May 23, 2011 at 1:33 pm
I had a similar symptoms with my power vented water heater
, which over a period of a few years, increased in frequency of occurances. During that period of time, I had technicians work on it two different times – each time, replacing the ignitor/sensor unit.
The symptom continued, even increasing to 2-3 times a day! After countless shutdowns, I finally had enough! I found the installation manaul for my A.O.Smith Power Vent WH. After doing some reading, I suspected the exhaust vent.
I went over the PVC diameter and length calculations, and found that the installer had reduced from 3" to 2" and used to many 90 degree elbows – all within the first TWO feet of piping!! Plus, the rest of the 2" run was right at the max length. So, the power vent could not “breath”.
We demo the first three feet of pipe, replace with (1) sweeping 45 and (2) 22.5 three inch elbows, THEN a 3 to 2" reducer, and finally connecting into the resat of the pre-exiting system. Haven’t had one ‘mis-start’ in about six months.