[FoxV]

Thanks to the sulphur spewing portion of the paper mill a couple of blocks from my house closing down (PO related to), I thought I would try venting my drier's air intake from the outside. Now before anyone says "Just hang them on aline", I can't stand clothlined dried clothes, and its not a very practicle solution when its -20C outside.

Also I like playing around with stuff and I figure it'll cost under $100cnd

So here's what I was thinking:
Build an enclosed box (1ftX1ftX6ft) with openings for Cold intake tube, and Warm exhaust.
Add a drip pan and removable panel at the bottom
coil the intake tube inside the box using flexible tinfoil drier duct
Attach Warm drier exhaust so it free flows through the box to vent at the top (which vents to outside), heating the cold intake tube

The advantages of doing this is:
no waste of AC or heating because drier is throwing air outside
Less electricity use for drier heater (assuming temperature regulated heater)
Extremely fast drying time during the winter when outside air has 10% humidity

Concerns I have:
- With warm humid air free flowing through the box do I need to put a vapour barrier on the inside (I suspect I should as a matter of course)
- Can I let the cool outside air free flow through the box and duct the warm humid air of the exhaust. This elimnates the need for a vapour barrier and drip pan, but I'm concerned about moisture in the duct causing lint to become sticky and clog the duct, as well as water pooling and flowing back into the drier
- Will I freeze the crap out of my drier when it goes into the wrinkle reduction stage and its -20C outside (or is this a temperature controlled phase)
- Is my assumption of a temperature regulated heater wrong and I A) will have my drier continously go into an overheat shutdown mode or B) stand to burn my house down

anyways I though this would be a neat little summer project, its not to expensive, and hey, who know's, maybe it'll actually reduce my electricity bill. Let me know if you have any thoughts/additions

[Tanada]

Thanks to the sulphur spewing portion of the paper mill a couple of blocks from my house closing down (PO related to), I thought I would try venting my drier's air intake from the outside. Now before anyone says "Just hang them on aline", I can't stand clothlined dried clothes, and its not a very practicle solution when its -20C outside.

Also I like playing around with stuff and I figure it'll cost under $100cnd

So here's what I was thinking:
Build an enclosed box (1ftX1ftX6ft) with openings for Cold intake tube, and Warm exhaust.
Add a drip pan and removable panel at the bottom
coil the intake tube inside the box using flexible tinfoil drier duct
Attach Warm drier exhaust so it free flows through the box to vent at the top (which vents to outside), heating the cold intake tube

The advantages of doing this is:
no waste of AC or heating because drier is throwing air outside
Less electricity use for drier heater (assuming temperature regulated heater)
Extremely fast drying time during the winter when outside air has 10% humidity

Concerns I have:
- With warm humid air free flowing through the box do I need to put a vapour barrier on the inside (I suspect I should as a matter of course)
- Can I let the cool outside air free flow through the box and duct the warm humid air of the exhaust. This elimnates the need for a vapour barrier and drip pan, but I'm concerned about moisture in the duct causing lint to become sticky and clog the duct, as well as water pooling and flowing back into the drier
- Will I freeze the crap out of my drier when it goes into the wrinkle reduction stage and its -20C outside (or is this a temperature controlled phase)
- Is my assumption of a temperature regulated heater wrong and I A) will have my drier continously go into an overheat shutdown mode or B) stand to burn my house down

anyways I though this would be a neat little summer project, its not to expensive, and hey, who know's, maybe it'll actually reduce my electricity bill. Let me know if you have any thoughts/additions

It sounds like you are trying to build a reverse flow heat exchanger, but the way you describe it makes it seem very complex. It seems like a tube in tube approach would be better for this, like a high efficiency gas furnace uses for the intake air. Put the exhaust tube through like normal, then build a box around the tube so that the air drawn into the drier intake absorbs heat from the exhaust tube before entering the direr intake.

Look for something like http://japancorp.net/Article.Asp?Art_ID=10961 if you really want to save heat and energy.

[Tanada]

I’ve been thinking of basically the same thing, both for clothes drier exhaust, and a second one for bathroom exhaust. The warm air being exhausted is very humid. Cooling down that hot humid air will result in considerable amounts of condensation. I was planning on making an airtight sheet metal box for the hot air, with a water drain line.

I think that doing the reverse (with hot air in the tube and cold in the box) would be more difficult to drain and clean.

If you are hand enough with sheet metal to make the box I have confidence you can make the drain line for the ehxaust tube

Put a small fabricated section with drain right on the output from the drier, then just above that put your bottom end of the cold air intake box, so that the exhaust has the drain, thengoes up through the cold air. The moist air will condense in the tube but with your drain properly sited the water will trickle out the drain tub instead of back into the dryer.

[Keith_McClary]

So here's what I was thinking:
Build an enclosed box (1ftX1ftX6ft) with openings for Cold intake tube, and Warm exhaust.
Add a drip pan and removable panel at the bottom
coil the intake tube inside the box using flexible tinfoil drier duct
Attach Warm drier exhaust so it free flows through the box to vent at the top (which vents to outside), heating the cold intake tube

The advantages of doing this is:
no waste of AC or heating because drier is throwing air outside
Less electricity use for drier heater (assuming temperature regulated heater)
Extremely fast drying time during the winter when outside air has 10% humidity

There are "condenser" driers that vent inside, they have a heat exchanger that recovers some of the heat and condenses water into a drip pan or drain. We had a really ancient one (50's) - the heat exchanger would get totally cludged up with lint. There are modern ones from Bo$ch, etc. - I don't know how they deal with the lint problem. Also you would probably want to avoid perfumed fabric softeners - unless you can get "Pulp Mill" scent that you are used to. And they don't condense all the water, so you may have a humidity problem (if you live in the Land of Liquid Sunshine).

[Caoimhan]

You may not like line dried clothes, but there are other ways to improve the energy efficiency of the clothes-drying process.

1. Use fabric softener. Fabric softener takes up space in the fabric that water normally occupies. Your clothes will dry faster.
2. Use a fast spin washer. The final spin cycle of the washer removes a lot of water. The faster the spin, the more water is removed. This means shorter drying times.
3. If possible, line dry your clothes until they are NEARLY dry, then machine dry them the rest of the way. You won't notice a difference. This is particularly good to do with towels and denim, which soak up a LOT of water.

[pea-jay]

I live in a well insulated, all-electric house in the damp Pacific Northwest. Air drying is out of the question a good part of the year (though I would "pre-dry" some clothes by hanging them first before finishing them in the dryer.)

So here is what I do: WARNING: DONT DO THIS WITH A GAS DRYER
I have an electric dryer and vent it straight into the utility room next to the central air intake. No fancy contraption, no condenser, just a simple hose. When I dry, I turn on the furnace blower (no heat) and circulate the air throughout the house. To prevent excess moisture build up, I run some exhaust fans. Since my place is a well insulated manufactured home, one fan is always running anyway. I will turn on some of the other ones while drying. (I can run up to four). If it is cool and not raining, I will crack a small opening in the utility room window for fresh air. If it is cold or raining I do not. I can tell if it is getting too humid by watching for window condensation. If I get some, I run more exhast fans. If it is exceptionally cold or wet, I will run the heat part of the furnace as well. It always does the trick. On laundry days in the winter, I run the furnace less often. Dryer use can raise the temp as much as one degree per load during the day (and prevent indoor temps from falling at night.)

If you are wondering about lint, I have three filters for that. One, built into the dryer, one built into furnace and one makeshift one on the intake grill. I check for lint build up on the heating elements to be extra sure (there never is), and clean the filters regularly. The system works great and I notice the impact on the electric bills. My next step is to sign up with a time of day usage plan. Where I live, if you use electricity off peak, they will discount your electricity by one cent per KW/HR. Electricity is already cheap here, but every little bit helps.

The only catch is you gotta like the smell of clean laundry. The house smells like a laundry mat after a few loads. It is certainly better than blowing all that heated air out of the house.

[pea-jay]

This subject has come up before in other threads

Dryers and energy Use (Good thread on this subject)
http://www.peakoil.com/fortopic4871.html

Cost of drying clothes
http://www.peakoil.com/fortopic13319.html

Clothesline usage
http://www.peakoil.com/fortopic8339.html

[gnm]

Keep in mind that warm air is not the only thing those blow out. You are introducing a whole lot of malicious lint dust into your indoor air.

As far as the heat exchanger box goes make sure it can easily be taken apart and cleaned since the lint dust will be slowed in the heat exchanger and will probably clog fairly rapidly. This can result in a fire. I tried a heat exchanger briefly and was dissapointed with how often it clogged. Maybe you could vent it into a greenhouse or somesuch?

-G

[strider3700]

I was thinking about building a heat exchanger for a whole house air exchanger last week. my thoughts on an air to air exchanger construction was to use copper piping and copper plates ( I have the plates and pipe is easy to get but $$$ at the moment) I'd go with 1/2" pipes probably 12" long but maybe as big as 18"

it would be constructed like this

start with a plate of copper 12" x 12"

on top place a row of pipes packed together with 1/2" gaps inbetween so 6 of them should cover the sheet. solder them down to the sheet very well.
place another sheet on top soldering it down as well.
on top of that sheet rotate the popes 90" to the bottom pipes
repeat moving up until you're as thick as you want.

then you just put outgoing/dirty/warm air through one set of pipes and you suck clean/cold air through the other side. With any luck the pipes will absorb and transmit at least 50% of the heat from one side to the other. You just then need to set up ducting to get the air to the correct locations and some fans to keep it moving. Good PC fans move about 100 cfm but I'm not sure if they're enough to use on an entire house.

Anyways this project is halted for me until I get some free time and track down some dirt cheap copper pipe.

[FoxV]

Hey thanks for the comments guys, this topic was dead for so long I almost forgot about it.

One of the reasons why I was going to have warm air in the box and the cold air in the tube was specifically because of lint. That way when lint builds up, I can simply remove a wall and clean it out.

However a few things have changed in my house since I posted this topic (and pea-jay reminded me) is that my laundry room is now has a second doorway/opening to it. And to circulate more air through the basement, I was able to open up a cold air return to the laundry room. This should go a long way to circulate the humidity through out the house

This would actually be great as the humidity in the house is already reaching 35% (love my new digital thermometer) and my hands are starting to crack already . So I think for now (because I'm spending lots of money on other improvements) I will just vent the dryer inside the house (with an exhaust filter).

In the summer I'll reconsider the heat exchanger idea for air conditioning. but there is little cost effectiveness in it (AC is cheaper than heating, and pumping humid air from out side will make the drier work harder), and I don't think the wife will like the look of my heat exchanger anywas.

[gg3]

Caomihan's on the right track (above) except: fabric softeners cause accelerated breakdown of fabrics, i.e. your clothes etc. wear out faster.

Given the complications of heat exchangers on dryers, it seems to me the most practical plans for most cases are the following. Item (b) is the simplest solution for the largest number of people.

a) Fast spin, 1000 rpm or higher. Even a little bit of extra water extracted in the spin cycle makes a large difference in terms of drying time. You don't need to buy an expensive European washer to get fast spin, look around and read the manufacturers' specs.

b) If your washer doesn't have a fast spin cycle (or even if it does), get a SpinX. This is a stand-alone spin dryer, about 3,000 rpm., cycle time is about 3 minutes. It's about the size of an oldfashioned round kitchen trash can, so it doesn't take up a lot of room. Handles about 5 lbs. (dry weight) of laundry at a time, which is about half the load from a conventional top-loading washer. Reduces time in the regular dryer by about half. Cost is about $400 via the SpinX website, and typically pays for itself in about a year depending on how much laundry you do. I've heard from people who have these and swear by them.

c) Lower-cost version of the above: get a twin-tub washer such as Danby DTT-420, about $300. The spinner on this machine does 1600 rpm. The washing process requires a bit of manual intervention (moving the load back and forth from the wash tub to the spin tub). I have one, it's fast, relatively quiet, does a great job, and also uses about half the power per pound of laundry compared to a regular washer.

d) Line dry until almost-dry, and then if needed, into the regular dryer. If rain or cold are problems, set up indoor clothes lines. I use indoor clothes lines and they work fine all year 'round. However, they do extract heat from the air, i.e. evaporating water absorbs heat, so do your drying overnight or at other times when you can let the house cool down. On the other hand, during hot summer months, indoor clothes lines will also help keep your house cool.

e) When using the regular dryer, use the automatic settings rather than the timed settings. The auto settings use a sensor to detect when the load is dry. Saves time & energy compared to timed settings. Note, fabric softeners can produce a buildup that fouls the sensors, so if in doubt, clean the sensor according to manufacturer's instructions.

f) Even with filters, venting your dryer indoors produces fine dust that can trigger allergies and is generally annoying. Also lint buildup in dryer exhaust hoses can be a serious fire hazard.

[Auntie_Cipation]

Another dryer option -- I have a combo washer/dryer made by Equator. It does NOT need to be vented to the outside, as it does not dry by blowing hot air, but by centrifugal force, fast-spinning, as has been mentioned here. When items come out of the dryer, they feel kinda clammy, like they're not totally dry, but once outside the dryer they are dry within 5 minutes. This kind of drying does take a bit longer than the hot-air option, but it's very energy efficient.

[Doly]

I use a clothes airer to dry my clothes. There are some really compact models out there that let you dry indoors a lot of clothes in a fairly small space.