Two Pipe Vacuum or Vapor?

Davidho

My suspicions about my system being different finally confirmed after 7 years.  I nursed the old boiler long as I could.  Three years ago fixed the very end of my supply.  Last 10 feet, a 90 and 18inches into a tee.  After I did that I would have to hold my yellow handle drain valve open awhile for “pressure” to equal.  I can wait hours and still have a vacuum. I thought whatever. No one near me within a 50 mile radius would help me out.  Called a lot of places when came time for replacement. No one would touch it or show up.  Want me to change.  I live in central Missouri.  Finally found a mechanical company that works on big commercial places like hospitals and colleges.  I payed a lot of money but the dude they sent here drove hour and half one way for 7 days and than would talk to me about steam in the evenings when I got home from work for a hour sometimes.  I got my money worth.  He kept saying these gauges on here are useless. He never worked on anything like this but only read about it and heard about it.  He even recommended I get the lost art of steam book once he saw what my system does. So after being a lot invested in this now I figure time to learn everything I can and keep this thing going for a very long time.  Last boiler installed in 1996.  I learned I have three valves on my system.  One is original and has never worked since we have lived here; now that I understand whats going on. It is a Hoffman No.6 that is on the very end of my supply.  I than have two Hoffman #76s on the end of return. Only one of them work.  I always figured they did whatever they did because after the boiler would run my house stays comfortable for awhile before runs again. Never thought anything wrong.   I have “The Trane Co.” traps on the ends of my radiators.  I am very interested in controlling my burners with something other than my thermostat.  I used to work on machines that pulled vacuum so I thought that would be how I could control this.  I have gauges and new hoffman valves on the way.  Searching around here seems like everyone controls off of the temp.  Looking for a little help setting up something to control on and off time. 

clammy

First get yourself a copy of the lost art and second from the sound of it you have a vapor vacuume system . Don’t get rid of those Hoffmann 76 vacuum vents they are essential to first removing the air and second not letting it back in hence forming a vacuume . You most likely could use a vapor stat to keep the pressure low which most vapor vacuum system operate in this range . Installation of a low pressure gauge ( please leave the required 0-30 psi a gauge code required everywhere ) either a 1-3 psi or better yet a 0-32 ounce gauge . Without the receiver and a boiler return trap your system will have to operate w gravity so low pressure is key as to not have to stack to much condensate for it to gravity return . If the boiler and its wet return piping has not been flushed it a good idea ,mud and decades of rust and crap is not ideal for any steam system and the more it over looked I guarantee it’s not getting any cleaner . Usually on most vacuume systems at least old one that where original a lot of the installer would add a boiler drain or petcock on the pressuretroll piping so they could break the vacuum instead of opening the boiler drain and or low water cut off and having it suck air and churn up a bunch of junk . When I run into this type of system I do the same .
As much as a lot of gentlemen will say go to a air vent system I say if it still can maintain vacuume stick w it ,when switched to a air vent system it will never still pump out heat after burner off for any extended time and the start up steam distribution will never be as quick and that you can take to the betting parlor . Sad part is those Hoffmann 67 vacuum air vents are the highest price of all steam main vents but when installed in the correct system the pay back in savings in venting time I believe would be recovered in no time .
Best of luck and get that book .
Peace and good luck clammy
Happy turkey day now get to work

Mad Dog_2

Amen...Listen to The Clamster...he knows.  Mad Dog 🐕 

PMJ

@Davidho ,

You are on the right track.

I have a two pipe system that I run in natural vacuum between burns. I realized about 25 years ago that some control other than the thermostat was needed to get anything like truly even heat out of the system. Over the years since I have also learned that there are two main enemies to steam heating systems. Enemy #1 is fresh water. Enemy #2 is fresh air. The less of both coming into the system the better, for efficiency, comfort, and life of the components. The results I get now vs the standard vented system and its standard tstat/vaporstat control I had before are dramatically better. Not sort of, not maybe, not close.

As Clammy observes, in a natural vacuum system steam in the mains never stops flowing into radiators when the burner goes off like it does instantly at that time in all open vented systems. And, if you install a control that pulses the burner evenly at a net burn rate closer to the actual demand than a thermostat alone can possibly do, steam flow into the radiators basically never stops in colder conditions and you achieve a much more comfortable and efficient steam delivery.

Happy to discuss any time.

Jamie Hall

Do keep those #76 vents. Yes you can still buy them -- but they are pricey, and they are essential to the functioning of the system.

So, incidentally (though often overlooked) is the use of crossover traps. One of the keys to vacuum systems -- as @PMJ sort of hinted at -- is that when the burner goes low or off, the entire system drops into a vacuum. Not just the steam mains. Not just the returns. The whole thing. In fact, in such a system, functioning well, the pressure difference between the steam mains and the dry returns never changes -- just the absolute pressure in both.

Davidho

I have so much to discuss.  My wife thinks I have gone bat crazy.  I have been in the basement every minute I have been home reading watching listening.  

@clammy
Installation of a low pressure gauge ( please leave the required 0-30 psi a gauge code required everywhere ) either a 1-3 psi or better yet a 0-32 ounce gauge . 

I have both of these gauges on the way. If I install a vaporstat can the pressuretrol be removed?

@PMJ
Enemy #1 is fresh water

This is where I am with my boiler and want to get correct first or a plan for.  Brand new boiler has been running since Saturday. Installer skimmed for four hours right away because it was horrible he said.  I have been opening drains and flushing.  Wednesday, last night, I opened drains first time in 24 hours after I skimmed for 2 1/2 hours straight.  Skimmed two 5 gallon buckets in that time.  Drains are clear water now, but still have more skimming to get oil.   Do I need to wait to skim more or can I just skim just hours and hours now?  I had just the littlest line of stuff on my water in the sight glass but than after a cycle it looks bad again.  I have only one galvanized nipple in the whole system and it is where my water feeder line connects with my end of supply return loop at the bottom and it has started a very very slow drip. I have a VXT-24 water feeder coming I only have a few pieces of pipe that hasn’t been replaced at the boiler return piping .  I am not sure if I should attempt doing these things now or after the season is over since anything that should be a simple job rarely goes as planned.  Peerless says to use arm and hammer super washing soda no later than than one week of initial start up.  So my question is.  If I am going to be doing this arm and hammer thing and all this fresh water, is it better to do it all now or okay to wait and drain everything again at end of season and replace and add all new water again at that time?

“if you install a control that pulses the burner evenly at a net burn rate closer to the actual demand than a thermostat alone can possibly do, steam flow into the radiators basically never stops in colder conditions and you achieve a much more comfortable and efficient steam delivery.”

I have MS and pretty sensitive to temperature and this is how I KNEW it could be better.  I could feel a temperature change and sure enough within 5 minutes the thermostat would than drop a degree every time. It may be another 30 minutes before the heat kick on and it will run, and have to wait for all the air to be removed and all that.  Example house set on 72 I could feel when it went from 73 back to 72.

I attached couple photos of what my water looked like after I skimmed and brought down to full level and what it looks like now about 20 hours after last skim.  Also a photo of what my return to boiler piping looks like.  The vertical drop down with a flange, a 90, a few T’s all that is left of what is probably original. 

Happy Thanksgiving everyone.

PMJ

I don't know anything about skimming. Other folks here can take you through that. When you are on the other side of that we can talk control.

Jamie Hall

I might add to my previous comment. Unless this system uses traps on the radiator outlets as well as crossover traps, it is essential to control the pressure differential between the mains and the dry returns very closely (probably between 4 and 6 ounces per square inch) to maintain satisfactory control over steam passing the radiators.

Now this can be done. Problem is, the conventional vapourstat (a pressuretrol is useless) is sensitive to gauge pressure on the steam main, and knows nothing about the pressure differential. If the dry returns are open to the atmosphere (such as with a conventional main vent rather than a vacuum main vent), this isn't a problem, of course.

As @PMJ observed, one approach to this is to have a system which pulses -- cycles -- the burner on and off to produce a net average output which matches current system demand. It would, ideally have a cycle timer controlled both by outside temperature, for the base demand, and by an indoor temperature sensor (not thermostat, which is either on or off) to trim the cycle timing up or down as required by factors which the outdoor reset can't sense, such as wind load or solar loads. You would still have a pressuretrol as a safety device -- if nothing else, your building inspector, never mind insurance people will require it -- but it wouldn't be in control of the system.

I will happily grant that such an arrangement will produce very even heat. However. This is a completely custom setup, and unless you find someone who is willing to install and program it, which is going to take time, this may be difficult.

On the other hand (don't shoot me, @PMJ !) if you were to go to an atmospheric vapour system, with conventional main vents, a vapourstat will be something which at least the better steam people will readily understand. Something to think about...

mattmia2

What is the name on that canister thing the vent is screwed in? It looks like boiler return trap.

Davidho

@Jamie Hall My boiler steam header goes in a big circle around my basement and comes back to the boiler.  There is a single pipe coming off that which goes directly into top left of radiator with a valve on it.  Than on bottom right has trane trap on it.  That all then runs into pipe starting at the first boiler and circles all the way back to boiler each radiator’s cold return pipe connecting into it.  So each radiator is connected into the 3 inch pipe coming out of boiler. Attached a photo of what is at the end of the circle. The white valve on right is the end of steam supply.  The two greens 76s are on the cold return side.  The highest one is the only one that works out of the three. I have three new ones suppose to be here Monday. I just spent what I did on this boiler what those 3 valves cost was high but it is without question I am replacing. Considering ordering a few more soon to have them before unavailable one day. Only other pipe I have is this small one running off direct return trap.  

Mad Dog_2

That's the steam main wrapping around the basement. The "Header" is really only the mostly horizontal piping above the boiler that us supplied by boiler takeoffs (vertical pipes) leaving the top or sides of the boiler.  Mad Dog 🐕 

Jamie Hall

Nice system. Replace in kind and you should find it working very well. That is a boiler return trap -- and it helps return condensate to the boiler should the pressure differential become too high. Shouldn't need service.

PMJ

@Jamie Hall ,

Your points are well taken. For clarification I add the following:

Yes this is a custom setup, so sadly very few will ever experience it. And, likely mostly because of your counsel I did install a single switch that converts right back to the original control which I never disturbed. See attached photo. Maybe I should add a label and call it the Jamie Hall switch. The only actual physical intervention in the original control is another contact in series with the gas valve circuit. The PLC prevents firing when the original control would be. This switch turns that contact permanently closed. Note - 95% of what the PLC is used for has been data collection for my studies and displays to watch what is going on. The actual control aspect of what I do here is desperately simple.

Regarding the pressure difference between the steam main and the dry return - there are no components in my system between the two except radiators and the water loop. I never allow my boiler to run long enough to fill the radiators so traps are never closed. Mouat return elbows don't actually "close" anyway.

For some reason there is a notion that maintaining the pressure differential where the main is higher than the dry return requires intervention of some kind. I have years of actual experience now showing that the difference is very small and that it takes care of itself. Steam is always condensing the fastest in the radiators creating a void there. Since the dry return is totally closed off except where it attaches to other radiators which are also condensing the resulting pressure in it is necessarily lower than the pressure in the main which is condensing at a much slower rate due to insulation. The main also has a continuing source of new steam (albeit a small amount) due to continuing steam production as the boiling point drops. Peak vacuum isn't reached until 30-45 minutes after the fire goes out and since wait times are more like 20 minutes the system pressure is still dropping at the moment of every new fire. So the flow into the radiators, though the rate continually drops during the wait periods never really stops altogether. And I did nothing to facilitate this except to remove all the vents and replace them with one solenoid controlled opening on the dry return. There is also a very cheap check valve on the dry return which I installed in case the solenoid fails which will work too without needing any control at all
.

This pressure difference is barely measurable. But then as we have observed many times very small pressure differences are all that are required for steam flow, and steam will always flow from high pressure to low pressure.

So I fear that much of the the hesitancy to natural vacuum in two pipe is the idea that it is complicated to control. I submit that at least in Mouat two pipe it is quite simple.

Jamie Hall

I'm right with you, @PMJ ! The real trick -- which you have managed -- is to match the boiler power to the radiation demand. Do that and your troubles are over.

Daveinscranton

This thread is a great education.  I am not a steam guy.  But I love it.

My suggestion is meticulous notes.  Theory of operation/diagrams/parts sourced/replaced/.copy of Dan’s book.  Print out of this thread etc.  Anticipated maintenance schedule.

I suffer the delusion that I will remember years later without notes.  I can’t.  It will make it easier for the next person too.  When I add/replace something, I tag it with the date.  I put a note near the boiler where to find the instructions and spare parts.  Somewhere in my notes, after all is running beautifully, I write: “change it at your peril”.

Art/elegance is in the eye of the beholder.  My friends are certain there is something wrong with me as to the lengths I go to.  They are right of course.  I no longer argue.

Davidho

I got my vacuum valves early and installed them last night.  With working vacuum valves now they each have their time to work.  Supply one when boiler going and than the tallest one on the cold return side shortly after, thats only one that has ever worked.  After boiler is shutdown the valve on top of the return trap is letting air out for over 25 minutes.  I have only got to watch it do it’s thing twice so far.   

Would putting 30-0-15 gauge with these valves give me beneficial information?  I have been hinting to my wife and mom about the art of steam book for Christmas.  I dunno if I can wait a month.

Jamie Hall

Bravo! Good luck with the hinting. I'm not sure a 30-0-15 gauge would be all that helpful -- at least not on the pressure side. If you could find one which was more like 5-0-5. though, that could be really interesting!

reggi

Did you skim your boiler since this photo

Davidho

@reggie. I am actually getting ready to do it now. Needed a couple more ball valves to get rid of these “boiler drains”.

109A_5

Hello @Davidho,
Can we see a picture(s) of the whole boiler ?
Are you skimming it correctly ? You should be using the skim port tapping not the drains.

https://youtu.be/Hb4uIE3Mldg

reggi

@Davidho Was a skimport installed on your boiler? Draining isn't going to get those oils out , they just cling to the walls as the water level drops and rise back when it's filled and fired. .. the steam wants to break the surface of the water and continue it's trip but the oils smother it at the surface and there's a lot of turbulence every time, that throws oil into your pipes and just everything has to be cleaned... skimming will drain the oils floating on top of the water... Has to be done..

Davidho

@reggi
Yes I installed skim port as well today.  Couldn’t get a 1 1/4 ball valve so had to reduce to 3/4. I’ll get bigger one during the week.

leonz

You definitely need to use the Arm and Hammer Washing Soda as it will break down the oil and make skimming it off easier.

clammy

Can you take a picture of your boilers near boiler piping and a shot of the equilizer drop off of the header and timing into the boilers inlet and Hartford loop . Just curious .

mattmia2

Unless something is weird about the internal structure of that boiler that skim port should be fine. In fact getting the water flowing off more in the middle of the port can help the oil collect on the surface instead of sticking to the interior of the boiler.

Davidho

@clammy

 

So after doing an almost 5 hour skim and than removing nipples and gauges and flushing from every direction I think I may just have to skim a couple more times.  They removed a shutoff valve on my return pipe and I questioned them not putting it back.  It is a tight spot but I am thinking the boiler and most of the new pipes could have been skimmed first before the oil mixed with the crud. Also got a oz/in gauge installed. I got to fire her up at 5 this morning.  It was cold last night house was 65. I set thermostat to 72.  From cold start up I was around 3 3.5 oz/in after running 30 minutes the radiators were hot end to end even the large ones.  I figured good enough for now set thermostat to 70 went to bed.

I have a vaporstat that does ounces on the way. I have watched it run 3 cycles it has been set on 73 all day. I have idea I need something set on 3. Looking for experience to help me with starting point. First thing of note is I go into vacuum 10 seconds after burners turn off.  On this third run pressure started up at 1:48.   2.5 minutes heat at first radiator pressure around 2.25 2.5 oz.  I get flutter in the gauge.  When I am first making steam and getting warm my gauge flutter ranges from 2 to 3 but the longer I run the more it likes to stay at 2.5.  After about 15 minutes it will actually pause and sit there at 2.5. Before bouncing between 2-3. Radiators are hot end to end.  What would be good starting point for the vaporstat?  Is it going to refire soon as goes into vacuum or does the diff. go into the negative (vacuum)?

Jamie Hall

Your pressure is fine. The pressure fluttering like that is quite normal, assuming that the vapourstat pigtail goes to the boiler and not the header. Not to worry.

The vapourstat will refire the boiler when the pressure drops to whatever the cutout minus the differential is.

Remember that vapourstats are sensitive to gauge pressure, and will not read -- nor react -- to a vacuum in the system, nor to variations in differential pressure. Nor will your pressure gague read a vacuum -- it, too, is reading gauge pressure.

As to dropping into a vacuum in 10 seconds is not unreasonable for a smaller system.

mattmia2

It sounds like the boiler is well matched and the vaporstat will never cut it out. If the pressure never goes about 3 oz/in^2 g then the system is more or less condensing as much steam as the boiler is producing. The vaporstat only needs to act if it gets above 8 oz or so. Set it so the cutin is above 0 gauge pressure so it will fire if the system has lost its vacuum.

Davidho

@Jamie Hall @PMJ
So going back to using something more than a thermostat.  I have good experience with vacuums.  To melt silicon and pull it out of molten and return back to zero defect silicon for computer chips and solar panels it takes a lot of controlled heat that is super hot and under an unbelievable amount of vacuum.  My head still can’t believe it is like I have a tiny crystal puller.   Anyways.  Boiler stays in vacuum until my water cools to some temperature I am guessing. Hours I know that.  Once again probably in the book.  I want to compare when I “think” the boiler should fire vacuum reading to how much vacuum when the thermostat says to fire.  Or is everything sitting in vacuum and I should read it at an inlet of a radiator?

mattmia2

Once most of the air has been vented out it stays in vacuum until air leaks in through things like check valves that don't seal quite perfectly and valve packings. It will stop steaming at whatever point the water cools to a point where it won't boil at the reduced pressure in the system but it will still be in a vacuum unless the leaks break the vacuum first.

109A_5

Hello @Davidho,
Once you get a feel for the pressure and vacuum extremes of your system, you may enjoy a Dwyer Magnahelic gauge like this. Many variations (new and used) available on eBay.com

An example;



https://www.ebay.com/itm/385280872963

clammy

That near boiler piping leaves much to be desired . The tee on the return inlet serves no purpose as for flushing the boiler bottom out and should have been full size to a reducing tee 2 1/2 x 2 1/2 x 2 .That companion flange w a rubber gasket will fail as they always do that is not a steam union flange . And even though I don’t know your boiler size unless it’s a 4 section or smaller both risers should have been used . Another note all the extra elbows on the supply off the header the equilizer is really not correctly off the header but it is what it is and as I always say how forgiving steam is that even piped half baked it works so so but not as it really should . . On another note do yourself a favor and add a cross tee to your capped 3/4 inch nipple off of the skim add a another tee and a 3/4 x 1/4 tee and put your pigtail there w your pressure gauges and pressuretrol and chances are in my experence is that the pigtail in that position will never get clogged . It’s never happed yet on any job I ve piped in that manner in respect to the operating controls . Just remove the 3/4 nipple out of the boiler add a brass nipple and 3/4 brass cap ,the cap may be removed and the top of the boiler may be wanded out across the boiler sections for this access and the bottom would be from the 2 1/2 return inlet . As I’ve stated skimming is great and take some time ,wanding on the other hand done correctly washes all that crap out and saves hours of skimming and in my experence a lot of free return visits . I would rather wand a boiler 2 times and then skim and be done then 3 or 4 visits to perform one of the most exciting duties of steam boiler installers does . Not .
On a smaller note a lot of customers look at our propasals for replacement and or multi repairs and think that where over charging and to expensive ,well in my experence it’s not true it’s just the other guys are clueless and usually they end up making more money on the job then a pro would doing it correctly but the biggest difference is experience and doing it correctly the first time not cutting corners or leading the home owner to finish the loose ends like skimming and cleaning the boiler and deal w poorly installed steam piping and of course the never to return issue . I firmly believe if the installer is not going to leave a clean steam boiler then he’s not a steam guy just some dude that connects pipes and dot to each other and may be decent at it but in reality is clueless and offers zero at many levels ,but gets work and leaves other to deal w the mess . Ps get rid of the cycle guard it’s the death of a long cycle but it does deal w issue of poor piping and low water content in larger systems instead of adding a resourve tank , by cycling off before the fireworks start ,and after a non cycling lwco is added you will find out if your over sized if so a 2 stage gas valve and another vapor stat may be in order to smooth things out . Some times some bringing a little reality to a issues should not be viewed as being negative it’s just my view of reality it may be different from others not that of them is bad but just a view .
Peace and good luck clammy

PMJ

Davidho said:

@Jamie Hall @PMJ
So going back to using something more than a thermostat.  I have good experience with vacuums.  To melt silicon and pull it out of molten and return back to zero defect silicon for computer chips and solar panels it takes a lot of controlled heat that is super hot and under an unbelievable amount of vacuum.  My head still can’t believe it is like I have a tiny crystal puller.   Anyways.  Boiler stays in vacuum until my water cools to some temperature I am guessing. Hours I know that.  Once again probably in the book.  I want to compare when I “think” the boiler should fire vacuum reading to how much vacuum when the thermostat says to fire.  Or is everything sitting in vacuum and I should read it at an inlet of a radiator?

First start thinking about the firing control as just about finding a method to get the burns evenly spaced and at a net burn rate that exceeds the coldest day demand by some small amount. Once you have a timer that can adjust both on and off times independently you find these times through trial and error. The vacuum will take care of itself between burns, does its thing, and requires nothing from the control.

The only downside of this method is that cold starts are a little slow. In times you actually need heat it works great. I recommend starting there because it is inexpensive and so easy and then move to ways of getting around the cold start problem and using vacuum to make the cycles more self-adjusting. There are threads on this method here that show timers to use but I will get it back out if you need.

Davidho

I want to thank all of you for sharing your experience and knowledge.  I hate this cyle gaurd low water cut off.  Soon as I get rolling it shuts down and then it does again 10 minutes later.  Installer talked like this is modern and great.  I noticed he took my old McDonnel & Miller float ball type. 

 

@clammy
I don’t know your boiler size unless it’s a 4 section or smaller both risers should have been used . 
It is 4 sections I believe.  It came in two halves.  And those two halves were two sections put together. Peerless 63-06-SPRK.  I got photos from installer actually yesterday because I am trying to keep track of every change and when made.  I attached photos of how that piping was on last boiler and maybe I should be back to that.

clammy

Yeah look at the I n O manual ,2 risers is suggested ,any less does and is effecting the exiting velocity and amount of carry over increasing both . The installer should have looked closer at the manual ,pretty sure there’s even a pretty simple diagram can’t get much easier than that also tells ya how many risers to use per boiler size just in case your a beginner but ya gotta read the manual overwise forget about it . Because at this point its just a near boiler repipe or better put a re install 1 caveat is the boilers down there and the old ones gone .
Peace and good luck clammy

Davidho

I was confused about why I wasn’t getting the boiler repipe kit peerless sells for this thing with the price I was paying.  So all this labor skimming and wanding the next day i am off and the money for the boiler repipe.  Thanks again Clammy.  I have a 7 and 4 year old  and I hope to pass this stuff down to them I don’t see why it can’t go another 100 years.

clammy

Upon really looking at your pics I think your installer knows no better and is clueless any further attempts by them is clearly a waste of time or unless as much as you think you paided for the job the payment was based on just reusing and reconnecting into a existing piping set up zero improvements which is very common , pretty much left exactly as it was previously piped but it works . Where are you located ? Mechanically speaking it must be thin pickings on decent piping mech that can turn a few pages and read or look at stick piping diagrams I wish school was that easy but I kinda know this is nothing new in the industry I see it all the time and when push comes to shove they usually stay the way they where and people deal w it . The rare few bite the bullet and pay the piper and end up w usually zero issues aside from age issues nothing in life doesn’t get its hiccups once in a while
Clammy

Davidho

I am in central Missouri multi hours from big cities of St. Louis and Kansas City.  Columbia is biggest city near me and it is 1hour 15 away, doing 80.  I knew I was going to be paying a ton for travel time.  Took em a week.  Remove old one pour pad install. Every business under a hour drive is mom and pop HVAC one guy said he look at it called night before and said he had doc appointment.  I was in a corner and just grateful I had the means to get a new one in the basement.  I will take it from there with some help on here. I have found out no one wants to touch an old house and no one will meet my expectations so I better learn everything, take my time,  and enjoy it.