Question - on theory.


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Old 08-18-14, 12:44 PM
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Question - on theory.

I purchased and installed a Rheem XG40T09HE40U0 hot water heater today. It went in and fired up without issues so far.

My question is how the Control Valve gets its power. There it a single LED that flashes one time when its working, (and it does) and is supposed to flash multiple times for a fault, so there must be some type of logic in there.

There is a link to the instruction manual if interested.

Rheem Performance Plus 40 gal. Tall 9 Year 40,000 BTU High Efficiency Natural Gas Water Heater-XG40T09HE40U0 at The Home Depot

I'm hoping there is not a battery involved...
 
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Old 08-18-14, 01:02 PM
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Rather than having a simple thermocouple that generates only enough power to hold open the gas safety valve the new water heaters use a control that has a thermopile (that may be Honeywell brand name) and the thermopile generates about 750 millivolts (about 3/4 of a volt) and that is sufficient to operate the gas valve and the diagnostic electronics. As far as I know there is no battery involved but I have not taken mine apart to check.

Also, using the thermopile control allows for using an electric thermostat instead of the mechanical thermostat of the older controls. This allows for a closer temperature differential between the firing and not firing temperature of the water.
 
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Old 08-18-14, 01:03 PM
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Its powered but the t couple... I assume if the pilot went out the light is powered by a slow discharging capacitor on the PCB...( capacitor charged buy the pilot/t couple)
 
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Old 08-18-14, 02:06 PM
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Thanks to both of you for this -
 
 

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