Dryer efficiency: high or low heat?

[AC_Hacker]

Originally Posted by Daox

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?

The tumbling action of a dryer has a wearing effect on clothing. I have even heard that some folks in Germany and other European countries do not use dryers for that very reason.

So, if you gotta use a dryer, you not only pay an energy cost, but also a clothing-lifetime reduction cost, and all the energy that is embodied in the clothing.

If you reduce the power to the resistance element, you are going to lengthen the time that the tumbling action is breaking down the fibers of your clothing.

It would be easy to chart power consumption, but difficult to calculate the cost of clothing wear.

As I recall, you have had a problem with winter air being uncomfortably dry. And you have loads of laundry that are uncomfortably wet.

Surely there is a solution to both of these problems at once, that would save energy.

-AC

[Mikesolar]

When i was in Denmark in the late 90s, the laundromats all had very high speed spinners to wring out as much water as possible to reduce drying times. Never saw one of those here.

[MN Renovator]

Originally Posted by Mikesolar

When i was in Denmark in the late 90s, the laundromats all had very high speed spinners to wring out as much water as possible to reduce drying times. Never saw one of those here.

Laundry spinners are available online and there are videos of people using them on Youtube. I've never been able to get good numbers on dry time comparisons before and after owning one though. My clothes drying takes 40 minutes after going through a top loading spin cycle. I've heard that front loaders usually spin faster and I've seen some at the store with higher RPM drum spin speeds advertised so I'm wondering if going with the fastest front loader spin speed would be enough or close enough because laundry spinners are a bit pricey.

[Daox]

Originally Posted by AC_Hacker

As I recall, you have had a problem with winter air being uncomfortably dry. And you have loads of laundry that are uncomfortably wet.

Surely there is a solution to both of these problems at once, that would save energy.

-AC

Unfortunately I can't solve two with one here. My dryer is gas heated, and thus venting to the inside is not a good idea.

[bennelson]

I just replaced my gas dryer, so this is an interesting subject to me.

Lots of people don't care for airing laundry outside (nothing like my underwear hanging outdoors right at the entrance to my neighborhood!)

Additionally, many of us live in a climate where outdoor clothes-drying just isn't practical. (Where I am, I literally haven't seen the sun in three weeks. No joke.) Add freezing rain to that, and it's just not good weather for clotheslines.

Apparently, all the lint in a dryer is just bits of cloth, worn off from the tumbling action. On that alone, I would think that more heat, for a shorter tumble time would be better.

We have a front-loading clothes washer, and it does spin fast. Much faster than our original top-loading washer. Clothes come out of the washer ringed-out compared to the top-loader.

What's interesting about places like Germany and Belgium is that I've heard of air clothes-dryer's that are built into the house, much like a typical closet, only designed specifically for the purpose of drying clothes. This makes so much sense - clothes are protected from the weather, but it's still a passive and low energy way to do it.

I've never seen one in person (mostly just architectural drawings) but it's a great idea. Like passive-solar and other great ideas, it's integrated, so it needs to be designed for during building construction.

[jeff5may]

My dryer has an automated heating schedule built into it. Whirlpool calls it "senseon". All of the automatic cycles use it. The unit actually saves energy, believe it or not.

The underlying technology senses the moisture level of the clothes in the drum by measuring the resistance as the clothes tumble past a pair of metal bars. When the clothes are wet, the resistance is low, and the dryer pours on the heat to drive off the water quickly. As the clothes begin to dry, the dryer throttles back the heat. The heat input and the resulting exhaust temperature and run time are all adjusted by the controller built into the dryer.

When the clothes are mostly dry, it depends on what cycle you are running as to how the machine acts. For the heavy duty and towels cycles, the heat starts out on high and throttles down quickly. The cycle ends before the items are bone dry. In contrast, the bulky items and delicate cycles start out on medium heat and throttles down more slowly, but the cycle continues until the items are completely dry. Towards the end of the cycle, when the contents are too dry to measure a resistance value across the sensor bars, the exhaust temperature is monitored and controlled.

In true ecorenovator spirit, this unit cost me basically nothing. When my old whirlpool dryer finally pooped out (dead electric heating element plus timer motor stopped advancing), I found the "senseon / calypso" unit on craigslist with a description something like "The unit is posessed and works great when it is in a good mood..." Having had experience in the consumer service industry, I know better than to ask a consumer very many questions, or to discuss my plans for the unit once I purchased it. Many people become attached to their devices and view them as "pets". The seller even included the power cord with the unit for under $50.

Arriving home, I unloaded the dryer. I had to move the old one out of its spot before I could plug in the new one, so I just threw it on the truck while I was moving it. I removed the power cord from the old unit and listed it on craigslist before proceeding to the scrap yard. I got $35 for the old, dead unit. When I returned from the scrap yard, I had already received replies to my cord listing, and responded to the first reply, giving the buyer directions to me. The buyer arrived quickly and paid me $20 for the old cord.

The "new to me" dryer was plugged in and run to find out what was going wrong with it. The unit worked like it should for an hour or so, then began malfunctioning. The root cause was found to be an overheating problem. It seems whirlpool designs their dryers with a little vent hole in the top of the heating chamber to act as a chimney in case all the safety measures built into the unit fail. Natural convection keeps the heating element from catching the unit on fire in case the heater runs with no forced air.

This little "chimney" hole is not too far below the island that houses the control panel and control board assembly. When the dryer is run nonstop for a few hours, the heat escaping from this hole rises into the control panel cavity and roasts the microprocessor until it loses its wits. The quick and permanent fix for this problem was to "levitate" the control panel housing above the main dryer housing. I simply released the two spring clips that secure the control panel island to the main housing, creating a half inch gap that allows the heat to dissipate before it can build up in the island. The unit has worked flawlessly ever since.

[oil pan 4]

The moisture sensing thing seems to always never work for me.
I set it, walk away and come back an hour later with the dryer still running on high heat.

Did you sell your old dryer cord for $20?!
You are the man.

[jeff5may]

I have employed another gimmick that works quite well in the winter. Please note that for safety reasons, this will only work for electric dryers. I would hate for someone to get carbon monoxide poisoning by trying this with a gas dryer.

I disconnect the exhaust hose of my dryer from the vent and cork up the vent leading outdoors. I route the exhaust hose to a five gallon bucket with a "micron screen" placed on it in place of a lid. These are available dirt cheap from dudadiesel. They call them an "ez-strainer". I call them a "lint trap". I chop a hole in the sidewall of the bucket and feed the hose a few inches in.


A 100 micron trap worked fine for me, but they make them down to 25 microns. Due to the added resistance of the finer mesh, I would probably go with a screen made for a 55 gallon drum if I was going to use a 25 micron screen. That being said, none of the lint filters I have ever seen on any dryers have mesh that fine in them.


In close proximity to this rig, I run a large dehumidifier unit or a small window air conditioner (both units move about 5000 btu per hour). I set the units so they run when the dryer does, and so that the intake is near the bucket. I believe I set the dehumidifier for 40% RH and the air conditioner at 77 DegF. The sole purpose of the refrigeration units is to remove the excess moisture created by the dryer. The heat generated by both the dryer and the water remover is recycled, while the moisture is disposed of.

This method works well for rack-drying bulky items in the same area if you have room. Especially with an aircon unit, if the room is rather small. Unless the room is very well insulated and airtight, thermal runaway is not a problem. While the dryer is running, it gets pretty darn warm in there. But guess what? The water remover drains off A LOT more water than its ratings state, and the dryer doesn't spin your electric meter as fast.

[Servicetech]

I'm surprised by how many all-electric homes are up north. I would think Natural gas would be a MUCH cheaper way to dry clothes if it's an option.