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Navien combi units

AndrewHern Member Posts: 8
Hi, we are currently looking into remodeling our basement. We currently have a standard water heater and gas boiler setup. We have baseboards and radiators running throughout the house. We wanted to create more space in our basement. We are currently looking into combi boilers. Are Navien Combi units reliable? I understand the installer is the most important aspect, but i just wanted to hear different opinions. Is it worth installing a combi? I am very confused. 

Thank you


  • Alan (California Radiant) Forbes
    What are your DHW demands? Storage-tank type water heaters will give you a buffer when a lot of hot water is being used. Combi units will typically only give you around 3gpm of untempered hot water which will let you shower and do the dishes at the same time, but any more than that and you will run into trouble.
    Navien's seem to have a good reputation and good tech. support.
    8.33 lbs./gal. x 60 min./hr. x 20°ΔT = 10,000 BTU's/hour

    Two btu per sq ft for degree difference for a slab
  • AndrewHern
    AndrewHern Member Posts: 8
    hi Alan, I am not a plumber or have any experience at all. To be honest, I did not know what dhw means. What I can tell you is that the house has three bathrooms and three kitchens. It also has a washing machine for clothes. We don’t have dish washers. 

    Alan, thank you so much for your reply as I need all the help in the world. I am so frustrated as finding the truth is so difficult. I keep hearing horror stories about Navien and videos on YouTube. There is a YouTube channel called Navien leaks. It is very very interesting. 

    Thank you Alan 
  • Hot_water_fan
    Hot_water_fan Member Posts: 1,917
    edited March 2023
    There are plenty of combi brands out there so don’t get hung up on Navien, the installer is likely more important anyway. A tankless heater is great for saving floor space if you don’t exceed its capacity. They’re great for shower flows and the like, but sudden, large draws like clothes washers and tubs aren’t their strength. 
  • kcopp
    kcopp Member Posts: 4,448
    Never Navien for me.
  • hot_rod
    hot_rod Member Posts: 22,472
    I think the decision should be based on how you use hot water, and how much. If you can space out the loads 3 gpm is plenty for most residences.
    What size tank have you been living with?
    What size is the current boiler, what type of heaters?

    As a plus a combi would probably save some $$ on the heating bill also, if you have a standard cast iron boiler now.
    I have own and lived with combis for going in 20 years. They work fine for applications like yours.
    A household with a lot of children,multiple hot water loads running at the same time, not as good as an option.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • EzzyT
    EzzyT Member Posts: 1,297
    Might want to look at NTI S20W wall hung indirect tank partnered with a wall hung boiler. 
    E-Travis Mechanical LLC