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Navien CH240 - No Heat in radiators but has domestic hot water

APNY
APNY Member Posts: 6
in Gas Heating
I have a six year old Navien CH240 combi boiler. Worked fine for the last six winters. Only thing I had to change besides cleaning filters was expansion tank so far. However when turned up thermostat this few days ago, hot water is not circulating via radiators. replaced the circulator pump thinking that is the issue, but did not resolve. One Navien authorized technician looked at and claims the piping is all wrong it needs to be re-piped (besides the fact that it worked fine as is for six years). From what I can see piping seem to match the specs on page 25 of the navien manual .

I am posting a picture of my installation. As you can see from the picture, air scooper gets super hot to the touch. My neighbor and I opened the T to verify that it is not clogged. Any ideas?

Comments

  • Ironman
    Ironman Member Posts: 7,550
    Has any air been properly purged from the system? What’s the cold static pressure?

    If both of these are good, the changeover valve may be stuck.
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
  • Ironman
    Ironman Member Posts: 7,550
    And yes, the piping IS wrong! Just because it functions doesn’t mean it’s right. It should be piped primary/secondary. The way it now is, the house circulators are in series with the internal boiler Circ which may be causing your problem.


    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
  • APNY
    APNY Member Posts: 6
    Purged multiple times by the technician and by myself. I don't know about the pressure but I think it is good. I also saw in another forum the comment about the three way valve being stuck. I may have gotten a bad diagnosis from the first plumber. May have to try my luck with a second person.
  • Ironman
    Ironman Member Posts: 7,550
    Was it purged CORRECTLY? I can’t tell you how many times I’ve gone behind other techs, as well as home owners, who tell me that the system had been purged when it wasn’t. It’s not that they hadn’t tried, they just didn’t do it correctly.

    I’m not necessarily saying that you don’t know how because i don’t anything thing about you or the tech that you had out. However, a lot of people don’t think abstractly and try to do it by rote memory. That seldom works because no two systems are piped exactly the same way.

    You've got to be able to picture in your mind the pathway that the water takes from start to finish in order to properly purge or follow the flow.
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
  • Ironman
    Ironman Member Posts: 7,550
    CORRECTION:

    I didn’t see your piping correctly from my phone. When I enlarged it on my iPad, I was able to see what you have: it’s p/s with a crossover bridge. It’s more complex than what a simple 2 zone system needs, but nevertheless correct.


    I don’t see a purge valve on one of the loops. That, plus the fact that you don’t know what the system pressure is, lead me to suspect that it may not be completely purged of air.
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
  • APNY
    APNY Member Posts: 6
    Thank you Ironmon for your help. I guess I will have to get a second opinion from a different Navien certified plumber. I have to admit I know very little :). I did some research six years ago and thought this was a good system to replace my oil furnace at the time and it worked pretty well for the most part. It is certainly possible, neither the technician nor I have done the bleeding correctly. I just repeated what I saw the tech did and what I saw in some videos.
    I just found it hard to swallow a solution that requires complete re-piping at a cost more than what I paid for the initial installation six years ago. Especially when the piping looked pretty close to the diagram from navien (at least to my untrained eye). Unfortunately I can't find the plumber who originally installed as I think he retired a few years later. I noted the in picture the three purge valves.
  • Ironman
    Ironman Member Posts: 7,550
    What type of radiators do you have? Baseboards? Standing cast iron?
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.
  • APNY
    APNY Member Posts: 6
    for the main loop all radiators, for the second loop for the basement is al baseboard. All radiators were bled also.
  • Big Ed_4
    Big Ed_4 Member Posts: 3,019
    Sounds like another bad Three way valve . Can you purge though the supply ?

    There was an error rendering this rich post.

  • APNY
    APNY Member Posts: 6
    I am guessing you meant that third purge valve in the bottom. Yes we purged via that too. I am having a different Navien authorized installer looking at it tomorrow afternoon. I will share these suggestions with them. Thank you.
  • APNY
    APNY Member Posts: 6
    Three way valve looks to have been the issue. Had a Navien certified plumber replace it yesterday and looks like we are back in business. Thank you for all your help
    Ironman

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