ROI on converting from steam to hot water

Steve Garson

I have a 70 year old Burnham Steam Boiler with modern oil burner. I burn around 1100 gallons a year. The steam heat is even and the water loop makes no noise. In short - it works fine, although I seem to be adding a lot more feed water this winter. The boiler heats the thin tube radiators with steam and a room with 30 feet of baseboard. I also have a master suite heated with radiant floor through a Bradford-White water heater.

If I replace the steam boiler with a modern boiler, installation costs will be lower, but steam is not as efficient as water. Anyone able to help me with this?

Converting to water, I would use the same radiators, but installed new feeds and returns. I could also move the radiant to a more efficient boiler and leave the water heater for just the domestic HW.

Does anyone have a sense of what savings can be expected so I can make a well informed decision?

Thad English

uh.....

You might not save as much as you think, once you fix all of the potential leaks that may result. Steam runs at less than a pound of pressure, while H2O is above 15. Those old fittings may not be able to take the pressure.

And a properly installed new steam boiler and insulated mains will save you a bunch of oil and thus $ over that old beast.

There is an article on this website under 'hot tech topics' (I think) that outlines why converting to hot water from steam isn't necessarily the most economical thing to do.

Thad English

here's the article

here is a link to that article:

http://www.heatinghelp.com/newsletter.cfm?Id=22

Steve Garson

Thad:

Yes, I've read that page. I'm not really daunted by the work involved. My plan is to replace all the present pipes with copper or PEX, use manifolds as apprporiate. But I can't seem to get anyone to help me sense the savings of modulated water versus steam.

DanHolohan

I think

there are too many variables to make an accurate prediction.

Constantin

All me then to step in...

...with a staw man to burn.

Most steam boilers don't make it over 80% AFUE combustion efficiency. Never mind the startup and standby losses. If you stick with oil, the bees-knees of CI heating is the Vitola, which will offer about a 90% AFUE with a radiant system (low return temps), outdoor reset, and other energy-saving features... for beaucoup bucks, naturally.

Here then my straw-man: You're likely to save around 20% on the discrepancy between the insulation, start-up, standby, etc. losses if you new system has a lower water temperature, a well-insulated 87% AFUE boiler, etc. Then, outdoor reset and other modern control strategies might save you an additional 10%, for a total of about 30% fuel consumption reduction.

Why can I say this? Because I'm a mere homeowner who simply aggregates information. Luckily, you can't hold me to that prediction since I'm not a contractor nor are you my client. :-)

On the gas side, there are more choices and more results to go by. For example, Mike T has experienced a 40% reduction in his fuel consumption (on a corrected degree-day basis) over his old CI boiler. Granted, Mike has gone further than most (by installing TRVs on all radiators) and his heating system is optimized to return cool water to the Vitodens to make it condense its flue gases all the time.

However, many other folks have reported 25%+ fuel consumption reduction over their older equipment with no changes in the emitters. In other words, if you're going with a hydronic system fueled by gas for the long term, get a condensing, modulating boiler.

You could also go for the 94% AFUE Monitor FCX, which is a small (75kBTU) condensing oil boiler, if you're the adventerous type and a stickler about getting the unit serviced properly. Expect the about same energy savings as with a modulating, condensing gas boiler, as long as your heating system can take advantage of a condensing boiler (return water temps below 117°F for oil, 140°F for gas).

Lastly, I would seriously reconsider the use of that water heater. Chances are, you can heat potable water at a much higher efficiency with an efficient boiler and an indirect water heater than you could ever hope to achieve with a conventional gas water heater.

Steamhead

If you're going to tear all the pipes out

it would no doubt take much longer to recoup your investment.

If a steam system and a hot-water system are designed for the same load, and both systems use similar boilers, and are well-installed and maintained, they're pretty close in efficiency and comfort. Also steam has the advantage that it won't freeze up in an extended power failure like hot-water can.

When you look at condensing boilers, also consider their reliability. It's true that most of those out there are doing well so far, but they are definitely more complicated than non-condensing ones. Those of us who are not "early adopters" are watching these units closely to see how they hold up over time.

Also consider that we have had owners of steam systems report considerable fuel savings just by doing basic stuff like insulation or venting upgrades to their steam systems. One regular on the Wall cut his fuel bill by 70% or so! I recently did one that was between 30% and 43%, depending on how we compared the numbers. This was far more cost-effective than a tear-out would have been.

Your best ROI just might be to upgrade what you have.

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Robert O'Connor_7

my 2 senz

By installing another medium efficency steamer (lets say it's 84%), then compare it to a top-o-thee line condensing boiler at say 94% then add in all that labor and material for a product that may crap out long before the steam boiler does, my though would be it would not pay for itself (depending on your age) in your lifetime. Don't get me wrong, I love the idea but you asked the question. If your looking for a payback from your investment forget it. If your looking to invest in comfort then go for it. To touch on another statement you made about reusing the existing rads, these may not handle the load since your no longer sending steam through them but hot water at much lower temps. Get a heat loss done first then see if there is a way to reduce the load by installing insulation and good storm windows. Stick with the steam..Robert O'Connor/NJ

Steve Garson

The rads now in place have plenty of BTU at 170 degrees water. This old house is now very well insulated with new low-E windows and every other possible air sealant. I'm surprised to hear all the pro-steamers, but I guess when you factor in the installation costs it makes sense.

I totally buy into the concept that the super-efficient boilers cost so much more to buy and service that it can offset any fuel savings costs.

Thanks for all the feedback.

Tony Conner_2

There Have Been...

... several posts lately from people with old steam systems that were costing a fortune to run, and who were actively considering converting to hot water. After getting a few tips from people like Steamhead, and spending a small fraction of the conversion cost to install a few air vents, etc,. their fuel bills just plummeted. And with the big drop in operating costs, the payback on the conversion project disappeared over the horizon.

Constantin

Very good points!

You're spot on. IIRC, the biggest fuel savings to date on a steam system was 80% simply by getting the venting right and the condensate to drain properly. If I owned the house that I am currently renting an apartment in, I'd tear out that lonely Hoffmann 75 that vents the main and replace it with at least 1 if not two Gorton #2's...

Usually, the marginal cost of going with a condensing piece of equipment only becomes fiscally interesting when the previous boiler failed and hence a new boiler, a repipe, and so on become necessary as opposed to optional.

The only circumstances under which a HO might be able to justify it economically is if they do all the work themselves and place little to no value on their free time. Hey! it's fun for some people to be doing this sort of stuff. Ask me sometime about all the work I did on my mothers boat, for instance.

Steamhead

Steve, we're always here

if you have more questions. Let us know how you do.

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Unknown

170° water isn't condensing

Figure it at 120° F water.

Or get a non-condensing boiler. It won't be condensing, anyway.

Noel

t. tekushan

My experience at the building I'm in now has taught me how wonderfully efficient steam heat can be. Without changing anything expensive (i.e. a boiler), we reduced fuel consumption by about 35%. Relevelling pipes, reinsulating the main, insulating the return (where it passes through unheated spaces), replacing steam traps, and de-scaling the boiler (Cleveland's a hard water town), replacing return vents,etc. I should scan the section on effects of boiler scale upon efficiency from one of my favorite references, "Instructions for the Boiler Room" (1898). We discovered long-existing leaks in the return system when I got involved here an began to estimate how much scale that could amount to even in a 10 year old boiler. Scalex to the rescue. Immediate improvement in steam generating time upon start-up and resultant improvement in steam delivery to the most distant radiators.

In an lovely but drafty uninsulated 1926 building, the heating costs are more manageable than with any other type system imaginable. Plus, its simple as a brick. Of course, I'm a steam heat junkie. For what its worth.

colbydoglvr

how about

why not add two little boilers, a primary loop, a tekmar 262 two stage boiler control, a secondary loop, a tekmar 370 house control, hmm... im getting uot of control again...

jeff_51

steam vs hot water

Just finished coverting a six plex from steam to hot water.
this was a two pipe system and by the time we tracked all the drip legs down and capped them, tested the lines for soundness and installed a new buderuss 265,000 boiler we had spent $35,000 and we charge alot less here in the midwest than you guys do out east. I'm definately a wet head, but stay with the steam. Ya, we did more work than that, but its expensive to do the coversions.

Steve Garson

Great threads... Now that I'm convinced to keep steam...

Sounds like a compelling case to stay with steam. Now with that out of the way, I need this advice:

1. One room has 30 feet of baseboard with the loop heated from the steam boiler (with tempering to avoid flashing to boil). This is simply tapped off the boiler. Can I do the same with a new steam boiler which will have 2 or 3 fewer gallons? Should I get a tankless coil and run the loop off of that?

2. I have 12,000 BTU of heat for a radiant loop that is heated from a Bradford White gas water heater (designed for both a potable and heating loop). From an energy efficiency perspective, should I include this into the equation, or just leave as is. I would love to stop having to manually lower the heater temp when the whether is warm before I become an old man

Thanks for all the insights guys. I love this site!

Steve

Steamhead

Why not use

a very small hot-water boiler for the radiant and the baseboard, and an indirect to replace the Bradford-White? You'll get a LOT more hot faucet water with an indirect. I have a similar setup here in Baltimore where the main system is Vapor, and a little 2-section Weil-McLain heats a baseboard loop in an addition and also the indirect. Works great.

I'm not thrilled with potable and heating service running off a water heater, mixing these two can cause Legionnaires' disease.
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Steve Garson

second boiler

If I install a second boiler, I may have a venting problem: today, the oil burner and gas water heater vent to the same chimney. Can I run an third vent for a small gas boiler for the hydronic.

I can't use a wall vent because there is no place to take the vent that isn't far enough from a window to meet code.

Steamhead

With the setup I described

the only chimney connections would be from the steam boiler and the hot-water boiler. The indirect is basically a tank with a heat exchanger that transfers heat from hot boiler water to domestic water being heated. It does not have a flue connection.

In a house that old, the chimney would likely be big enough for these two units. But you would need to make sure.

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Steve Garson

Water heater

Steamhead:

Will it really be more efficient to use an indirect heater off the boiler than the new gas water heater now in place?

Steve in Boston

Steamhead

Yes it will

A good indirect will have much more heat-transfer surface than a standard gas-fired heater, which translates to much fater generation of hot faucet water. The setup I described in the previous post has passed the teenager test without running cold- and it's only a 40-gallon tank!

Here's a shot of the installation. This unit is a Smart 40 made by Triangle Tube, fed by a little 2-section Weil-McLain. It replaced an oil-fired water heater that had begun to leak. The big boiler in the foreground serves the Vapor system.

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Steamhead

Yes it will

A good indirect will have much more heat-transfer surface than a standard gas-fired heater, which translates to much faster generation of hot faucet water with less fuel. The setup I described in the previous post has passed the teenager test without running cold- and it's only a 40-gallon tank! Plus, since there is no flue running thru the tank, it doesn't cool down nearly as fast as a standard heater will.

Here's a shot of the installation. This unit is a Smart 40 made by Triangle Tube, fed by a little 2-section Weil-McLain. It replaced an oil-fired water heater that had begun to leak. The big boiler in the foreground serves the Vapor system. This boiler room has two chimney flues, the Weil used to share its flue with the water heater.

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Steve Garson

I guess it makes sense that it would be efficient with the gas water heater always has air running up the middle.

Let me ask you this (which you may have seen as another thread on this forum):

All my investigation focuses around replacing my steam boiler. Dan says that I can run the hydronic loops off the boiler.

My present water loop off my boiler follows which works fine, with the tempering bypass and thermometer, so the temp never goes over 180.. The heat loss in the room that has that loop is 13,000 BTU.

The radiant loop that now uses the water heater has 12,000 BTU of heat loss. If I add that to the boiler, the total would be 25,000 BTU.

A new steam boiler will be sized for the 461 square feet of radiation that I now have, so a WM SGO-6-2 with 542 Sq Feet Net IBR rating seems to fit, since the next smaller provided 450 Net IBR.

With the above info, can I run both hydronic loops on the new steam boiler?


Steve in Boston

Steamhead

That would be close

The difference is 81 square feet or 19,440 BTU per hour. The "pick-up factor" would add some more capacity, but may not leave room for both unless you used priority zoning.

I think you'd get better overall performance and efficiency by using the second boiler and the indirect. Also I forgot to mention, some indirects, including the Triangle I believe, have limited lifetime warranties. Try to find this on a direct-fired heater- good luck!

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