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kochmon Member Posts: 9
Want to replace DHW heater and boiler. Like to install 50-60 gal indirect hot water heater and a boiler that would support that water heater. This boiler has all ready two zones with that feeds about 100 feet of baseboard. DHW heater is going to be the third zone. I called three plumbers but all of them have given me different BTU's for the boiler, starting from 50,000 to 150,000. None of them are close to one another. I am totally confused. Like to install gas saystem in house but National Grid says that it would take 6-8 months because i am not from the emergency list. SO SOMEONE  PLEASE ADVICE WITH GIVEN SO MUCH DETAILS, WHAT SHOULD BE THE BTU's ON THE BOILER. NEED TO REPLACE THE DHW HEATER ASAP. THANK YOU.


  • SWEI
    SWEI Member Posts: 7,356
    system sizing

    Needs to be done properly before you spend any money.  This starts with what is called a heat loss calculation -- an estimate of how much heat will be required on the coldest day you are likely to encounter in that area.  Next comes an estimate of the domestic hot water requirements.  These two together determine the sizing of both the boiler and the indirect.  Any contractor who does not go through this process is not someone you want to hire.

    You do need some help.  Where are you located?
  • Robert O'Brien
    Robert O'Brien Member Posts: 3,541
    100' baseboard?

    The actual heat loss will be less but if you have 100' of baseboard anything larger than 60K is useless. If that won't meet the DHW demand,use a larger indirect. Oversizing boiler to meet domestic load is a mistake,use more storage rather than a larger boiler. I'm assuming the new indirect will have a mixing valve?
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