Gas Dryer Efficiency Ratings


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Old 05-31-01, 12:40 PM
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Are different gas dryers rated for energy efficiency like gas water heaters? That is, I believe some water heaters have an efficiency rating of 85% to 97% in contrast to electric water heaters that are 100% efficient. I realize that the difference there is mainly that you have gas heat going up the flue and the electric element is in the water. In addition, does the rating (if there is one) take into account the intorduction of water vapor from the gas burning process? Thanks in advance for your help!
 
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Old 05-31-01, 06:06 PM
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Arrow Doesn't Matter Much

Hello and Welcome wickend to the Do It Yourself Web Site and thanks for posting a question in my Gas Appliance forum.

There isn't any real concern regarding energy efficiency at the purchase lever nor the home level.

There is some good reasons for this. Dryers have low BTU ratings, only use gas when manually turned on to dry and compared to other appliances, don't get used near as many hours per day.

Most dryers have 22,500 BTU burners. Therefore do not consume much energy as compared to water heaters and furnaces. We hardly ever, if ever, have any customers concerned about the gas energy dryers use.

Since water vapor is a natural by product of burning natural or propane gas anyway, no concern is paid to this aspect of energy efficience.

Regards & Good Luck
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Old 06-01-01, 06:49 AM
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Gas Exhaust

Thanks Tom. One additional question. I realize that there is only one exhaust vent for the dryer. So - is there a heat exchanger in the dryer so that the gas fumes do not get vented through your drying clothes but join the moist air later in the exhaust process?
 
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Old 06-01-01, 08:02 PM
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Hello wickend

That's an excellent question. If gas gives off some water vapor during the burning process, it's amazing the clothes dry so well... Actually, the moisture content given off by the burner is realatively low.

There is no heat exchanger in a dryer. The hot air goes directly through the drum, to the clothes and gets exhausted. Below is a brief non technical summary of how the dryer functions.

The burner only cycles off upon the initial startup, after the drum reaches temperature and the moisture sensor determines the moisture content being exhausted.

When the correct balance of temperature and moisture content is meet, only then does the timer begin to advance towards the off position.

During this burner on/off processes, the thermostat and moisture sensor balance the hot air inside the drum and purge the moisture along with the warmed air before turning the burner back on, as the cycles continue.

Near the end of the drying cycle, the burner does not turn on do to the timer and the cool down process begins. The incoming air also helps purge any trace amounts of moisture.

Amazing machines we take for granted...

Regards & Good Luck
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