Confessions of an old boiler fighter

Reading thru a lot of posts on Permies related to various efforts wrapped around agenda of producing hot water, it slowly began to occur to me that experience I gained in a previous  life working with a steam boiler might be of some benefit here. Either to help with planning, give guys some ideas on avenues to explore, or prevent some form of catastrophic event. So what follows is a bit of hot water heat technology 101. Please accept it in spirit it is offered.

Setup: So building I worked with got it's start in life circa 1915. A 3 story residential dormitory structure, with basement. So 4 floors in total, with total floor area of about 10,000 square feet. As near as I can tell, when new  it was fitted out with a coal powered live steam boiler to heat the building. Each room and hallway given one or more cast iron radiators. And 100 years later, the steam distribution system was still pumping out vast amounts of comfortable, warm, radiant heat. No complaints from residents, unless they were unable to throttle the heat down, in which case they would open windows to cool things off to livable condition. It was that good.

Along about 1960, an additional 20,000 square feet was added to building. This time, instead of expanding live steam to the new building, a hot water radiant heat system was grafted on to the steam boiler. Hot water heated by means of a heat exchanger. At some point, the coal fired boiler was replaced by heating oil fired boiler, which lasted many years before going kaput, at which time that was replaced by an AO Smith natural gas fired steam boiler. So 4 floors with nearly 30,000 sf of living area heated by a steam boiler no bigger than a large side by side refrigerator.

When I became involved in building operations, the heat system was not working right, so one of first things I did was to make contact with the professional heating guy tasked with maintaining the system. He spent several hours with me explaining how it all worked. At first glance, it looked to be only slightly more complicated than a nuclear powered submarine. But after him explaining it all, it quickly became evident that whoever had designed and built the thing was brilliant. Utterly brilliant. Once it was all patched up and working as designed, it was a thing of beauty to watch.

Operation of Steam Side: A live steam system is a closed loop pressurized system. As steam is generated in the boiler, it flows into supply pipes (schedule 40 cast iron), following a one way directional pathway. Each run eventually reaches a termination point. So from boiler source to termination point, system is under pressure. This one running at only 9 psi, which may not sound like much, but I assure you it is. Anyone who has ever purged air from a home pressure canner prior to putting the jiggler weight on knows how hot that runs at 0 PSI. Temp of live steam up to nearly 240 degrees or more.

But again, system loops dead end. To distribute steam as heat, the radiators have a supply valve. Ours fitted with normal gate valves. Crack one of those open even a little bit and you could hear the steam hiss into the radiator, at which time radiators would quickly heat up. But by heating up radiators, live steam gave up it's heat and would condense as liquid water. Each radiator has a drain in the bottom of it, which allows the condensate in radiator to flow out. It was then picked up by a return line. First radiator in the loop was start of return line back to boiler room. Return lines sloped to drain by gravity. They ran parallel to supply lines.
When condensate finally makes its way back to the boiler room it is held in a return tank. Once level in that becomes great enough a pump kicks on to pump water back into boiler to repeat cycle. It is still hot, just not as hot as the live steam side is. So not much energy needed to bring it back up to steam.

When a boiler first fires up from a cold state, everything cold, it is a slow, scary process. The boiler I worked with was controlled by a series of thermostats. Once the system was activated, the boiler would turn on or off depending on outside air temp. Ours set to fire at around 50 degrees. Once thermostats began calling for heat, boiler would fire off. It started at a low idle to get water tank and all systems warming up so as to not thermal shock anything. But at some point, it then went full blast. As the water reached boiling point and steam was beginning to form, steam would flow into cold distribution pipes, at which point it would condense and start to flow backwards toward the boiler. At some points it would pocket or pool, which created a plug in the line. One steam and pressure began to build behind those pockets it would eventually break thru, at which point it shot off down the pipe like a gunshot.  This process of warming up is what creates the clanking sound in steam boiler pipes. Not good and is a horrible stress on the system, but is a normal part of the process. If it happens all the time, something not right. But once the pipes warm up, condensation in the supply side lines stops and clanking goes away and system starts to function as intended. Heat distribution handled entirely by the pressure of the steam in the supply lines. Top floors worked just as well as the lower floors. Warmest rooms in the entire building were interior utility or storage rooms where steam pipes flowed thru, but did not even have radiators. There was enough radiant heat lost from pipes to get those rooms up to 80*F or more.

Best operation of this boiler was achieved by having burners run 24/7 at a low idle. It would even out peaks and valleys. High level output kicked on when PSI dropped to around 5 PSI and returned to slow idle at 9 PSI. It would just sit there and purr and all was right with the world. Boiler was sized for climate and at no time was it not able to keep up. During really cold weather it would cycle on and off more often, but never did run full blast 24/7.

Hot Water Side: As mentioned, in new building, heat distribution was by means of hot water, heated to about 140*F using live steam from the boiler, which surrounded a heat exchanger. Remarkably the size of this was only 20 gallons of water or so. Once water was heated, it ran thru distribution loops that ran to various zones. Each floor was a zone. If memory serves there were a total of 5 of these and again, provided heat to nearly 20,000 SF of living space.

The hot water side was controlled by a system of thermostats. The reservoir in the heat exchanger had one. If temp dropped too low, a valve would open, live steam would flow in and temp would increase. Once it got hot enough, steam cut off. Each floor had a thermostat and if those were calling for heat, pumps would kick on causing water to flow heat exchanger, then on thru the loop. Instead of radiators, where heat was wanted, the hot water flowed thru a fin tube. Small at first room when water was hot, very large and end of loop where water had cooled. Since this was a 3 story building with basement, hot water was quick to rise, and cooled water flowing back to boiler room sinking, so a natural flow loop was created. (thermosyphon). The only requirement was there could be no break in the system, otherwise the syphon would break and flow stop. So critical was this that at peak of each loop, an air bleeder valve was installed on a riser to make certain the syphon was intact.

Now might be a good time to mention that all heat appliances........radiators or fin tube and warm air ducts in forced air heat systems.......are located on exterior walls directly below windows. I asked and it is done that way on purpose. Something about mixing heat from appliance with cold air infiltration from window balances heat in the room. Something to ponder.

When I first came on the scene, the hot water side had not been working right for years. The thermostats / pump connections down. But it turns out I had a past history with the building, so with a little detective work, managed to find a full set of working blueprints for the building, from which heating guy was able to located a blown transformer hidden away in a remote service panel. Once that was replaced, it all came to life and began working as designed.

But prior to that, it actually had been working.....kinda, sorta. It turns out that once a thermosyphon is established, it is actually powerful enough to overcome a lot of resistance in the line. The greater the elevation, the greater the affect. And when pumps are installed in the system, they work by enhancing suck/pull (negative pressure) on the return side. That seems to work better than trying push head pressure on the supply side. I should also point out that all our line loops were made from 3/4" lines. Cast iron or copper. These days, Pex would also work in areas you are just moving water thru, then swap to copper and fin tube where you want heat.

And one last remembrance. One heat appliance that we struggled to get working right were some fancy radiator wall devices. An electric fan pushed air thru a small radiator (like a mini car radiator).  Small feed lines clogged, Radiators clogged. Fans quit working. If memory serves, we never could get about half of them to work. Low tech, straight line fin tube worked well. Fancy tech stuff bombed.

Moral to the story......despite the attractiveness and effectiveness of steam, it is a dangerous, high tech solution to heating problem. Steam boilers, real steam boilers have to be inspected by licensed heating contractors. Boilers have been known to blow up and once upon a time, a boiler had to have it's own insurance policy. At one point we had to replace two high capacity hot water heaters, and in both cases, were cautioned to keep the size no larger than 75 gallons. At some point even a commercial, high refresh rate hot water heater is viewed as a boiler and has to be inspected as if it were. Skip inspection and if anything goes wrong, insurance does not cover.

Having said that, a high capacity 75 gallon commercial hot water heater creates an incredible amount of hot water. Enough to be used as a boiler in a hot water heat system. Either by thermosyphon or by means of small circulation pump. Hot water running thru a series of fin tubes is a highly effective way to distribute heat to remote building locations. Thermosyphon will work if heat destination is elevated, circulation pumps if it is not.

Ill also mention I have seen a lot of older homes that have what appear to be upright cast iron radiators......what look like they could have been used with live steam, being run with circulated hot water systems. Am not certain about that, but if so, might be an alternative to fin tube.

With that, my fire is going dim. May go back and make some edits.

Others, feel free to set me straight or add to the discussion.  






 

Not sure where you got your pressures for steam, but 9 psi is ridiculously high.  The empire state building runs on 2 psi. Me, I'm at about 1.5 psi. If you need help reducing your consumption or fixing your system, check out heatinghelp.com Edit to say, if you can't turn the psi or your system to 2 and have all the rads heat appropriately then you have a problem, likely with venting and/or traps (system dependant), or rad/line pitch.

Going from memory, but pretty sure it was that high.

Good or bad, does not matter any more. About 5 years ago, they pulled it all down and built a new one in it's place.

A couple more things.

Both hot water and steam sides had float valves to add make up water to system. If level in boiler dropped to a low evel, make up water from buildings water supply replenished it. Same on hot water side.

In addition, hot water side also had an air pressure expansion tank. As water in system heated up, it would expand. Without the expansion pressure tank, the system would blow itself apart. So any closed loop hot water system has to have a place for expansion water to go as it heats up.

Eugene Howard wrote:Going from memory, but pretty sure it was that high.

Good or bad, does not matter anymore. About 5 years ago, they pulled it all down and built a new one in it's place.

Here in Maine, anything under 12 PSI can be handled by an average HVAC repair person. Anything above 12 psi requires a high-pressure license to operate, or a special welding certificate in which to build high pressure steam vessels. I have both, although I know work in hydropower.

When I worked at a trash-to-energy plant where we burned garbage to make electricity, our operating pressure was 750 PSI for making 31 megawatts out of (2) boilers. Other boilers in the area operate at 900 PSI, but of course are a lot bigger. To give people a point of reference, ours boiler was 7 stories tall, where as the 900 PSI boilers are 12 stories high).

It is incredibly dangerous pressures because you will not see the steam at that pressure, it must drop down to 400 PSI before its visibly seen. This means a steam leak could be on the other side of the boiler house, and yet won't show up until it hits the other side. To check for steam leaks, we used broom handles. At that pressure, a pin hole leak will cut a broom handle in half. Fortunately, that only happens a few times a year.

Want to thank Denise and Steve for adding to the discussion.

Now that we have thrown down a marker on how dangerous steam CAN be (not IS, but CAN be), guys will have some healthy respect for what they are working with. Having said that, perhaps all hope is not lost. It may well be we can use it after all.

Without thinking too hard, I can come up with at least three different version of steam boilers in my house right now. First is the high tech version......my All American pressure canner. It even comes with a pressure gauge and 3 variable pressure relief valve, which doubles as a warning device. The jiggler. It maxes out at 15 PSI. When canning, it operates at 10 PSI (same PSI as our old steam boiler), so in concept it is essentially is a twin to what we heated an entire building with. It only takes a couple inches of water in the bottom to heat a couple dozen pint jars, half of which are not touching water at all. They are heated entirely by live steam in the canner. Condensate just drops down and is heated again. Unless the jiggler is juggling, system is not losing steam or water.

I also have a stove top pressure cooker that does the same thing, smaller scale. It maxes out at 12 PSI.

And the simplest of them all, a sauce pan with tight fitting lid. I routinely cook a dozen eggs or more in that by using no more than 1/2" of water in bottom, get that boiling, pile in the eggs......top 2 or 3 layers not even touching water, then slap the lid on. The top eggs all cook in a low PSI live steam. Pressure relief valve? The lid lifts.

If you think about it like that, it is not a stretch to come up with ways to scale that up to be able to use live steam to transport heat energy to various destinations. A quick example would be to put 2 or 3 inches of water in the bottom of a 55 gallon drum, screw a 2" piece of schedule 40 pipe into the bung hole in the lid, then start fitting away. Provided the entire run is vertical, there is no place for condensate to pool, so it simply flows back to source where it will drip back into the barrel, or if pipe is hot enough, return to steam before it gets there. Pressure relief? If you don't do anything but place the tight fitting lid on the barrel loose, pressure would eventually lift it. If you want more pressure, pile bricks or other weights on the lid. You can always install a pressure canner gauge and relief valve  with jiggler in the lid if you want to monitor it or need a warning system. And as Denise suggests, these can operate with as little as 1 or 2 PSI. My sauce pan does.

At the top end, where you want the radiant heat to go to, install a radiator device. A piece of fin tube, or make your own by creating a manifold with step down junctions to smaller pieces of pipe. Or, if you want a big one, how about another drum, full of large rocks or bricks, tight fitting lid, turned upside down with pipe coming up from below to bung hole? Steam heats drum, heats rocks and where is all the heat doing to go? All you are doing is increasing the surface of the radiating area. Just keep supply lines vertical to all condensate gravity feeds back to the barrel and it should work.

As to heat, the heavy duty high volume quick version (the scary version) is to put your barrel over top of the riser core on a RMH, or if you build a bell, put it on top of the hot top, or inside a bell. Anything hotter than boiling point is going to create steam. You are only heating a few gallons.

IF you think a 55 gallon drum is too much, what about a 30 gallon? What about a 5 gallon metal bucket? As long as loose fitting lid has a bung hole, it could work.

And if you think about it a bit, once you have a means to transport live steam to a destination, it would be an easy step to make a heat exchanger from a length of copper coil inside a bucket or drum. Water flowing thru it to a larger storage drum for domestic hot water. Thermosyphon or pump. You need the source of makeup water and pressure relief, but easily doable.

Pretty much exact same setup as our building had.

Eugene Howard wrote:And if you think about it a bit, once you have a means to transport live steam to a destination, it would be an easy step to make a heat exchanger from a length of copper coil inside a bucket or drum. Water flowing thru it to a larger storage drum for domestic hot water. Thermosyphon or pump. You need the source of makeup water and pressure relief, but easily doable.

Pretty much exact same setup as our building had.

You would need a way to remove the condensate too though. As soon as the steam deposited its heat energy into the cool, it would condense back into water and need to be separated and drawn back to the make up water.

Eugene Howard wrote:

IF you think a 55 gallon drum is too much, what about a 30 gallon? What about a 5 gallon metal bucket? As long as loose fitting lid has a bung hole, it could work.

The problem with having a loose fitting
Lid though is that you will not get a lot of pressure. That is good for safety but not so good for doing any appreciable work or heating.

Getting the pressure up is what also ups the boiling point of water. Get that higher and you pack more work into a given pound of water.

Without high enough pressures and super heating, you will only get wet steam and that is not really good for much. It will pack some heat into it, but since it’s only a few degrees above returning to liquid again, not much. It will also be very custic since the nitrogen won’t be dissolved.

I love steam, but it becomes very circular; get some meaningful work out of it and it is dangerous on a DIY scale. Keep the pressures low for safety sakes, and it’s not able to do much.

If memory serves, I once asked my boiler guy about a system like this and seem to recall his response was if the supply pipe was large enough and no obstructions or places to pool, condensate could flow back down same pipe it came in. Ships passing in the night.  Basically same process used in my sauce pan. Condensate on glass lid just drips back down where it came from.

On the other hand, you do not want clanking pipes.

Eugene Howard wrote:

Now might be a good time to mention that all heat appliances........radiators or fin tube and warm air ducts in forced air heat systems.......are located on exterior walls directly below windows. I asked and it is done that way on purpose. Something about mixing heat from appliance with cold air infiltration from window balances heat in the room. Something to ponder.

Definitely something to ponder - in a permie sort of way:
1. My parents  bought a small house built around the late 1940's which originally had some sort of gravity return heating system, which was long gone by the time my parents bought the house. So the hot air ducts were in the center of the house, and the cold air returns were under the windows - exactly the opposite of what is currently being done.

2. One of Permaculture's design principles is one of "Zones". Why would I want all the air in a room to be the same temperature? If the room had "warm spots" (in permie words, heat traps) I could organize the room to take advantage of that. My computer and sewing area where I tend to sit and can get chilled, would go in the warm zone.  In a bedroom, put a little furniture to trap the warmer air and you've got a great spot for changing and therefore can keep the over-all temperature a bit lower.

3. Parent's user test report - they thought it was wonderful! The cold window air tended to drop right down the return pipes to get heated by the furnace. They set up their favorite chairs for sitting and reading in, right by the hot air output and created a heat bubble that enabled them to reduce the overall house temperature.

4. Another point - from my experience mixing the cold window air with the hot furnace air tends to create air currents. Moving air tends to feel cooler than "stationary" air. (Yes, air is *never* stationary - but I'm speaking relatively here.) So my guess is that having the warm air mixing with "slightly" cooler air, rather than the "coldest in the room" air, might generate less dramatic currents and be subjectively warmer.

5. Last point: I know soooo... many people who say in-floor radiant heating is *much* more comfy. I'm betting a chunk of that is that the thermal mass the floor represents helps hugely in balancing the highs and lows most forced air systems generate.  However, after reading this thread, I'm thinking that another chunk is the lack of "forced air" - the air is still and the heat radiates gently. If an in-floor radiant system is well designed, I'm betting it could be organized in genuine 'zones' so that heat could be more easily increased in zones that want it (read bathrooms - I *hate* showering in a cold bathroom) and decreased in areas where we want people to be active and generating their own heat.

This may not exactly be the intent of this thread, but if we don't question "beliefs", we may not come up with better alternatives!

Jay, you are right. One of the reasons why radiant heat is so comfortable is because of the very even set point of the space heated. It has to do with controls. It
Is Very hard to control temp with a plc, but because of the delay that radiant floor heat has, it can do it very well. My plc adjusts the temp outside and ticks the water flowing through the floor up or down so that it stays about a degree from what the set temp is. If the temp outside drops, the radiant water goes up to compensate.

The other reason is that radiant heat warms the contents of the room and not the air. So a heated person lies down in a heated bed the same temp.

As for zones for radiant floor heat, adjusting zones  is very easy; just put your pex lines closer together like just as you step out of the shower, or by the toilet so as your feet rest on the floor they are warm. In places like bedrooms just set them further apart so it’s cooler, or set up more zones and control the temp with thermostats and zone valves.

My ex wife used to lay her pantyhose flat on the floor in the laundry room to dry. Our boiler is there and with all the pex pipes meeting right there, the floor was very warm… and dry. All her delicates she dried in the winter that way.

Aside: Acronym translation. PLC = Programmable Logic Controller, a computing device that takes inputs from, say, temperature and flow sensors and translates that to the actions of valves, burners, heat pumps, and related heating/cooling equipment.

Eugene Howard wrote:If memory serves, I once asked my boiler guy about a system like this and seem to recall his response was if the supply pipe was large enough and no obstructions or places to pool, condensate could flow back down same pipe it came in. Ships passing in the night.  Basically same process used in my sauce pan. Condensate on glass lid just drips back down where it came from.

On the other hand, you do not want clanking pipes.

Like in a column still!

I am one of those guys that really wants to make a diy boiler work.
In the process I have thought of a still that is fired outdoors but deposits it's condensate indoors.
Different from what you described because
returning the heated condensate directly to an outdoor boiler would be counterproductive, so I would use a series of   buffer tanks to store the heat indoors.

I would only need to carry the steam a mere 10 feet into  the house.
I think the narrower the pipe size the more the potential pressure?
I'm not sure there would be any advantage to that in my situation.
To move a large amount of low pressure steam  I would be inclined to use a heavily insulated  large diameter pipe.
Could that work?