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  1. #1

    Navien Boiler Problem

    I have a Navien CH-240 Combi (new install) in my second home, and the domestic hot water temperature is unstable. I have the temperature set to 120*F, and when I open a faucet, the boiler ramps up, the water gets hot, but then the boiler cuts back and the water gets cooler, and this continues. The water never really gets to 120*, and the temp goes up and down and up and down...can't even take a shower.

    Anybody ever seen this happen and have any idea what causes it? Tech support had some ideas, but we haven't gotten to the bottom of it yet. Been through the dip switches, etc, tried running with and without the remote controller, but can't seem to get it working. My plumber and I are kind of tag-teaming it, but we're not getting anywhere, so if anybody has experienced this, I appreciate any help. Would a dirty flow sensor cause this? Or low gas pressure?

  2. #2
    Join Date
    Oct 2009
    Location
    God's country - Shenandoah Valley, VA
    Posts
    339
    Are you on well water or municipal?
    Bob Boan


    ​You can choose to do what you want, but you cannot choose the consequences.

  3. #3
    Well water. We already tried switching the setting for well/municipal bit it didn't help

  4. #4
    Join Date
    Oct 2009
    Location
    God's country - Shenandoah Valley, VA
    Posts
    339
    Check to see if your well tank is water logged which will cause the pressure to surge.

    Which flow restrictor is installed on the Navien?
    Bob Boan


    ​You can choose to do what you want, but you cannot choose the consequences.

  5. #5
    Join Date
    May 2006
    Location
    Bedford,Ohio
    Posts
    27
    This is the Ask Our Pro's forum. In order to post a response here, you must have verified qualifications and have been approved by the AOP Committee. You may ask a question by starting a new thread.

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    Last edited by jpsmith1cm; 01-22-2013 at 05:39 AM. Reason: non AOP Member

  6. #6
    Join Date
    Sep 2008
    Location
    Western PA
    Posts
    25,400
    6t7gto

    This is the Ask Our Pro's forum. In order to post a response here, you must have verified qualifications and have been approved by the AOP Committee. You may ask a question by starting a new thread.

    You can find the rules for posting and qualifications here.

    Additional infractions may result in loss of posting privileges.

  7. #7
    Join Date
    Jan 2009
    Location
    Keokuk, IA
    Posts
    5,520
    You may want yous contractors to talk with a Navien rep about this to make sure your settings and installation is configured correctly for well water. Just reading the manual, there are are several parameters related to using a well pump with the unit and as mentioned, it may need a flow restructor ot maintain a more constant flow leaving the pressure tank. In a normal municipal system, the pressure drops occurs more gradually and are proportional to flow and mostly after the water heater as more fixtures are used. IMO, the installation manual sucks, and expalins very little on the "why", and only gives very basic "how" instructions, which tends to be useless. Maybe it for guys that are experts in hydronics, but are "old schoolers" and suck at technology.

  8. #8
    Join Date
    Jan 2008
    Posts
    1,965
    Make sure there is no mixing of hot and cold at any faucets.
    I had a similar problem that took a while to track down, but finally found a slop sink with a spray hose attachment that had the hot and cold valves open.
    "Hey Lama, hey, how about a little something, you know, for the effort." And he says, "there won't be any money, but when you die, on your deathbed, you will receive total consciousness." So I got that goin' for me, which is nice. - Carl Spackler

  9. #9
    One additional comment...I have gone through 100 gallons of propane with this boiler in 17 days!!!?! I have been using it to keep the basement of my second home at 55 degrees (1200 SF basement), and 100 gallons in 17 days. Has anybody ever encountered a situation where something is wrong with the burner and it's burning very inefficient? Other than that, all I can think of is a leak in the line that leads to my home from the propane tank.

  10. #10
    Join Date
    Jan 2009
    Location
    Keokuk, IA
    Posts
    5,520
    Thats an average of 22k input btus per hour. Whats the average temp been and how does that coorelate to you calculated load and hot water use.

    Sent from my SGPT12 using Tapatalk 2

  11. #11
    Join Date
    Jun 2007
    Location
    Minneapolis, MN
    Posts
    725
    Condensing boilers burning propane must be set up with a combustion analyser. The Navien is more tankless water heater than boiler and as such is very sensitive to flow.

    The inconsistent nature of the typical well system can vary pressure and effect flow. You will also want soft water and filtered water since the lack thereof will shorten the life of any tankless water heater.

  12. #12
    Join Date
    Jan 2009
    Location
    Keokuk, IA
    Posts
    5,520
    I thought the unit had a water flow sensor, air pressure sensor, gas pressure sensor, id fan speed sensor. What would you adjust? The install manual only says to check it. It self adjusts for gas pressure and air flow. I think it uses 2 processors for speed.


    Howeverr I could se variances in water pressure making it unstable. I think thats why there are some settings for well pump use.

    Sent from my SGPT12 using Tapatalk 2

  13. #13
    Join Date
    Oct 2005
    Location
    Pacific Northwest
    Posts
    2,266
    Have your service tech call Navien's technical support while he's standing in front of it with the door off.

    It's probably a sensor failure. (Very common.)

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