Question about flame color

The Tank Question about flame color

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    Well, after keeping my circa 1989 Reliance 40-gallon NG water heater alive an extra 10 years (we bought the house in 2003) with Randy and Larry’s advice and replacement anode rods, I finally decided to replace the old dear over the Thanksgiving holidays.

    I had gone to flush the sediment out of it and found that this time the valve was plugged. I had not replaced the stock valve with a ball valve since doing so was tricky given the location of the heater directly over our kitchen – I was always afraid that even with draining it I would ruin the kitchen ceiling when I went to R/R the valve.

    So, I chose a Kenmore 12-year 50-gallon tall unit to replace it. I chose Kenmore because of good reviews and I could see from the bump in its main anode rod that it is magnesium. I wanted to stay away from aluminum (Whirlpool, I’m talking to you) because the old Reliance originally had aluminum, and we had discovered that it was causing my daughter some pretty serious skin problems which always were the worst after a bath, and which went away once I replaced the aluminum with magnesium.

    Anyway, my son and I did the Kenmore install (I put a ball valve on it first!) and all is well, but I noticed when I fired it the first time that the main burner flame color was mostly yellow. I watched it for a couple of minutes to see if it would turn more blue, and shrugged when it didn’t. Later I began to wonder if this is normal. What are the guidelines for determining if you’re getting proper combustion?

    P.S. Can someone explain to me how a water heater with no electrical connections can blink a status LED?


    Briefly, combustion is a affected by the mixture of oxygen and fuel with an ignition source. Flame characteristics are also affected by the amount and quality of air available as well as gas pressure, temperature of the flame and dirt/dust (as well as other things). Perhaps there was dust in the burner chamber or the flame was cool on start up due to the cold water in the tank? Perhaps someone else can way in on that possibility.
    The only definite way to truely know the combustion of an appliance or equipment is with a combustion analyzer; this is an electronic device that samples the flue gas to assess % of oxygen, CO2, CO (carbon monoxide), draft and temperature of the flue gases. Do you have enough combustion air for the water heater?
    As far as the LED, water heaters generate there own power through the thermopile generator. This device generates millivoltage when heated by the pilot flame to open the gas valve and power the electronic control.


    Well, after my shower this morning I went up and took another look, and the flame is much different now. It’s pretty much all blue. I guess it was just looking a little off at cold start.

    There is plenty of air for combustion. It’s in the attic with plenty of space around it. The attic is vented at the soffits and ridge.

    Thanks for the LED answer. I knew, of course, that the electricity was coming from the heat somehow, but I didn’t know the word “thermopile”. Now I do. 🙂

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