One floor hotter than the other with one-pipe steam

mattm

We have a one-pipe steam system, in a three story row house. When it is cold out (mid-30s and below), the third floor gets quite hot (80F). When it is in the mid-40s outside, it seems that the steam doesn't even make it to the third floor, with indoor temps in the high 60s. The thermometer is on the 2nd floor in a hallway, away from any radiators, and is set to a fairly constant 67F.

The first floor recently replaced their radiators with forced air, so it is possible that the boiler is now over-sized. What are peoples thoughts? Is this an issue of an oversized boiler, a venting problem, or a thermometer problem?

Jamie Hall

Well, the boiler is oversized now -- even if it wasn't before. However, that doesn't account for the temperature imbalance. What you describe sounds like a combination of at least two different problems: most likely inadequate main venting plus too short a call for heat. The latter is the first thing to check: most modern electronic thermostats have a setting for "cycles per hour" or sometimes they will have settings for type of system. If it's cycles per hour, make sure it's set for 1 cycle per hour (2 sometime works, too -- but try 1 first). It if's looking for type of system, look for steam or gravity hot water.

See what that does...

mattm

Thank you for the advice! I think I definitely have a problem with the main vents. The only one I can see looks like it is completely rusted and non functional...

mattm

I should clarify though that it is not a modern electronic thermostat, it is an older dial type thermostat. In that case, would it still need to be set for the correct number of cycles per hour?

mikeg2015

1) Stack effect. Hit air leaks out leaks on the 3nrd floor and cold air leaks in lower levels. The greater the indoor ot outdoor delta T the greater the effect. My house is balanced at 30F, above that downstairs is overconditioned, below, the upstairs overconditioned. I use TRVs to balance it, but that creates some balance sues and makes the boiler even oversized.

2) Oversized boiler are harder to balance. They become too dynamic. Radiators like slow changes in heating.

First floor probably have 40-50% of the overall system radiation. SO boiler is probably about 2x the size needed now. It probably works OK on very short runs.

I wish they made a cheap, easy to plug in “duty cycle” or pulse width modulation timer. You can make one with a couple on delay and off delay timers. But a built in one would be nice. I’d like one in my house. More efficient that relying on a vaporstat to cycle it.

mikeg2015

I take that back. They make one. I think I bought one a while back. I need to wire it in and test it out.

https://www.supplyhouse.com/ICM-Controls-ICM305-ICM305-Duty-Cycle-Timer-Time-Delay-in-Minutes

mattm

Thanks Mike! This is very illuminating. What would the duty cycle timer accomplish? I.e. why would delaying the cycle help?

Fred

Get enough venting on the Mains, based on length and diameter of those mains, we can suggest the type and number of vents you need. Once that is done, then you can balance your radiators. Based on what you have said, it sounds like you need to slow the venting down on the 3rd floor rad(s) and maybe go a little faster on the vents on the 2nd floor but it's hard to say until the main venting is optimized.

PMJ

mattm said:

Thanks Mike! This is very illuminating. What would the duty cycle timer accomplish? I.e. why would delaying the cycle help?

Because once you have tripped on a vaporstat or any pressure device, it doesn't take much observation to see that a pressure device is a very poor way to determine when the next burn should start. Condensing steam drops the pressure in the system so fast that the same device that stopped it fires the boiler again far sooner than just about everyone on the planet knows is actually needed.

This is encouraging. Some thinking going on about using time for control. Go for it guys. Time can be used very cheaply and effectively to enhance your control a lot. Once you get into it you'll find it can eliminate a lot of the fretting about boiler size.

Jamie Hall

@PMJ -- kindly relax. If a vapourstat is used, correctly, as a control device -- not a safety -- it is a very good and simple way to modulate a fixed firing rate boiler. I've tried to be nice about that; now you can relax and admit that there are other ways to handle modulation than yours. Thank you.

Now -- on the older round style thermostats there is a control inside, referred to as an anticipator. It's basically a sliding contact on a resistor. If you take the cover off the thermostat -- not the thermostat off the wall! -- you can find it. The thing to do is to see where it is adjusted now, and make a note of that, than move the slider half the way to one end from there -- either way. If that makes things better, try a little more -- if that makes things better... and so on. If it makes things worse, try starting from the original point and going the other way, half way. This is, to put it mildly, slightly tedious, but once you get it right it works very well.

PMJ

@Jamie Hall , at no time have I ever suggested that my way is the only way. I merely champion the trying of new things - especially with steam heat where so little new is even being tried.

I have suggested and will continue to state clearly that a residential system that generates enough pressure to be possibly used as control by such a device as a vaporstat is running far less efficiently than is possible. Run well, as has been shown many times by others here too, low single digit inches of water pressure is all that is required. So no, I do not agree at all that a vaporstat is a good control.

Your resistance to any new methods of control of any kind is striking. There are probably tens of thousands of steam heated homes bouncing off vaporstat upper limits every cycle right now wasting fuel while providing less even heat than could be. I am astonished that the most common advice for this condition is to buy a smaller boiler barely able to cut it on design day, buy more vents and then find an old tstat with an anticipator to run it. Yikes. Steam heat doesn't stand a chance if that is all we have to offer folks trying to improve their situations.

coelcanth

just to add, in case it's not obvious:
the anticipator scale inside is usually marked with an arrow pointing 'faster' or 'slower'

moving the lever in the 'slower' direction would result in longer (less) cycles and the opposite way gives you shorter (more frequent) cycles

Jamie Hall said:

Now -- on the older round style thermostats there is a control inside, referred to as an anticipator. It's basically a sliding contact on a resistor. If you take the cover off the thermostat -- not the thermostat off the wall! -- you can find it.

Fred

@PMJ, I certainly don't disagree with your research and promotion of efficient and even heating and a vacuum system may be one of the best ways to achieve that. I think where I have a problem is when we encourage that approach when people come here, typically homeowners who, for all practical purposes don't even know the correct terminology, let alone how their systems work or should work. Most of these people are looking for practical solutions to an immediate problem, in the dead of winter. For the most part, they are not interested in their systems except that it provides heat where it is needed. They are not typically interested in long drawn out experimentation, the cost to take a one pipe system and somehow make it a vacuum system or learning how/if that is possible. We try to offer solutions that can be implemented quickly and as inexpensively as possible, either on their own or using someone on this site that we know is local, to them and has the expertise to get them back up and running.

There are exceptions, and for those who don't have an immediate problem but aspire to be a Steam Head (sorry @ Steamhead) it is my opinion that we aren't helping them achieve that goal by just pushing any approach without guiding them as to how to achieve that and let them decide, fully informed, as to the potential cost and outcomes and/or failures. It's not good enough to build their expectations and leave them wondering how to get the great results you have achieved on your two pipe system. Translate that into an implementation plan for those who have one pipe systems, like this OP.
In the meantime, lets recognize that most want to fix a problem in the next few days. They don't have the luxury of waiting until the weather breaks and/or making steam a full time summer job.

Teaching all of us how to get the most out of our one and two pipe systems, with documented processes and illustrations will go a long way towards what you promote.

PMJ

@Fred , Thanks for the time and consideration you show here.

I will make some comments as soon as I have time to give you the same consideration.

Peter

Motorapido

Good thread. After buying a simple ICM Controls Delay on Break timer, I realized after wiring it in series between my vaporstat and LWCO that it didn't work. After the vaporstat shut off the boiler on pressure, my automatic stack damper closed the damper, and the burner would not reignite in the time that I had set on the timer. I'm bad with thinking through wiring schematics, so I think maybe my wiring it on the 24v wire from the vaporstat to the LWCO is the issue, and maybe it should be wired elsewhere in the network of 120v/transformer/burner/safety-devices. I'd be interested in commentary on where to insert the timer into my wiring system. I should note that I'm one-pipe steam, 50% oversized boiler, massive amount of Big Mouth main venting, insulated mains and risers, carefully balanced radiators, etc.

Gsmith

@PMJ: I'm a homeowner with a one pipe steam system, currently pretty well balances, operates almost always at less than 0.5 psi and very much interested in converting to vacuum, because of the information you and others have posted. But,.....while I'm pretty confident I can figure out how to convert my system and operate it properly under vacuum, I am hesitant to do so, because I know I will at some point not live in this current house and am concerned that the next homeowner will have no clue as to what is there or how to maintain and operate it. And, as you well know, from the many posts on this site, most of the heating contractors have no clue about steam, much less about a non-standard one-pipe system converted to vacuum. And even if I left them a very comprehensive set of documentation and instructions about how it operates and how to maintain, the heating contractors cannot be relied on to actually read and follow the information (see the many badly piped new boilers discussed here). So, it may be the old chicken and egg issue, unless there are a lot of systems out there, with commonly available components, and wide spread knowledge of how they operate, it may be that upgrading to vacuum will remain rare even if more efficient and comfortable.

Sometimes simplicity is better in the long run than highly efficient but complicated. I'd love to try it, but fear that I'd leave the next guy with a big problem.

Jamie Hall

@Gary Smith -- you describe well one of my main concerns. I have no argument that some sophisticated improvements can increase the overall efficiency of steam systems, though I do have some as yet unanswered questions as to how much. But... you describe well the problem of what happens if you sell -- or, even if you don't, if you become unable to care for the system. When we look at highly complex -- and very good and efficient -- systems in other areas, such as aviation and particularly the automotive industry -- what we note is that they have become almost entirely plug and play. There are a very small number of manufacturers which create and program the computer systems which actually control everything in your car -- everything. If something goes wrong with the magic, simple: go or be towed to the dealer and swap out the offending computer. The dealer's mechanics have no more clue as to how it works than the proverbial little old lady in tennis shoes. Not that this is necessarily wrong -- but it is a different model. The good technicians can diagnose and bring up to good condition a simple steam or hydronic system and its associated -- very limited number -- of controls. But a system with custom controls? It's a bit much to ask.

PMJ

@Gary Smith and @Jamie Hall ,

I too have thought about this.

First, the level of complication envisioned by most everyone about what I do is for some reason significantly exaggerated. I think it is much more simple than envisioned - in 2 pipe. One-pipe no off the shelf vents exist anyway so more complicated for sure. But control-wise not complicated.

Secondly, I have not removed any of the original control stuff. The vaporstat is still there and able to function. The solenoid valve would be removed and the same single dry return vent ( I still have it) gets put back on. Back to original state it goes. Maybe 1 hour.

Third, I don't know about other places but I am convinced my system won't make it through another transfer. The age of my boiler and the reputation of steam in general makes it a total non-starter in this market. A rehab outfit will gut this place when I let it go as they are all around me.

Bottom line, what I am doing is fairly simple and control wise just inserted in series with what is already there. Easily removed.

Jamie Hall

Good show, @PMJ ! Just the way I would have gone about it! I hope you're pessimistic about the ultimate fate of your system -- I do admire what you've done, even though it doesn't always sound like it.

I tend to get a slightly distorted view, since the only buildings I work with are National Register and are in long term trusts -- and they play by a very different set of rules!

Kjmass1

> @mikeg2015 said:
> I take that back. They make one. I think I bought one a while back. I need to wire it in and test it out.
>
> https://www.supplyhouse.com/ICM-Controls-ICM305-ICM305-Duty-Cycle-Timer-Time-Delay-in-Minutes

This is very intriguing. I have a 2-3x oversized 1 pipe steam system. Starts to build up pressure under 15F and vents start to make a ton of noise, especially with those nights at 0 a couple weeks ago. Could I run this between thermostat and boiler to tweak those cold nights to limit run times? 20 minutes on with breaks to drop pressure would be great. Essentially endless call for heat until satisfied.

ethicalpaul

Isn’t your pressuretrol doing that for you? What PSI do you get to?

Jamie Hall

The pressuretrol certainly should be doing it -- set it to cut out at no more than 1.7 psi, 1 psi differential. However, with a boiler which is that oversized you could take some of the work off the pressuretrol with a timer to essentially cut the boiler size in half -- I'd set if for 5 minutes on and 5 minutes off to start with, to minimize losses from the boiler cooling too much between on pulses. Then adjust the cycle rate within that 10 minute overall time to get satisfactory performance.

Fizz

I am a home owner who started here years ago, tho not soon enough for my Richardson System, spending hundreds of $ unnecesarily because the repair guys had no idea what they were doing. The advice received here was so enlightening and interesting it was refreshing and inspiring to the point of trying and reccommending stuff to techs. That said, I found info here on putting the system in vacuum, especially from PMJ, that I bought vacuum vents to replace the ones in place, did nothing else in line with vacuum and with luck the system is amazing. My t-stat setting is on 3 cph, and the heat so steady, no spikes. That's the good news, the bad news is I've since moved, into 1 pipe house and, well, no comparison-hikes in heat and cool downs, long runs, but it's better than electric or hot air. I continue to look here hopes of putting system in vacuum.

PMJ

Thanks for this @Fizz. At least there is one person out there who doesn't think I am a nut case.

We are apparently among a very few who have actually experienced natural vacuum at 3 CPH and know for sure how much better it really is. I do wish more would try - especially in two pipe as simple as it is.

Keep the faith. Somehow someone here is going to come up with one pipe vacuum vents to try.

gfrbrookline

@PMJ I don't think any of us think you are a nut job for trying to get the most out of your system. If anything you should be commended.

The problem we all have is that most of our systems have been screwed up by low bid contractors over decades and the number of people that actually know how to work on steam systems decreases every year. I go back to 2005 when we had our last boiler was installed and every pipe and radiator in the building banged like crazy, I was in the basement when he said could this be a vapor system. I didn't know much about steam at the time but if he saw the old boiler worked off a 0-16oz vaporstat he probably should have picked up on that. We all want to make our systems work as efficiently as possible the problem is we can't find contractors that understand steam vacuum, let alone vapor, so unless you have a knowledgeable steam guy if anything goes wrong we just get screwed up again.

I was luck enough to find @New England SteamWorks who was able to set me on the path of making my system work properly. If only I could talk my condo board into installing one of his drop headers I know we would be much better off with nice dry steam.

mikeg2015

Jamie Hall said:

The pressuretrol certainly should be doing it -- set it to cut out at no more than 1.7 psi, 1 psi differential. However, with a boiler which is that oversized you could take some of the work off the pressuretrol with a timer to essentially cut the boiler size in half -- I'd set if for 5 minutes on and 5 minutes off to start with, to minimize losses from the boiler cooling too much between on pulses. Then adjust the cycle rate within that 10 minute overall time to get satisfactory performance.

I have a vaporstat and it gets noisy over 2oz. Still noisy on hot starts. I suspect it’s due to mainly wet steam that calms down once everything is hot. I tunrned mine all the way down (might need recalibration) and it shuts off at an indicated 8oz, on at 1oz. Takes only 15 seconds to drop in pressure. Builds again in about 2 minutes. Not a good long term solution.

For now I plugged the 2 outside burners (20% reduction) Running a lot smoother now, but still noisy at times due to the TRV’s dropping load and still need ot slow venting down more. I’m losing some efficiency. But over heating room and the whole the upstairs wasn’t helping and I was using too much water due ot leaks from high pressure.

I think adding a hot water coil on the downstairs AHU would go a long way. It would also drop the steam output and ensure upstairs and downstairs are balanced. Adding a indirect tank would also take some more load off.

Next I’ll have to wire in that timer. 10’ ON, 5’ off should work well enough. WOuld give me 200k BTU total.

Fred

@mikeg2015 , be careful with plugging those two burner tubes. I know some have plugged one with no obvious ill affects but most manufacturers will tell you that the uneven heating of the underside of the boiler block will cause hairline cracks and potentially premature failure. I can't say if that is totally true but it seems plausible.

PMJ

PMJ said:

@Fred , Thanks for the time and consideration you show here.
I will make some comments as soon as I have time to give you the same consideration.
Peter

So @Fred ,

I really do understand where you are coming from with your comments. A homeowner in crisis mode is not the place to discuss theoretical solutions. In my defense I will point out that I really don't but in that much here. I joined 2 years before you and have made 1/10 the total number of posts you have. I really do let you guys handle it. When I see some interest in trying something different as was the case in this thread(the OP seemed interested in a duty cycle timer) I try to offer something. I try to at least get everyone thinking in the broader picture about duty cycle and vacuum. I just ask that people consider these things as they work with their systems, homeowners and pros alike. I think a lot of improvement is possible over time if folks gradually work some of this into their thinking.

It is in that spirit I will comment on those two subjects. This could easily get terribly long so I will resist that as best I can.

Boiler size and duty cycle. I do disagree with the regular advice given to homeowners here that there is little to do about an oversize boiler except to replace it with a smaller one. I find this a very unfortunate thing to be telling homeowners - that their only path to improving their situation requires the biggest expense of all. The duty cycle approach is not a theory. I have done it for years. My boiler heats my house burning only 40% of the time when it is -25F outside. Quite oversized right? It is a net 400KBTU/hr output boiler. One simple impulse/pause timer for less than $100 in series with the tstat turns that boiler into whatever (smaller) size I want. Two little knobs control burn time and wait time as you wish. You control total % of time burning /hour and cycles/hour as you wish. I won't do the rest of the math here. This isn't rocket science. Pros don't need me for a wiring diagram. Bottom line, you only need 200K for design day? 3 cycles of 10min burn 10 min wait then. You now have a max output 200KBTU/hr boiler. You also have no pressure. Your vaporstat never does anything. Ah but in one pipe that remote rad will never get any steam some will say. I already do something simple for that. You get one adjustable temperature switch($75) on the feed pipe of that remote rad and run every burn until that switch sees steam....always. Then the duty cycle timer starts in. You want a safety out back to original setup? One wired switch to bypass all the new stuff. I am saying for the problems of oversize boilers this is a very good and very simple solution. I ran this way for years. It will provide a much more satisfactory result than a vaporstat ever will with a big boiler. Oh yes, and that temp switch above, turns out it is a pretty good indicator of when the next firing should start for the next burn. I'll leave that for another time.

Vacuum. I probably shouldn't even get started here. There are very stiff headwinds here to vacuum, not the least of which are several notable names documented in print saying that vacuum is only for the coal days and will just cause problems now. That is really not true so things are, well, awkward. There is also this idea that for vacuum to be beneficial you need to be all in with a perfectly sealed system and pumps too. Again, not even close to true. Any pressure below atmospheric is vacuum. Even a little helps. Even if it only lasted 1/2 hour in a leaky system that is plenty long enough to help a lot running 3CPH. My system will stay in vacuum about 4 hours from the last time the burner ran. 2 pipe systems really only need a vent on the dry return. Change that to a simple check valve and you have a vacuum system. Combined with a 3CPH timer control and the only way you could possibly have steam in the dry return is a runaway boiler. What can I say, vacuum is a huge improvement in my system. No air to remove every cycle, automatic balancing, significant steam generation with the burner off, next to zero water consumption and corrosion. My piping is 90 years old. And I did very little to get vacuum going. In sum, I simply can't explain the lack of interest in it here. One other note - anyone who actually tries vacuum will want a big boiler. Vacuum works its magic between burns. If there is to be any off time when it is cold out for it to work for you there must be significant extra boiler there.

I'll quit there @Fred. Again thanks for your consideration. I am working on and am pretty excited about a simple control where the amount of vacuum generated automatically adjusts the cycle burns/waits to the conditions without a PLC. I will charge ahead with it despite the headwinds.

I am happy to share anything I have with anyone reading this who is interested. One only needs to ask.

Fred

Thanks for the explanations @PMJ . I do understand how committed you are to the benefits of vacuum and I really don't think there is that much headwind to your concepts/implementation. I think maybe you are disappointed that the Pros here don't jump on that opportunity and that can sometimes bruise the ego. I will only say there are probably a couple reasons for that:
1. The Pros who install/maintain systems simply don't have the time to want to return to a customer's home to "tweak" a system multiple times and the customer probably isn't willing to pay the cost for anything other than "Get my system up and running".
2. The majority of Homeowners probably don't even understand what you have said, even in the basic description stated above. Not that they can't, just that they aren't that interested.

I think what you maybe consider resistance or headwind is just passive appreciation of the potential or simple scrutiny of anyone's implementation that hasn't been accepted as "main stream". Should someone call a Pro and say "Come help me do this. I'll pay for whatever time it takes to implement, monitor and tweak, and I won't hold you responsible, if for some reason you can't make it work on my system (greater risk on one pipe systems), some will jump in with both feet.

If it's any consolation to you, I also have to say people come here for help, some just lurk in the background. What is unknown to any of us is how many ideas people walk away with and actually implement and never acknowledge doing so.

PMJ

@Fred ,

I have posted in the past that I imagined it quite difficult for a pro to get paid to try things. May I just say now though that I used to run around tweaking valves a lot when I was atmospheric and above trying to coax steam to different areas. Then I realized that the changes required were weather driven and chasing them was a fool's errand if there was any other way. Those days ended with vacuum - don't touch them anymore. Valve settings don't make much difference in vacuum - that natural balancing to colder areas is that strong. Pro's might actually find it cut down on their fiddle time. And again, I think the perception of what I do is way more complicated than it actually is. Actively looking for an opportunity to try is a long way from actively steering away because it is thought impossible. I'll let you decide where on that spectrum most pro's are today.

In the mean time I will continue to fiddle and maybe throw out some results here and there for anyone interested.

Jamie Hall

May I second @PMJ 's comments on duty cycle timers for oversize boilers? If the boiler truly is oversized -- and many are -- it is a simple and straightforward way to manage the situation -- and relatively easy to implement on a basic level (and one could get fancy here -- for instance, one could gain some of the advantages of a two stage boiler using the concept).

What I don't know -- although I have a moderately strong gut feeling about -- is what is the optimum off time for the cycle? My own feeling on this is that the shorter the better, within reason, as I believe that that reduces the inevitable hit on efficiency which comes from reestablishing a stable flame in a cold or cool boiler -- but I don't know of any actual studies on that.

@PMJ ? Got anything on that aspect?

PMJ

@Jamie Hall , sure , I have comments about that.

At the most basic control level where there can be only one set cycle, that cycle must cover design day. So the total run/wait combination must burn enough in one hour to heat on the coldest day. This will be way more burn than needed on an average day but still way more spread out and even than just tstat/vapostat control with a big boiler. So wait time depends on how much extra boiler you have and how many cycles/hour you want. In my experience 10-15 minutes off on a boiler with automatic flue damper doesn't cool enough to be a factor.

There was a recent post where someone in Chicago said a 50% run covered record cold. That is like my boiler and I think actually quite common. I think many boilers like mine were put in the same size as the coal fired one they replaced. The missing factor was that the coal one was sized to be in the middle of its range on design day so a fire could actually be managed. For a boiler sized like that I really like 3CPH which means 3 burns and 3 waits per hour at 10 min each.

Now of course I can't resist this opportunity for another advertisement for vacuum. Blame @Jamie Hall for this one.

For most having never experienced it, standing next to a boiler doing 10/10 pulling vacuum during the waits would convince the most hardened skeptic of the value of vacuum. My boiler is still rumbling producing steam 5 minutes after the flame went out. At refire in the deepest part of the vacuum full boil occurs maybe 30 seconds in. Standing next to it one realizes how much steam delivery is enhanced by the vacuum and any concern over refiring losses vanishes.

coelcanth

well i, for one, would love to give running under vacuum a try..

but there's just no off the shelf parts available for one-pipe systems

mattm

I've found the discussion very interesting! At a more basic level, I'm still trying to improve the functioning of my steam system. Following the suggestion from @Fred and @Jamie Hall I'm focusing on the main venting. I am in a row house that is moderately narrow, and quite long. There are two return lines, one at the back of the house, and one coming from the front. The one at the front has been walled off (done before I got here).

From what I can tell, there is a main vent on the return line (in the attached picture), that looks completely rusted. Presumably there is a main vent at the front too that I may not be able to access. My question is, if I tried to replace this vent and take it off, am I liable to break the little pipe leading to it? And possibly mess up the thread on the bigger pipe? What kind of vent does this look like to people? Thanks!

Fred

That old vent most likely is plugged up and not venting any air. Even if it did, it is way too small. To your question, yes, that 1/4" pipe will likely break off. The hole in the pipe was drilled and tapped by someone over the years to get some venting on the main/return. If it were me, I'd use the larger vertical pipe next to it that is capped. I'd take the cap off and put a reducer on there and install a Barnes and Jones Big Mouth vent there. My inclination would be to leave that small pipe and vent alone until the weather breaks so you have time to either take that pipe out, drill and re-tap the hole and put a plug in it or clean the surface on the main/return pipe and install a saddle clamp with a steam rated gasket.
Getting larger venting on that pipe will probably go a long way towards fixing to your 2nd floor heating. You will likely have to do the same thing on the front Main/return. This fix will only get you half way there if that vent is similar to this one.

gfrbrookline

I would also leave to old vent alone until the end of the heating season, then remove it and plug the hole. You hot the jackpot by having that plugged nipple right next to it. I would use that to install a new vent. What is the diameter and length of the main? Depending on that you will use a Barnes and Jones Big Mouth or a Gorton No. 2.

mattm

What would you consider the length of the return main? What points would I measure the length between?

Fred

You actually want to measure the Main, from where it takes off of the header to where the old vent is currently installed.

Motorapido

PMJ said:

@Jamie Hall , sure , I have comments about that.



At the most basic control level where there can be only one set cycle, that cycle must cover design day. So the total run/wait combination must burn enough in one hour to heat on the coldest day. This will be way more burn than needed on an average day but still way more spread out and even than just tstat/vapostat control with a big boiler. So wait time depends on how much extra boiler you have and how many cycles/hour you want. In my experience 10-15 minutes off on a boiler with automatic flue damper doesn't cool enough to be a factor.



There was a recent post where someone in Chicago said a 50% run covered record cold. That is like my boiler and I think actually quite common. I think many boilers like mine were put in the same size as the coal fired one they replaced. The missing factor was that the coal one was sized to be in the middle of its range on design day so a fire could actually be managed. For a boiler sized like that I really like 3CPH which means 3 burns and 3 waits per hour at 10 min each.



Now of course I can't resist this opportunity for another advertisement for vacuum. Blame @Jamie Hall for this one.



For most having never experienced it, standing next to a boiler doing 10/10 pulling vacuum during the waits would convince the most hardened skeptic of the value of vacuum. My boiler is still rumbling producing steam 5 minutes after the flame went out. At refire in the deepest part of the vacuum full boil occurs maybe 30 seconds in. Standing next to it one realizes how much steam delivery is enhanced by the vacuum and any concern over refiring losses vanishes.

I'm not ready just yet to tinker with vacuum on my one-pipe system, but after reading many posts about duty cycle timers, I'd like to try the concept. Before thinking about a duty cycle timer, I had tried a Field Controls ICM203 delay on break wired in series between my vaporstat and LWCO, but it did not function, I think due to the wiring scheme for the flue damper. Anyhow, what make/model of duty cycle timer would I need to buy if I want to wire it between my t-stat output wire and the boiler? What formula would I use to set it, for starters? If I set the run time to, let's say, 10 minutes, with 10 minutes off, I would probably have to run two on-cycles from a cold start to begin supplying steam to my system. At that point, the next 10-minute run time would probably get interrupted by the vaporstat, because I would probably build up to the vaporstat's 10-ounce cutout (that's where I have it set now, with cut-in at 4 ounces). My boiler is a little more than 50% oversized for my EDR. It seems to me that in subsequent on-times, I would still be cycling on the vaporstat rather than the timer, but I'm probably not thinking clearly. Can you propose a setup for my one-pipe system using a simple duty cycle timer wired in series with the t-stat feed wire, with a good proposed on/off time? And recommend a specific duty cycle timer for me to buy to test this?

SteamCoffee

PMJ said:

Thanks for this @Fizz. At least there is one person out there who doesn't think I am a nut case.

Well, the are probably a few more.....I, for one, have appreciated the discussions about vacuum since I joined. It seem people bring thier experiences here, sticking to what you know is a subconscious part of life. Coming here with ZERO experience may make one a tad more open... one thing for sure, talking to a Dunham Steam designer in 1935 would be interesting. Designing a system that runs optimally vs. dumbing it down for the least interested is a thankless task. ASHRAE MANUAL in 1936, the eve of the end of widespread residential steam, said that lower pressures, even sub atmospheric, were the wave of the future. The definitive version lost the race vs. forced air gas after the boom of 1946. What many are seeking, it seems, is to finish the task of making the “ultimate” home steam system. That won’t happen without pushing ahead, learning, discussing, ruffling a few feathers and making some sound scientific observations... many here enjoy the process! Carry on!

PMJ

@Motorapido ,

Sure, happy to help with that. I do everything from a PLC because then control changes become just keystrokes on the computer and there is no limit to the possibilities. However, give me a few days and I will buy a dedicated timer to hardwire and work this through that way. Give me a few days.