"I drained my tank about 6 months ago, and there was absolutely no sediment in the tank"
Not the issue then.
"I'll also get on the roof to see if the vent cap is blocked."
Still a good thing to check. Gas appliances need correct airflow to operate correctly and safely. Intake and exhaust airflow is extremely important. More to follow below.
"I noticed this problem immediately with this WH. I had a similar problem with my previous WH, too - but not as frequent."
You've had this problem since new, for 18 months? Did you contact AO Smith right away and seek some sort of resolution? Or the place you purchased it from? Did you install it, or someone else? Did you replace the old WH for this similar reason?
Side note: You state it has a Honeywell tstat. Sorry, just saw that. I'm not 100% sure, but I believe AO recently went with the Honeywells because of the numerous issues they had with the other brands. Is this newer design time tested? Not sure yet, but AO Smith will know.
So, some things to check:
1.) What is the blinking light status when it is, and more importantly, is not heating properly? You will have to monitor it closely and frequently in case it throws an error and then resets itself. You state "occasional flashing red LED that I believe indicates everything is working OK". How is the light blinking and what does the chart say when it is not heating properly?
2.) You stated this WH is in your garage. Is your dryer also located in the garage? If so, it creates even more dust and "fluff" in an already dirty environment. Are you cleaning the 360 degree air filter regularly? It is very important you clean this for proper combustion chamber operation whether the dryer is in the garage or not. Here"s why: When the thermopile initiates a burner on command, and then senses insufficient air intake, it will not stay lit long enough to achieve the desired water temperature setting. It's doing what it is designed to do . To protect you. And say your garage daytime ambient temperature is 130 - 140 degrees F (common for AZ summers) and your your tstat is set for 120 degrees F. It's not going to heat the water until the tank temperature is below 120 degrees (night time), and then perhaps it gets caught up in this error cycle again.
3.) Take a look through the view port and see what the pilot looks like. Is it blue? Staying lit all the time? Is it in constant contact with thermocouple? What does the burner flame look like while operating? It must look like what I described above.
4,) Is the gas shut-off valve functioning properly? Have you checked the flex gas line for kinks and leaks? Use dish soap/water solution, looking for bubbles. You can contact your gas company and request them to check the gas pressure to your home. Probably free also.
5.) It just seems odd you had similar problems with the old WH. Is there other information you can add here?
There really isn't much to the WH. It may have a flakey TCO. Try resetting the button several times. Check all the wire connections. Simple, common sense stuff. If after all that, try contacting AO Smith. This should still be under warranty at only 18 months old.
Edited by beam current, 15 August 2014 - 05:24 AM.
I think this will work. I once saw it on a cartoon.
Or, on the other hand.....
Troubleshooting the appliance's complex electro-mechanical systems is the methodology in which one must, by using analyitical techniques and the process of elimination, determine the cause or causes of a specific failure. Rarely does this cause of a failure directly present itself for you to see.
To be better equipped to troubleshoot, you will need:
1.) To follow this: Safety first and foremost. Trust your instincts.
2.) Basic hand tools.
3.) A decent DVOM meter. Buy one. Borrow one. You need one.
4.) Last, but certainty not least, common sense. Most of us have it. Slow down and use it.
Now, let's have some fun!
Hope is the power that gives a person the confidence to step out and try.
Success is the maximum utilization of the ability you have.
It always seems impossible until it's done.