1 or 3 furnaces for a multi unit?

Discussion in 'Plumbing Forum, Professional & DIY Advice, Tips & ' started by mmcdade, Jul 15, 2007.

  1. mmcdade

    mmcdade New Member

    Messages:
    7
    Location:
    New England
    I have a 3 unit I live in located in Portland, Maine. I pay for the heat for the whole building since there is only 2 furnances.One furnace is a old steam unit that is about 50 yrs old that heats the 1st floor unit I live in. The other furnace heat is hot water baseboard (about 30 yrs old). It heats the 2nd & 3rd floor unit. So I have to pay for both the units heat since there utilities are not separated. The heating bills are killing me. I have replaced most windows in this 100 year old house, and will replace the remaining one this summer. I'm trying to decide if I should spend the money and purchase a boiler for each unit so they would pay for there own heat & hot water. Or should I buy one furnace that would take care of the entire building? I plan on staying here for a long time, so my gut feeling is to get a separate boiler for each unit. I have quotes being given to me for combi units for each apartment. For the 2nd and 3rd floor units, one contractor suggests a baxi HT 330, the other a biasi riva combi with has a 15 gallon integrated indirect water tank. I think these are both condensing boilers; both are for heat & hot water. Each unit is about 1600 sq ft with one bath. For the 1st floor unit, which I live in, I want to continue to use the nice cast iron radiators. One contractor thinks I can change them over for hot water use with a Prestige Solo condensing boiler with an indirect fired SMART Phase III water heater. My unit is about 1600 sq feet a well.
    After look through the site here, it looks like many in the Northeast are recommending the Buderus boiler with a mega Store indirect water heater. It seems they have a branch in NH. jadnashua , the moderator seems to have gone this way. Any advice for other solutions for me to look at would be appreciated.
  2. GrumpyPlumber

    GrumpyPlumber Licensed Grump

    Messages:
    1,404
    Location:
    Licensed Grump
    I think you meant "Superstor", the Ultra comes with a lifetime warranty, as does the Buderus.
    First and foremost You need to sit down and know what you can spend.
    The more efficient the more money, you can pay as little as $4500 - 5K per boiler, or as much as 15K for a high end Buderus or Viessman condensing boiler that runs better than 95% AFUE, and you might not want, or have that much to spend on 3 seperate units.
    As you stated, you're there for the long-haul...so this is something you definitely want to research..I'd be more than happy to help, as long as you're not too hard on your plumber...he could wind up grumpy like me.
  3. mmcdade

    mmcdade New Member

    Messages:
    7
    Location:
    New England
    I'd be happy with any help you could provide. I have been quoted $5950 for each Baxi HT 330 units. They are condensing units with a 98% efficiency. It seems kinda high for this unit?.. but I'm just comparing the prices found on the net. If I purchased a small Buderus boiler for each unit what would that cost? Should I get a indirect for each unit? I guess the reason one contractor suggested a indirect water heater for my unit is that my old cast iron raditors would require a good deal of flow. Again, I just guessing.
    Also each unit only has one bath, but I will be adding a 3/4 bath in my unit.
  4. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,641
    Location:
    Cave Creek, Arizona
    boilers

    The largest reason for going with individual boilers is that the tenants could then set their own heat level. Otherwise whoever has the thermostat determines how warm or cold the other one will be. How will you separate the fuel and electical costs if there is only one meter?
  5. GrumpyPlumber

    GrumpyPlumber Licensed Grump

    Messages:
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    Licensed Grump
    You're in this for the longhaul, so start first by looking up the warranty info.
    I know Buderus, Munchkin and Viessman offer limited lifetime warranties.( I'm too lazy to look up baxi online...I'll leave that to you!)
    You'll need to know something...condensing boilers work best at lower temps.
    Where a regular Burnham or Weil MacClain might operate at 180 degree's...the condensing boilers run at full efficiency at lower temps...around 130-160.
    I know the buderus only runs at about 95% at 130 and about 90% when it's at max temp of 190+.
    (Which is still pretty good)
    The pricers you stated sound about right, but thats a very open ended question...all depends on the BTU requirements (based on square feet, windows, wall insulation..etc) for each unit, number of zones, and how labor intensive the replacing will be, and also whether you're adding 3 DHW (indirect water heaters)
    For example, the vents aren't able to go where the existing draft vents go...so they have to be run seperately to the outside of the house...which depends on accessibility, windows, door openings are a restriction for where the vents can go, they also require intake vents, unlike the old boiler.
  6. mmcdade

    mmcdade New Member

    Messages:
    7
    Location:
    New England
    Baxi have a 10yr parts & Labor warranty for these units. Its about 4oo extra for this, but I think worth it.

    You'll need to know something...condensing boilers work best at lower temps.
    Where a regular Burnham or Weil MacClain might operate at 180 degree's...the condensing boilers run at full efficiency at lower temps...around 130-160.
    I know the buderus only runs at about 95% at 130 and about 90% when it's at max temp of 190+.

    Thanks, I didn't know that

    (Which is still pretty good)
    The pricers you stated sound about right, but thats a very open ended question...all depends on the BTU requirements (based on square feet, windows, wall insulation..etc) for each unit, number of zones, and how labor intensive the replacing will be, and also whether you're adding 3 DHW (indirect water heaters)
    What are the benefits of indirect water heats???

    The vents are going out the basement wall. Each apartment has its own thermastat to control heat in just thier apartment. Thanks again for your help.

    I'll have to figure out what BTU are required for each 1600 sq ft unit.
  7. CHH

    CHH New Member

    Messages:
    225
    Location:
    Denver, CO
    The BTU requirements for an existing system are fairly straightforward assuming the units have baseboard heat. Just measure the baseboard radiator length and multiply by 600 BTU/ft. Ok, your particular baseboard radiator might not be exactly 600 BTU/ft so check that it is a single 3/4" copper tube with aluminum fins. Next check the average heat load requirement based on square footage. Now check the heat load calc based on structure.

    So now you've got three different BTU numbers. What to do? Well, ya can't radiate any more than the max capacity of the baseboard radiators so there's not much sense in putting in much more heat capacity than that. Unless one of the units is cold in the winter then ya gotta add radiator but that is a different problem.

    The good thing about the mod-cons is that they can handle a range of heating requirements. When you're looking at units, they'll have a minimum and maximum BTU input. Multiply those numbers by the average efficiency of the unit to get an idea of the BTU output range. Typical burners range down to 1/4 or 1/5 of max output but check the ratings for a particular unit.

    While you're doing all this check with local utility for rebates on installing mod-cons and check tax code for credit based on boiler efficiency.

    Or just call a qualified HVAC guy. Your choice.
  8. GrumpyPlumber

    GrumpyPlumber Licensed Grump

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    Ironically I multiply actual sq footage by 35, but thats a generic formula to establish a basic btu need...you still need to factor in exterior wall insulation, windows (especially older non insulated, non thermal pane)...height of ceilings...etc.
    Also...you can take the figure you get from dividing by 570 (your 600 number is close) for linear footage of slantfin #30 baseboard.
    I have a calculator from slant fin on my pc thats much more "accurate", ironically it's usually about the same.
    Last edited: Jul 17, 2007
  9. GrumpyPlumber

    GrumpyPlumber Licensed Grump

    Messages:
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    Location:
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    I will say this, the Buderus's smallest wall mount would likely accomodate a 1600 ft unit, would likely cost the same, but comes with a lifetime for no extra money.
    Ask your plumber to research it, he might sigh, but this is your longterm investment.
  10. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,015
    Location:
    New England
    An indirect wh is one is configured like a heating zone for the boiler...it doesn't have any self-contained heating like electric elements, or a burner and flue. It has a coil inside, heated by the boiler. It is as efficient as the boilerl often in the mid-90% range. Because it has the max heat of the boiler to reheat the water, you can often get by with a significantly smaller WH, and still get great recovery.
  11. mmcdade

    mmcdade New Member

    Messages:
    7
    Location:
    New England
    I will figure out the BTU requirement as several have suggested. Thanks

    jadnashua
    So your saying you are able to use a smaller boiler like the Buderus GB142-24 if you use a indirect water heater. I assume this is the setup you went with and you seem to be happy with it.

    Also since you live near by can you recommend any installers that know this unit (Buderus) that I could get a quote from?
  12. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,015
    Location:
    New England
    Harry Wells did mine. They aren't the cheapest, but they come when they say and do a decent job. I did have to have them come back and fix the vent, it was icing up, and was actually installed upside down (although intuitively, they did it in a logical manner - but it needs the exhaust on the bottom or it ices up in the version I have, they had it on top). The smallest boiler they have is 80K BTU, which is twice the value of most WH, which is why you get a good recovery rate when using an indirect. Most of these treat the WH as a priority zone, which means it can direct all of the heat to the WH instead of heating the house for that short time needed to bring it back up to temp.
  13. mmcdade

    mmcdade New Member

    Messages:
    7
    Location:
    New England
    Thanks for all the help. I will have a Buderus unit quoted out for me with a indirect WH. I like the idea they have a location in NH and that many here seem to recommend them. What size Superstor Ultra Indirect Hot Water Heater would I need for my unit. It is just me & my wife with a occasional visitor visiting for a weekend. Would a 20 gallon unit be enough for showers, laundry and for the old cast iron raditors?


    Thanks again for all the help.
  14. mmcdade

    mmcdade New Member

    Messages:
    7
    Location:
    New England
    Thanks for all the help. I will have a Buderus unit quoted out for me with a indirect WH. I like the idea they have a location in NH and that many here seem to recommend them.
    Thanks again for all the help.
  15. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,015
    Location:
    New England
    The best thing to do is go to the site for the super stor and look at the first hour recovery rates and the other numbers. BTW, it doesn't have anything to do with the rest of the heating system. They have charts on their spec pages that show how much water you expect to use at one time and for how long. A shower uses about 2.5 gallons per minute, so that will give yo ua reference and starting point to decide.
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