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Solutions for a small hot water zone

I have an old house with steam heat with a newer 2-story addition. The addition, both floors, has hydronic hot water baseboards; each level is about 400 sq ft. Bottom floor has a recently install mini-split A/C and heat pump, and as such is no longer dependent on the baseboard for heat. That is, baseboard can come out of the bottom floor of the addition.

The Problem: The hot water zones are not tied into the steam boiler properly and are causing several issues. The proposed solution is to establish hot water circulation using a heat exchanger from the steam boiler. However, it is looking like this is a technically difficult solution to implement. I'm thinking that I may just want to separate the hot water zone from creating issues with the steam boiler.

Does anyone on this board know of alternative ways to provide hot water for one small zone having only about 20' of baseboard on the top floor of my addition? Would a second hot water heater (maybe an electric tankless) be a possible solution? Since the required zone is small, maximum energy efficiency is not a top concern; rest of house would be on steam boiler or mini spit heat pump.


  • SWEI
    SWEI Member Posts: 7,356
    Is there a tankless coil (or provision for one) in the steam boiler?
  • BergenTodd2
    BergenTodd2 Member Posts: 4
    There is not a tankless currently. Whether one can be put in I do not know; it is a Weil-McLain EG-45 about 20 years old. I found someone who can do the work of running the hot water zone with a heat exchanger off the steam boiler or by pumping the boiler water directly (as it is set up currently) but with a bypass loop to keep the water zone at 180F. The current situation is that current set-up of pumping 212F water is problematic.

    But again it is highly involved and I'm worried about creating a "Frankenstein" system that no one will be able to work on; and any work will always be $$$. After diligent search, I have literally only found 1 person able to do this work. From most plumbers I've heard: 1) you can't have the hydronic loop go to 2d floor, 2) maybe you should install a second hot water boiler, 3) after I researched the proper way to do it (heat exchanger), "I've never heard of that."

    Since this is just a small zone, not a whole house, I'm trying to see if there are any other angles I may be missing. I'm also considering disconnecting the water-zone and installing a mini-split heat pump and a separate supplemental electric heat for the bathroom served by the current hydronic zone. Good thing I have upgraded 200 amp electrical. That way I'll have a plain old steam boiler with no complications. I'd also be able to redirect the central A/C to better serve other parts of the house.
  • Steamhead
    Steamhead Member Posts: 16,843
    Heat pumps do not provide the level of comfort you get from steam or hot-water. I wouldn't decommission the baseboard loops- once they're fixed so they work properly, you'll like them much better.

    In most cases, heat pumps switch over to electric-resistance backup when the temperature drops below 40° or so. Since the cost per BTU of this is much higher than oil or gas, your electric supplier will love it as much as you'll hate it when the bill comes in.

    Of course, if that were my house I'd change the addition over to steam.
    All Steamed Up, Inc.
    Towson, MD, USA
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service
  • BergenTodd2
    BergenTodd2 Member Posts: 4
    I hear your comments with regards to traditional heat pumps. That is why they are typically used for heat only in the South. But the minispits are supposed to more efficient (don't think they even do electrical resistance) and have improved performance in lower temps. But that is the marketing and the sales pitch from the HVAC contractor. I'll see how my one minisplit warms this season; I'll try it out for that purpose although I installed it primarily for A/C. But your warning that there is a risk going down that road is well taken.
  • bulldoglax
    bulldoglax Member Posts: 38
    Most mini split brands operate at full efficiency at -5 degrees in cold climates. Not industry jargon it is a fact.

    I would get a steam pro involved they may be able to pull a zone from below water line in steam boiler and circulate to additional zone.

    Never use electric tankless at full capacity some can draw 90 amps.

    There are gas water heaters with side loops for small baseboard zones

    You may be able to use existing water heater and have open loop with bronze or stainless circulator deepening on local code
  • BergenTodd2
    BergenTodd2 Member Posts: 4
    I have located a stupendously excellent steam pro. Again, the issue is that the solution is a lot of pipping, a lot of pumps and valves, and the cost of all of that. But my main worry is that getting anyone to work on the system/replace boiler in future may get complicated. I'll ask about the steam.

    Good to hear that the minisplit may operate as performed. The HVAC guy told me that for winter heat I could operate the minisplit for much less than the water loop in that area of the house. We'll see. I got a $300 energy rebate from the state for it. The A/C has been terrific. The central A/C was not extended to that part of the addition. I think it's biggest weakness would be getting clogged with ice during (or buried in snow). But I'm unsure if I want another minisplit compressor outside of my house, and the evaporator will have to be a recessed ceiling one for my bedroom piped through the attic (don't want it blowing on me in my sleep if put on exterior wall near bed); will likely cost quite a bit more than my last one. They can also have problems with their electronics over time if one is unlucky.