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Switching to gas heating - Navien - any input?

ACE203 Member Posts: 3
Hello, my current oil heating system needs oil tank replacement and furnace needs new burning chamber; investing 4K into 30+years old system which at this point I think doesn't have even 60% efficiency; I'm considering gas boiler system.

Currently I'm looking at Navien CH-180 which is supposed to be 98% efficient with on-demand domestic hot water.

My heating runs on hot water radiator, switching to gas boiler heating system shouldn't be very complicated. After tax credit and rebate, this will cost me about 1.5K more than maintaining the old system, so is it worth it with this Navien brand and gas heating instead of oil.

Any input will be greatly appreciated. Thank you for your time and efforts.


  • Ironman
    Ironman Member Posts: 6,869
    Some Considerations

    The Navien "Combi" is unique unit that combines an on-demand and space heating in one unit by incorporating an internal plate heat exchanger. This makes it less in cost than a boiler, but there's some trade-offs to consider.

    First,  it's 91% AFUE, not 98%. Their on-demands that are DHW only are 98%.

    Second, It is an on-demand water heater, not a boiler. It will not have the longevity of a boiler, that's why it cost less. You get what you pay for.

    Also, it will not have outdoor reset which can save considerably and is not reflected in the AFUE rating. You could add a third party system reset control, but that is more $$$ you'll spend.

    Another consideration is the issue of scaling and possible clogging of not one or two, but three heat exchangers. If you have hard water, this should be a major concern. Remember, you'll be running domestic water through the unit continuously - it's an open loop. The heat exchangers have narrow passage ways, particularly the plate exchanger. A boiler would be a closed loop and this would not be an issue. You could add a water softener if needed, but again, that's more $$$ and maintenance. And you'd have to de-scale the unit periodically.

    Also, you must pipe the heating circuit in primary/ secondary as per the installation instructions. You can't just connect the old pipes directly to the heater. This should be done on a mod/ con also.

    A boiler with an indirect water heater, or one with an internal indirect (such as Triangle Tube's Prestige Solo), will cost more initially, but have more longevity and much less maintenance. Personally, I recommend the boiler. You'll be happier in the long run. :-)
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
  • CMadatMe
    CMadatMe Member Posts: 3,086
    I Agree

    With Ironman. Also doesn't have an AHRI number so that means no tax credit..
    "The bitter taste of a poor installation remains much longer than the sweet taste of the lowest price."
  • HDE
    HDE Member Posts: 225

    Corrections to the misinformation provided

    Regarding the federal tax credit, the Navien CH series is listed on both Energy Star and DOE as a boiler meeting the 90%+ requirement for the Federal Tax Credit. AHRI (formally GAMA) has nothing to do or control that. Thus the tax credit is available till end of year, we shall see what happens next year.

    It's 92% AFUE is really and you may check, CA-AFUE, (combined appliance) rarely reported or provided by combi boiler manufacturers. This means the combustion efficiency for the closed heating side is still up to 98%, but the domestic via the plate heat exchanger is about 86% since it is heated indirectly, thus the annual combined appliance efficiency is 92%.

    The Navien CH series has outdoor reset capabilities by simply purchasing the outdoor reset sensor, retail about $45, which plugs into port on circuit board, then the values are selected via the included Navien remote control.

    Unlike the Navien Tankless, the double heat exchangers are the closed heating side thus it should not be seeing significant fresh water, the domestic hot water is heated via the plate heat exchanger, at much lower temps, significantly reducing chances of scaling since no flashing is taking place.
  • bob eck
    bob eck Member Posts: 929
    new boiler

    Take a good look at Triangle Tube Prestige Excellence 95% AFUE boiler with built in stainless steel indirect water heater. Water heater delivers 3 GPM or 180 GPH can run two showers with Alsons 1.6 GPM shower heads. Any time there is a call for heat and domestic hot water the hot water gets priority over heating. you can set the amount of time you want the boiler in priority for domestic hot water. TT boilers also come with outdoor reset control and that is where there are big time savings by only making you boiler water as hot as needed to heat the house instead of always running 180* F water into your system. Email me if you want a price on the TT boilers
  • JGR
    JGR Member Posts: 6
    New Boiler

    Another boiler you might want to check out is a Rinnai E boiler.  There are two combi models with AFUEs above 96%, they come standard with the outdoor rest controls and sensor and most importantly I feel is that they come standard with a low loss header plumbing kit that is pre-assembled and will save a half days labor during the install. This plumbing kit is a huge bonus.  It will save time, money, and operate better than closely spaced Tee's.
  • meplumber
    meplumber Member Posts: 678
    Check that info Home Depot

    The info circulated through the trade is that the equipment must have a manufacturer's certification statement before it qualifies for the tax credit.  They cannot certify it without an AHRI number.  No number = No certification statement = No tax credit.

    I am not a tax accountant but I had more than a couple of customers come back to me asking for a copy of the manufacturer's certification statement for their tax preparer.
  • EddieG
    EddieG Member Posts: 150
    My 2 cents

    We have installed the Navien Tankless (not Combi) units with good results. As stated water quality can be an issue with any tankless on the market. They need service as does any appliance. I am willing to try there Combi unit on applications were there are small heating loads, such as a bathroom. However when it comes to an entire heating system, I will use a boiler. Such as the Excellence or what ever the application may be. A boiler is for heating and a water heater is for heating domestic water. JMO
  • cheapskate
    cheapskate Member Posts: 1
    Navien ch-210 working great

    I just installed the combi unit I can't say enough about how great it is. I replace a 2001 154k btu New Yorker fired on Oil. I did all the work myself the whole project with fittings new zone controllers etc cost me 2400.00. I made sure I ran my oil tank dry to make removal easier I was burning 5 gallons per day. With this new combi unit I can run the clothes washer dishwasher take a shower and people can also use the sink with no fluctuation in hot water temp. Most importantly I'm saving huge money I now use 5-7 CCF of gas per day at a cost of 1.35/ making my dailey heating cost $ 6.75-10.00/day my old oil furnace cost me a minimum of $20.00/day on a mild day. Not to mention the fact that you can call and talk to tech support with out being a licensed install *****. Unit has all stainless steel heat exchangers and a 10 year warranty. I figure it will pay for it self in one year. So if it only last ten years that is fine with me all the work is now done its easy to swap it out.
  • Slimpickins
    Slimpickins Member Posts: 323
    nice of tech support

    to talk to you because I bet your home insurance person won't talk to you if a problem arises with a non permitted installation or non licensed installation. 
  • HomeOwner1
    HomeOwner1 Member Posts: 134
    You are incorrect.

    It does indeed apply towards high efficiency rebates. Please stop spreading bad information, it is very frustrating to home owners researching their options.
  • heatpro02920
    heatpro02920 Member Posts: 991
    edited March 2013
    WOW, I have NEVER seen so much Navian interest..

    Heres my thoughts, lol... Seems like I am repeating myself with every thread tonight since they are all Navian based..

    This is a glorified 80lb water heater!!! It is not a good idea for primary space heating, IMPO...

    To throw ontop of this, in my experience tech support and cs in general was slow, and not very helpful. The units break often and are also known for arriving DOA {this scares me the most, I can picture having 2 techs costing me $100 an hour install a unit and then plug it in only to have my customer go with no heat for the night and lose faith in the system I am charging them for... NO THANKS}

    I stay away from the Navian products...

    What is your homes heatloss?


    OK NOW I'M PISSED, LOL I just replied to a 3 year old thread, offering someone advice on a boiler that no doubt has already been installed years ago... I know if he installed a navian its probably time for a new one by now, but there is still no reason to bring these to the top of the list... This is just getting bothersome now, congrats on your good luck homeowner1, we got it, you love your Navian Unit, its the most wonderful 91% efficient combi tankless water heater in the world, it will last forever and solve all the worlds problems, lol....

    Honestly a better option would be a rinnai tankless with a brinze circ, 3 way zone valve, and brazed plate exchanger. At least you will get high 90%s vs barely 90%... And it will have a shot of seeing 10 years old, vs the navians aren't going to make 7...
  • JGR
    JGR Member Posts: 6
    real boiler

    I would suggest not using even a Rinnai tankless for a closed loop heating system with a plate heat exchanger, these are not meant to be boilers either and depending on how you install it the warranty could be voided and it would not work correctly regardless.  You should look only for products that were designed as boilers, if you like Rinnai, they offer a number of different boiler models, but there are also a number of other real boilers out there that work very well.  Pick something with outdoor reset, real boiler controls, and a heat exchanger that was designed for closed loop heating.
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