worked fine for a while, but I started to look for "no moving parts" solution because problems started with check valves, - had to remove/clean them. It was OK for 6 radiators apartment, but for multifamily house would be unacceptable.
Vacuum pumps came as logical solution for starting cold steam system. Also, vacuum pumps are used along with naturally induced vacuum in order to keep system under vacuum long time after boiler stop and pull more heat into radiators. Vacuum lines are to be added to each radiator in order to get it completely heated.
IMHO, small/mid size two pipe heating system might be converted into naturally induced vacuum heating system. For large/big buildings the pressure drop between boiler/nearest and boiler/farthest radiators is significant, so system would be heated very unevenly.
Another problem for the system with naturally induced vacuum is using 212-4oF steam each time at the beginning of heating cycle. That's fine in frosty cold weather, but the heat load of these cold days counts for only ~30% fraction of the total seasonal heat load (from DOE and CARB operational data on seasonal thermal efficiency, Boston/NYC). For spring/autumn weather it would be overkill and inefficient especially when heat is distributed unevenly through the large building.
And regarding vacuum pumps. I got piston vacuum pump at ~$500 and expect 30-35 years life span (based on 10000 hrs of continuous work warranty) because pump is employed for 1-1.5 hours/day. The tested earlier steam system with naturally induced vacuum saved 10-15% of fuel versus 25-30% for vacuum boost system (with vacuum pump). In my case it's ~1.5-2 years ROI plus better comfort and control flexibility. I believe it's a good bang for a buck.
Hope you'll find it useful.
Igor

SteamCoffee

Eastman said:

@SteamCoffee

SelectTemp mini-tube systems maintained steam in the main lines throughout the heating season. Each radiator utilized a TRV. Hence it makes sense that the installation manual for the system recommended sizing the boiler based on heat loss and not some other combination of EDR and piping and pickup factor.

I would think a vacuum version could only be an improvement in every respect.

I should have stated that I wanted Minitube piping, like Gerry Gill did at his house. Regular cast iron radiation fed and returned by Minitube copper. Not the selectemp/iron fireman units. That's a big savings in btu's right there. Plus natural vacuum going deeper because of the small cross section of supply/return piping. That sounds pretty interesting...