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Navien 240

Xmytruck Member Posts: 85

Question about my heating system on really cold days single digit day it takes a very long time for the house to come up to temp. The supply is set to 180 and it does start at 180 but them it seems that the system turns down the system down to 160 even thou the house has not reached the desired indoor temp of 72. I am use to the old style of boilers where the system turns and the water is set to 180, so is it normal for a condensing boiler to be running for longer periods?



  • HDE
    HDE Member Posts: 225

    From what I understand, If it modulates down, that means your return water is coming back to unit above 160, meaning a 20 difference is not being met. This is for vent protection, as sch 40 PVC with no water pressure on it (used as venting), has a temp limit of 158 degrees.  

    There is an option to overide that wiith the high temp board operation with internal settings, and also requiring different venting than sch 40 PVC to take higher temps.

    Ask Installer to do or investigate.
  • Jimbo_8
    Jimbo_8 Member Posts: 11
    Navien 240

    Exacally  Right the early units were shipped with low temp boards you had to install 6' sch  cpvc send pictures of it they would ship high temp board
  • Xmytruck
    Xmytruck Member Posts: 85
    High temp


    Your both on the money the plumber came out and installed the high temp board. The weird this is that the system starts at 180 and after a few minutes it sets the water temp to 160 then 150. Just weird to me because I am use to the older systems where that water tempter does not change. I was also told today that with these new condensing systems I should just set the indoor temp and for get it. Instead of turning down the temp when I am off to work and turning it up when I get home.

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