Navien NPE-240 Frequent Ignition Failures now that it's below freezing out

[whatchawant17]

Some may remember a post I made months back for a backfiring issue. I've since had someone in and thought all issues were resolved. It appears not.

Below are pictures, video and a timeline of events and attempts.

I have a different person coming (soon hopefully), but any feedback is helpful. Sorry if this is lengthy but I think the info can be helpful in diagnosing the issue.

I appreciate anyone's advice in advance. Thank you.


Video

Heard it failing to ignite, took video:


After failure code, hit reset and it failed again:



The hot water was being called by furnace’s built in humidifier at the time of these failures. That’s the hissing sound

It was 24 degrees outside when this occurred. As seen in the pics my venting pipes are mostly in unheated garage. I wrapped some insulation around it recently with no affects. Probably less than 2 feet of the vent sits inside house temps.


Timeline

• Installed May 2019 (installer has since dissolved the company and manages a plumbing dept for another company) Will no longer service
  
• Intake was originally inside small closet with louvered door, exhaust was to existing spot on side of house
  
• Had one instance of ignition failure in first 5 or 6 months, reset the unit and it started right up
  
• End of August 2019 noticed a poof sound outside from exhaust, started noticing it more while inside, maybe once every day or two that I could tell. Not sure when it started, but that’s when I noticed it first.
  
• New Service company came to diagnose on Sept 3, 2019. Did diagnostic tests with Navien but DID NOT CHECK GAS PRESSURE. Found no issues.
  
• Called Gas Co after they left on Sept 3, 2019 to check meter gas pressure. Found that regulator was wide open and no longer functioned. Was giving approx 10-12 inches of pressure.
  
• Found high gas and CO readings in exhaust
  
• Replaced the regulator outside and set to approx 7 inches of pressure (said that was normally what they set)
  
• Tested exhaust again after new regulator was set and found very little gas and what he deemed a more acceptable CO reading (said the decreased pressure likely made it burn more efficiently and therefore produced lower CO level in exhaust)
  
• After that I did not hear any backfire/poof sounds for a few days, but eventually caught one. The frequency seems to have decreased but did not solve the issue completely.
  
• Shortly after this I also had Gas Co come back and upgrade the entire meter to a larger capacity BTU that is more than sufficient for my furnace and water heater combined.
  
• Service Co returned since issue was not resolved and Navien suggested running a concentric vent to take air from outside.This was done on September 9, 2019
  
• From that point I did not notice the backfire/poof sound for many weeks
  
• I can’t remember the exact date, but when we started getting below freezing temperatures in December, the unit began having daily ignition failure E003 codes. Sometimes it occurred multiple times in a day.
  
• When the weather would warm up above freezing for a few days at a time, the unit could go days without any ignition failures.
  
• Most recently I’ve noticed occasional backfire/poof sound again.
  
• The unit has never failed or acted abnormally while providing hot water. Temp and pressure is consistent for entire showers and dishwashing periods.
  
• Have not received any other error codes.
  
• I have heard the ignition cycle go on where it sounds like it makes quite a few attempts to light, rather than lighting on the first “click” like usual (See videos)
  
• When I’ve been lucky enough to catch it in action, it seems like the backfire/poof occurs immediately upon the first or second ignition attempt, usually will light after the poof. (No video of this yet)
  
• The Ignition failure occurs more randomly, most times I’ll wake up to find it in the morning but it has occurred throughout the day as well.