Experience with condensing clothes dryer
 

In response to another post: http://ecorenovator.org/forum/43445-post100.html

I very much wanted to stop pulling unconditioned air into our house through myriad shell leaks only to heat it, add some water, and then exhaust it outside (a typical clothes dryer scenario).

I ended up focusing on condensing (ventless) dryers. I found a used Bosch Axxis on CG for $100, brought it home and cleaned it up. I also did one mod that I feel addresses one of the unit's major shortcomings.

We've been using it for about 3 months now and this is what I've found.
- It works well if you are willing to tolerate longer drying cycles and increased maintenance.
- With this increased maintenance, however, comes a heightened sense of fire safety since we have no duct work to clog and catch fire.
- The dry cycles seem roughly 1.5 to 2 times as long as those of our previous Maytag electrical resistance vented unit.
- The capacity is less but it seems to work well for us as we mix heavy and light clothes in the wash for better spin extraction and then hang the heavy items on a line in the basement to dry.
- I'm not sure how total cycle energy usage compares but I do know that I now heat my basement/house with hot dry air when using the dryer.
- You have to remove and clean the heat exchanger regularly, about monthly for us, a family of 4. This takes only about 10 minutes and is very easily done in a kitchen sink.
- You have to have a place for discharge of condensed water. Not a big deal, a pump in the dryer sends it out through a small hose to the clothes washer drain.
- You have to clean the air coming into the unit. The Axxis I bought was full of lint and dog hair. I'm pretty sure it wasn't working well and probably why it was sold. The air enters at the bottom right front and enters the heat exchanger after passing through a felt sound dampener channel. The heated air exits through louvers in the rear of the unit. Only problem is that there is no sort of filtering of the inlet air and detritus on floors nearby gets sucked into the unit. I did two things to address this. I elevated the unit above our washer, also for convenience and space. And, I installed a washable air filter inside the louver front inlet, a pretty simple task.
- Another issue we've experienced is that lint and hair accumulate around the front door during a cycle. We have dogs and wash their beds and really see some buildup. We usually open the front door mid-cycle and remove this stuff when drying something with lots of lint or hair. There is an easily accessed lint filter inside the door but it doesn't catch all the lint. Even with this issue I feel better with this unit knowing that at least we're catching all the lint somehow rather than it accumulating inside a vent and becoming a fire hazard.
- This dryer is located in a room shared by our Geospring HP water heater and I'm sure that at least some of the dryer heat is "recycled" to heat our water. The cool dry air exiting the HPWH and the hot dry air exiting the dryer make a very nice environment for drying clothes on a line. We used to put some clothes on a line outside but find they dry very quickly in this room.

Which model Axxis are you running? I see they can be obtained fairly affordably used, and I really do hate the 5kWh my Samsung electric dryer uses to dry most loads.

Bosch Axxis WTE86300US

I am not familiar with these units , does it have a drain connection for the collected water ?

Good idea using a filter on the unit , I would of thought the manufacturers would of sold it with a second filter on it.

I did a little reading on these dryers yesterday and the review said that they are really only meant to be used in cases where you don't have a place to vent to the outside. Also mentioned that they are not as efficient as compared to other drying machines. However, if they offset the heating inside the house, I wonder how much that would save?

They're more efficient (as compared to a conventional dryer) in heating dominated climates and less efficient in cooling dominated climates. Note that heat pump dryers based on compressors offer even higher efficiency regardless of the climate. It's possible to DIY one out of a window A/C and it's even possible to use a dehumidifier as-is in a closet.

In respect to being less efficient than other models heating wise all resistance heat strips would have the same power to btu ratio, 4.13 btu per watt . Reusing the heat in a basement with a clothesline and heat pump water heater seems to be a perfect way to reuse the heat while reducing the infiltration. I've seen inline dryer vent lint traps designed for scenarios without a proper vent to exterior. This could be applied the same way to a traditional dryer. You could then swap between venting depending on the season.

Yes. There is a small port on the back of the unit and water is pumped out by a small impeller pump when an internal basin fills.

Even in the summer our basement stays relatively cool and we do not normally use AC anywhere in the house. Even in the summer, the additional hot air produced by the dryer should increase the efficiency of the HPWH. The HPWH makes more than enough cool dry air to compensate for the hot dry air produced by the dryer.

An improvement of my setup would be to link the dryer and HPWH electrically so they run at the same time. This would increase the efficiency of both units. I'd probably hack the dryer so that it would only run when the HPWH starts a heating cycle.

As a follow up:
there are new Whirlpool and LG heat pump clothes dryers available in the US. A review of the Whirlpool unit is featured on greenbuildingadvisor here:
http://www.greenbuildingadvisor.com....dvisor-eletter

Edit: hmm. somehow the URL above is altered when I paste it here:

This one seems to work from here:
http://www.hearth.com/talk/threads/w...4#post-1892521