Click here to Find a Contractor in your area.
Welcome! Here are the website rules, as well as some tips for using this forum.
Need to contact us? Visit https://heatinghelp.com/contact-us/.

NCB-240/130H HIGH EFFICIENCY CONDENSING COMBI-BOILER

Can I ad 20g Indirect Water Heater to my Navien NCB-240/130H HIGH EFFICIENCY CONDENSING COMBI-BOILER ?

Comments

  • Jamie Hall
    Jamie Hall Member Posts: 17,161
    And why? Since that Navien already has a built in water heater?
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • waldemar kawalko
    waldemar kawalko Member Posts: 14
    at high point usage maybe not enough of hot water supply
  • Jamie Hall
    Jamie Hall Member Posts: 17,161
    One reason (of several) which I don't like or recommend indirects. However...

    That Navien should be capable of around 6 to 7 gpm good hot water. If it's not, first thing to do is to make sure that it has been serviced -- which includes cleaning and adjusting the combustion using proper test equipment.

    Then, yes, if you need more hot water than that you can add an indirect.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • waldemar kawalko
    waldemar kawalko Member Posts: 14
    I want to install direct vent tankless combi Navien NCB-240/130H, for 2500sqf heating water radiators ( 8 radiators flat panel 24"x 32") DHW for 3 bathrooms with shower and 3 kitchens sinks , total 6 people
    Should be sufficient ?
  • kcopp
    kcopp Member Posts: 3,830
    No
  • EzzyT
    EzzyT Member Posts: 1,167
    No wall hung combi unit be able to deliver the domestic demand that you’ll require plus it will most certainly short cycle during the heating season.
    Better off going with boiler and indirect tank.
    Ironmankcopp
  • Ironman
    Ironman Member Posts: 6,598
    IDK how you could add an indirect to a combi boiler without disabling the ODR when there's a call from the indirect.

    A simpler way, short of getting a good heating boiler + an indirect, would be to add a large electric water heater as a holding tank that the combi would load.
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
  • Jamie Hall
    Jamie Hall Member Posts: 17,161
    I think I was somewhat mislead by your first post -- probably quite unintentionally. I assumed that you already had the Navien and wanted to upgrade the hot water.

    If that is not the case -- you haven't installed anything yet -- then the situation is quite different. Without a building heat loss you don't know whether the Navien would be the right boiler for either the heating or domestic hot water side.

    And that leads me to say -- start with the heat loss. Find a quality modulating/condensing stand alone boiler to match the heat heat loss -- not a combi. And use that for space heating. Then really evaluate your domestic hot water demand -- which may be quite high -- and find a water heater which can handle that, but don't limit yourself to an indirect, direct fired gas, electric -- or even possibly a big hybrid.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • waldemar kawalko
    waldemar kawalko Member Posts: 14
    I am in process of replacing old ( steam heating and gas tank DWH) I consider hydronic radiators , but also HVAC split system and DHW get gas tankless ( RUR199IN ) for 3 showers and 3 kitchen sink. It is small 4 story 2o' x 35' townhouse in Brooklyn.
  • Jamie Hall
    Jamie Hall Member Posts: 17,161
    See my PM. If you haven't already started demolishing the steam, STOP and reconsider!
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • waldemar kawalko
    waldemar kawalko Member Posts: 14
    Hi,

    Steam heating is already gone, now decision about split HVAC and DHW gas tankless , it will be most likely Rinnai RUR199iN and if not going to handle demand we will add another tankless wall hang, in NYC we can have gas direct vent up to 350k BTU input without enclosure. Right now I have gas tank 50g for DHW and is more then enough.
  • Hot_water_fan
    Hot_water_fan Member Posts: 201
    Why a tankless heater at all? You might consider a high efficiency, high capacity tank heater and be done with it.
  • Larry Weingarten
    Larry Weingarten Member Posts: 2,294
    Hi @waldemar kawalko , Is heat pump technology a possibility? It's looking like fuel burning appliances are being pushed out of NYC. I wouldn't get something that must be tossed years before the end of its useful life. See link: https://www.beicities.org/cities/new-york-city I'm not advocating one way or the other, just looking at what is now and what could be. And, like Jamie says, a heat loss is the first thing.

    Yours, Larry
    Hot_water_fan
  • waldemar kawalko
    waldemar kawalko Member Posts: 14
    What kind of electric heat pump would you recommend ?
  • Larry Weingarten
    Larry Weingarten Member Posts: 2,294
    Hi @waldemar kawalko , Here is a link and an attachment for some current research on what's available: https://redwoodenergy.net/research/

    Yours, Larry