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Is it possible? Convert 200kBTU Steam Boiler (2017) to Low Temp Hydronics

mrmikesimonsmrmikesimons Member Posts: 7
I'm closing on a house in central MA next month. It is a 2500 sqft home built in 1909 with single pipe steam heat tied to a 200kBTU boiler installed 2 years ago. This system provides the distribution for the main part of the home, and a 70kBTU hydronic boiler for an in-law apartment for the addition. For the last ten years, I have worked in energy efficiency (Mass Save program) and will be retrofitting the home and (hopefully) significantly bringing down the load.
Here are my concerns-- for a regional conference this year I have looked really closely at Manual J sizing for different envelopes of homes. For an equivalent home, I was getting around 36BTU/sqft which would put the home's design load at ~90kBTU. So I'm thinking that with the home's existing systems they would be over 200% over-sized when taking into account distribution losses, cycling losses, etc.. I have seen the previous owner's gas bills and they paid around $1,000 this past January in heat, which makes me feel like my already horribly over-sized assumption is correct)

About a year back I attended one day workshop on pellet boilers ran by John Siegenthaler, were I was introduced to the concept of thermal storage and pairing it with low temperature hydronic distribution.

So a few thoughts--
*Is it possible to pull out the steam distribution system, save the boiler and lower the temperature of the system that it is just supplying heat to thermal storage? Which would be tied to new low temp hydronic radiators?
I'm interested in low temp hydronic, because I'm looking forward to the day that air-to-water heatpumps are market ready in the US, and would love to power my heat off renewables + storage (when that day comes) and/or tying the system to Solar Thermal to provide the bulk of the heat during the shoulder months.
*Would it make much more sense to just leave the steam system alone, and any new distribution should just go off of the existing hydronic boiler? That system is over 20 years old, and I would love to only have one system to maintain.
*Should I just slap in a few ductless mini splits because it will be both cheaper and easier, and wouldn't have to deal with window A/Cs.

Many many many thanks,

Putting the fun in fundamentals of energy | Central MA


  • ethicalpaulethicalpaul Member Posts: 1,623
    edited July 8
    I like where you're mind's at. I too have often done work where I had no chance of payback in my lifetime.

    But a couple questions come to mind:
    - The system may well be oversized (almost guaranteed) but why would that be the cause of high monthly fuel costs? Even in an oversized system, the BTUs go into the house envelope, yes?
    - You mentioned air to water heat pumps. I love heat pumps but have you considered water to water?
    - The thermal solar heating sounds great, but it's really hard to get enough btu to heat a house with it I think.
    - Get ready for a barrage of opinions that you should keep the steam system in place (and I would agree with them)

    People will also be interested to know the EDR of your attached steam radiation. If any of my questions are annoying, feel free to ignore them, but those are what came to me. (I’m a fellow homeowner)

    I'll be interested to see if anyone else thinks something to look into would be to keep the steam boiler as is for the main house and run hot water loop(s) off of it for the addition, getting rid of the old water boiler.

    I think some folks will say it's OK to convert your steam boiler to water...many boilers are either with minor changes at the factory.

    1 pipe Utica 112 in Cedar Grove, NJ, coal > oil > NG
  • jumperjumper Member Posts: 1,464
    Anything is possible. I've repurposed steam boilers to HHW boilers. Remove level control. Main issue is return size.
  • george_42george_42 Member Posts: 86
    Some water to water heat pumps deliver water as high as 145 deg. You need about 159 ft of well for each ton . around here two 300 ft wells are about 6 to 8 thousand . I have it in my own home and would have nothing else
  • Jamie HallJamie Hall Member Posts: 12,947
    You can do it. Yes. Question is, do you want to, and what would it gain?

    As @ethicalpaul said, you'll likely get some folks who think you should keep the steam. With which I agree. The fact that the boiler is almost certainly oversized does have an effect on efficiency, but not as much as one might think. Most of the efficiency hit can be removed with proper control strategies.

    The very first thing to keep in mind is that a BTU is a BTU, no matter what the energy source is or how it is delivered to the structure.

    With a two year old boiler, the chances are that its efficiency is very good already, assuming that it has been properly maintained (a big assumption) and was installed properly in the first place (another big assumption).

    So let's look at this. The first step with a steam system is sizing. Steam heat boilers are NOT sized by manual J. Rather, they are sized to match the installed radiation So, to find out how much too big your boiler is -- if it is! -- you need to determine and add up the "EDR" of the radiators to which it is attached. Then we can begin to think about control strategies to maximize its efficiency. Those are invariably relatively cheap -- and very cheap, in comparison to ripping out the existing system. Perhaps more to the point, similar control strategies (just different switches) would have to be used to use that boiler for low temperature hot water heat -- so nothing would be gained.

    If the boiler is really significantly oversized, what you could do is to replace the existing hot water boiler for the in-law apartment with a system taking the hot water -- though a heat exchanger -- to serve that load. That works very well in a number of applications.

    Bottom line: keep the steam, work on the system to get it running right, and use the excess capacity to heat the in-law apartment and ditch the 20 year old boiler used for that.

    Now. Down the road you may want to spend the capital -- and it will be a lot -- to switch to some low temperature arrangement. That will require a new heat source (otherwise there is no gain in efficiency) -- either a mod/con boiler or, if the technology advances enough, a heat pump and all new plumbing and radiators.

    A much better bang for that buck will be to tighten the house up as much as possible -- better insulation, draught sealing, better storm windows, etc.

    Unless the house was designed and built with solar thermal in mind, you won't be able to get enough to heat it in the winter time. Not that it can't be done -- it can, in new construction -- but not as a retrofit. And please learn as much as you can about where your -- and your community's -- electricity comes from. It's not renewables, and won't be for quite some time.
    Br. Jamie, osb

    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England.

    Hoffman Equipped System (all original except boiler), Weil-Mclain 580, 2.75 gph Carlin, Vapourstat 0.5 -- 6.0 ounces per square inch
  • SteamheadSteamhead Member Posts: 13,867
    @mrmikesimons , @Jamie Hall said it all. Keep the steam and use the knowledge you gain in your work with MassSave.

    Besides the total radiator capacity (EDR), tell us how long your steam mains are, what pipe size they are, and what main vents are on them. Also, the make and model of your boiler.
    All Steamed Up, Inc.
    "Reducing our country's energy consumption, one system at a time"
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service
    Baltimore, MD (USA) and consulting anywhere.
  • The Steam WhispererThe Steam Whisperer Member Posts: 520
    Improving the thermal performance is first priority. I had a similiar age wood frame home of around 3200 sq ft on 2 floors and with the thermal upgrades we completed the annual natural gas bill was about $1000.00 ( no new windows except in a small new addition) in northern Illinois ( 6300 DD climate, pre global warming) Heat loss @ -5F was around 45,000 btu/hr or 12 to 15 btu/sq ft. The home had large glass areas to the south and east so a lot of the heat load was picked up by passive solar. Going from the old 1960's CI boiler to a condensing boiler running with an exhaust temp in the 90F range ( about 98% efficiency) only saved about 20% on gas, but the increase in electrical usage and maintenance on the high tech boiler easily wiped out those savings. Steam requires almost no electricity, so there is an additional savings there.
    To learn more about this professional, click here to visit their ad in Find A Contractor.
  • jumperjumper Member Posts: 1,464

    saved about 20% on gas, but the increase in electrical usage and maintenance on the high tech boiler easily wiped out those savings. Steam requires almost no electricity, so there is an additional savings there.

    My experiences with multiple efforts to save energy. Most cost effective is sweater & hat for anyone who doesn't enjoy 55°.

  • GWGW Member Posts: 3,766
    If you’re on a tight budget, sure. By the time all the kinks get worked out, for a few bucks more you can have the real thing.
    Gary Wilson
    Wilson Services, Inc
    Northampton, MA
    [email protected]
  • The Steam WhispererThe Steam Whisperer Member Posts: 520
    Essentially what I did was put the sweater and hat on the house. Solar gain was enough to keep the heating system off for about 7 hours a day on typical winter days. The last winter we owned the home, we were not living there and had the stat set at 60F. With the passive solar our midwinter worst gas bill was around $60.00 that year.
    To learn more about this professional, click here to visit their ad in Find A Contractor.
  • mrmikesimonsmrmikesimons Member Posts: 7
    @ethicalpaul Thanks so much for taking the time to comment and add your insight. I think the big thing for me going into this is knowing that I'm going to be paying someone, and I would much rather be sending my dollars to a good plumber than the utilities, and when I am spending money for energy, I would like those dollars to be going as much as possible to growing the renewable energy marketplace in the northeast. So yes, it isn't totally about payback!

    But a couple questions come to mind:
    - I have a lot of reading ahead of me, to get a better understanding of EDR and seeing what I can likely do about the extra capacity of the steam system. There are two disconnected single pipe steam radiators in the basement, and there is electric baseboard in one of the bedrooms, so I think step #1 is going to be getting a good plumber into the home to help me figure that out, and teach me what I need to be doing to properly maintain the system.
    -As for geothermal systems, earthwork is super expensive in MA. I don't have a full picture of why. But most geo-systems for the earthwork, ground loop, hardware, and distribution is around 30k. I don't think that I have the tax liability to take the full 26% federal rebate. Also in MA, we have these alternative energy certificates that really helped offset the cost of these systems, however they recently allowed combined heat and power systems to qualify and they have completely tanked the market on how much these would be worth.
    - As for solar thermal, I was just thinking that maybe we could get enough on the roof to cover just the shoulder months the majority of the time. I am strongly considering it for the domestic hot water, which is somehow configured into our steam boiler (I currently don't know if it is tied to the return condensate side, or if there is already a separate hot water loop tied to the heat exchanger, zero idea). I think either way, I'm interested in preventing the boiler from firing as many month of the year as possible.
    - As for the barrage of opinions keeping the steam, I'm grateful for them all! I read Dan's book "You got steam heat..." a few years back (before I had steam heat!) and saw him present at a conference, and became aware of this forum. Like it is good to know that while yes, there is currently something less than ideal in my basement-- with some sweat, and money, I can at least gain control of it, and understand what is needed to make it right.

    I'm really curious about exploring the separate hot water loop, covering the load of the addition and being able to remove the FHW boiler, but then I'm thinking that maybe a lot of the extra capacity of the boiler may be going to the indirect DHW? We shall see.

    Thanks again for you thoughtful comments and the warm welcome.
    Putting the fun in fundamentals of energy | Central MA
  • mrmikesimonsmrmikesimons Member Posts: 7
    @george_42 I would love to get geo but it is out of our budget, right now. And with planning on doing a lot of weatherization work and hopefully dramatically bringing down the load I'm not wanting to pay for earthwork that we won't later need. Is your distribution forced air or hydronics or both?
    Thanks for chiming in!
    Putting the fun in fundamentals of energy | Central MA
  • mrmikesimonsmrmikesimons Member Posts: 7
    @Jamie Hall
    First off extremely thankful for taking the time to reply so thoughtfully. I have a lot to learn and look forward to getting in the house, and getting the Steam system back to how it was originally operating!

    I just want to get on the same page as you when you say control strategies. By that term are you referring to making sure that the thermostat is set to one cycle per hour, or are you talking about thermostatic control valves for each of the radiators, or is this more tied to the controls around the actual boiler?

    With your comment about BTUs, I guess where I'm looking for more insight into this, is I know how many BTUs are in a kWh of electricity, a therm of gas, etc. I guess what I'm not 100% on here, is that from my training (BPI) with Steam systems that you more or less discount the efficiency by 75% for distribution ( Standards for the Heating Professional.pdf).
    Compared to a ductless unit, were all the energy is being transferred right into the living space. Is it your belief, that a well maintained, insulated, and tuned steam system has much lower distribution losses than the table that they have on page 6?

    With the boiler being only a little over two years old, could have much damage been already done by neglect and not maintaining it? It is gas, and I do know from my experience with energy auditing that for a lot of home-owners they never get their gas systems serviced annually compared to oil fired systems. As far as the install goes, I guess I'll be finding out very shortly on whether it was installed right.

    If in very layman terms, could you add some insight into how I should be thinking about EDR and capacity. Say the boiler is 85% efficient, it is 200kBTU/hr, I believe that I would have 170kBTU/hr output. If I calculate the EDR of all the radiators, and they sum up to 100kBTU/hr, does that mean that I have 70k left over for supplying the indirect storage tank and the in-law addition? And then I guess the follow-up question would be what would be the consequence of not having anywhere for those additional 70kBTUs to go?

    I think that everyone on here has me convinced to just keep the steam for hydronic heating. Maybe I'll supplement / offset it with ductless just sized for the cooling load in MA. Gas is cheap up here and electricity is not. And tying back to your comments about the fuel mix going into our grid, yes it is currently 70% natural gas. However every year it is getting cleaner and cleaner as renewables get cheaper and cheaper.
    One thing that I wasn't really thinking about with Steam that got brought up by a few comments is how little electricity it uses, which is a huge plus for solar+storage and being able to stay in your home all winter long when there are power outages.
    Central MA was hit by a pretty bad ice storm a few winters back and I personally know people that were out of their home for 2 weeks-month. So being able to stay in the home with the heat on, because the steam heat isn't chewing through the battery sounds fantastic.

    Once again, thanks so much for your considerate comments, your insights have been very helpful for me.
    Putting the fun in fundamentals of energy | Central MA
  • mrmikesimonsmrmikesimons Member Posts: 7
    @Steamhead Thanks for your comments. I can't wait to get in the home and get this steam system figured out. I look forward to having the best running steam system in Central MA!
    Putting the fun in fundamentals of energy | Central MA
  • mrmikesimonsmrmikesimons Member Posts: 7
    @The Steam Whisperer
    Thanks for your insight. What was the annual bill before tackling the improvements. The seller of the house is paying $3,000 a year for heat and hot water which is pretty crazy for a 2500sqft home. Our home gets great southern exposure, what strategies did you use to get the most solar gain out of the windows? I think for the 1st year, I'm planning on building interior storms for the windows on the north and east side of the home and will eventually replace them as finances allow.
    I think my curiosity of moving off of steam wasn't so much a boost in the boilers efficiency but more in the distribution efficiency, however your comments really highlighted that steam systems would pair extremely well with Solar+Storage because the heating system won't be draining the battery like a forced air/water system would.
    Curious to hear what weatherization projects you were able to tackle in.
    Thanks again,
    Putting the fun in fundamentals of energy | Central MA
  • george_42george_42 Member Posts: 86
    My distribution is forced air but they do make water to water units that can give temps high enough to go radiant.I have 3000 sq ft in Penna and for air or heat my cost is 70 to 80 per month average. Remember there is a federal tax credit for geo of 30% , also some utilities and states also give rebates
  • mrmikesimonsmrmikesimons Member Posts: 7
    @george_42 That bill is what I'm wanting. hahah! I believe that the federal rebate dropped down to 26% like Solar PV, but I don't think that I have the current tax liability to be able to fully take advantage of that. Also in MA the incentives for geo kind of stink right now. It isn't one of the qualifying technologies for the 0% interest loan for energy efficient equipment, and as I mentioned in reply to someone else's comment there is a program in MA called alternative energy certificates, but they recently allowed combined heat and power systems to qualify and it has completely tanked how much these credits would have been worth. What type of COP do you think that your geo system is running at?
    Putting the fun in fundamentals of energy | Central MA
  • george_42george_42 Member Posts: 86
    I am running a climatemaster tranquility 22 4 ton with about 4 cop
  • Jamie HallJamie Hall Member Posts: 12,947
    @mrmikesimons -- a few comments on your post.

    Control strategies. It's partly making sure the thermostat is really compatible with steam (some of the modern whizzy ones aren't, really, without a lot of tweaking) and set to one cycle per hour, and making sure the pressure control is adjusted correctly, but if the boiler really is badly oversized, it may also mean adding a time delay arrangement on the cutin after it cuts out on pressure. This can do wonders on a seriously oversized boiler.

    On the hot water for the inlaw apartment and domestic hot water Keep in mind that the rating of a steam boiler, in EDR, includes what is know -- perhaps misleadingly -- as a pickup factor. If the rest of the system is operating properly -- particularly good vents -- but the boiler is oversized (we do need to know that!) that pickup factor output can be used for the hot water heating loop with no problem on the steam side. It's also available for domestic hot water, but if your system has -- or could have installed, an indirect tank of some reasonable size, that's actually a pretty small average load. Even if it is just a tankless coil in the boiler, it's usually not a problem.

    Two years of deferred maintenance shouldn't be a problem on the boiler -- though the technician may use moderately strong language while working on it.

    Efficiency of steam systems is much better than that publication suggests -- provided that they are installed properly and maintained. Among other things... pressures correct. Venting adequate (both of these things are very commonly not done) and the pipes are insulated. I honestly don't know of any hard numbers on distribution system losses, but one can make a rough estimate based simply on how much heat the pipes radiate (which isn't a true loss, of course, if they are in the conditioned space), and if they are insulated the losses are minor; if they aren't, the loss is around 120 BTUh per foot for a 2 inch iron pipe -- so if you have 100 feet of pipe, total, and a connected load of say 120,000 BTUh, the uninsulated pipes will cost you around 10% of that. Insulated pipes would cut that to around 2% to 3%. As I say, that isn't a true loss, unless the pipes are in an unconditioned space such as a crawl space -- in which case, add more insulation...

    Your numbers on Gross Input and so on are basically correct. It's worth remembering, though, that the net output and efficiency are very much affected by good maintenance and adjustment of the burner. It is important that the burner be adjusted with accurate instruments, used correctly -- it can't be done by eye or ear. This applies to any fuel burning equipment, though -- whether it is your boiler or hot air furnace, or your car (well, maybe not your car anymore -- modern cars have sensors and computers which are constantly measuring and adjusting the fuel/air ratio -- and which are very expensive)(that's what drives the dreaded "money" (check engine) light!).

    And yes, if it turns out that your net output is 170k BTUh, and your connected EDR works out to 100k BTUh, you have 70K left over for the DHW and the addition. Where does it go if it isn't being used? That goes back to control. The pressure will rise because you are making more steam than you condense in the radiators, and the pressure control will turn off the burner. The pressure then drops as the steam condenses and the boiler turns back on. And so on, until the thermostat is happy. This effectively reduces the average output of the boiler to what the radiators can handle. If the boiler and the radiators are matched, it doesn't happen. In many systems, with the boiler only slightly oversized, it happens only towards the end of longer calls for heat. In those cases, not a problem. If the boiler is really oversize, then the constant cycling is not only annoying, but does reduce overall efficiency -- a very good argument, in your situation, for heating that addition and the DHW with the boiler!
    Br. Jamie, osb

    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England.

    Hoffman Equipped System (all original except boiler), Weil-Mclain 580, 2.75 gph Carlin, Vapourstat 0.5 -- 6.0 ounces per square inch
  • The Steam WhispererThe Steam Whisperer Member Posts: 520
    We were doing a complete renovation and the walls were 2x6 Balloon framing. We installed R-19 or R-21 batts in the wall, carefully trimmed. We also followed the air tight drywall methods ( Canadian) to air tighten the house... The drywall was sealed to the studs were it meet an outside wall, The conduit and outlets were sealed in place, the drywall sealed at the top and bottom. The ends of the joist bays were blocked with foam board and sealed. The original double hung windows were reglazed and weather stripped with bronze weatherstipping to tighten them up. The windows had old aluminum storms to boost the r valve ( today I use low e storms on our current home). Finally we laid a layer of r-19 over the finished attic floor that had blown in Rockwell between the 6 inch joists. WE rebuild and weattherstripped the original basement window and sealed the seal beam edges and to the top of the foundation. This last item (completed after most of the other work) increased the basement temperature about 7 to 10 F on a typical winter day.

    The BPI data is probably for a very poorly maintained and performing system. Typical old basements with properly insulated steam piping will stay in the lower 60's or even 50's, so there is very little waste, since some heating is needed in basements to prevent freezing pipes.
    When it comes to electrical usage, a typical gas steam boiler for a home uses about 1/80 the electricity ( not 1/8) of conventional forced air and about 1/10 or less than hot water. "HI Efficiency" hot water boiler use substancially more electricity than old cast iron models, due to typically 2 circulators ( running all the time with outdoor reset), a draft motor, sometimes condensate pumps, and all the electronics.
    To learn more about this professional, click here to visit their ad in Find A Contractor.
  • dopey27177dopey27177 Member Posts: 306
    keep the steam system. If your boiler is very over over sized for the your heating load and domestic hot water you can remove the hot water boiler and install an insulated storage tank with a coil to heat the water needed to circulate in the water heating section of the building. the steam boilers duty cycle will be greater as it is used to heat two systems. As far as saving energy I can not give you a percentage but you will save on the installation of a new boiler for the water heating system of the house.

    In your case insulating all the stem piping, water heating piping and the structure is the way to go for rel energy savings.

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