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Multi Family Heating Help

ChrisS1981 Member Posts: 1
edited December 2022 in Gas Heating
Hope you guys are staying warm and healthy. I'm new here and can certainly use your advice.

My mother in law owns two *identical* multi family homes in Hartford CT. These are big houses, 4300 SQ FT, 3 floors. They are currently heated by oil (hot water radiators), one house has a newer oil furnace (200k'ish BTU), and the other has a complete dinosaur that I'm looking to replace. This thing is over 100 yrs old. Probably original to the house, it's huge, certainly not efficient and it's just time to go.

The house has Natural Gas for the water heaters and stoves.

I want to replace this dinosaur with a new Condensing boiler (not necessarily a combination unit). I spoke to a plumbing company and they put together a quote for me for a unit that was 165k BTU input and at least 140k btu output. When I looked up the Condensing boiler in their quote, I saw it was discontinued so I'm not too confident in this company. They did take the measurements for the radiators into consideration, and how many radiators there were in the home and said we needed 140K BTU.

I don't know if they're trying to pass off their old stock to me, but I'd rather have something that isn't discontinued, there should be a new (better?) model in my mind.

What I'm asking of you guys, is what is your recommendation for a Condensing Boiler keeping into consideration the building size, 8 radiators per floor, and 4300 Sq Ft. Also considering this plumbing company recommends 140k BTU output. I don't mind going larger. What are your thoughts and recommendations? Really want a condensing unit.

Thank you


  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 6,753
    Steam boilers are sized by the amount of connected radiation. NOT HOT WATER.
    Since you have a hot water system, you may be oversizing depending on the condition of the building. If those radiators were sized just after the Spanish Flu era, you may have oversized radiators. If the home has had upgraded windows or added insulation since the system was sized, you may have more radiation than you need. The boiler size appears to be correct for the building size at first glance. Having an accurate heat load calculation by ACCA manual J or at least a Form 1504WH heat loss calculation, will confirm the actual size needed.

    See if you can find a boiler man that can do the load calculation. Just as a side note, when I worked at a supply company in NJ over 20 years ago, there was a load calculation program in the computer system. As the HVAC Technical Support person, we offered to do the Load Calculation for our Contractor Customers that were purchasing air conditioners, furnaces and boilers from us.. So there are a ways to get this done.
    Edward F Young. Retired HVAC ContractorSpecialized in Residential Oil Burner and Hydronics
  • MaxMercy
    MaxMercy Member Posts: 456
    edited December 2022
    I wouldn't worry about it being discontinued as much as its reputation. Maybe you can post the make and model and see what pros think about it. I mean, if you had it installed this same boiler last spring it would still be discontinued today.

    Unrelated, but if your MIL has no plans to sell the property in the near future, then you have to consider the strong possibility that the mod/con boiler will need replacing on or about the 12 year mark - that's the nature of the beasts. And while a typical Beckett or Carlin burner can be repaired within hours in most cases by pretty much any plumbing or HVAC company, specialty parts for the mod/con might be several days away or available with overnight shipping (tenants don't like to wait, which is why my rentals were electric).

    Mod/cons also won't tolerate indifferent maintenance, so plan on hiring someone who really understand these boilers and spending more for routine maintenance and a lot more for repairs during that lifetime.

    I honestly don't know if the fuel savings will ever recover the other costs. They didn't for me which is why I went with a quality traditional cast iron boiler for my house. It replaced a fairly modern steel boiler and is about 30 percent more efficient.

    Question - how much oil is each house burning? It would be interesting to know what the dinosaur is using compared to the newer boiler.

    Long Beach Ed
  • pedmec
    pedmec Member Posts: 822
    You need to do a manual j load calculation. No need to guess on new equipment. Also i would try and explore all the rebate programs available regarding insulation. Its much more cost effective to keep the heat in than to try and make up for the lost heat.

    And request for the newest boiler. No sense taking a chance on a discontinued boiler. Might not mean its a bad boiler. It just might mean they just did a line upgrade like cars. But i'd prefer to have the latest model.
  • mattmia2
    mattmia2 Member Posts: 8,874
    I would prefer the boiler that has been debugged vs finding what they missed on the new design.

    If you do connect a conventional cast iron boiler to a gravity system, make sure you have some scheme for return water temp protection.