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High efficiency added to 250 year old house! Help!

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Hey fellow boiler heads. Im a contractor in the north east who has the unfortunate job of installing a 95 percent boiler, going with Bosch greenstar , thanks to the allure of rebates, in a 250 year old house. The house is all mono flow operating multiple pieces of baseboard and monoflo radiation’s off two thermostat. The rest of the house is 3/4 micro zoned based board on the addition part of the home which is the new 25 year old part of the house. 

The home is built like this, the main house is all mono flow radiators. They look like The heat emitters when I was in school with something that I assume is an old school trv.  that remains inside the unit on the supply side. It’s flared and about a 1/4 wide and has a bulb on it. My guess is that  and the bulb would open and close to allow more heat due to  the rads being installed before electricity ( I will post pics of said units). I plan on converting those to bleeders as done on some of the other units. 

My problem is this: some of my zones have 20 feet of 3/4 baseboard on a thermostat. I’m  terribly afraid of short cycling my new boiler to death. The old boiler Was a 205k peerless Gas for about a 1500-2k sq foot home but it had thermal mass and could handle these tiny zones. 

There’s about 5 zones two 007 one that serves the indirect and one that serves the old house mono flow. Then 3 taco zone valves that micro zone the new part of the house 

There is zero insulation in the walls of the old house and we get cold winters here. I haven’t done the load yet as I’m waiting on figuring out how to determine the heat the old school rads give off. Then I can accurately size my boiler probably plus 25 percent for lack of insulation and for the indirect

My issue is I don’t want to mess with a mono flow system . I know with mono flow failure to take into account the operating characteristics of all the heat sources and flow requirements  can cause trouble in a mono system.

I was thinking I’d prob install a 130 Bosch greenstar (or something close to it) once my load calc is done on the emitters and for the new micro zones pull them off a buffer tank to save the boiler from short cycling to death? Not sure what to do exactly never worked on a house this old. 

Thanks all

Comments

  • leonz
    leonz Member Posts: 1,154
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    You have a home with no insulation and this home
    was most likely heated with coal to begin with.



    Mad Dog_2
  • Jamie Hall
    Jamie Hall Member Posts: 23,415
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    Well, actually it probably had no central heat at all in the beginning!

    Don't fuss about the lack of insulation, but do take it into account in your load calculations. Find a good Manual J calculation program or handbook, and go through it honestly. Do this -- room by room -- before you do anything else.

    The microzoning is going to be a problem unless you do something about it, and I would suggest either eliminating it -- it probably isn't needed if you spend a little time balancing -- or adding a big buffer tank.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
    Mad Dog_2
  • Mad Dog_2
    Mad Dog_2 Member Posts: 7,092
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    What City?  Thats Colonial Era....Love to see pics of boiler room & Home too Mad Dog.. 
  • leonz
    leonz Member Posts: 1,154
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    I agree with Jamie about the micro zoning as repiping it all in series would simplify things for you and the homeowner.
  • tim smith
    tim smith Member Posts: 2,765
    edited October 2023
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    pipe it primary secondary per manual, I would lean towards a Lochinvar KHB WHB as we have used tons of these and they really have been reliable. Piping it primary secondary won't foul up the flow of the system and will allow you to tie in boiler to the closely spaced tees with no ill effect. As long as system performs now you should be good.
    I am sure a rework of radiation would be nice but we are not always given a budget to do the best practice.
    Good luck.
  • pecmsg
    pecmsg Member Posts: 4,880
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    Those emitters are designed for 180* supply water.  That boiler is only high efficiency below 140*F. 
    mattmia2
  • Hyrdonic_Nut88
    Hyrdonic_Nut88 Member Posts: 11
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    Thanks guys it’s in Massachusetts. I’m not concerned about a Manuel  as I can only put out the amount of heat my rads allow for and they don’t have the cash to add any radiation plus I hate redesigning mono flow systems. 

    I am going to use a Bosch green star with a hydraulic separator. Because there’s no insulation im considering running the boiler off a plate heat exchanger. This way I can antifreeze the system and simultaneously protect the boiler from the glycol. Is this overkill? I mean As long as I monitor my corrosion inhibitor I should be good right? I have worked on many high efficiency glycol systems that seem to last a while and work fine so im going back and forth on what to do.


    for the micro Zones I was either going to make them into one zone which would add like another 20 feet of high temp baseboard for a total of 40 feet which will still short cycle. Again the old boiler was 205k btu. To solve this i was thinking of using a reverse return indirect but I could use some feedback on there effectiveness


    I have to figure out how to size these emitters and figure out what to do with these capillary tubes that look like ancient temp controls before electricity. I’m going to try to post pics to get some help on thisZ 
  • Hyrdonic_Nut88
    Hyrdonic_Nut88 Member Posts: 11
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    pecmsg said:
    Those emitters are designed for 180* supply water.  That boiler is only high efficiency below 140*F. 
    Yeah I know the return temps are not going to really be “high efficient” but they get a rebate and financing  for this pos so that’s what they want. 

    I need to learn how to size these old school emitters so let me post some pics see it if I can get some help