Why not Energy Star rating for dryers?

[Shawn Clark]

Okay, this seems like an absurd hole in the Energy Star ratings and Energy Guides to me. Why don't we have Energy Star ratings for dryers? There is clearly an advantage for moisture sensors vs. time dry for example, but that just scratches the surface.

There appears to be a tremendous amount of room for improving U.S. dryer performance. Europe has condensing tumble dryers for example. I would like to hear more about those, in particular whether they are manually drained or if it is a seal overflow drain. My father-in-law described the one he was using as manually drained. The second concern for me is whether or not the cross exchanger system requires annual or other moderate frequency cleaning by the homeowner.

And yes, line drying is nice where allowed and when/where possible. However, it hasn't worked decently for about 6 months of the year in the last two local climates I've been in. Those with dry desert, mountain, or high plains climates wouldn't have this problem.

[mikepaul]

Clothes Washers and Dryers Best Practices : ENERGY STAR

"ENERGY STAR does not label clothes dryers because there is little difference in energy use among models."

You'd have to design something different about a dryer then get the right folks to notice it...

[Shawn Clark]

Originally Posted by mikepaul

Clothes Washers and Dryers Best Practices : ENERGY STAR

"ENERGY STAR does not label clothes dryers because there is little difference in energy use among models."

You'd have to design something different about a dryer then get the right folks to notice it...

Wanna bet?! What you really need to do is have standardized measuring and reporting of actual energy use so that consumers can decide if a feature makes a difference. If you have no standardized test and reporting then how is the consumer going to know?

Reread my original post rather than parroting what they've said. That may be the claim, but it is bogus from what I can tell. There are already designs in other countries that apparently do better, and moisture sensors in the U.S. certainly make a substantial difference already. So why not do what the agency is supposed to do, encourage best practices rather than an inefficient status quo?

The govt. claim is just lame. If any heat recovery is done there will be a difference in performance. Plus there are other tangential aspects such as air infiltration into the home. I'm not sure what the performance is of the condensing systems, but it isn't hard to see that not having to fully heat an extra 5-10,000 cu.ft. of air in the dryer, then dumping it for every load will make a difference.

Besides, even if they were all identical they should still have Energy Guides. People should be informed about what energy the appliance will use. This is especially true for folks comparing gas and electric options.

By the way, the same applies to ovens and ranges. Consumers need measures of the operational cost of each appliance.

[mikepaul]

Originally Posted by Shawn Clark

Reread my original post rather than parroting what they've said. That may be the claim, but it is bogus from what I can tell. There are already designs in other countries that apparently do better, and moisture sensors in the U.S. certainly make a substantial difference already. So why not do what the agency is supposed to do, encourage best practices rather than an inefficient status quo?

Parroting? I thought I was answering your question of "Why don't we have Energy Star ratings for dryers?".

You apparently think moisture sensors work forever. The ones in my Duet dryer haven't worked right in quite a while, so I just use the timer now which might not be Energy Efficient but the clothes aren't wet when it stops. And I'm not spending money on repairs when I have a viable workaround.

Hopefully I haven't upset your soapbox...

[Politburo]

I didn't read through all the details, but what I got from this link is that condensing dryers aren't that great. In fact their conclusion is that they use more energy.

Condensing (Ventless) Clothes Dryers

[fuzzy1]

Originally Posted by Politburo

I didn't read through all the details, but what I got from this link is that condensing dryers aren't that great. In fact their conclusion is that they use more energy.

Condensing (Ventless) Clothes Dryers

Thanks for this link. For those of us unfamiliar with condensing driers, this helps.

It appears that most of these units use cold tap water for condensing. There is no heat recovery. And in much of the U.S., that trades one scarce resource for another, so any tradeoff benefit is very unclear.

The air cooled units do have heat recovery, but that would be inappropriate in cooling-dominated climates. I think that more of the U.S. population is now in cooling-dominated, rather than heat-dominated, zones.

We need more information about what condensing driers on the market before passing real judgement. With tradional diers, performance is driven mostly by how well the washer wrings out water in the spin cycle.

[a_gray_prius]

I would argue that the lack of dryer ratings makes sense if you think about the concept of efficiency as "how much input energy is being used to do what I want"? For example, an incandescent bulb in a cold room (that has to be heated) is 100% efficient because it provides the desired heat and light. I will make the assumption that it takes a rougly equal amount of energy for the motor to spin the tub across models. After that, the only energy consumed is heating the air, which goes directly into the tub. This is a process that is not really subject to much difference in terms of efficiency because you simply need a certain amount of energy (in Joules) to heat a certain volume of air by a certain amount.

[Shawn Clark]

Originally Posted by mikepaul

Parroting? I thought I was answering your question of "Why don't we have Energy Star ratings for dryers?".

Yes, parroting. When you repeat something back verbatim without even thinking about it or considering what was originally posted it is simply "parroting." Did you really think I hadn't read that exact same nonsense?

You apparently think moisture sensors work forever. The ones in my Duet dryer haven't worked right in quite a while, so I just use the timer now which might not be Energy Efficient but the clothes aren't wet when it stops. And I'm not spending money on repairs when I have a viable workaround.

That's really intelligent: waste money on extra electricity when you might repair it. I never said anything worked forever.

But let's say as a result of the failed sensor you over dry by 20% on average (say 10 minutes on what should be a 40 minute dry.) It's not just a waste of energy, but hard on the clothing. My old dryer had no moisture sensor, and that was one of the reasons to replace it.

Furthermore, what is the most efficient way to dry? Warm and slow (high volume), hot and fast (lower volume of air)? I'm not sure but this does not appear to be a "one size fits all" answer with respect to energy consumption. If you have to heat an extra 5,000 cubic feet of air that you then expel outdoors, there is a cost to doing that. How efficient is any given dryer at actually contacting a load with the airstream and making use of the driving potential of the heated air?

Hopefully I haven't upset your soapbox...

No, you've fired me up instead. I've had some pretty good projects arise out of frustration with bewildering complacency or lack of intellectual curiosity of my coworkers. Low expectations produce poor results. Some people like being treated like 'shrooms, I'm not one of them.

[Shawn Clark]

Originally Posted by fuzzy1

Thanks for this link. For those of us unfamiliar with condensing driers, this helps.

It appears that most of these units use cold tap water for condensing. There is no heat recovery. And in much of the U.S., that trades one scarce resource for another, so any tradeoff benefit is very unclear.

The air cooled units do have heat recovery, but that would be inappropriate in cooling-dominated climates. I think that more of the U.S. population is now in cooling-dominated, rather than heat-dominated, zones.

We need more information about what condensing driers on the market before passing real judgement. With tradional diers, performance is driven mostly by how well the washer wrings out water in the spin cycle.

This I agree with. The Canadian report is full of self-contradiction. If any climate would benefit from the safe heat recovery indoors, it is our northern neighbors. Furthermore, the report leaves me wondering if an engineer even was involved in writing it...or if they were, did they skip the heat & material balances course in their freshman year?

Even in the U.S. in a cooling dominated climate, air cooling could still fare better than simple resistance heating. In the humid South one is sucking in air that must be both cooled and dehumidified, then is rehumidified in the dryer (via resistance heating) and expelled. So how would instead removing the heat in a COP 2+ refrigeration cycle (AC or heat pump) be less efficient?

The one my father-in-law described using in Europe was air-cooled. With efficient heat recovery, the primary heat that would be rejected in the form of condensing water. But remember that that condensed water was originally...liquid water...not steam. Now if the Canadian authors can explain how this would be inefficient, I would like to see their thermodynamic basis.

I would really like to hear some reports of folks who had compared these kind of units side-by-side. Combination units with cooling water don't interest me in the least, but any stand alone unit designed with air cooling and heat recovery in mind should spank the single pass, zero recovery units we use in the U.S.

Expelling hot, humid air without heat recovery is wasteful. I've been through this sort of battle in commercial interchanger/preheater design. (Take a look at the core exchanger in a cracking plant, if you want to see the ultimate in this sort of thing--damn those are cool to work with.)

The telling line is, "There is no test standard to measure the efficiency of condensing dryers." Exactly, that is the problem...that and the fact that noboby is even measuring the efficiency of them at all. Here it is, the single largest electric user outside fo the HVAC or electric water heating, and it is being completely ignored. One needs to define some standard laundry loads (top loader, front loader, etc.) and some climates to do a full box analysis. It won't be perfect, but holes in standardized tests can be accounted for later.

And as I've pointed out before, the Energy Star/Energy Guide ratings for washers don't account for how well washers remove water before drying. The Energy Guide info for washers is only capturing a small fraction of the real value of a front loader.

[Shawn Clark]

Originally Posted by a_gray_prius

I would argue that the lack of dryer ratings makes sense if you think about the concept of efficiency as "how much input energy is being used to do what I want"? For example, an incandescent bulb in a cold room (that has to be heated) is 100% efficient because it provides the desired heat and light. I will make the assumption that it takes a rougly equal amount of energy for the motor to spin the tub across models. After that, the only energy consumed is heating the air, which goes directly into the tub. This is a process that is not really subject to much difference in terms of efficiency because you simply need a certain amount of energy (in Joules) to heat a certain volume of air by a certain amount.

Partially correct as best I can tell:
1. Incandescents put much of that heat in places that don't need it so the efficiency is nowhere near 100%. Typically that input is high and in more frequently used rooms. Where it is most needed is low and in less used rooms. We tend to set thermostats to keep the less occupied (but still used) and lower level rooms warm enough. Pick an appropriate fraction out of the air to determine what percent of the heating input is useful during the heating season.
2. The heat from incandescents is useful to me about 4-6 months of the year. In the other periods I'm trying to get rid of that same heat...and for about 4 months use AC to do it. In some southern climates the net of the two cases will be a wash...but the wasted electricity is still wasted.
3. The "certain volume of air" is by no means fixed. Efficiency of the air mixing in the drum is important as well. Ideally air leaving the drum would be 100% saturated (in a zero heat recovery case)...but that is highly unlikely. If I lived in an arid climate I might want the dryer to draw arid outside air...and might only need "fluff air" or the lowest heat setting to dry.
4. The quantity of heat required to dry is not fixed. It can vary greatly depending on how much is recovered--very little in current U.S. systems. At present much of the heat added is expelled outdoors. I can actually see the impact on nearby vegetation which shows faint evidence of warmer/higher humidity conditions...this is apparent in spring and fall. Conditioned air (from heating or cooling) is consumed in the process and must be regenerated.
5. The amount of water left in my typical load is less than 5 lbs (yes, I actually measured several loads to establish that.) The latent heat of vaporization of water is roughly 1,000 btu/lb, so the duty to expell the water as vapor would be 5,000 btu/load if it simply boiled away, that's roughly 1.5 kwh. Actual drying in my current machine was measured at about 2.6 kwh/load.