Is Steam Inefficient?

RayWohlfarth

Many people tell me steam is an old technology and a very inefficient way to heat. I respectfully inform them that a well-designed steam system can be very efficient. When water turns to steam vapor, the steam zooms through a building at speeds up to 40 miles per hour without using a compressor, pump, fan, or blower. What does it cost to transport steam throughout a building? Only a few ounces of steam pressure. Did you know that the Empire State Building in New York City at a height 1,250 feet and 103 stories heats their building using 2-3 pounds of steam pressure and also has a LEED Gold Certificate? When looking at the next shiny thing for your next heating project, remember the advantages of a tried and true system, steam.
Ray

Jamie Hall

Good show, @RayWohlfarth !

Steamhead

This.

EBEBRATT-Ed

Most compare modern hot air or hot water systems to steam but the steam they compare it to is Grandpa's old coal fired-now converted snowman boiler.

Not really fair is it.

RayWohlfarth

Thanks @Jamie Hall I was getting tired of hearing how the uniformed know without a doubt that steam is bad
@Steamhead This? Hoping that meant you agree? LOL
@EBEBRATT-Ed That is so true. We installed modular steam boilers in a large apartment building here in Pittsburgh and owner said that building has the lowest costs per square feet to heat

jumper

Well Henry is certainly not uninformed and he touts his million dollar conversions to HHW. OTH his pics look complicated so I predict lots of money will be spent to maintain efficiency. I also suspect lots of electricity used to power all the pumps.

My experience is similar to Ray's. In the seventies when steam boilers in Toronto were replaced with modular, fuel consumption decreased markedly.

People here are practical types so they may dislike my theoretical argument that a partially hot radiator is better than a whole warm one.

Jamie Hall

Your comment on Toronto, @jumper , really goes right along with @EBEBRATT-Ed 's observation: If you replace old technology steam with modern technology hot water, the gain in efficiency is only slightly the change from steam to hot water -- almost all of it is from old technology to modern technology.

Canucker

I think steam suffers more from the measurement process. If you only look at the efficiency of the combustion, it's lower than hot water and the like, but when you add how that heat gets moved(no pump, no electricity) I feel it should get more credit than it does. It's a lot closer when the total energy use is considered

SlamDunk

I have both. if temps are in 40’s +, my gas bill is $125/ month with forced air

Below 40 day time temps, i switch to steam for comfort and my gas bill is $125-160.

house is not insulated

RayWohlfarth

@jumper I have alwasy heard a radiator only heats all the way across when the weather is at design temperature.
@Jamie Hall I have seen substantial saving by even changing one boiler out with the exact replica because the old was covered in scale.
@Canucker I agree. The transporation costs are much lower with steam I have a comparison of transportation costs below and steam is even lower than hydronic.
@SlamDunk Nothing better than coming inside from the cool and standing in front of a radiator

mikeg2015

We have a large wall radiator right next to where we let the dog outside to the yard. Wonderful. I can set a pile soaking wet boots hat and gloves on top of the radiator and they are dry in a couple hours.

hot_rod

A number of efficiencies come into play. Fuel to heat energy, a low temperature mod con probably wins that race.
Distribution efficiency, ECM circulatory have changed that game, not sure what technology was used for that graph? Ssmall diameter Pex with high delta will move a lot of energy also.
Standby loss from the boiler mass and fluid capacity, so a mod con with1 gallon at 120 would be the least energy loss.

Steam seems to be on the rise for low temperature systems at brew facilities an any process that can leverage those temperatures.

The efficiency question is a bit complicated until you define the question better.

The least expensive heating technology to condition a space, show your math😗

Voyager

I’m with Hot Rod. Opinions are like something else that we all have. Only actual test data or solid mathematical analysis sway me much. Given the energy required to heat water to boiling and the heat lost in the boiler exhuast stream, I can’t imagine steam comparing to low-temp hydronic. Maybe if you had a process that could condense the flue gas and use that latent heat for something useful, but I have not seen that on any small steam system. The energy used in circulation of water is pretty minuscule in all but the worst designs.

Steamhead

But in a steam system, there is a lot less water to heat up/boil.........

RayWohlfarth

@hot rod_7 and @Voyager It was not my intent to say that steam is the most efficient heating system, far from it. My intention was to simply say there are many variables to consider when factoring in ownership costs for a building owner. Thanks for the input

Voyager

Steamhead said:

But in a steam system, there is a lot less water to heat up/boil.........

I am not sure that is true compared to modern mod cons. Many of them have very little water in the boiler. There is more water in the piping and radiators, but not sure the difference is that great in total. And, in any event, that makes little different in energy consumption and thus efficiency, unless the boiler and pipes are uninsulated and in space where the lost heat between firings is not beneficial.

Voyager

RayWohlfarth said:

@hot rod_7 and @Voyager It was not my intent to say that steam is the most efficient heating system, far from it. My intention was to simply say there are many variables to consider when factoring in ownership costs for a building owner. Thanks for the input

I agree. The topic header though asked the question “Is steam inefficient?” This has no answer as efficiency is a matter of degree; it isn’t a yes or no question. Steam is almost always less efficient than other heating systems, but the question is: does that matter in a given installation? And, as you say, that depends on many factors.

Personally, if I had a working steam system in an old structure, I would maintain the system and run it and put my money in projects that minimize the heat loss. Reducing heat loss is almost always the best investment. Losing lots of heat through drafty windows and doors and uninsulated attics is poor economy even if you are producing that heat with 95% efficiency. 😁

Jamie Hall

The problem is -- and has been for quite some time -- that when people say something like "steam is inefficient" they are almost always referring to an old system, while they should be talking about systems which are all equally (or not!) modern. Otherwise you are comparing a Model T to an Insight hybrid. Concrete example. The original boiler in the main place I care for -- Cedric's predecessor by a couple of generations -- was a giant HB Smith, with a Quiet May burner. State of the art -- in 1930, when it was installed. It burned 5 gallons per hour of #2. I have no idea what the boiler efficiency was -- the modern measurements didn't exist then -- but it can't have been good. Cedric, on the other hand, thanks to the administrations of one of us, usually runs about 83% (it's a little lower right now, but @Charlie from wmass has been busy...) and burns 2.75 gallons per hour -- and heats the same structure, no other changes, better.

As several folks have said, with the very latest state of the art modulating condensing burners (either forced air or hot water) and the controls optimized, you can do better than that, even considering parasitic losses. However, it is at best unwise -- if not plain dishonest -- to compare systems and methods without being certain that one is comparing similar levels of the state of the art with equipment in similar condition. If one does do that, though, one quickly realizes that other factors in the overall system make small variations -- even 10% is small -- almost irrelevant.

ChrisJ

Steam it self is incredibly efficient.

I believe you get back 100% of the energy used to convert water into steam.

Charlie from wmass

Fact: hot water has always used less fuel than steam to heat a building. Fact steam systems require less heat emitter for the same level of heat output. Fact: steam requires very little electric power to run even with the most modern of boilers. Fact: people seem to have an aversion to properly installing it. Fact: proper maintenance and upkeep of a steam system can get within a few percent the same savings as a complete conversion to forced hot water without the capital investment, mess and additional maintenance items added while not increasing the risk of water damage from a leak. Practical efficiency is best. Would I install steam in a new building? Absolutely not. Would keeping it in an existing building be my absolute first choice? Yes. Until electricity gets to be Canadian low pricing. Then we will all be out of business.

Steamhead

Charlie from wmass said:

Would I install steam in a new building? Absolutely not.

Why not? I would, and have (in houses that were being rehabbed). And don't forget- steam has much less risk of freezing up during a power or fuel failure. Sure, you can put glycol in a hot-water system, but that carries its own maintenance and environmental issues.

Can't beat H20's Gaseous State!

Charlie from wmass

@Steamhead cost of installing it and freezing is a minimal risk versus the operating cost difference.

John Mills_5

How does the Empire State Building heat? Radiators? Fan coils? Anybody know about the cooling system in it?

ChrisJ

Steamhead said:

Charlie from wmass said:

Would I install steam in a new building? Absolutely not.

Why not? I would, and have (in houses that were being rehabbed). And don't forget- steam has much less risk of freezing up during a power or fuel failure. Sure, you can put glycol in a hot-water system, but that carries its own maintenance and environmental issues.

Can't beat H20's Gaseous State!

@Charlie from wmass is a good man, one of the best in my opinion, but he's not perfect and he's not always right. Fact.

Before he says it, no, I'm not always right either.

jumper

Homeowner is supposed to periodically visit steam boiler? Then steam is a non-starter in XXIst century. But it's a different situation for a building with a superintendent or even a maintenance contract. Toronto was a HHW area so I prefer steam. Each heating season some building needed drain down for repairs and then it was the old bleeding routine.

I also could not demonstrate that HHW used less gas. Especially compared to two pipe steam heated buildings with TRVs.

Finally there's tenants who complain unless rads are scorching hot. Same people who greet you in their underwear. Some supers overheated whole building to spare themselves those experiences.

Charlie from wmass

@ChrisJ I am not always right. But since my wife is not involved in this thread I am reasonably confident in my accuracy.

Jamie Hall

@jumper -- absolutely right about people not taking care of their things in the XXIst century. And it's true that steam is apparently a little less forgiving of total neglect than some other heating media (it really isn't -- consider what happens to a hot water boiler which is never cleaned or descaled... never mind forced air where the filters are never changed).

And @Charlie from wmass . You made me spill my tea. Now you owe me a cup.

SeanB

From a pure cost POV, my system isn't running well (I'm in the process of getting it fixed) and it's heating my new home for slightly less per sq ft than the forced hot air system in my last condo.

I'm curious to see the difference once I get it running right.

Charlie from wmass

@SeanB there is also the likely hood your forced air system was also not running correctly. It just would be less vocal than a steam system that was out of order. The difficulty is we seldom have apples and apples comparisons.

ChrisJ

I'm betting 99% of residential forced air systems "aren't running well".

SeanB

@Charlie from wmass You are probably correct. I am not an expert by a long shot. That being said, the forced air system was brand new when I bought the condo. Obviously, not the case for the steam. Of course it might have been set up wrong, too.

ChrisJ

I still say I'd rather a really tight and sprayfoamed house with a 40% efficient snowman in the basement vs a drafty poorly insulated house with a 95% system.

jumper

ChrisJ said:

I still say I'd rather a really tight and sprayfoamed house with a 40% efficient snowman in the basement vs a drafty poorly insulated house with a 95% system.

Yes. I'd add that in a leaky house radiant should waste less energy than warmed air. Latter is trying to heat outdoors. Ideally you want occupants to feel warm at lower air temperatures. Primitive log cabins in frigid weather can actually feel too warm when the pot belly gets too hot.

Solid_Fuel_Man

By it's very nature a steam heating plant cannot transfer heat to the media as efficiently, part of the boiler is dry. Why is the output of an identical input boiler less when steam than hot water?

I'm not getting into the debate of controls, I'm just saying that a steam (operating in the positive pressure range) heat plant by the laws of thermodynamics must have higher stack loss.

A condensing boiler's exhaust temp is far less than steam's operating temp, therefore its stack temp must be higher.

As far as the electricity used to move water, a residential sized system would be less than 200 watts, even running 24/7 200 watts (and I'm being generous as ECM would be less than 50 watts) would cost $14.40 a month at $0.10 a kWh.

A commercial sized steam system will have condensate pumps (I service many). Same sized water system likely 10horsepower circulators throttled with VFD and DP controls. I'm just not buying the cost less because of the lack of pumps arguement!

Also most of the steam systems I encounter are commercial sized and have had rotted condensate lines. Far more of the systems I encounter are water and a rotted pipe anywhere is an extreme rarity. Plus copper and PEX can be used with water, not just limited to iron/steel piping of large diameter.

Bottom line in my OPINION is that steam, when existing is a good form of heat, but in all but the rarest of cases cannot be made to be as efficient (total system) as a typical low temp water system with either cast iron of radiant radiation.

Flame suit on😑

ChrisJ

I really need to get some free time, and money, and build my dream hermetically sealed steam system that runs at condensing temperatures.

Dave0176

Is steam efficient, hmm well as far combustion efficiency which is what it’s all measured from no. However I’ve lived in two houses with hot water, one I installed after ripping out the terrible crap warm air. I’ve also lived in three houses that were heated by steam. And here is my opinion, you can’t put an efficiency number on the comfort level I felt with steam, those big radiators just felt very comfortable on cold winter days.

And would I install a new steam system in my house? Yes I would in a heartbeat. My wife and I are currently looking for a house and I could care less what type of heat it has as long as there is a basement where I can run pipe.

Steamhead

Solid_Fuel_Man said:

By it's very nature a steam heating plant cannot transfer heat to the media as efficiently, part of the boiler is dry.

Three-pass steamers, like the Burnham MegaSteam and its cousin, the Crown Freeport II, have all their heat-transfer surface below the water line. That's why they're as efficient as they are.

Solid_Fuel_Man said:

Why is the output of an identical input boiler less when steam than hot water?

Because the pick-up factor used to establish the Net rating is higher for steam than hot-water. These are arbitrary factors that have been used for generations.

ChrisJ

Steamhead said:

Solid_Fuel_Man said:

By it's very nature a steam heating plant cannot transfer heat to the media as efficiently, part of the boiler is dry.

Three-pass steamers, like the Burnham MegaSteam and its cousin, the Crown Freeport II, have all their heat-transfer surface below the water line. That's why they're as efficient as they are.

Solid_Fuel_Man said:

Why is the output of an identical input boiler less when steam than hot water?

Because the pick-up factor used to establish the Net rating is higher for steam than hot-water. These are arbitrary factors that have been used for generations.

It's also because pin type steam boilers are a cheap compromise to make a HW boiler also do steam.

It's not a properly engineered "steam boiler" like a 3 pass.

Jamie Hall

There is yet another subtle effect in here. Folks have mentioned that steam boilers do not condense -- which is true. There is a reason for that: there simply isn't enough water (condensate) coming back from the system to do it, even if one make the entirely unwarranted assumption that the condensate would be cool enough anyway (it usually won't be).

Let us suppose, for the moment and for ease of back of the envelope arithmetic, that we have a 100,000 BTUh input steam boiler, operating at 85% efficiency. Now that means that 85,000 BTUh is going out in the steam, and 15,000 BTUh is in the stack gas. That's 85 pounds of steam going out -- and 85 pounds of water coming back, every hour. Suppose we want to cool that stack gas and extract the 15,000 BTUh in it. We have 85 pounds of water. That heat will raise our two buckets of water by 176 degrees... really? Ah... starting from where? No can do. So we're stuck.

But... there is flip side in the structure. Steam operates at a significantly higher temperature than water, so all the radiation can be smaller than would be required for hot water. This is sometimes a plus; sometimes a considerable plus.

There is no universally acceptable best answer. The best we can say to the question of "which is better" or even "which is more efficient" is... it depends.

jumper

Happened to be looking at old literature lately. In 1965 Cleaver-Brooks guaranteed 80% fuel to steam. In 1975 claimed 85%.

Is any extra efficiency significant?

Solid_Fuel_Man

I still think most people associate hot water with fin tube baseboard, and steam with cast iron radiators. Fact is that those two emitters are much different in how they emit those BTUs.

Apples to apples as far as we could go is, hot water and steam both heating radiators in a home. Granted the HW would have to be bigger and sized for whatever water temp. And see how that makes one feel comfort wise.

Like the radiant floor thing, radiation from everywhere!