Pickup Factor...

Jamie Hall

Seems to me that we need a really good scientific/engineering discussion on pickup factor. A number of us have opinions on the subject -- some rather strongly held! -- based on various observations or practical experience or...

But what I am looking for here is what, really, is the reason for a pickup factor? What effect on such things as speed of steam reaching all radiators? What effect on the difference in time between the farthest and nearest radiators? What effect on cycling on long runs?

What is the physics behind it?

And why do some systems seem to run very well with very low pickup factors, and others seem to run very well with much higher ones?

Thoughts? (not opinions, please, but really well supported thoughts and explanations!)(and @Charlie from wmass you could give me a hand here -- I know that Cedric has a 2.75 gallon per hour nozzle, but I don't know what it is really flowing at...)(shame on me!)

BobC

One way to tellwhat the real time flow rate is would be to put an elapsed time meter on it. My old v75 ran off a oil tank without a working gauge for 7 years, when i found out how much they wanted for a new gauge I said screw that. I put an ETI on it and I knew EXACTLY how many hours it ran between fuel deliveries and could calculate the gal/hr the boiler was using.

I kept a log for years where I wrote down the ETI reading and logged any observations (water added, vents leaking steam, etc.) every day. it's also probably the easiest way to know if the rate of fuel usage is changing.

You do have to know how your gun works, many guns run for set times after the fuel stops flowing to purge everything. With modern guns timing the fuel solenoid is probably the best bet.

Bob

Jamie Hall

BobC said:

One way to tellwhat the real time flow rate is would be to put an elapsed time meter on it. My old v75 ran off a oil tank without a working gauge for 7 years, when i found out how much they wanted for a new gauge I said screw that. I put an ETI on it and I knew EXACTLY how many hours it ran between fuel deliveries and could calculate the gal/hr the boiler was using.

I kept a log for years where I wrote down the ETI reading and logged any observations (water added, vents leaking steam, etc.) every day. it's also probably the easiest way to know if the rate of fuel usage is changing.

You do have to know how your gun works, many guns run for set times after the fuel stops flowing to purge everything. With modern guns timing the fuel solenoid is probably the best bet.

Bob

There's an even easier way for me to figure out... ask @Charlie from wmass what he's set it at!

Fred

Great topic @Jamie Hall . On a One pipe system,there is another component that I would think has some impact but I don't think I've seen it discussed when the debates occur around pick-up factors. Beyond the initial cold start, there has to be some "cooling" effect on mains/run-outs with condensate running back to the wet return(s). I would think that also has to be a consideration at all points in the heating cycle. The temp of those mains/run-outs has to be maintained for steam to reach its destination. Clearly not what it takes from a cold start but a factor. The amount of mass also makes it difficult to say "one size fits all", even if it is insulated.

ChrisJ

During a cold startup your piping has 100% of the boiler's output to heat it. It doesn't need extra because nothing has reached any radiators yet. Once steam does start reaching radiators all of your piping should be hot. If this isn't the case, you need to balance the system better.


This is my steam pressure at the boiler during a completely cold start, no pig tail and a 0.0015 snubber. At this point, steam is just entering the radiators including the furthest ones on the second floor. All 10 of my radiators get steam within a few seconds of each other, I won't tolerate any worse. I've had people hold the valves and call out when it gets hot. Yes, I'm picky.



https://youtu.be/zyxLbXq61-U

Charlie from wmass

145 psi

Jamie Hall

@ChrisJ -- I know that your system works for you, and works well. The question is... why? What are the factors which go into making some systems -- such as yours -- work well with a very low or nil pickup factor (maybe we should even call it something else?) and others -- such as mine -- need a much larger one, but which also work perfectly well.

ChrisJ

@Jamie Hall What makes you think your system wouldn't work equally well or better with a much smaller pickup? Has it been tried and if so, was venting changed and fine tuned as well?


Please take time to read this as I took the time to write it and feel it's accurate.

The theory is, you have to heat all of that steel and cast iron up at once and if there isn't enough steam you go around, some radiators may starve, correct?

As mentioned previously, we don't heat our piping and radiators together, no one does. First piping, next radiators. In a hot water system all of it slowly heats together, this doesn't happen in steam.

That said, now lets look at the radiators. How do they heat?
Depending on venting speed, and the design of the radiator they either heat section by section, or perhaps first section or two, and then across the top, and then the next few sections fill in etc.

Obviously we are not heating the entire radiator at once like with hot water. Further more, the radiators are all made up of the same sections. A 50 sqft radiator uses identical sections as a 10sqft radiator of the same make and model, it just has more of them. This means from the boiler's point of view a 50sqft radiator is the same load in the beginning as a 10sqft one of the same make and model. The load slowly increases as steam fills the radiator which with a smaller boiler and slower venting, happens slower. In the beginning of each heating cycle the boiler sees absolutely no difference between a huge 50sqft radiator and a tiny 10sqft one. I realize there are many variations of radiator sections, some are tall, some are short etc. I have 10 radiators, almost all use identical sections from tiny 5 section ones to large 20 section ones.

Installing a bigger boiler because one system has more sections than others which may never even need to heat, makes absolutely no sense in my opinion. And if they do need to heat, they will as long as the boiler's output matches the piping loss and connected load.

Wanting a bigger boiler because it will heat everything faster also does not make sense to me. This idea also works in hot water, but do we install a boiler that is 50-100% too big just to heat our baseboard faster? We'd get all of that baseboard hot good and fast but no one does this.

Faster doesn't win the race in heating. Better matching and balancing does. If faster even played into it, radiant heat would never even be considered. Forced hot air would be the ultimate heat in that world and what does fast get us? Hot, cold, hot, cold, hot, cold.

Slow and steady wins the race to both fuel economy and comfort. This is true for heating, this is true for cooling. The slower you can heat or cool a space, the less people will notice it, this is why a totally steady source is the ultimate solution. A huge pickup factor on a steam boiler is literally the complete opposite of this.


My steam system behaves totally different than most single pipe systems I've seen. My vents are always silent, they never spit. I can install a Gorton D or even a Varivent on any of my radiators and it won't spit or bang. All of the radiators heat slowly and silently. I can do deep setbacks, nothing cares or hisses. It always heats completely evenly. Going from an EG-45 with 33% pickup to an EG-40 10% was a significant improvement. It's slower that's for sure, but that was the whole idea. It uses the same fuel, perhaps a tad less but it produces a much nicer, more steady temperature.


Those are my feelings on the subject. Not everyone has to agree with them and I'm sure not everyone will. There is nothing wrong with that, we're all entitled to our opinions. I'm not here to start arguments or insult people or call names. That's never my intent.

DanHolohan

In 1940, the pick-up factor for both steam- and hot-water systems was 1.56. They reduced this to 1.33 in 1945. In 1967, they further lowered the pick-up factor for hot-water systems to 1.15.

All of this had to do with the types of construction there was during different eras.

One of the questions to ask is what happens when I install a steam boiler in a building built before 1940?

Charlie from wmass

Most of the Steam boilers I install are in buildings built before 1940.

DanHolohan

Yep.

Jamie Hall

Your arguments, @ChrisJ , are certainly well thought out. And I would agree, in principle, with many of them. However, it is clear to me that there is something, somewhere, wrong with the arithmetic or our -- collective our, all of us -- understanding of what is happening. Cedric is rated at 1300 square feet of steam -- presumably including that horrible 1.33 pickup factor. The actual total radiation installed is 1230 square feet. So -- very conventionally sized, by a professional. Now by some arguments, it should show a real pressure rise moderately quickly because of that. But... it doesn't. It will reach six ounces (the cutout) if it runs for more than about 45 minutes to an hour -- which it never does, except if we've had a power failure and the temperature of the house has dropped, or if we are running at close to design (there have been days!).

There is some other variable here which we are missing... maybe, as @Dan Holohan and @Charlie from wmass have just suggested, it has something to do with the age of the building -- the place I care for was built in stages between about 1800 and 1893. But if so, what is it? And can it be quantified?

Charlie from wmass

The question I have is was the pick up Factor changed due to the construction of the boilers and more accurate ratings on the boilers? Is it due to the Advent of automatic fuel and more steady Rise in temperature in the boiler?
@Jamie Hall I down fired Cedric to match the connected load closer. I took the load used a 1.33 pick up factor and 83% combustion efficiency to determine the fire rate. Cedric is not stock.

ChrisJ

Jamie Hall said:

Your arguments, @ChrisJ , are certainly well thought out. And I would agree, in principle, with many of them. However, it is clear to me that there is something, somewhere, wrong with the arithmetic or our -- collective our, all of us -- understanding of what is happening. Cedric is rated at 1300 square feet of steam -- presumably including that horrible 1.33 pickup factor. The actual total radiation installed is 1230 square feet. So -- very conventionally sized, by a professional. Now by some arguments, it should show a real pressure rise moderately quickly because of that. But... it doesn't. It will reach six ounces (the cutout) if it runs for more than about 45 minutes to an hour -- which it never does, except if we've had a power failure and the temperature of the house has dropped, or if we are running at close to design.

There is some other variable here which we are missing...

No,
My EG-45 would run quite a long time before pressure would start building. It took 1 hour 20 mintues to hit 1.5 PSI and trip the Pressuretrol. That happened only one time early on and now, can never happen.

You're asking where the error is, why would a boiler that is making 33%+ more steam than can be condensed takes so long to build pressure?

Here are my guesses.

The radiation sizing is a guess. Even the manufacturer of the radiator doesn't exactly know how much heat it can radiate and it depends on many things such as air temperature, floor and wall temperatures and even things in the room. If a radiator is in a room with a cold toilet full of water that radiator will likely use more steam than one that's not. Sizing up a radiator is just as much a guess as a heatloss calculation is. It's a ballpark figure and it's assuming a steam temperature of 215F and a room temperature of 72F I believe? Cooler room temperatures will increase this number and cooler steam temperatures will reduce it.


Boiler output.
Does a boiler with a DOE output rating of 100,000 btu/h actually produce that? Does anyone know? I've heard conflicting info on this and I've yet to figure out a way to actually test it.

Apparently, everyone was fine with reducing that 56% pickup for hot water even though it was the rule before to 33%. Then even further to 15%. Steam, just like with our antiquated boilers was left behind with the 33%.

Steam needs to follow. This is 2016, not 1945.
Steam also needs high efficiency boilers.

My steam system was built somewhere around 1925 based on radiator dates.

Jamie, I bet your system would heat just as well with 15-20% less boiler. It may be perfectly fine now, but that's not really what you asked. You asked why your system works fine with this and others don't. I don't think that's entirely true. I think all of them work fine as long as the boiler is reasonably sized with the load and venting is adequate. I never said it didn't, I said less is more. Smaller can be better.


We're no longer assuming a 1600sqft house needs a 4 ton air conditioner anymore. Let's stop assuming all steam systems need a 33-50% pickup factor.

In the end, it's up to the mechanic in the field to determine what size boiler he wants. He's the one looking at the piping and radiation. I just wish guys would realize 33% isn't a law. 10-15% can work better.

DanHolohan

Charlie, the vapor systems and gravity hot-water systems had larger pipes. There was more metal cooling the steam and hot water in those days.

ChrisJ

I also wish to ask everyone read Dave Bunnell's article on the subject again.

https://heatinghelp.com/systems-help-center/taking-another-look-at-steam-boiler-sizing-methods/


Something else to keep in mind, I highly doubt when you lit a coal fire you loaded the boiler up and got a roaring fire going when it was only chilly out. You lit a small fire to warm the house up and because things were vented slow in the coal days it worked fine.


Here's a quote from Dave's article.

"Now compare this to our current boilers sized with current methods. The chief goal is to get the system piping heated up very quickly and the radiators completely filled with steam ASAP. This is a complete opposite to how these systems originally worked.
Even with this goal in mind and a generously sized boiler, the radiators rarely if ever heat all the way across because the thermostat is satisfied long before the system is completely filled with steam. This then begs the question….. Why are we sizing steam boilers to completely fill the system with steam? And another follows….Why do we need to get the system up to temperature so quickly, when the system originally did not work that way? "

Charlie from wmass

I understand that they had larger piping especially with the hot water. But we are currently sizing our replacement boilers with a 1.33 pick up factor on systems where the original boiler was sized with a 1.5 6 pick up factor and we are not repiping the buildings.

DanHolohan

That has been on my mind for 46 years, Charlie.

Charlie from wmass

I am thinking it works because the boilers are rated more accurately than they were and a controlled repeatable fire rate each time also helps.

DanHolohan

Charlie from wmass said:

I am thinking it works because the boilers are rated more accurately than they were and a controlled repeatable fire rate each time also helps.

I think they rated them well, Charlie, but a big variable was the type of coal and the quality of the coal. The manufacturers would pitch on how many hours the boiler would run on a load of coal. From what I read, the women were in charge of making the fire, and they really knew how to manage that. I remember reading in one of my old engineering texts the recommendation that the firebox be increased in size by 75% because the husband may try to make the fire. ;-)

The dampers also played a big role in how much coal got burned on any given day. And at night, the woman would bank the fire so that it smoldered. In the morning, she'd just have to toss in the new coal to get it roaring again.

Those were some tough ladies.

KC_Jones

DanHolohan said:

Those were some tough ladies.

Off topic, but still interesting. When my mother first met my grandmother (parents dating) she was out front patching the concrete stairs on the house. She was 5' tall and 100 pounds wet, but did all the home repairs and kept the house running. My grandfather could barely swing a hammer. I still miss that woman dearly.

ChrisJ

@Jamie Hall


https://www.ideals.illinois.edu/bitstream/handle/2142/4349/engineeringexperv00000i00455.pdf?sequence=3




The entire reason for a piping and pickup factor larger than the piping losses alone is to do a rapid recovery. And yet, we are telling steam owners not to do setbacks. And with oversized radiation, we do not need the extra boiler in the first place.

Also note, this chart seems to indicate time to do a recovery on design day. Something we're told no properly matched system should be capable of in modern times.






(1) The same piping and pick-up factor may
be used for both steam and hot-water heating systems
which are automatically fired.
(2) A piping and pick-up factor as low as 1.1
may be used for selecting the boiler for a system
designed to maintain room-air temperature at a
constant value at all times; however, this low a
factor will not provide sufficient reserve for operation
with reduced room-air temperature at night.
(3) A piping and pick-up factor of 1.3 is adequate
for the successful operation of automatically
fired steam or hot-water residential heating systems.
The following is a summary of test results:
When the outdoor temperature was near the
design temperature, the method of operation had no
measurable effect on the length of the warm-up
period.
For each piping and pick-up factor the rate of
warming the room air when operating at design
indoor-outdoor temperature difference was the same
regardless of the type or size of the system.
At a piping and pick-up factor of approximately
1.1 the heating capacities of the systems
were not sufficient to raise the room-air temperature
at the end of a night setback period to the
normal daytime value.
As the piping and pick-up factor was reduced
below 1.3 there was a marked increase in the
length of the warm-up time. On the other hand,
the decrease in warm-up time was relatively small
as the piping and pick-up factor was increased
above 1.3.
Oversizing both the boiler and radiation in the
hot-water system by 12% reduced the length of
the warm-up time by as much as 50%. Oversizing
the boiler only (use of large piping and pick-up
factor) resulted in only a slight reduction in the
length of the warm-up time.
Due to the small heat storage capacity of a
steam system, the rate at which the room-air temperature
decreased at the start of a night setback
period was about 40% greater when the steam
system was being used than when using the hotwater
system.

DanHolohan

Yes, 1959 was an interesting time. Before WWII, half the buildings in the country were heated hydronically. After the war, when building started again, the furnace took over. The Institute of Boiler and Radiation Manufacturers did their research at the University of Illinois, and one one of their goals was to lower the price of hydronic systems so they could compete with the furnace manufacturers. Note how they went from 1.56 to 1.33 in 1945, and then to 1.15 for hot water in 1967. By '67, few contractors were installing steam.

There's some business and politics mixed into the engineering.

DanHolohan

KC_Jones said:

DanHolohan said:

Those were some tough ladies.

Off topic, but still interesting. When my mother first met my grandmother (parents dating) she was out front patching the concrete stairs on the house. She was 5' tall and 100 pounds wet, but did all the home repairs and kept the house running. My grandfather could barely swing a hammer. I still miss that woman dearly.

I love this. Thanks.

ChrisJ

DanHolohan said:

Yes, 1959 was an interesting time. Before WWII, half the buildings in the country were heated hydronically. After the war, when building started again, the furnace took over. The Institute of Boiler and Radiation Manufacturers did their research at the University of Illinois, and one one of their goals was to lower the price of hydronic systems so they could compete with the furnace manufacturers. Note how they went from 1.56 to 1.33 in 1945, and then to 1.15 for hot water in 1967. By '67, few contractors were installing steam.

There's some business and politics mixed into the engineering.

What I'm learning right now is how much room conventional ductwork takes up. It's actually amazing.

People complain about the size of steam radiators but the amount of real estate you loose to ductwork is unreal. Steam piping is so much smaller and hot water pipe even more so.

It's sad we're stuck in a world where all people want is cheap. Build a huge 3000+sqft house with wood floors, huge entrance ways and forced hot air with the cheapest furnace they could find and ductboard and flex duct.

I would be nice to see the US heating industry do a 180.

DanHolohan

The Interstate Highway Act led to the development of the suburbs, and that brought in the tract housing and the furnaces. Hydronics couldn't compete with that. It was just heating in those days, no AC.

There's also a lot of sociology in all of this.

Jamie Hall

"At a piping and pick-up factor of approximately
1.1 the heating capacities of the systems
were not sufficient to raise the room-air temperature
at the end of a night setback period to the
normal daytime value.
As the piping and pick-up factor was reduced
below 1.3 there was a marked increase in the
length of the warm-up time. On the other hand,
the decrease in warm-up time was relatively small
as the piping and pick-up factor was increased
above 1.3."

Well... so perhaps a "pickup" factor is, in fact, needed in situations where there may be an occasion to raise the temperature of a building? Which brings up two thoughts: first, not to put to fine a point on it, building temperatures do drop now and then for reasons other than misguided setbacks. Are we to suggest that we don't want the occupants to be able to return to the normal temperature? And second, while the above is almost certainly true -- one does need some extra capacity to get back up to speed -- how much does one really need, and what are the factors used to determine that amount?

Which is my original question... !

DanHolohan

I see it as being all about specific heat. When you start, you have so many tons of steel and iron to bring from ambient temperature to 215 degrees F. The piping is the transportation network, and once hot, it drops out of the heating equation. The radiators are what heat the people, and most are probably oversized. Lowering the pick-up factor doesn't change the existing piping's ability to change steam into water, and once it does that, it stops moving. I always saw the goal as getting the steam to the radiators as quickly as possible.

Interesting conversation. Thanks for making me think!

Charlie from wmass

I was ruminating on this as I'm changing this wet return. I have never told the customer that they can't do a setback, I have also never designed a system that could not do a setback. What we tell people is that the setback will consume a lot of energy and is not worth doing as there are not the savings they think there will be. Systems should be designed to come back from Deep setback in case of emergencies such as power outages or fuel interruptions. I'm not advocating for the old 1.56 but I am advocating for the 1.33.

ChrisJ

DanHolohan said:

I see it as being all about specific heat. When you start, you have so many tons of steel and iron to bring from ambient temperature to 215 degrees F. The piping is the transportation network, and once hot, it drops out of the heating equation. The radiators are what heat the people, and most are probably oversized. Lowering the pick-up factor doesn't change the existing piping's ability to change steam into water, and once it does that, it stops moving. I always saw the goal as getting the steam to the radiators as quickly as possible.

Interesting conversation. Thanks for making me think!

I agree Dan,
But before the radiators get any steam 100% of the boiler's output is dedicated to just that, heating the piping.

There's no way any network of insulated piping could ever use much of that for very long. There's just not much there to dissipate heat. I think all of my mains and piping loses something like 2,000 btu/h with 1" insulation. It's been a while since I calculated that so I could be off. Even uninsulated I think it was only around 10,000-15,000.

@Jamie Hall Depends on who you ask, some guys feel a heating system shouldn't be capable of recovering on design day. Others feel it should. If a steam system's radiation is already oversized for the house, it will be capable of recovering all on it's own. My system with a tiny 10% piping and pickup factor can heat my house down to about -30F. Design day temp in my area is +6F though the record low is -17F.

This is in the same realm as guys that feel my central air shouldn't be capable of a 70F indoor temp on a 95F day. I am planning on sizing the system for that, but at the same time I won't be using a 4 ton condensing unit with a 3 ton coil. The condensing unit will be matched to the indoor coil of course.

DanHolohan

Chris, is your house tight?

ChrisJ

DanHolohan said:

Chris, is your house tight?

While during the manual J I selected the closest option which was "colander"

It's an 1860s house with balloon framing, empty walls and clapboard right on the studs, no sheathing.

My actual heatloss is around 68,000 btu/h @ 0F according to the Ecosteam. House is 1600sqft.

DanHolohan

Colander! HAHAHAHA!!!

Jamie Hall

Ah ha! I think @Dan Holohan may be onto something here (no surprise, that), which I'd never bothered to calculate. According to the hen scratchings on the back of this envelope, the radiators in the system which Cedric plays with will take around 80000 BTU to get from room temperature to steam temperature. That's a pretty fair amount of heat.

Now this isn't a loss, before someone jumps on the efficiency question, since it will give all of that back to the space when the boiler shuts off -- but it is still heat which needs to be provided near the start of a cycle.

And that 80000 BTU expended in the 15 minutes or so it takes to get everything up to speed is at least 30% of the running BTU capacity of the system...

Hmmm...

Find another envelope here to continue thinking...

DanHolohan

Exactly.

ChrisJ

Yes,
Except you don't heat the entire radiator at once with steam.

PMJ

Sorry this is a little long - consider it just more food for thought.

To me, pickup factor has always basically meant safety factor. A safety factor is built in to engineering designs to handle the various non-standard conditions that may need to be faced. So to say a boiler is matched properly we have to ask "to what conditions?" All systems face many different conditions. Is a properly matched boiler one that will keep my already warm building at the temperature I want on design day running 100% of the time? Obviously it can't be smaller than that. As we have previously discussed, that is probably a much smaller boiler than one matched to the installed EDR in our homes - a good percentage of which is never needed. No boiler that can cover the coldest day is perfectly matched on the average day anyway.

A bigger boiler will get steam to rads faster on cold start. Is 20 minutes from cold start with the entire system at 70 degrees vs say 35 minutes really that important? Probably not, but if we are discussing theory it is a real difference. And, of course, during the periods you really need heat there aren't any cold starts.

What Chris points out is all during basically "normal" operating conditions. Extra capacity will help a lot with non-normal conditions. He is primarily talking about maintaining temperature (matching heat loss) not raising temperature. These are very different animals. Recovering a whole house at 38 degrees after a power failure one would surely appreciate extra capacity. Those same rads will condense one hell of a lot more steam per minute when the room is 38 than when it is 68. Raising a structure 30 degrees when it is windy and -20F outside may not happen at all without significant extra. Saying a system will heat (maintain an already heated structure) down to -30F is entirely different than saying it will RAISE the structure 30 degrees in a reasonable time in those conditions if at all. A much bigger boiler will recover the house much faster. Stuck in this situation I don't think slower is better at all. Is this worth the extra up front money for something that rarely happens? Again, personal choice I think. When I look at these olders systems it seems to me the dead men purposely put in a lot of "extra". Lots of big pipes (low pressure) and big rads you probably won't ever need all of. The down side to the extra was only up front cost. Kicking in up front used to be something you did out of consideration for those that follow you. Today we seem bent on leaving them only the certainty that they will get stuck replacing everything. Personally I love the extra in my house.

It also seems to me that mother nature determines the minimum rate at which we must put heat into a room to maintain its temperature - we don't. If we do it too slowly the temperature drops. Too fast and it goes higher than we want. What we need as a method of control that closely monitors the constantly changing loss - and then fires the boiler (be it a bigger or smaller one) accordingly. And we need a boiler that can cover a pretty wide range of demands. Don't forget that the original coal fired systems did exactly this by monitoring minute changes in pressure thereby increasing and decreasing the fire to make more or less steam accordingly. Trying to run the same system with an on/off fire and only a max pressure setting is no where near as good. Much more expensive and fancier controls like Chris has are now required.

I'm not sure I can agree that slower is always better. My system spends most of its time in sub-atmospheric pressure and steam in forward motion at all times from boiler to the rads unlike vented systems that stop and the steam goes backwards on every cycle. Using natural vacuum I get significant steam generation and forward movement when the burner is off and the flue closed. I don't think it would be more efficient or more comfortable for me to switch to a smaller boiler, run it a much higher percentage of the time, and make little or no use of the natural vacuum the way I do now.

DanHolohan

Good points, well made, PMJ. Thanks for sharing.

Charlie from wmass

I've been to several apartment buildings in Albany New York where the boilers we are what we would consider undersized using standard practices. Boilers for size for the heat loss of the building not the radiation. The issues that these systems have I refer to as the wandering radiator. On severe cases the first and third floor of a building if it is three stories high either heat fine or overheat. The second floor of the building does not heat enough. I realize that the steam can be pushed around by restricting venting on overheating radiator and increasing venting on cooler radiators. When this task is taken on by semi skilled labor the cold radiators begin to migrate around the building. The Wider the footprint of the building as a compared to the height the more difficult balancing becomes. Also as a contractor my clients seem to be fixated on every radiator heating acrossed folate during every heat cycle no matter how many times I explain that is not necessary. Ideally it would be preferred that the radiators only enough for the heat loss of the room which is the design behind most vapor systems. In order to make sure that we get paid and the customer does not become disgruntled contractors hold fast to the 1.33. Most consumers do not want a degree in Steam engineering to understand the working of their system. This is unfortunate because it ends up costing them fuel but if we stay at 1.33 that is minimized. We are also restricted by manufactured boiler sizes when it comes to atmospheric steam boilers. With the power burners we do have some latitude in adjusting the fire right which is why oil was traditionally favored in my area for steam boilers. Oil nozzles are easy to match to the load.

Jamie Hall

DanHolohan said:

Good points, well made, PMJ. Thanks for sharing.

Agreed. And in response a couple of @Hatterasguy 's comments:

First, the 80,000 BTU figure I mentioned is not the steam piping. It is the radiators themselves. Now the actual physics is a lot more complex than just dump in 80K BTU, then you get heat, but that's frosting on the cake.

Second, and much more to the point, I'm not sure that one should assume that the installed radiation is automatically too much. It probably is, in some houses. It most assuredly is not in others -- the place I care for being an example. I have no idea what the system was designed for, but in current conditions I can assure you that there have been days when dear old Cedric ran for more than 24 hours at a whack, taking about 2 minutes off every hour or so when the pressure got above 6 ounces. The temperature in the house was not increasing!

ChrisJ

@Jamie Hall
I've said repeatedly a heatloss should be done.

Also, I understand your 80,000 is the radiators, but you don't heat 100% of the radiation at once. No one does.

Every little bit of steam that enters the first section of each radiator delivers some heat, pretty much immediately. In fact, there are few things that can compete with steam when it comes to the speed at which it delivers heat to objects.