Pilot Light Goes out When Increasing Gas Temperature


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Old 07-26-17, 05:57 AM
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Pilot Light Goes out When Increasing Gas Temperature

Hello,

I need some help with a "new" water heater in my home. I purchased the house and moved in on Monday. The water heater is dated early last year. It has a closed chamber heater. I can light the pilot light successfully and turn the light knob to "ON" without issue.

However, when increasing the temperature for the gas the unit will click (assuming heat is turning on once the thermostat reaches above the current temperature), and instead of igniting the pilot light goes out.

Ideas/recommendations?
 
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Old 07-26-17, 06:19 AM
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Does the water heater have a thermocoupler?
 
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Old 07-26-17, 06:35 AM
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I can't really say. Like I said, it is a closed chamber, and I have yet to open it. I am just observing the behavior of the pilot light through the observation glass. I have not disassembled anything (yet). I was working with this before going into work today and am trying to get ideas so I can work on it when I head back home this evening.

Here are some examples of what my unit looks like:

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No idea how to identify the themocoupler from what limited view I have here.
 
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Old 07-26-17, 06:43 AM
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Did the water heater ever heat you a tankful of water?

Most likely reason: The FVIR system has tripped. If flammable vapor, such as from cleaning fluid spilled on the floor in the basement, enters the water heater combustion chamber, a little gizmo inside may give way, causing a damper to physically block the air inlet to keep the burner flame from following the vapor out to ignite the rest of the spill on the floor. Instead the burner will use up all the remaining oxygen in the chamber and the pilot light goes out also. In a few minutes enough oxygen might seep in to allow you to relight the pilot but not restart the burner.

Try vacuum cleaning any vent slits on the side of the water heater and any space under the heater.

You would need to purchase a replacement gizmo, open up the hatch, disconnect and withdraw the burner, and replace the gizmo. It may take some force to get the damper back open to fit the new gizmo in place and being careful about fragments of glass left from from the old gizmo that tripped.

Something you can try while waiting for Fedex to deliver the new gizmo: Remove the outer hatch cover, unscrew the inner hatch cover, peel off the gasket, and withdraw the burner slightly so the inner hatch cover is ajar with about a quarter inch of space around all four sides. Do not unhook or disconnect any tubes or wires. You might now be able to relight the pilot and fire up the heater.
 

Last edited by AllanJ; 07-26-17 at 07:06 AM.
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Old 07-26-17, 07:03 AM
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No, that is why I inspected the unit to begin with. I was only ever getting room temperature water since I moved into the house.

However, they just installed a brand new gas furnace directly next to the water heater. I wonder if they could have jarred something causing a safety mechanism to trigger? I'll disable the service line and crack this open and take a look tonight. I will get back with any findings!

Thanks!
 
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Old 07-26-17, 07:25 AM
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When you eventually unhook and withdraw the burner completely, take a barbecue skewer and run it through each of the holes in the rim of the burner and running through to the center.

The four lines from the control box through the hatch are: the thermocouple tube (actually a thin coax cable), the pilot gas feed, the main burner feed, and the pilot igniter cable. Do not make sharp bends or creases in any of these lines.

The thermocouple itself is probably about 2 inches long and 3/16 inch in diameter located at the end of the pilot feed tube at the burner inside. It is probably not the problem.
 
 

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