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Old 08-26-14, 09:51 AM   #61
AC_Hacker
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Originally Posted by Mikesolar View Post
I'm on the move with the hacked heat pump dryer as well...
Wow! This is great, just great.

Hopefully the two parallel projects will offer mutual inspiration.

Do you guys have concept drawings of your projects yet??

-AC

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Old 08-28-14, 07:43 PM   #62
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This is why I need to do my hack. What you're seeing is the energy usage in real time of my current condensing dryer. It takes about 3 hours to do a small-medium size load and uses 2KW during that time (average). I do a load per day because my units are so small.
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Old 08-28-14, 08:48 PM   #63
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This is why I need to do my hack. What you're seeing is the energy usage in real time of my current condensing dryer. It takes about 3 hours to do a small-medium size load and uses 2KW during that time (average). I do a load per day because my units are so small.
Yeah, I feel your pain.

I don't know if you live in your own house, but if you had some kind of very small room like a closet, you could do an initial test. You could put some sheet plastic down on the floor, and take some spin-dried clothes, and hang them on hangers, and put your air conditioner in there with the clothes (you would need a drip pan to catch the condensation from the clothes), and close the door while the A/C tries desperately to cool down your closet, but since the condenser will be kicking out heat, the A/C will just keep trying.

What would make this different from a real de-humidifier is that the de-humidifier will automatically cycle so that the frost that forms on the evaporator coils will melt.

So you wouldn't want to do this for very long because your A/C will not know to cycle, because the closet will never get cool.

If I were you, I wouldn't let it run more than 15 minutes or so.

But this experiment might give you some sense of how it could work, or not work.

I do nutty stuff like this all the time.

-AC
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Old 08-28-14, 08:57 PM   #64
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My plan is to use an electric dryer with minimal modification. I want to disconnect the 220 electric heat elements and run them to a 220 AC unit. That way the dryer will tumble, run the blower, and kick out 220 to the air conditioner.

The air conditioner will be modified to remove the fan and separator from hot to cold. Then air will just run in a circle from dryer inlet to outlet into ac unit and back to inlet of dryer.

A dehumidifier is packaged better for this but they are all 110 units. This poses the problem of not enough BTU's/dehumidification and more complicated electronics to turn it on with the dryer's 220 coil. I suppose I could use a 110 dehumidifier and possibly a hacked gas dryer w/o the gas connection.

The reality is that i'm not sure what's best but it should be fun messing around The bar is set pretty low with my dryer currently taking 2 KW to dry a load in 3 hours.
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Old 08-28-14, 10:54 PM   #65
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To get an idea of what you are up against, 220v dryer is on a 30 amp circuit, draws around 5kw. 4.31 btu per watt=21 kbtu an hour.
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Old 08-29-14, 06:05 AM   #66
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To get an idea of what you are up against, 220v dryer is on a 30 amp circuit, draws around 5kw. 4.31 btu per watt=21 kbtu an hour.
Typo dude, 3.412btu/watt
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Old 08-29-14, 07:05 AM   #67
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this does pose a challenge. If I run it as I proposed I will only have a net heat gain from electrical resistance the compressor is using. Still should be a KW or more but probably not as much as an electric vented dryer. Then again my current condensing dryer is horrible so we'll see. My goal would be to dry clothes in an hour with large energy savings.

One of the things I'd like to do is set things up so that I can add the humidity to the house during winter months. This would save me having to add one to my current heat pumps.
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Old 08-29-14, 12:08 PM   #68
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Quote:
Originally Posted by Zooomer View Post
this does pose a challenge. If I run it as I proposed I will only have a net heat gain from electrical resistance the compressor is using. Still should be a KW or more but probably not as much as an electric vented dryer. Then again my current condensing dryer is horrible so we'll see. My goal would be to dry clothes in an hour with large energy savings.

One of the things I'd like to do is set things up so that I can add the humidity to the house during winter months. This would save me having to add one to my current heat pumps.
I think this is a great project, and you are blazing a new trail, I encourage you to keep blazing.

One thing you will have going for you is an ACTIVE de-humidifying component that regular dryers do not have. That really counts a lot.

I do see a potential problem... that you will need to monitor frost build-up on your evaporator (that is how it actively extracts humidity). And you will need to provide some way for the periodic melting of frost (don't use resistance heat).

This frost build-up is a feature and a problem... but it can be solved.

You might find that your new dryer will need to periodically stop all but its de-frost activities, and then kick back on after de-frost is done.

I'm just guessing that your dryer will end up more efficient, but it might not be so fast.

Keep going, this is a great project!

Oh, and it just occurred to me that most appliances are built as cheaply as possible, and that while you have 'the beast' apart, you can do things that a manufacturer would not do because of cost, like put in insulation to retain heat, and maybe heavy tar-paper applied inside with some kind of mastic.

-AC
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Old 08-29-14, 06:46 PM   #69
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Use the existing A/C thermostat to stop the compressor when the suction line gets below a certain temperature. If that causes short cycling, add a delay on break timer.
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Old 08-29-14, 06:57 PM   #70
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I have a dehumidifier I rigged up to heat with:


It is a whirlpool gold or pro or primo model. Has the same compressor as many of the 5000 btu air conditioners. This thing will straight up own a 1500 watt space heater after about 2 minutes. It consumes very close to 500 watts (plus whatever fan power to move air).

Initially, it had a capillary tube for a metering device. By design, the cap tubes in these units are too long for the airflow through the unit. The refrigerant quickly gets compressed (liquefied) and remains mostly in the condenser heat exchanger. Due to the long cap tube, the evaporator quickly starves, and the liquid refrigerant that makes it through the cap tube equalizes to a very low temperature and pressure. Unless you force feed the evaporator a stream of water or lots of air, it will eventually freeze into a block of ice.

What I ended up doing to make this unit a beast is simple: I swapped the cap tube for a TXV. I found a danfoss 1/2 ton valve on ebay for under $10 shipped to my door. A TXV basically matches the refrigerant flow so the evaporator is transferring the most heat it can the whole time the unit runs. This is like installing a turbocharger on a naturally aspirated car. The warmer the evaporator gets, the more the TXV tries to cool it down. When it's cold, the txv makes it a little colder. This unit sucks out much more water from the air now than it ever did with a cap tube.

I tinkered and experimented a lot on this unit. It survived the abuse and torture testing I threw at it and still functions today. The best performance I got out of it as a heater or a/c unit was running it like a packaged portable unit. The coil of utility recycled space air, while the other coil sucked space air and exhausted its waste heat or cold outside. The condensate was reused to water houseplants.

After installing the TXV, the evaporator was no longer constantly starving. More importantly, the evaporator doesn't freeze up now. The TXV regulates the refrigerant flow so that the evaporator coil reaches the dewpoint of the incoming air quickly, then just yanks moisture out of the air like crazy. It doesn't just drip little drops of water any more: if set outside on a muggy day, it can collect close to two gallons an hour!

The only time the evap coil ever froze on this unit was when I was running it as a portable heat pump in the winter. I had split the airflow so each side got its own air supply. The condenser sucked in room air and exhausted to the room. The evaporator got attic air, and exhausted into the attic. When the attic approached freezing temps, the evap coil froze if the dewpoint was high enough. If it was a dry night, the coil might not freeze at all. When the unit wasn't running, any frost that formed on the coil would thaw from indirect exposure to the heat from the room the unit was in.

On cold, snowy nights, the unit would run until the evap coil was frozen solid, and could not breathe. I moved the frost sensor to a point low on the coil, from about halfway up, so the unit would not short cycle. Even then, the coil wouldn't completely thaw before the unit thought it was warm enough to restart. Most of those frigid mornings, I would wake to find the thing in shutdown (frost) mode, due to a frozen evaporator. All I could do was unplug it for awhile.

I eventually rigged it so the evap would suck room air and exhaust chilled air into the attic so the coil wouldn't freeze. It performed so well that I was encouraged to build larger, more powerful units that would help heat the rest of the house for pennies on the dollar.


Last edited by jeff5may; 09-11-14 at 07:14 PM.. Reason: words
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