Steaming

Tinman

I've thought about this for a long time and saw something similar in a recent thread here so I thought this would be a perfect time to share. Here goes -

I know that we size steam boilers by EDR and we size hot water boilers by the heat loss of the building.

If we're being very energy conscious, why not do this for a steam system?

• Perform a heat loss calculation on the building.
• Perform an EDR calculation on the radiation.
• Let’s assume for now that the EDR outweighs the heat loss significantly.
• Remove or resize radiators to match the room by room heat loss of each room.
• Size the new steam boiler to reflect the new EDR that we now have.

To me, this makes perfect sense. I know there's a considerable amount of work involved but for large multifamily buildings the therm savings has to very significant.

Am I missing something?

Robert O'Brien

How about TRV's instead?

Tinman

I don't know? Maybe? I don't think the savings would be nearly as much. Most of these 100 year old buildings that we work with have been buttoned up really well; new windows, air sealing, and insulation.

Jamie Hall

Well, of course. Provided you want to change all the radiators... would you, in fact, gain much in energy use?

Tinman

Help me out here, Jamie. Can you elaborate?

ratio

Isn't someone running a well-'undersized' system (closely matching the heat loss, not the EDR) with good results?

Tinman

For the most part, I'm suggesting the same thing here but on a much larger scale. Hundreds of large multifamily buildings heated with steam in Chicago.

Jamie Hall

Consider to begin that any heating system -- including steam -- is wildly oversized relative to the heat loss most of the time. How often do we get a design day? In the case of a building which has been tightened up over the years, the radiators will be even more oversize. But is this really a problem (let's assume for the moment that the boiler is properly sized to the radiators. I know, yeah right... but play along)? We simply don't run the boiler all the time. There is an efficiency loss involved with turning it on and off -- consider some of the debates I and @PMJ and @ChrisJ get into from time to time!-- but it truly isn't that large. The result, averaged over time, is that the heat we put into the boiler, minus those nasty losses, equals the heat loss of the building -- and the radiators, averaged over time (assuming that the system is well balanced and so on... yeah, right again...) provide an average temperature to radiate the amount of heat needed for the space they are in.

Net result? Just a different way of modulating the system. As I noted above, there is an efficiency loss from cycling the boiler (on a timer, on a vapourstat, whatever -- see debates!) but it is relatively small -- a few percent, at most, and is related to the pre-purge and initial firing to come up to stable combustion -- which, with good adjustments, can be reduced.

JUGHNE

I also have given this some consideration.
If there is 1/3 more connected EDR than needed to heat the building, could we just ignore the last 1/3 of the radiator?
Isn't that cooler 1/3 just then part of the return piping, especially in a 2 pipe system.
In a 1 pipe wouldn't the steam only travel the hot 2/3 and then the tstat hopefully shuts down the system?
Maybe I am being too simplistic in this thought process.

However, this summer I installed orifices in a 2 pipe system.
Sized to heat only 60-80% of the EDR of each radiator.
This is in an old school house that has had major window upgrades or removal.
This is the coldest winter we have had in many years, if kids/teachers were cold I would be made aware of it.

Tinman

Let me add some more information -

Again, large buildings with large boilers; 750mbh to 4000mbh. Hundreds of them so the potential savings would be epic.

Industrial Combustion modulating burners with tight control, 1.2 psi max.

EBEBRATT-Ed

A simple case of balancing. If the radiation is oversized how do you balance the system if you only size for heat loss and the boiler is undersized for the radiation??

In my way of thinking a small job like a house you could probably get an undersized boiler (for the radiation) into balance by messing with the vents

Of course changing the radiation is the right answer in a perfect work....that is a lot of work.

So are TRVs the answer? They make TRVs with electric actuators as well
Change the radiation?
1.33 piping and pickup factor can this be ignored? With frequent cycling is the pickup factor really necessary?

A lot depends on the available budget.

Probably could remove some radiator sections but is that viable?

Tinman

Also, I have no skin in the game. I’m not a contractor anymore. I work for a well established, non-profit company in Chicago whose mission is “Smarter Energy Use For All”.

We facilitate and provide oversight for projects such as lighting upgrades, air sealing, insulation, hvac, and smaller measures as well.

I’m just trying to get the gas and electrical meters to spin slower.

Jamie Hall

Steam can be remarkably efficient, though never as good as a fully properly designed, installed, and controlled hydronic system with a modulating and condensing boiler -- and neither one is even close to a heat pump system. However, any heating system will benefit -- sometimes dramatically -- from attention to detail, as well as correcting gross problems. That said, the biggest bang for the buck on upgrades is going to come from air sealing and insulation, provided it's feasible (it can be a headache in an historic building -- or a big older building with lots and lots of post-war glass).

One thing which sometimes gets lost in the enthusiasm to upgrade by tearing one thing out -- or substantially changing it -- and putting in something new is that there is a large energy and environmental cost to that. This needs to be taken into account in your line of work.

PMJ

@JUGHNE says: "I also have given this some consideration.
If there is 1/3 more connected EDR than needed to heat the building, could we just ignore the last 1/3 of the radiator?
Isn't that cooler 1/3 just then part of the return piping, especially in a 2 pipe system.
In a 1 pipe wouldn't the steam only travel the hot 2/3 and then the tstat hopefully shuts down the system?
Maybe I am being too simplistic in this thought process."

No, not too simplistic. I've been trying to get this idea across for years now with very few takers. So not only yes to this @JUGHNE , but hell yes. I need to buy this man a cigar. There is hope out there yet!

This is exactly what had to happen with a continuous coal fire. Lots of extra radiation, not very full, no pressure, very adjustable by damping the fire. There simply was no other way to run it. The coal boiler had to be big relative to the radiation and running in the middle of its range so that a relatively small damper adjustment was a significant change in volume of steam delivered relative to the radiation. There was no such thing as a coal fired boiler at true maximum fire for the physical unit. There were no "full" radiators either as then nothing would then be adjustable.

I launched my many years long steam adventure thinking about how the radiators would have had to run when my house was built and had a coal boiler. I worked on getting my rads to be more like that - the original design. I tried to do this because the heat would be more even. I didn't want the radiators always going from burning hot to dead cold.

My rads today change fill level depending on the conditions and oscillate between say 200F and 150F 3 times an hour. The fill is about 1/3 to 1/2. The colder it gets the longer the calls for heat are - into hours when it gets really cold. In milder weather the calls do get shorter and the stat actually satisfied more often.
The higher the percentage of the total elapsed time that rads are actually condensing steam, the much less full they need to be to get the same job done. Much less full, much more of the time is what I try to do. So yes, the unused portion of the rads is just part of the return system. You can't ever match the radiation to the heat loss! You install extra and run it partly full. I have much extra radiation and much extra boiler. Neither of those two things is critical at all. I control the run time of the boiler, that is all.

And all I can say about losses due to 3CPH is that with vacuum in between I am absolutely convinced running this way is significantly more efficient.

Steamhead

@Steve Minnich , have you talked to @The Steam Whisperer about this? He's done quite a bit of this, mostly "resizing" 2-pipe rads with orifices.

Tinman

@Steamhead - I have not but I will. I have to have a way of quantifying the savings too. Maybe he can guide me on that too?

JUGHNE

For me, this came about from the systems I work on.
90% of the boilers are oversized due to new envelope upgrades and removal of radiation.
Also if not that then there is simply usually to much radiation in the original design.
Maybe not if you leave the windows to comply with the 1918 pandemic. But everyone (except me) gets a flu shot so that is no longer a worry .

I did ask Dan at a seminar in the Twin Cities if rads were orifice controlled to 80%, then could the boiler be sized to 80% less than the connected EDR. He replied that could be done.
Surprising was that this was almost the only steam question asked. Actually it was about the only question posed. Most attending were there either under duress from the boss and also it was easier than working....I assume they were still on the time clock. But we enjoyed a glass of wine and a chat afterwards. (If you read this Dan, I was the nerd in the front row with most of the questions)

Tinman

@JUGHNE - The nerds in the front row are the ones the teacher never has to worry about.

I like the idea of orifices as long as it has the same effect as I was driving at, and it sounds like it does.

I was willing to die on this hill because for really old, large buildings it just doesn’t make sense to keep replacing boilers, over the course of an entire century, that far exceed the loss of the envelope.

Steamhead

Steve Minnich said:

@Steamhead - I have not but I will. I have to have a way of quantifying the savings too. Maybe he can guide me on that too?

I believe he can.

Tinman

Thanks everyone for your input! It’s much appreciated.

There are some heavy hitting, steam guys in Chicago that do textbook work. There’s one in particular but I don’t have permission to use his name so I won’t. Three generations ran this company and they’re still going strong. Every job looks almost identical and it’s as close to perfect as you’ll see.

I just wanted you to know that this midwestern city is representing the world of hydronics very well.

mikeg2015

ratio said:

Isn't someone running a well-'undersized' system (closely matching the heat loss, not the EDR) with good results?

I’ve had 20% of my burners plugged and ran on a 2 stage gas valve. Output was estimated lower than radiator outout with no balance issues. It makes me believe that I could install a smaller boiler where low stage is the same as heat loss, install TRV’s on all upstairs radiators so it’s effectively a non calling zone, and run on high stage until it build pressure, then drop ot low stage.

However, I think this only works on a vapor system. So you need a oversized header, and very slow radiator venting to match boiler output so radiators heats evenly.

mikeg2015

Boilers also get oversized because if it’s -10F and the customer can’t setback from 68 to 72F on a windy cloudy morning, you get a call back. Call backs cost money. Same reason we still slightly oversized furnaces and AC’s. Too risky to size tight and too often load calculator underestimate loads because actual air leakage, stack effect and insulation values are lower than believed.

Dave in QCA

Both Henry Gifford and The Steam Whisperer have written on the possibilities of downsizing steam systems. Henry Gifford focused on using inlet orifices in two-pipe radiators. He pointed out that since the orifices separate the radiators from the boiler and mains, the pickup factor is not needed. Also, by adjusting orifice capacities it is possible to downsize a radiators that may have been erroneously oversized, bringing the system into balance. Also, since pickup factor is not a part of the equation, this means that the boiler can indeed be sized for the building loss as opposed to the connected radiation. Similar gains by downsizing one-pipe systems may be possible, but it is a more delicate balancing act. Steam Whisperer has written and article or two on this too and they can be found on this forum. ChrisJ is running a system with smaller than normal pickup allowance, maybe no allowance. It does not cycle on pressure and yet the system is balanced and heats evenly.

A few years ago I helped a friend straighten out a Moline system in his house that was a disaster. The guts of the moline valves had been removed and so it was a two pipe system with no traps and an oversized boiler made it worse. We installed inlet orifices in all of the radiators. The boiler started leaking about the same time, so the W-M Egh-12 with an input of 550,000 BTU was replaced with an Egh-75, with an input of 299,000 BTU. The system has connected radiation of 1197 and the new boiler had an EDR rating of only 750 sq. ft. But, there is more to consider when connecting a boiler to an orificed system such as a Moline, or any other similar system. First, since the radiator is separated from the mains and the boiler by an orifice, it never sees pressure. Not even the 6-8 oz. that is in the mains. So, instead of 240 BTU/sq. ft., its more like 225 BTU/sq. ft. Then, you leave out the pickup allowance. If you keep the piping loss allowance, it's 15%. But, if the mains and risers to the upper floors are insulated, and if the system is oversized, you can leave that off too. In addition, we made the conservative decision to size the new boiler at 90% of the radiator capacity, with zero allowances. That brought down to needing a boiler capable of outputting 242,530 BTU. The Egh75 has a DOE output of 247,000.

How does it work? Like a charm. Silent with the exception of a rare clank from expansion of one radiator. On a prolonged firing, coming out of a setback, the radiators feel fully heated to the touch. But, no steam ever gets into the returns. The sound of steam going through the orfices is barely audible. Overall, the heat is even. All radiators heat uniformly steam distribution is even throughout the entire system. Operating cost has gone down significantly (I don't have the numbers) and the cost of the replacement boiler was significantly lower than a conventionally matched boiler.

Could the boiler have been smaller? Yes, it appears that it could have been possible. The boiler never runs all the time. Probably not much more than about half the time during design conditions.

foresthillsjd

As the least experienced and least knowledgeable person on this thread, I am going to chime in. I am replacing most of the radiators in my house (for reasons more to do with design aesthetic and less to do with efficiency), and I purchased the replacements based on heat loss calculations because I thought that was how you were supposed to do it. (Is that not how people do it?) So @Steve Minnich to put real numbers to your hypothetical:

1. Perform a heat loss calculation: Mine came out to about 44,000 BTU/hr.
   
2. Perform an EDR Calculation on the radiation. Current radiators: 75,000 BTU/hr.
   
3. Removed or reside radiators to match the room by room heat loss: I built in a fudge factor so the new radiation totals 50,000 BTU/hr.
   
4. Size the new steam boiler to reflect the new EDR: So... my current boiler is a Weil-McLain EG/PEG-50 (or 55... I never bothered to count the burners) kicking out 145,000 or 167,000 BTU/hr. It's running just fine, but when it finally kicks the bucket, I was planning on replacing it with a much smaller one. I was actually surprised that the boiler is so oversized relative to the existing radiation. By a factor of 2, is that industry standard?
   

@mikeg2015 said:

I’ve had 20% of my burners plugged and ran on a 2 stage gas valve. Output was estimated lower than radiator outout with no balance issues. It makes me believe that I could install a smaller boiler where low stage is the same as heat loss, install TRV’s on all upstairs radiators so it’s effectively a non calling zone, and run on high stage until it build pressure, then drop ot low stage.

However, I think this only works on a vapor system. So you need a oversized header, and very slow radiator venting to match boiler output so radiators heats evenly.

@mikeg2015 Whoa, you can do that? Does that mean I could make my current boiler run like a smaller one? If so, I have 3 years of gas bills that I can compare to my next 3 years and report back with hard data.

The other thing I'm wondering is, could there be any other advantages of running a smaller boiler? Would the system be quieter? Would it even out the temperature fluctuations? Would it be faster to heat? Would it be easier to run it as a vapor system? (and forgive me if these are dumb questions, up to now, my only steam skills are packing bonnets, changing vents, cleaning pigtails, and doing a lot of math)

Jamie Hall

In a brief answer, @foresthillsjd , looks like since you have already done the radators, you're on the right track here. And size the new boiler to the new radiation. And no, two time te connected load is not the industry standard -- general agreement is no more than 1.33 times, and many would suggest less (Cedric is 1.1 times). Is twice the connected load unusual? Sadly, no...

ethicalpaul

I too have been adjusting my radiation, but I recognize I am way outside the normal curve on that kind of thing

Dave in QCA

In a situation where the radiation is in place and difficult to change out to smaller radiators. The capacity of the radiators can always be decreased by lowering the temperature of the steam. But, that is a whole other perspective and discussion.

The Steam Whisperer

The Moline system was also my inspiration for using supply valve orifice plates in two pipe steam systems. We have a number of homes and multi-unit buildings that we've done over the past 10 years and those system work exceptionally well. On two pipe systems we always look at the historic fuel usage and with some educated guesses on the heating plant efficiency, work out the actual heat loss of the structure. For two pipe systems installed before WWII, the typical radiation capacity calculates out to be about 60% higher than needed for design conditions and this is assuming that the piping is making no heat contribution to the structure. When we size the orifices we typically size them to this number. Back in the boiler room, we either downfire the existing boiler or if replacing, install a much smaller boiler that is sized to this new radiation loss plus a 15% pick up factor. This process still has a lot of built in extra capacity ( the contribution of the pipes heating the building, for instance), but results in a heating plant usually about 1/3 to 1/2 the capacity of the existing or less. This process has also allowed us to do many other things that normally are not possible. One big one is to eliminate the need for a vacuum pump on larger systems. Since Vacuum system piping is about 1/2 the capacity of pressure systems and we are now running about 1/2 the steam to feed the system, the new piping is now the optimum size for the new system capacity. This assumes you have no lifts in the system.

When possible we couple an orificed system with an outdoor reset boiler control that modulates the burner based on outdoor temp.
We currently have these running two ways, one system is resetting the burner output based on the outdoor temperature while the other is modulating the target pressure in the system based on outdoor temperature. Out of the two, the first is probably the best choice due to the nature of flow through an orifice. Orifices flow a very large amount of steam at very low pressure differences, so as the pressure is increased across the orifices as the outdoor temperature drops, the increase in heating is relatively small. You end up with much more heat than necessary in warmer weather. We'll probably be reprogramming the pressure reset control to direct reset of the burner output for next heating season.
The chief problem we have run into is that there is a limit to how low a burner can fire, so in warmer weather there is on and off cycling of the burner. In addition, with on/ off cycling, the system needs to be primed with an adequate amount of steam or else the farthest radiators will not heat. Since steam travels the path of least resistance, steam will favor mains that rise up into the building over those that drop down, for instance. Once primed and when the burner is operating in its modulation range with tightly set control curves, the boiler will fire nearly continuously, but at very low capacities. In the first building we completed this set up, the manager was monitoring the burner operation through a remote camera and for 6 weeks never saw the burner shut down in normal winter weather.

The results of these change naturally mimic those of a hot water system upgraded to a modulating heat source with outdoor reset. Very stable and even heating throughout the structure and extremely quiet operation. Even with systems of questionable piping (some sags in steam mains or radiator runouts) noise is nearly eliminated since the piping almost never cools to allow water hammer to occur. Expansion noises also disappear.
And, of course there are fuel savings, despite areas that were previously too cold are now heated. While most of the systems we have worked on have had multiple changes made at the same time as the installation of orifices, the analysis of the first seasons fuel usage was a reduction of about 40%. This system had orifices installed and the radiator traps gutted, new radiator supply valves (with a few TRV's added), some bad drip traps replaced and the boiler firing rate was cut about 40% The return main was still flooded, however, and could not properly vent the system since there was a lift right at the inoperative vacuum pump. We abandoned the vacumm pump and installed a condensate pump to allow the piping to drain partially through the season. I am sure these other items also helped in the fuel savings.

This current heating season the system is running with a modulating burner that goes down to about 400,000 btu/hr and tops out at about 1,100,000 btu/hr, IIRC. It is firing into the existing 2,800,000 btu /hr Cast iron sectional boiler. WE also had to acid clean the boiler, due to all the lime that came loose last season. I haven't reviewed this years bills yet to see the impact of these other changes.

Reducing the firing rate below radiation capacity is more chancy on one pipe steam, especially in multi-unit buildings since people will tinker with the radiator vents, eventually throwing the system out of balance. In a single family home, however, it seems to work.

Tinman

@The Steam Whisperer (Formerly Boilerpro) - If you don't mind, I'd love to have a conversation with you at some point in the near future. Maybe next week?

The Steam Whisperer

Sure, my work load is a little light right now, so the timing is good.

RayWohlfarth

@Steve Minnich Just a thought. Dan Holohan mentioned how paint can affect the radiator output. If you simply paint them with a certain paint, they are derated by 20%. A boiler 20% smaller seems like a nice tradeoff.

foresthillsjd

@RayWohlfarth , so here's a question, enclosing the radiator can also reduce the output, so would painting the radiator and then putting an enclosure on it have a [meaningful] cumulative effect, or if you have done only one already, should you bother with the other?

RayWohlfarth

@foresthillsjd I wondered about that same exact thing. My gut tells me the paint would impede heat transfer from inside the radiator out while the enclosure would not. That is just a guess from a boiler guy.

Tinman

The enclosure would impede heat from getting into the conditioned space which in turn should slow down heat transfer from inside the radiator.

BobC

A plain shelf (smooth bottomed) a couple of inches above the radiator would probably increase the output because it enhances convection.

Fred

It would seem to me that once you spent the money burning fuel to make steam, doing anything at the radiator like paint or covers, that prevents the radiation/convection to the surrounding air/surfaces would be financially counter productive.
Orifices, on the other hand, I can understand as they can be sized to limit the amount of steam production/utilization to satisfy the heat loss.

RayWohlfarth

@Steve Minnich That makes sense
@BobC Thats a good point
@Fred I am twisting over the oriface idea. Steam is going to fill that radiator and the oriface just makes it go slower. Buts its Friday and my mind is not as sharp

Fred

@RayWohlfarth , my assumption was that, with the orifice, it would only completely fill a radiator, if the radiator was sized to the heat loss and it was a design day. Any other times, or with an over-sized radiator, the boiler wouldn't run long enough to fill the radiator, from end to end and the orifice would be sized to ensure that.

RayWohlfarth

@Fred Hmmm I see what you are saying. That might work Thanks for explaining it LOL

brandonf

I think the only way to know for sure is for somebody to build a brand new house and install a brand new steam system. 😎.

mikeg2015

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@mikeg2015 Whoa, you can do that? Does that mean I could make my current boiler run like a smaller one? If so, I have 3 years of gas bills that I can compare to my next 3 years and report back with hard data.

The other thing I'm wondering is, could there be any other advantages of running a smaller boiler? Would the system be quieter? Would it even out the temperature fluctuations? Would it be faster to heat? Would it be easier to run it as a vapor system? (and forgive me if these are dumb questions, up to now, my only steam skills are packing bonnets, changing vents, cleaning pigtails, and doing a lot of math)

It’s risky. Could cause uneven heating that would crack the block. My boiler however is over 900lbs, and a older design with 18 gallons of water and thick castings.

My efficiency dropped 2-3% when I downfired it. I was just pushing more excess air out the chimney. 2 stage valve worked better, but still lost 1% efficiency.

Undersizing is a it risky. You might end up being unable to control the steam. My system was originally configured as a vacuum vapor system 110 years ago. Had Hoffman 2A vents and a vacuum main vent to go with it’s coal boiler.

But if I slow the venting way down I seem to be able to control it and heat the radiators fully an evenly.

However, the biggest advantage of sizing smaller is
1) lower installed cost
2) lower standby losses because it runs longer
3) Not overshooting space temperature.
4) able to zone with TRV’s.
5) In my installation, it might allow me to common vent with a inexpensive gas water heater rather than spend $1600 on a indirect tank, piping and pump. can’t vent a 40k water heater to a 8” vent 30’ tall. But with a 6” chimney liner I’m good.

Downsides:
1) more loses on the header in mild weather as it will spend more time heating the header before steam reaches the radiator.
2) there could be a “minimum output” where you lose control of the steam.

Before I were to commit to a smaller boiler, I’d probably plug 4 burners and test the header to see if it will still heat the radiators evenly. That would give me about 150k input on low stage and efficiency probably knocked down to 70% so 110k output in my boilers current condition. That would still meet my homes heat loss at design. Radiators in theory would only heat about 3/4 across if all are calling. Right now the system swings and will heat radiators fully, but then cycle off and radiators cool off. WOuld be nice to use hi/lo stage just like a furnace. Lo stage 90% of the time, and hi stage only for recovery or very cold weather. I have 2 air handlers calling, so I could use downstairs to call 1st stage and upstairs calls 2nd stage. Logically is upstairs is cold, the downstairs probably is as well if I balance it properly. But if a call comes in upstairs, then I likely need a little more heat ot satisfy both.