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Water Heater Pilot Behavior

Jerry Simon

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I turned up the water heater to watch the burner ignite, and when done, turned the heater back down. When the burner turned off, the pilot flame went out. I lit it, and turned the burner on and off a few times, watching the pilot while doing so. Each time the burner turned-off, the pilot flame would waiver, quite a bit, and that's why the pilot turned off the first time I turned on the burner.

I must admit, I've really never watched a pilot flame before when the burner shuts down, so is this normal? If so or if not, what would cause the pilot flame to waiver on burner shut-down, almost like someone was blowing on it?

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If I recall correctly, water heaters have different types of back draft sensors. I have heard them called ECO probe, temperature sensors, and temperature probes. If the flame flattens out or the probe gets too hot, it will kill the unit. If it is an ECO probe, the complete gas valve has to be replaced. If it is a temperature probe, you have to wait for everything to cool down before relighting the pilot light. (check to see if there is any type of drafting issues or a dirty thermal coupler)

I have also heard of condensation dripping on the pilot light and putting it out.

Jeff Euriech

Arizona Prime Property Inspection LLC

Peoria Arizona

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What kind of water heater is it?

For the standard water heater with a natural draft and standing pilot.....

There's a lot of possible causes, and often it's multiple issues.

1)Thermocouple issues:

a)Weak thermocouple--thermocouple just puts out enough milli- voltage to hole the magnet open. When the pilot wavers, MV drops just enough to kill the pilot.

2)Weak electromagnet in the gas valve. This is the magnet that is energaized when you are lighting the pilot. When you hold the knob down and light the pilot, you are holding the magnet down until energized enough to stay open. If it's a weak magnet, the gas valve needs replaced.

3)Loose G-bushing: That's the gas valve end of the thermocouple. Check and make sure it's tight.

4)Dirty pilot: Ensure there's a sharp blue flame. A blue flame itself doesn't mean anything. The pilot orifice could be partially plugged causing a weak pilot that may not be striking the thermocouple well. When the flame kicks off, the weaker flame can dance off of away from the t-couple, causing the pilot to drop out.

There's probably plenty more, but I'm going to bed and don't want to think too hard right now.

Typically, the main causes are a combination of a dirty pilot along with a weak magnet or bad/weak t-couple.

NOTE: Thermocouples burn out fairly quickly when the flame isn't hitting the proper area. The pilot flame should only hit the top 3/8"-1/2" of the t- couple. (hot junction).

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