Wide temp differential on gas WH

Old 05-05-04, 09:54 AM
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Wide temp differential on gas WH

Is it normal for gas water heaters to have a wide differential between "cut-in" and "cut-out" tempatures ?
I have noticed if the WH hasn't been used for over 16 hours the water seems lukewarm, but if used right after the WH cycles off the water is hot.
Tempature is set @ 120, setting to 130 has elimanated the "lukewarm" problem but I am concerned about unnessecary gas usage from the higher setting.
Old 05-05-04, 10:19 AM
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Hello: 54regcab

Water temp, under normal operating conditions, should not have wide temp differential temp spans over an expended time period. However, when rotating the dial on the control, it will give that impression.

The burner will not cycle on when small temp dial rotation adjustments are attempted nor will the burner cycle on very soon after cycling off.

The primary reason is, the temp sensing device, (a rod an tube element with a clicks-on device contained within it) is not sensitive enough to note the small temp changes.

The above should cover that aspect of temperature adjustments using the rotating temp dial on the control valve.

The vast differences between water temps over long time spans between hot water usages should not be occurring. Such may indicate control failures to sense internal water temps. (Assumption)

Or an internal problem inside the tank exists. Usually but not specifically the dip tube. Other conditions may apply.

What is not known is the tanks age and how you are specifically determining the final results to come to any conculsion(s) there is a wide swing in the temperatures.

Kindly provide more additional details and information using the reply button.

How old is the tank?

Where is the tank located?

How are you exactly determing the findings?

How have you determined the temp control is set to 120 degrees?

How is it known the setting is set to 130 degrees?

Answers to the above questions will help to determine if any specific problem(s) exists and how to correct a problem, if one does exist. Thanks.
Old 05-05-04, 10:40 AM
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The WH has done this since it was new, I have also seen several other gas WH's do the same thing when temps are set to the lower settings.
Tank is 2 years old, located in interior closet
Dip tub is ok.
The temp setting on the thermostat is given by the label on the WH.
The thermostat has been replaced recently due to the temp setting having tio be slow shifted up to maintain the same water temp (it was set @ 160 to get 120 degree water when it was finally replaced under warranty)
It seems like the thermostat has a tempature differential of 20 degrees according to the setpoint label on the WH.
Old 05-05-04, 11:00 PM
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Are you gauging actual temperature by reading of a accurate thermometer at a close faucet opening, and have you gauged the the number of gallons of water at a 20 degree variance?
Old 07-25-04, 02:41 PM
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Gas Water Heater Question

I'd like to know about a thermostat/gas valve on a 40 gal GE water heater bought at HD.

It is two years old and has just stopped "turning on." The pilot light is working. There is plenty of gas and water pressure. I have so much water pressure I have a pressure regulator on the cold water line, directly above the water heater.

I'm pretty sure it's not the thermocouple, since the pilot light stays lit.

I got the burner to "turn on" this morning by fiddling with the gas valve on the thermostat - turning it to the "Hi" setting - but when I turned it "down" a short while later, it turned off and I can't get it to turn on again. Something seems to be failing within the thermostat unit, but what do I know.

Do I need to replace the gas valve (thermostat unit as an entire entity), or replace something _inside_ the thermostat housing?

HD has new gas valves on sale for $54. If I replace the old one with a replacement, do I need to drain the tank first? Does that copper probe on the backside of the thermostat unit enter the tank in such a way that pulling it out will release water? Do I need to drain the tank first???

What might be my problem other than needing a new thermostat unit?



Last edited by DUNBAR PLUMBER; 07-25-04 at 03:42 PM.
Old 07-25-04, 02:55 PM
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Some have whats called a dry well and some dont. So yes Id turn the water and gas off and drain the tank. just to be sure.

Old 07-25-04, 03:40 PM
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Water heater thermostat problem?

Thanks Ed,

Nothing to do with wells just now, although I'd like to have one - save a lot on water bills.

It has happened twice now . . . when I bang (pretty hard with the flat side of a framing hammer) on the side of the thermostat unit, the burner comes on!

Can I get into this thing (thermostat unit) and change something inside of it that will fix this problem, or do I need to replace the entire unit? They have replacement gas water heater thermo units at my local HD for $54, just now.

If I open this thing up (gas off, of course) will I find something I can clean or replace which will fix this? The WH is only a couple years old . . . .



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