Does it pay to convert from steam to hot water?

Boilerpro

I am also going to move the thermostat closer to the big front windows. It is sitting near the back of the store and I think all the halogens are keeping it warm back there while the front of the store gets chilly. I expect this will help keep things more comfortable too. Then I'll set the cycle rate back to once per hour (it is now at three) BTW. I ran some numbers on warming up those steam mains from about 100F (I think?) and it would take about 3 minutes of boiler firing to warm up the mains to steam temp. Still making me wonder why you need to vent the mains in about 1 minute, but I think I mentioned this before.

I think you are right about the research....When I get a chance I'll call IIT in Chicago and get a hold of my former department chair of City and Regional Planning. He probably can give me some leads since he has headed up affordable housing research.



Boilerpro

Rick Fenton

Does it pay to convert from steam to hot water?

Hi. I have a big old two-storey brick house. It always has been a two-family, one unit up and one down. There is a gas steam boiler for each unit, both installed in 1936. We're taking over the house and want to get the most energy-efficient system that is practical.

I like the steam system, it's simple and reliable. But would a hot water system using the same radiators (adding the outflow piping to each) be more energy-efficient in the long run? I'm interested in knowing, bottom line, which system would use the least energy, and how much less, all other things being equal. My physics memory tells me that a lot of energy is used converting water to steam, so it seems that a hot water system would be better.

I'd like to have two zones - one up and one down. If I stick to steam, I hear I can get a system to do that, even if I put the whole house on one boiler. Do these systems work well?

What is the most efficient and reliable boiler I can get (assuming steam)?

Steamhead

That would be a major project

and may not be worth it. A well-functioning steam distribution system is about as efficient as hot water. Yes, it does take more BTUs to boil a quantity of water than it does to just heat it up- but there is much less water involved in a steam system than hot-water. And you can get steam boilers with annual efficiencies (AFUE) up to 85%.

The key here is "well-functioning". This means your steam pipes are insulated, main vents properly sized, radiator vents properly sized, traps (if used) in good shape, and the boiler clean and properly tuned.

There are some hot-water boilers that have AFUEs over 90%, but these are more expensive to buy and service.

Obviously it's going to cost a bundle to run a second set of pipes. And we don't know if your radiators will even work with hot-water- you may have to replace them too if you want to convert.

Since you already have two separate steam zones, it sounds to me like the best way is to install two good steam boilers and make sure the insulation, vents etc. are installed properly.

Use the Find a Contractor page of this site to locate someone near you who can investigate further. As to boilers, there are many good ones out there- it's the installation that really counts!

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Boilerpro

Another opinion

Steamhead is one of the sharpest in the business, but I don't completely agree with his assessment. The importance of a well functioning system, not just a boiler with a high efficiency rating, is paramount with steam, as Steamhead has said. However there are other factors when looking at a conversion to hot water. The first is what is the current coldest day heating capacity needed to keep the home comfortable. If your home follows the typical pattern it is much less than what the steam systems are designed for. This translates into an oversized boiler being needed (tyically) which operates less efficiently than one sized to the actual heating load (not the size of the radiators). Now I do believe that a steam boiler can be more closely downsized to the actual heating load (not the size of the radiators), however, there are not many that agree with this practice. In addition, since one pipe steam radiators tend to heat the air to a much higher temperature than hot water systems, you can expect more heat collecting at the ceilings, again decreasing the overall heating efficiency of the home (closer to the very inefficient operation of forced air heat). Hot water systems, especially with cast iron radiators, can provide exceptionally even heating comfort and are very well matched to the use of 90%+ condensing boilers. As to repiping costs, most residential sized radiators only need an 1/8 inch steel piping tapping at the top of the radiator (assuming that radiators can be used with hot water) and then immediatedly increaased to 3/8 or 1/2 inch pipe to provide adequete water flow. The big question is then how do the pipes get from the second floor radiators to the basement. If you don't mind a few exposed pipes, the repiping is rather easy. Down in the basement,you could now install one hot water boiler instead of two steam, with controls to keep the upstairs and downstaris on two separate thermostats. When looking at the savings in boiler replacement costs (one less expenssive to install hot water instead of two more expensive to install steam), you probably will cover your repiping costs of the system and have an eaasier to maintain and more efficient system. And there it is.



Boilerpro (Sorry Steamhead, that's how I see it)

Steamhead

Dave, I think you're pretty sharp too

no need to apologize.

I think the real question here is "what kind of efficiency can Rick get, for how much?". Or, is the added efficiency going from an 85% steam boiler to a 90% or 95% hot-water one worth the extra cost, effort and disruption to the house? And steam is much much less likely to freeze and burst in a long power failure than hot-water- yes, there's always antifreeze but that's another maintenance chore that can get overlooked.

We Wetheads like to go all-out on our own houses, but often our customers have slightly different priorities and budgets.

Rick, I'm sure this thread will soon contain lots of lively debate- which is one reason we're here. Keep checking in.

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Mad Dog

In defernce to my \"very sharp\" colleagues.......................

bottom line......you will spend a minimum of $8-10,000.00 for the heating work, and will have a tremendous amount of sheetrocking, plastering and painting to do afterwards (Additional cost!!!). Is it "worth it"? That is a subjective question with as many answers as people have opinions. I suggest....NO! it really isn't worth it....spend a few thousand to improve your system's performance,...and if you really want to spruce things up....add one of those beautiful Burnham Classic Radiators in the family room ....they are like an antique piece of furniture.....Mad Dog

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Boilerpro

However, are you really going to get 85%

If the system is too big and the boiler only runs 30 minutes an hour on the coldest day of the year and only 15 minutes on a typical day. Running a boiler at only 25% capacity most of the time I expect is going to really hurt the seasonal efficiency. This is one of the reasons why I am trying to downsize steam boilers to the heat loss,not radiation load, or convert to hot water, when appropriate. Also, as you well know, boiler efficiency is only one factor in determining fuel usage. How efficiently heat is delivered ( steady modulating heat like old gravity hot water or reset hot water compared to the blast of hot air from scorched air) to the space also effects how quickly the home losses heat. Hot water, I'd say, has a definite advantage here, since air temperatures are much more moderate coming off a hot water radiator most of the year, compared to the superheated air that rapidly rises to the ceiling with one pipe steam all winter, where it increases the homes heat loss and provides little comfort for the occupants. The lively debate is beginning!

Boilerpro

Boilerpro

I'd expect

That replacing two steam boilers, tweaking the two steam systems with new air vents, etc, will set you back this same price. In my parts, most steam pipng is exposed, so adding another small 3/8 or 1/2 inch line for 2nd floor returns, tends to not be a great issue, so little plaster is disturbed putting pipes into walls. The last one pipe conversion I did was in a church with standing rads built in the 20s. The old structure was one pipe the new addition two pipe convector. Replaced 12 year old atmospheric WM 1,000,000 btu input steamer, with two 245,000 btu Dunkirk atmospherics and a tekmar outdoor reset control with night setback of supply temps. In the first winter fuel usage dropped 60% (saving $4,500.00). I'd say about 20% was due to the fact that I disconnected a large snowmelt system that was getting left on accidently, the rest due to improved system and boiler efficiency. My portion of the work was about $17,000.00, with the congregation contributing about another $2,000.00 in labor. Pretty good payback, wouldn't you say?

Boilerpro

Floyd

Sometimes yes, mostly no...

I have converted houdes to hot water and saved money for the people and have
redone steam in others because their energy bills were so low already that there was
no way that I could get any kind of payback for them.....

So as the MAN loves to say .... "It depends"!!!!!!!

If you have a good working system that is working well and efficiently then just replace
the boilers.
If your bills are rather high now and it will take pretty much time and energy to repair existing
problems.... then maybe you should look at a hot water conversion.

Food for thought... I also find that many people who have steam systems tend to run their
temps. lower than with hot water systems. This would tend to help the steam system save.
Just an observation.:-)

Overall I feel that in a residential application you are better off staying with the steam.

Floyd

Unknown

Key words are \" Simple and Reliable \"

I would say in my travels , homeowners love their steam heat just as much as other homeowners love their radiant . Like Matt said , converting the heat to hot water would be extremely expensive . Replacing the two 70 year old boilers with new equipment would do wonders for your gas bill . If the house is working well with 2 boilers , I would keep it a 2 boiler house , unless the piping of both boilers can be incorporated into one boiler - with the proper sizing and pitch. You need a very good steam contractor to look over the system to see what your options are . Good luck , Ron .

Unknown

Last time I tried

pulling the plug in the other side of the radiator to make it hot water , it was a **** . We wound up cutting the plugs out of 8 rads - all day for 2 of us . Those plugs fuse in like theyre part of the iron . A typical house has maybe 10 rads . Add that time converting the rads to all the extra piping , and it looks like a hefty pricetag .

Unknown

my two cents

I've surprised myself sometimes when I thought one way or another way would always be less expensive. I also am surprised by people that WANT to keep; or to convert a system. It runs either way.

The key is to listen a LOT to find out what the goal of the people buying equipment actually is, ferret out any misconceptions of what might occur after the job is done, and weigh out the options that are left.

It goes without saying that I am delighted when the choice is to "keep the steam."

It isn't always about the bottom line. Sometimes it is, though. Gotta listen up front to find out WHY work is being considered and try to meet that goal.

In my opinion, anyway.

Noel

Bob Bona_4

As

wet in the head as I am, and as much as I love an old steam system, given the option for an average homeowner, I would convert. Steam systems are open systems, constantly corroding. They are really a hands-on system. The last thing a landlord needs is more maintenance, and tenant complaints. (I know this first-hand:)). Most steam boilers, new, are de-rated slightly in efficiency over their hot water brethren. How much will you save? Depends. It does stand to reason that heating water to 212+ degrees uses more energy than a modern boiler who's water temp can be modulated below 180.

There are two other factors that weigh in the favor of converting. Not that you can't make hot water off a steam boiler, it is just that it is much easier to do this with a hot water boiler. Then there is the matter of control, ie. zoning, more accurate temperature control, that can be achieved by converting. A hot water boiler just gives you more flexibility.

The old rad's may be a PIA to convert to hot water-there is always the option to replace or retrofit baseboard-, and there may be a some area's that need have walls opened up to run piping-what's a little drywall?- but all in all, IMO it is a project worth doing-for you. (sorry Steamhead)

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Mad Dog

All very good points, but....................................

not all steam systems were that oversized....here on long island..in the suburbs, you have average sized houses with steam systems installed in the 20's and '30s. By this time, the era of mass-oversizing was not as prevalent. Moreover, the last three "conversions" we did averaged $10,000.oo, required 2500.00 in carpentry repairs and another 1500.00 for the floor guy to make all the holes in the wood floors disappear. Furthermore, using your 1/8" tapping and "blowing it up" to 3/8 or 1/2" may work, but how "efficient" is that in and of itself? Additionally, Most people in this day-and-age DO mind exposed pipes. Lastly, "efficiency" as is so easliy bantied about by everyone and his brother - is overrated, misunderstood, and misused all too often. Jim Davis will fill you in on that scam.....Mad Dog

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Boilerpro

Pull the plug on pulling the plugs

I use the 1/8 inch tapping for the air vent at the top of the rad or the one pipe steam air vent tapping for the return flow tapping. This provides enough flow for most residential sized radiators using a 20 F delta tee and an NRF-22 circ or its equivalent. On big rads use both 1/8 inch tappings or increase the size to 1/4 inch. I'll try to attach a pic.

Boilerpro

Unknown

The 1/8 inch tapping will work ?

I would think that the small size , and the vent usually being in the middle of the radiator might give you problems ? Running small size tubing to the rads would be a breeze . What size and type of tubing do you usually run ? Sounds very intriguing . If you can find that pic , I would be grateful , thanks . Ron

Boilerpro

Yep

Just look at the internal diameter of an 1/8 inch nipple and then look at the diameter of a small standard port ball valve. I come out of the rad with a short 1/8 inch nipple and immediately jump up to 1/2 inch copper or come out with 1/4 inch and jump up to 3/4 inch. Got a home system set up this way for 4 or more winters and a church (big boy rads) for a couple of winters...works great. In fact the church is using a series 100 because the rads are on two zones with zone valves. I'll try the pics again.

Boilerpro

Boilerpro

And a converted big boy

found out the radiator tends to heat at a diagonal from the big supply on the bottom to the return taping on top. The previous pic with the return coming out of the middle of the side of the rad where the air vent was heats nice and evenly.

Boilerpro

Unknown

Thank you Boilerpro

Its just one of those things that you have to see done my someone else before you try it yourself . Sorta like seeing Noel's drop down header - I saw it and tried it on my next steamer , and worked great .

What did you do with the steam mains on that conversion ? If you kept them the same size , doesnt heating the extra water held in the bigger pipes factor in somewhere ? With steam , youre usually talking about heating a house in ounces of steam pressure , with a boiler that holds less water to heat , and usually no water in the big mains . I would love to see a side by side comparison of identical houses heated by steam and hot water - with the same radiators and boiler . I would bet the heating bill is pretty close ? Maybe . Take care .

Unknown

Which brings up another question

Hypothetical - Does it take longer to heat 2 boilers with the same water content - but one has no pressure and the other has , say 20 psi pressure ? I think I asked this question long ago about indirects - and excessive pressure slowing the heat transfer , but most responses said theres no relation between pressure and heat transfer .

Boilerpro

The mains are unchanged

the whole system is set up on full outdoor reset with two stage fired boilers piped P/S with Esbe thermix valves on the returns. Since the mains are usually under 140F, instead of near 200F or more, I would suspect the heat loss from the mains is less than it was with steam. I would suspect that a house with a steam system more closely resembles an older hot air system because both tend to superheat the air causing it to rapidly run to the ceiling, increasing heat loss and drafts. But steam radiator still has the advantage over hot air, because they deliver radiant heat. I'd also like to see a side by side comparison, including radiant floor, convectors and hot air. I believe the feds may have done this in the past, but don't know where to find the info... probably the Dept. of Energy.

Mark J Strawcutter

the only time

I mind exposed pipes is when I have to paint them :-)

Otherwise, we love our radiators and the downstairs rooms wouldn't be the same without a pair of pipes in the corner running up to a bedroom.

The kitchen looks rather naked since a previous owner's remodel concealed the set that ran thru there.

Mark

Steamhead

They did some of this research

at the University of Illinois, but I don't remember which campus.

And speaking of "improving a steam system's performance", BP- did you get a chance to Master Vent that system we looked at? If so, how far did the the fuel bills drop?

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Steamhead

But those hotter radiators

also radiate (rather than convect) more heat too. This is the kind of heat that warms you through to your bones, just like.... well, you get the idea ;-) . Not all of that heat ends up at ceiling level.

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Paul H.

hot water conversion



I have a new kink to this discussion.I have a vapor/vacuum system with a replacement boiler.I'm sure
this boiler is sized too big.There's also a leak in the
piping.What to do.Properly size a new boiler,fix the pipe
and keep the steam?Or is a conversion a better option now?

Paul

Unknown

Paul

What are your expectations? Is the cost of the change the priority? Is keeping the radiators a priority? Is total looks what you are after? Is the main thing the cost to operate and maintain it? Is the historical value of the heat an issue? Usually not, only nuts like me feel that way.

I feel that in general, if cost to run and maintain is the issue, change the piping and boiler and controls and design it from scratch for water, with new or old radiation.

The vapor would be cheaper to fix, boiler and all, usually. The variable is the leaks that you mentioned.

Vapor weighs a lot less in those old pipes, too. Water is pretty heavy. Check the hangers out if you re-use the old mains. The pressure will be higher, too.

Every job is different.....

Bob W._2

I face the same issue with my old house....

the old steam rads are part of the decor, and most have only a bottom manifold and can't be easily converted. I love the feel of the steam heat. I hate the cost. I also don't like the idea of heating the outdoors. But, a conversion to hot water would be really expensive here because we would have to buy all new rads, probably Burnhams, for the first floor, and panel rads for the other two floors. It been a real conundrum, thats for sure.

Rick Fenton

More Facts to Throw In

Man, I had no idea people actually read these messages.

All my radiators are hot water radiators (I think - they have plugs both sides, top and bottom). Again, they're now hooked up for one-pipe steam, a boiler for each of two floors. Also, all my pipes to the second floor are in the room - no need to tear into walls.

My goal is to minimize gas consumption over the long term. I'm willing to pay a little more up front than I would if my only interest were rapid monetary payback.

My system has always worked great. So simple - millivolt thermostat getting electricity from the pilot lights, so no worries about power outages, no pumps to break down, no water to freeze or leak. (The pilot lights are gone on new boilers, so the immunity from power outages is out with new equipment now, right?) A little noisy, but I don't notice any more. I'd be happy to stick with steam, even if I knew it only would use a little more energy. I hear there is a way to zone steam coming off a single boiler. But I want to look into all options, with the primary goal of saving long-term gas use in this big old house.