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Current oil steam & HW baseboard; going to gas, worth converting to all HW BB?

WWood_WWood_ Member Posts: 5
I currently have an oil steam & hot water boiler serving 3 hot water baseboard zones (part of prior homeowners renovation 10yrs ago) and a steam zone (running upstairs and downstairs) with cast iron radiators in the old part of the house (1930s).  We've only been in the house for 1 winter (Massachusetts) and there weren't any major issues I noted, other than a ridiculous heating bill.  Separate propane-fired hot water tank will get replaced.

Converting to gas, and trying to decide whether its worth the additional cost & headache of turning the steam zone into 2 hot water baseboard zones (one up, one downstairs) and thus only having a single high-efficiency hot water boiler.  There aren't any slam dunk routes to run piping for baseboard, so it may get a little messy.

So the main questions I have are: 

How much less efficient will the combo steam/radiator & hot water/baseboard set-up be vs a strictly hot water baseboard. 

What are some of the better gas-fired steam & hot water boilers? 

Does it make any sense to have 2 separate, smaller boilers - one for the hot water zone and one for the steam? 

Can I do an indirect fired hot water tank of a steam boiler.

Let me know if you need any additional details or clarifications.


  • BobCBobC Member Posts: 4,441
    How big

    is the house and how close is the boiler to the heating load of the house? What kind of boiler do you have and how old is it? A steam boiler has to be sized to meet the EDR (sq ft of radiator surface), if it's too small some radiators won't get hot all the way across on really cold days, on milder days they don't get hot all way across because the thermostat usually shuts the system down. If the boiler is too big it wastes fuel. A good steam system is VERY hard to beat on comfort and operating costs. As long as your not pulling a huge number of BTU's with a hot water loop it's usually very efficient. Don't just go by quoted efficiency claims because they are usually only acheived on very cold days and in Massachusetts we don't usually have a lot of frigid days. Your better off beefing up the insulation and air sealing.

    Unless it is a huge house separate boilers are not worth is because they don't make boilers small enough on the steam side (my 1100 sq ft house has 210 EDR and the smith boiler is rated at 283). i went with a wet based boiler with a gas gun in it because i know they are more efficient than atmospheric boilers but 290 is about as small as they come. With a gas gun you can dial the gas down and make it fire lower (30+%) than you can with oil (10-15%) and gas is a lot cheaper than oil.

    Before I thought about ripping everything out I'd get a good steam man in to see what needs fixing on the steam system. It's hard to make an economic case for switching over unless your willing to spend a lot of money and the installer you choose does everything right.

    You should be able to use the steam boiler to run an indirect water heater. Are your hot water needs high enough to justify one? My 40 gal gas hot water tank only costs me $16-18 a month in non heating months but my hot water needs are very modest.

    Post some pictures of you boiler and the piping around it and find a good steam man to evaluate what you have now.

    Smith G8-3 with EZ Gas @ 90,000 BTU, Single pipe steam
    Vaporstat with a 12oz cut-out and 4oz cut-in
    3PSI gauge
  • WWood_WWood_ Member Posts: 5
    edited September 2013
    I probably broke a cardinal role of heating systems

    But I already took out the existing boiler.  It was a ~12 year old Weil McClain steam & hot water boil.  It seemed to run fine, but the real driver was getting gas on the street and the savings vs oil.  I'll post the exact specs later (BTUs, etc..).  So with the boiler out and gas line and meter in, there's no going back.  I can take a picture of the pieces in the garage, but not sure it will be as helpful.

    The house is ~2,300 sq feet.  The boiler is in the basement effectively in the center of the house. 

    One of the upstairs bedrooms that is heated by steam is the coolest of the steam-heated rooms and is also the furthest away from the source, so it's possible the system isn't operating optimally.

    I imagine insulation isn't ideal in the steam-heated rooms since they remain original parts of the house.

    Our hot water bills have been $80-$90 per month in recent months.  20-25 gallons of propane at $3.65 or so per gallon.  It is only 2 of us, and while my wife likes long showers (probably 15-20 mins?  EDIT:  we have a Kohler rainhead, i'm guessing it is 2-2.5 gallons per minute)  it still strikes me as an absurdly high bill.  The 12 year old tank has recently began leaking and clearly in need of replacement.
  • BobCBobC Member Posts: 4,441
    Nat gas about 1/3 as much for hot water

    Your propane use averages 22.5 gal per month for hot water and that is 20.6 therms of gas. Natural gas in the Boston area was 90 cents per therm (gas plus delivery) plus a $10 customer charge last month so if a new efficient gas hot water tank  used 20 therms a month that would cost about $28 a month for hot water. You have to decide if the cost of an indirect (over and above a new gas hot water heater) is worth it to you; in the long run it would be but it depends on how long you think you will be in the house. BTW the cost of gas goes up in the heating season.

    If only that one room did not seem to heat well I suspect something is wrong with that radiators piping or it's venting and perhaps the steam system main venting was too small and that starved that radiators steam supply (because it's the last radiator on the line I'll bet the venting was not what it should be, assuming the piping was correct). It's worth having a good steam man take a look before taking a saws-all to all the plumbing. Tearing it all out  gets expensive, fixing that steam system might  save a lot of cash.

    I'm only a homeowner but I've lived with steam for over 60 years so I would look before I leap into a whole new system.

    Smith G8-3 with EZ Gas @ 90,000 BTU, Single pipe steam
    Vaporstat with a 12oz cut-out and 4oz cut-in
    3PSI gauge
  • Jamie HallJamie Hall Member Posts: 6,694

    to hot water baseboard would be, in my opinion, a last resort.  A much better approach would be to evaluate your existing steam radiation and get a boiler properly sized for that and hook it up.

    However, you will almost certainly also need to work on the main and radiator (if it's single pipe steam -- you don't say) venting to get it right.  You will also have to be careful, while installing the new boiler, to match the water line as closely as you can to the old one, and to make sure that all the pipes pitch in the right direction.

    Even with that work, a new steam boiler will be much cheaper over time and involve much less hassle than ripping everything out and putting in hot water and baseboard!

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

    Hoffman Equipped System (all original except boiler), Weil-McClain 580, 2.75 gph Carlin, Vapourstat 0.5 -- 6.0 ounces per square inch
  • WWood_WWood_ Member Posts: 5
    Interesting math

    Looking forward to savings any place I can get it.  I had not considered going with just a new direct hot water tank, but I will look into the cost difference and possible savings. 

    At this point it's tough to know how long we'd stay in the house but it could be anywhere from 5 years to forever. 

    Will certainly have a qualified individual take a look at the piping assuming I keep the steam system in tact (most likely).
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