one pipe steam or two pipe hot water

you would be well served to buy the book by Dan Holohan available on this website's store: The Lost Art of Steam Heating. Will provide you a wealth of basic knowledge to assist in your decision making, from which the input you get from the commenters to your post will then make much more sense.

Good for you! I'm sure you will have fun with the place -- and learn a lot.

On cycling and venting. The comments above are good; gas or oil boilers come up to steam very quickly, and then cycle off when the thermostat is satisfied. Only on the very coldest days will they stay on more or less all the time -- and then only if they are properly sized.

Depending on the sizing of the newer boiler vs. the radiation, you may or may not be significantly oversize. If you are the boiler will need to cycle on its pressure control. You will read here on the wall all kinds of words on that subject, but the bottom line is that it will have to cycle. Not a major problem.

Anyway -- you need good big main vents at the ends of all the steam mains. Get those, and then start fiddling with the radiator vents to get the various spaces heating the way you want them.

You mentioned somewhere up there that the water line of the newer boiler is some 18 inches below that of the original. This may or may not be a problem. It's a problem if some of the piping originally intended as wet return piping, and below the water line, is now above the water line. Otherwise, it's just a thoughtless install. So go around the whole system and take a good look at all the piping and decide whether it was a steam main, a parallel return dry main (likely to be up high) or a wet return from a drip (down low). Only the latter are a concern -- but they must be below the water line.

Eastman said:

I interpreted @cgutha's question as:

How did coal fired systems maintain balance? Surely they were not fired at the output level necessary to meet EDR for 24 hours a day. How did the steam know where to go?

No -- in fact, much of the time they operated at a simmer or not much above -- and very very low pressure at the boiler. But... when you went out to a radiator, you discovered that the colder the room was, the more steam the radiator could condense. The more steam that it condensed, the lower the pressure was there (even into a partial vacuum). So the steam went to that radiator preferentially. So that radiator -- and the space it was in -- got more heat and a hotter space got less.

The biggest single trick was to get the radiator(s) properly sized to the spaces, and the dead men were pretty good at that (modern redecorators and upgraders and remodelers aren't, which can be a big problem).

Bottom line: if you are blessed with a steam system which has not been knuckleheaded, and radiators remain in place, the thing will be, to an astonishing extent, self-balancing, provided only that you keep the pressure down and fire only to the load (let's be kind here, and not get into the various ways to do that!).

To give you a concrete example: the main place I care for is just such a place. Unless the wind is blowing, no room is ever more than two or three degrees warmer than any other. There is just one thermostat (a Honeywell mercury T87) and the boiler is controlled by a vapourstat. That's it.

Modern? Um... well, the boiler is reasonably so. I'm not sure of the date of the vapourstat or the thermostat; around 1960 I think. And nothing else has been changed since it was installed, in 1930 (actually not quite true; one radiator was removed in about 1950. We still miss it...).

The point about self-balancing, though, is that it is dynamic, and driven by the rate at which steam condenses. The pressure differences are very small, but enough.

Sounds like a nightmare indeed. And points out that the venting has to be correct on the mains; all bets are off if the steam can't get to the radiator in the first place, after all.

I would ditch the TRV ideas, and just aim for a balanced system, with excellent main venting, running at a constant lower temperature. With insulation, the boiler will fire for less total time. Removing sections of a radiator will be like opening a can of worms.
When the radiator vents are closed with the air out of the radiator, the steam will continue to flow into the radiator, and condense, losing 1600 times it’s volume.
Plug the lower tappings in your boiler, and fill it up as high as the piping will allow, and look for leaks. If it is watertight, you can pressure wash the mud out before putting it back in service.
Yes the boiler is probably oversized, but you can fix that when you finally install a properly sized new boiler in the future.—NBC

cgutha said:

Back to very low pressure one pipe heat: If the radiator vent closes with the proper amount of air for the load, does the steam continue to feed into the radiator replacing the condensed steam? Is this how the old coal systems worked?
If so, then could a modulated gas fire "replicate" the continuous coal? Would this be advantageous assuming operation at less then 18 oz. with a vaperstat? I plan to abandon the thermostat in favor of running TRVs in every room coupled with vaporstat.
It's just a theory to shoot at.

Trvs will close when temperature has been satisfied. As long as there is air still partially filling the radiator, and the trv has vacuum breaker to stop steam from being pulled in by a vacuum from condensing steam, the steam flow will slow to a crawl.

There is a lot at play and air vent trvs can still allow steam in because steam flows from high pressure to low. If the pressure in the radiator is lower than other radiators on that riser, that radiator will preferentially pull steam into it. This is where proper vent sizing is critical.

The trv body is a temperature controlled valve. The controller can be wall mount or on the knob. The body still needs a straight vent matched to the size of the radiator. If the radiator vent is too fast, air will be evacuated completely and steam will fill all sections, temperature will overshoot target, and other radiators further down the line may be starved of steam. The radiator valve style trv will not work on one pipe because condensate will be trapped.

Modulating the burner would require a staged gas valve and control of combustion air. The system I worked on recently had a two staged gas valve and two pressuretrols, one was wired, the other the installer told me was a “backup” even though there was a manual restart pressuretrol wired in line with the controlling pressuretrol. After I wired the second stage, the cycles increased in length but decreased in overshoot and fuel consumption because the system was running in the 1/2 psi range at 300,000 btu instead of up to 1.5 psi at 1,500,000, off for a few minutes, then back on at 1/2 psi.

To get that kind of result on your boiler would require a gas valve replacement. CO and insufficient flue flow gas (read not enough buoyancy to clear chimney and possible condensation of flue gas) may be a problem at lower fires.

I would not abandon the thermostat if you keep the 1 stage gas valve. Place it in the coldest room of the building. When that room is satisfied, all other rooms will be. If you run the system on pressure, rooms may overshoot temperature setting or overheat.

I would follow the Gill and Pajek vent charts and size mains by 1 oz column, risers by 2 oz column, and radiators by 3 oz column. This way air venting is balanced at main and riser level before hitting radiators. Then radiators will draw steam portional to size, which, if you remove sections (which is a lot of work) to size rooms by heat loss, will result in even heating. The trv will assist in balancing heat loss and steam supply.

cgutha said:

I am insulating the house which will change 7/8th of the individual room loads. The current boiler is 300k input, the estimated load will be 180k when complete. I assume I can remove radiator sections per the new loads.

Given the cost of replacing the boiler, My hope is to clean and bring the current boiler back to life. Can a 300k boiler work with a load of 120K? or will the cycle be too short. I doubt that modulating or changing the gas valve and burners would be cost effective. I have not priced the cost of a new furnace system even if the boiler is sound.

Oh well, I have all summer to work this one out.

ceg

My main concern with the old boiler is the corrosion on the right side of burners. It may be moisture from a damp basement, or it may be leaking between sections. If this is the case, a boiler replacement would be a great opportunity to correct the near boiler piping and get a boiler that has a two stage valve. Gas valve replacement isn’t difficult, and is about as expensive as a vapor stat, and the burners just set in the manifold and run in the $20-$30 range depending on type.

One other thing I noticed, your edr calculation didn’t account for the aluminum finish on the radiators. This will bring the edr per section from 3 to about 2.7 reducing your total edr to 1037. This brings your load with 33% pickup to around 330000 btu/hr.

I would install vents, service the boiler, replace the pressuretrol with a vaporstat and run the system to see where you are at. If possible I would see if natural gas is available as this would be much more economical than Lp.

Hello ceguntha,

The EFM underfed burn pot stokers burn very clean and they use an ash tub to collect the ashes under the burn pot.

You will not have issues with fly ash like you would with a hand fed coal boiler. I used a wood and coal fired hand fed until I switched over to a flat grate coal stoker.

You can purchase lids for the ash tubs to eliminate the ash flying around when changing the ash baskets.

It could work as long as you vent that air in 7 seconds and no steam goes up to the risers. But, steam will go into the risers and then get pulled by vacuum from collapsing steam ahead of it up and away from the main.

Coal had all day to vent so it mattered little if it took 20 extra minutes to get all the way around the perimeter main. But gas and oil cycles more frequently, even when load matched (1 hour compared to 24 is a big change, and that is a fairly long gas cycle). This is why converted setups use multiple mains to distribute steam. This broke up the loop and allow more even circulation.

The one pipe I have been working is broken into 4x65’ mains separated 30’ apart. Somebody removed insulation from the 3rd main from the boiler. Steam prefers this main ahead of the 4th naturally and even more so now because of lost insulation. It takes 14 minutes after steam hits the header to get enough steam to warm the 4th main.

In addition to this kind of imbalance, on each main, there are 7 risers. The riser closest to the vent, at the. End of 65’ run gets steam first. The riser closest to the tee from the main gets steam last and barely heats until 15 minutes into cycle. Both have the same venting on the radiators, no riser venting. The radiators at the end of 65’ are 4x larger than the ones near the tee. Steam hits the larger radiator and pulls more steam than the little radiators, which starves the other risers.

The longer the main, the harder it will be to get steam to each riser with it taking off into the riser and starving the main. Venting can help this by guiding steam to the end of main. Then risers vents, sized so they vent the correct amount at higher pressure will fill. Then radiator vents sized the correct amount for their size will fill, in theory, assuming insulated lines and low frictional lost.

Hello cguntha,

I have to disagree with Jamie about burning coal for heat. I have been doing it for 36 years now and going into my 37 year and I am glad I have coal heat as it costs me about six dollars a day on average to heat my very old leaky house that used to be a one room school house up until 1953. I would much rather have radiators for more thermal mass but I am stuck with 3/4 inch finned hot water baseboard for heat using hot water

As far as the coal dust goes I just sweep up the coal dust and toss it back in the hopper with no issues. All you need to do is wear a good dust mask like the 3M model 93 dust masks.

If you have time in your busy life I would you to become a member of the coal heating forum www.coalpail.com
Richard S. (the forum owner and admistrator) has an extensive section on bituminous coal burning and we have a huge amount of information there for anyone to look at.
Becoming a member is also free of charge and there are a lot of folks that use coal to make steam heat on the forum.

The folks on the forum would love to see pictures of your home and the old boiler and piping and they can help you a huge amount as well even though we are on the east side of the Mississippi River. We have a lot of folks that have one pipe steam systems that burn rice, buckwheat and Pea coal.

With the sub bituminous Wyodak Coal Seam you have in the neighborhood you will save a huge and I mean HUGE amount of money to heat the place.

Don't give up on your soft coal just yet.

About sub bituminous coal burning,

The three coal dealers near you are Baranko Brothers Dickenson, ND, Center Coal Company Dickenson, ND, BNI coal Bismark, ND.

The testing for the use of sub bituminous coal in the EFM DF520 coal stoker boiler was a success in 2016.

It can make steam with soft coal so you should be able to install it in your system easily by putting it in a concrete walled and floored pit with a Bilco Door as it comes in 2 pieces; the base ash pit and the steam chest and the cladding. You can always add insulation to the boiler too to hold in more heat.
It would not be hard to simply build a coal bin with a coal feeder dog house in the wooden wall of the pit for the feed auger to convey the soft coal from the storage pit to the stoker.

You could install a new dry steam header on the EFM DF520 and pipe the dry steam from the header to the steam lines in the basement through a hole cut in the foundation wall from the concrete pit that the new boiler is set in.

Its something to think about anyway as you have low cost coal for heating so close to you and the all canadian coal heater would be much more expensive to install and you could not make steam with it.

Keep us updated and please add pictures of the renovation. I love to see a work in progress.

Cgutha, I would be passing thru your town next week.
Going to relatives in Crosby, ND.
Steam engine show etc.
Will you be around?
I sent you a PM also.

Ceg, sounds like you have come a long ways.
I stopped there for a tour in the summer of 2018, we were on the way to Crosby ND.

Would you have to reslope the other 2 1/2" main to maintain parallel flow?

There is a lot of venting info in TLAOSH-revisited, Dan's 2 nd book.
Assuming you will be redoing a lot of riser piping, on page 201 of that edition, (perhaps in the first also) there is a method shown of venting 2nd & 3rd floor risers.
Simple use of a tee rather a 90 and then a straight thru valve.

Or, if you wanted to reuse the existing supply valves, you could also put a tee at the ceiling just below the rad and then with a nipple and 90 pipe up to an air vent for the riser next to the rad.

If the steam mains ends near the boiler you could add 1 or 2 3/4"
risers for main venting.
If you put valves on these risers and opened them as the boiler fires, then time how long it takes to get steam there with one open pipe......then try it with 2 open pipes.
IIRC, a 3/4" nipple will handle 4 gorton #2 air vents.
That number or more might be in the neighborhood of what you need. You could also consider the B&J "Big Mouth" which do more than twice the G2's.......but no float for water....you would want them as high above the main as possible.

I think that the cast iron sectional boilers of today have been designed to hold enough water in their operating levels to supply enough steam to fill all the pipes and radiators in the system. An exception might be had for a system with unusually long supplies, and dry returns, or some Weil-McClain boilers.
If you can do without a condensate tank, and go with gravity return, then you have eliminated one potential mechanical element which may fail in the future, usually on a Saturday afternoon, with subzero temperatures.
Some vanishing water levels, while steaming, may be due to over-pressure (over 1.5 psi), pushing excessive water back into the wet returns. You only need a few ounces to get steam quickly up to the radiators, as long as you have generous main venting, (or vacuum).
I have 55 rads on a 1,050,000 Peerless 211 A, and once the wet/dry returns were repiped, the water level is adequately steady, with only gravity return.—NBC