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Old 09-16-14, 07:32 PM   #1
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Default Dryer efficiency: high or low heat?

I have a gas dryer, and I was thinking about the most efficient way to run it. I would assume that using a lower heat setting would be more efficient. It will take longer to dry, but the heat would be used more efficiently (less losses). At least thats what I would think.

Thoughts?

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Old 09-16-14, 11:27 PM   #2
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Only way to know for sure is to test it.
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Old 09-16-14, 11:50 PM   #3
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Using my electric dryer on high heat, it uses between 2-2.5kwh total in high heat mode on a 40-45 minute cycle. The element is on constantly for the first 15-20 minutes and then cycles on and off for the rest of the time and the clothes are dry by the end. I've tried lower heat and even the air dry cycle for 70 minutes and the heat is what dehydrates the clothes and in the lower heat cycle, it takes longer but it doesn't seem to use less power because it still ended up using 2.5+ kwh of energy but my shirts ended up being more wrinkled because they were cold before I had a good chance to get them hung up and the towels were still more damp than they usually are when I pulled them out. Based on my experience, I've stuck to high heat. My washing machine takes 40 minutes so I can run the dryer back to back and it seems to cut the element time down by about 5 minutes on subsequent cycles.

I'd imagine it isn't too much different on a gas dryer. I've got the gas line right next to the electric dryer, not sure why the previous homeowner replaced the gas dryer with an electric one but the cost of replacing it in comparison to the infrequent laundry loads per month leaves me with no huge incentive to replace it.
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Old 09-17-14, 07:08 PM   #4
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I've read that it really doesn't matter. The heat and moisture loss have a linear relationship, so there is nothing to gain by changing the temperature, energy-wise.

I'm sure there are minute differences because the dryer may have less heat loss at lower temps and the motor energy consumption is a function of time only.

There is also the matter of infiltration losses in the rest of the house because the dryer is sucking air out of the house. Longer run time means more loss. Maybe high is actually most efficient, then?

It'd be interesting to see measurements of all this. But really, I just want a heat pump dryer.
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Old 09-17-14, 07:42 PM   #5
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Quote:
Originally Posted by mackstann View Post
I just want a heat pump dryer.
You could always get a portable A/C and pump the exhaust into the dryer.
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Old 09-18-14, 12:02 PM   #6
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- Quote mackstann -
There is also the matter of infiltration losses in the rest of the house because the dryer is sucking air out of the house. Longer run time means more loss. Maybe high is actually most efficient, then?

It'd be interesting to see measurements of all this. But really, I just want a heat pump dryer.
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Good point mackstann.
The longer dryer run time would be removing more of the houses warm air (in most people's cases) than a short run time. Its obvious now that you have mentioned it , until than I had not considered it.

That has got me thinking that it will be more efficient to have a 'cold air intake' for the dryer to breath threw ..?
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Old 09-18-14, 12:10 PM   #7
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- Quote mackstann -

It'd be interesting to see measurements of all this. But really, I just want a heat pump dryer.
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Your describing a dehumidifier , which will work great for extracting the water without wasting heat. The small dehumidifiers are very cheap to operate ,they use as little as 500w (as mine does) I would estimate that it would take 5 hours to dry cloths in a small room , as a by product from the electrical use it generates heat from the pumps mechanical work.


Edit to add: After the cloths are dehumidifier dried they could be placed into the dryer and fluffed into some degree of softness, especially for the towels etc.

Last edited by ecomodded; 09-18-14 at 12:27 PM..
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Old 09-18-14, 12:16 PM   #8
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Quote:
Originally Posted by ecomodded View Post
Your describing a dehumidifier , which will work great for extracting the water without wasting heat. The small dehumidifiers are very cheap to operate ,they use as little as 200w (as mine does) I would estimate that it would take 5 hours to dry cloths in a small room , as a by product from the electrical use it generates heat from the pumps mechanical work.
I've thought through these possibilities before. There's a great article on GreenBuildingAdvisor: http://www.greenbuildingadvisor.com/...clothes-dryers

But I don't think I could do without tumble drying. Line dried clothes just feel like crap to me. And I am not enough of a mad scientist to rig up something to my tumble dryer.

There are heat pump dryers finally coming to the US within a year or so. It's an exciting time.
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Old 09-18-14, 12:30 PM   #9
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Cool about the heat pump dryers , I will look into those.

Fluffing air dried cloths in the dryer will make them softer, I have done it in the past with said towels..

Last edited by ecomodded; 09-18-14 at 06:45 PM..
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Old 09-19-14, 06:12 AM   #10
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I have many thoughts on this issue but one which is not often thought about is cloth longevity. How many elastic band on underwear degrade prematurely because of high heat from dryers. (or maybe I am getting fatter and haven't gone up a size, haha).

I suspect that wash put on the line lasts longer than when put in the dryer on high heat. This too is an eco question.

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