We purchased a house with an existing tankless heater (installed in 2009). It would occasionally fail with error code 11 (no ignition). Over the past 2 months it has been failing more often and now fails every day.
The odd part is that it never fails first thing in the morning (6:00am) and almost always fails in the later afternoon/evening. We've tested this theory continuously over the past few weeks.
I've taken two videos: One in the morning where it works: https://youtu.be/l0XuhanKNCw
And one in the evening when it does not: https://youtu.be/drKBS0QDyhk
The unit was originally installed with a 1/2" gas line. I've recently had it replaced with a 3/4" line, as per the installation instructions, to see if that made a difference (it did not). It's unlikely it's a venting or air intake issue.
Why would time of day have any impact on the the unit working? Does anything seem off here?