Steam vs Hot water boiler heat

Brad White_204

Normally, given the blank canvas you have, I would opt for hot water over steam. The efficiency comes from the ability to modulate the water temperature inversely with outdoor temperature- matching output to heat loss more closely than any other medium.

Given your power outages being a common occurrence, steam seems to gain favor as Nicholas said. When "down", the water all drains back to a relatively protected core. If you had gas and a milivolt/power pile system, you could still have heat in a power outage.

With oil, no, you need electricity for the burner. Then again, a small generator will run that. (Generator Goes Outside, have to say that.) Even a modest HW system will run on a generator quite well.

One pipe steam uses iron pipe, probably less money than copper at this point still :) and less piping than two-pipe and all of larger sizes.

Next tier up might be gravity HW. Larger pipes in both directions but you can have virtual outdoor reset, warmer water in colder weather.

Larry Weingarten and his wife Susan have gravity HW radiant in their California home, so all things are possible.

That you are in a position to make over the envelope, you have abundant opportunity to do a lot of good things!

rich on heat

STEAM or FORCED HOT WATER

hello
We have an old 100 plus year old house with absolutely no heat installed. there is no piping of remainder of old systems. the house is located in the colder area of the northeast. we have done heat loss calculations and have a vast store of salvaged radiators. we would like to use the salvaged radiators instead of baseboard.
we only have a choice of oil as fuel.

we are trying to decide between installing a forced hot water system or a steam heating system.
we are in the process of installing good insulation throughout the house and attic. the walls in the house are open without sheetrock. the area is also prone to electric outages and blackouts sometimes for days during the winter.

We do not see options to do radiant heat although the floors are open below and could be installed. lacking a cement base to instal the radiant into - it does not seem to have enough thermal mass area to make for an efficient system.

what is the most efficient system to instal? hot water or steam? and which will provide the most constant equal rate of heat? if hot water is more efficient - could you please explain why ?? with the added costs of circulator pumps and electric used. thank you!

Tim_64

only oil?

Are you sure? that you are restricted to oil heat?

nicholas bonham-carter

heating choices

go for 1-pipe steam with gravity return, millivolt gas valve, and a UPS battery backup system. since you will be installing it from scratch, it will be more tuned up than an old sytem with lots of deferred maintainance,and you will love it!
perhaps even a retro-mouat vapor system could be arranged [with 2 pipes].
the battery backup will not carry you for days, but the current draw is so low that you will be able to use a very small generator[or even a small solar panel].
i expect that the construction of a new steam system could well be so interesting as to lure many contributors from here to help out with the project!--nbc

Charlie from wmass

Radiant can be installed in your home in an efficent manor. Steam has its place and I love them when they are humming along but radiant is less costly on the fuel if done correctly. Steam uses a lot less electricity. Millivolts do not work too well on oil last time I checked.

ttekushan_3

\"right sized\" steam

You definitely have the benefit of sizing the system for the actual heat loss of an insulated building. Any time I encounter a steam system thats actually about the right size for a structure, its owners claim its very economical to run.

We've seen this reported in the past right here on the wall. One instance in particular a new homeowner had done just this. They had a new house finished, being virtually identical to all those around it in the development. They had a home office so the temp would be kept at a constant and comfortable 68-70. They got this crazy notion to install steam heat and were finally able to find someone who knew how to design and install it. The result is a basic single pipe steam system of the proper size. The kicker: they're fuel consumption is half of what is was when they were using forced air, and 60% less than their neighbors with forced air systems.

It certainly appears that the average steam heating system out there is 50% oversized. This is where the real trouble lies, not with the steam medium itself. Whenever I work on a steam system that has persistently and stubbornly high fuel bills, it is always one of those thats grotesquely oversized. There are a number of strategies to deal with it, but thats another topic.

Right size it and you will be impressed by the economical operation, simplicity, comfort and longevity (> a lifetime!) of the system.

nicholas bonham-carter

oops forgot!

i did overlook the "oil only" so no millivolt for this one.

what about an industrial diesel engine running a generator, and refrigeration compressor whose waste heat provides the heat for the hot water loop.you still need a boiler, but the control system would be challenging to design!

most of the time the boiler would provide the heat but when the tree limb, laden with snow, takes the main power out,the engine takes over for heat, light, and fridge.--nbc

nicholas bonham-carter

back to steam

one more point to consider: many salvaged radiators come from old steam systems replaced mistakenly [in my opinion].those radiators may be made for steam only as they are not "flow through"-merely a series of connected chambers.they may be difficult to convert to hot water.
why not post some pix of them for us to see?--nbc

David Nadle

Interesting set of constraints

I love my one pipe steam system. I love learning about it and maintiaining it and trying to improve it. But if I had to replace the whole thing I'd go with hot water. I'd look at staple up radiant with insulation in the cavities for the first floor, and panel radiators or baseboard upstairs on a seperate zone. At the same time I'd set up indirect domestic hot water and if I was in your position I'd have the whole thing wired to be run off a generator.

The efficiency gain of hot water, with the proper controls, is a seasonal one. On mild days you are only heating the water to the temperature that matches the heat load. With steam you always have to boil the water, even in May.

Mark Custis

I like miles of pexA

and shinny brass manifolds with flow meters and actuators.

I also like what I learned from John in this months PM Engineer colume about panel radiators.

Here kitty, here kitty, I want to build a manifold distribution system with panel radiation.

rich on heat

there is also propane - but then we would need to excavate and bury a tank. from all i see oil is cheaper than propane.

rich on heat

hi - could radiant be really efficient installed in the first floor over an unheated unfinished dirt basement and dirt crawlspace in one area?

i always was afraid just the circulator pump electric charges would be astronomical as well as trying to keep pipes heated over an unheated space which frosts over - even with good insulation under it........

what would be used to protect the pex adequately?

rich on heat

we have a small honda genertor - for outdoor use that could be hooked up to provide the electric for the boiler. if that is a working scenario - would you still go with steam?

and do the electric costs of a hot water system make up for what savings one might find with the outdoor reset? thank you!

rich on heat

we are good on the radiators. only two of the radiators are steam only - the rest of the hoard can all be used with hot water if we choose to convert them.

if using radiators with a hot water system - would anyone use the monoflo valves? they seemed like a great solution until you realize that the water leaving the radiator is getting mixed with the hot water coming to the radiator....

amazed to learn it would be cheaper in terms of material to pipe a steam system vs copper.

we are not sure about the water quality and were concerned that it might be better to use steam vs a pex system where bacteria might be unhealthy or sediment might impede the flow and hurt the circulation.

with an extended power outtage - steam might be better also as it would not call for as much or additional water? thus the pump to the well would need power as well.

does anyone know what the window of time in 20 degree weather before a house and basement would freeze - pipes and boiler in a power outage? thank you!

Charlie from wmass

hot water systems are closed loops and require less water to be added over a year than steam does. Each cycle of a steam boiler even if it is running correctly looses a bit of water. a forced hot water system once filled and bled of air does not take on water unless the water leaks out. also the water can be treated with antifreeze if power outages are a common thing. A generator may be a wise investment as most photovoltaic or wind power systems use the grid for storage not batteries. From scratch hot water will cost less for fuel than steam even if both are sized correctly. Physics is at work. Steam was often considered back in the day as it was cheaper to install than Gravity hot water not because it was better than hot water. gravity hot water was considered the better system as it allowed lower temps but it required larger pipes. Why not install a gravity hot water system and a wood or coal fired boiler as back up? Buderus and Baxi have UL listed water boilers for solid fuel.

Steamhead (in transit)

I'd go with steam

but you knew that ;-).... especially since you are subject to power outages. OK, you have a generator, but if it doesn't start.....

The Vapor State rules.

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Brad White_204

Electrical consumption

Well, your oil burner (I am going on the premise that oil is your fuel in the end), is common to any scenario.

If hot water, then you have to have a few amps for a circulator and for controls. All of this, if a one-circulator deal, will take 100 Watts, less if you use an ECM circulator and low design head. If you have primary-secondary piping, your circulator electrical load would double, but perhaps you are still below 150 Watts connected if you plan it correctly. If you go "circulator crazy", well so much for simplicity...

It is hard to give an efficiency number, there are so many variables, but "hot water with ODR" in general would give you a savings over "hot water without ODR" of between 15 and 30 percent, more if the reset is aggressive.

So, comparing water with and water without, that savings swap versus electrical power is a no-brainer-you are talking just controls and maybe, just maybe, that second circulator.

But fail in the power reliability area and you had better have glycol in the system.

Steam can be remarkably efficient but can be beaten by HW most days if ODR is used. A badly controlled HW system will be thrashed by a good steam system any day in my experience on similarly sized houses.

I would love to see a good head to head comparison with identical houses at some point to give numbers to these experiences.

Mark Custis

Rich

I am about out of today, 11-28-08, and it is our 25th aniversery. Look at Caleffi Idronics 4 and think manifolds and all that CI.

Want more?

Email me.

I have to say good night to a trusted friend.

rich on heat

i have looked for those comparisons on the internet for months. none exist. not even guess-timates. your explaination and numbers are most appreciated and the most cogent thing i have read on this to date.

so how would hot water with ODR compare to steam? hot water w/ odr would win i assume?
thank you.

rich on heat

does antifreeze corode systems or cause problems. we have read a few messages that stated it was best to avoid it.
thanks again.

Bob Bona_4

add

the constant degrading and rotting from the inside out factor to the steam equation, on the wet side.

Also steam will need more baby-sitting-regular blow downs, safety checks, etc.. If you are into that sort of thing. It's more hands on, that could be a pain to the next person to inherit it.

I would opt for a hot water system any day for all the options the boiler can do handily.

Bob Bona_4

it can

and does, if you let it go. Out of the gate it has corrosion inhibitors, but they soon break down. Regular monitoring is needed to keep glycol from attacking seals, valve packings, etc. Come service time when the boiler needs to be opened up on the wet side, the solution gets compromised w/ fresh make up water post repair, and now the concentration is out of whack. It's a fussy and tedious thing.

It makes the boiler water thicker in viscosity, making things harder to pump, and reduces heat transfer. Avoid it any way you can.

Intelligent installation design is critical to avoid potential freeze ups, in addition, freezestats can be used in leiu. That, and a standby generator.

Bob Bona_4

this is

totally from personal experience (and some from client situations over the last 20 years). A house with some sort of insulation in the walls that was 68 inside can go 12-18 hours or more before things get to freezing. Of course, mileage may vary- a lot! Will things freeze in 6 hrs@ 20 out-doubtful, will things still be ok after 24-30 hrs-doubbtful. Exclude dopey piping setups like running on outside walls, cantalievers, attic lines..

Typical basements don't get below freezing, close, but not usually, unless the foundations totally stick up out of the ground.

Bacteria in heating PEX is a non issue.

"Monoflo valves" mean monoflow T's? They work well, but a home run manifold system is nicer way to go for many reasons.

Steam will always need water, just about daily.. Hot water, not so much.

Brad White_204

Cost Basis

It is fairly straight-forward to figure the electrical costs in a constant flow volume system. When the flow varies, one has to at least "bin" the results (so many assumed hours at various increments, then total them).

Hot water with ODR should indeed be more efficient compared to steam, sure. By how much is the mystery which requires side by side houses to compare. Gas fired modulating condensing HW is the highest efficiency of all.

Naturally in any of these system assumptions and comparisons is a common ratio of capacity to heat loss and use of appropriate control.

Steam nowadays, as practiced here, is probably as efficient as it ever was. All the more reason curiosity is piqued!

ttekushan_3

blow downs yes.

but corrosion is overstated, IMO. The below the water line piping on my current steam job required replacement about 35 years ago when the boiler was replaced and its still tight and leak free. Everything else is original, with no leaks. Did I mention that "everything else" is 123 years old? And two stories and 30 radiators worth of piping?

To think someone will be talking about whether to rip out functioning pex in 80 years let alone 123 years seems a little unlikely ;-)

rich on heat

agree on how amazing the existing steam systems can be. have lived in three homes now with 100 plus year old piping and they were all still good and going. only the newer fitings of the past 20 years had problems!

Terry in NJ

given the power outages

How about something like the Honda free-watt?

http://www.ecrinternational.com/secure/upload/document/698.pdf

rich on heat

that is a beauty - must be expensive? and it uses natural gas. not available in the sticks. thank you.

rich on heat

what else would you suggest in a best case scenario when you say opportunity knocks? thanks so much for the great info!

Terry in NJ

it says a propane version coming soon

Also another thing to consider is how well the system runs unattended. One pipe steam needs water added to the optimal level. My autofeeder is not set up to do that. In addition, you can flood the house through the vents if the autofeeder breaks.

rich on heat

take the electric outtages out of the picture........

If we take the one variable of electric outtages out of the picture and were not worried about that - would hot water be the choice vs steam?

Steamhead (in transit)

Do we

really want to do that? I think we'll see more outages in the future. Enron in California was the warning........

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Brad White_204

My Ideal

My ideal, epitomized when I say, "opportunity knocks", is to tighten up that house to the nth degree, take advantage of any solar gains, make the passive aspects the best they can possibly be..

Now you have the smallest heat loss imaginable (at least for this particular structure). Calculate what that would be.

That number will reveal if:

A. You can get a steam boiler and matched radiation small enough (nice problem to have!)

B. If not steam, then the ideal boiler would be "X"

C. Design the system for the lowest water temperatures, using hot boiler water (if you have oil only), decoupled for primary-secondary circuiting. This will allow full-range reset on the radiation side and narrower reset on the boiler side (to protect it).

Any of these and likely others will emerge once you know your calculated objectives. I envy you and the position you are in.

mark ransley

Propane is an option, Steam is no more than 83% efficent,[I cant find them ] HW can be 98% efficent at low water temps 140f and under and there are maybe 3 condensing oil water boilers made now of around 96% efficent. A system 2000 is worth looking at.You might look for dual fuel burner , oil- propane [I have no idea if they are made,] im no heat pro. Hot water will have more even heat and with a system 2000 or condensing boiler will save you alot up to 15%. Will you have AC, then propane furnace is an option with ducts. If you go Hot Water condensing boiler then oversize radiators so you can heat with 140f water for as long as possible, I dont need over 140f until 20f outside, the efficency of condensing HW boilers drops alot over 140f, im no pro but its what I have read. Zone heating water is easy, if basement ceiling is unfinished the first floor can be radiant tube which I have heard is more efficent by 10-15% since the heat is under you not at a cold wall, it is more comfortable, I have lived with all types of heat.

Steamhead (in transit)

Uhhh, Mark

there are steam boilers with AFUE ratings higher than 83%. The Burnham MegaSteam is one.

90%+ efficiency IS possible on steam- foreign manufacturers like Hoval and Gasmaster have marketed such boilers in larger sizes. If they can do it, so can we- but as usual we're waiting for American boiler manufacturers to stop dragging their feet.

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Charlie from wmass

Propane costs 15 to 30 percent more than oil for equal BTUs.