intermittent DHW

[mrcdub]

I have a Navien DH240 combi unit that has intermittent DHW, always hot water for the first 10 minutes or so when taking a shower, the DHW is set @ 120 but it seems to rise above that and maybe or maybe not a 30E shows up and the unit shuts down indicating a from what I read a exhaust flue above 65 degrees C, unfortunately I am waiting on the high limit switch....anything else anyone can suggest. After about 5 minutes all is good again as I have seen from a camera I have on the display since non of the errors are logged and as the manual says it is an automatic reset when it cools down so when my daughter goes to look the error is gone .......any help is appreciated

 

[Fitter30]

Unit ever been cleaned with vinegar and a pump? How bout the inlet water filter?

Table Of Contents - Navien CH-180 Service Manual [Page 3]

View and Download Navien CH-180 service manual online. Combination Water Heater / Heating Boiler. CH-180 boiler pdf manual download. Table of Contents: Revisions - Page 7; Navien Warranty - Page 8; Handling Of This Manual - Page 10; Abbreviation And Definition - Page 11; Safety...

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[mrcdub]

Unit ever been cleaned with vinegar and a pump? How bout the inlet water filter?

Table Of Contents - Navien CH-180 Service Manual [Page 3]

View and Download Navien CH-180 service manual online. Combination Water Heater / Heating Boiler. CH-180 boiler pdf manual download. Table of Contents: Revisions - Page 7; Navien Warranty - Page 8; Handling Of This Manual - Page 10; Abbreviation And Definition - Page 11; Safety...

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Yes, it has been flushed with the haymaker solution, the inlet water filter is clean and the DHW flow sensor has been replaced. The main and secondary heat exchangers have not been but the space heating is working fine. I didn't mention that it may go days or weeks before it happens again, lately it seems to be more frequent, but it always starts out with hot water for usually 10 minutes. I reduced the DHW water temp today to 110 from 120 to see what happens