Home made heat pump clothes dryer.
 

I have a spare fully functional electric dryer tjat i dont use and a portable 1 ton A/C unit (not a window unit) that I don't really use any more also.

Probably keep it simple, plumb the A/C discharge into the side of the dryer. Add a hot air bypass if needed.
Don't know how much I will modify the dryer beyond that.
Don't think I will use electric resistance heating at all.
Plumb the cool air into the house.
Locate the whole assembly out in the garage.
Keep it simple.

Cool project!

How do you propose to deal with the condensate / water removal?

Just blow the waste heat and humidity through the dryer discharge and out side like a normal dryer.
I'm not relying to recreate a consumer heat pump dryer.
Which acts like a wet clothes dehumidifier.
The purpose of this one is make some cold air, while drying clothes for use during warmer months. Which there are 7 or 8 of here per year.
Then during the winter I use my normal electric dryer that's just vented into the house. Which is what I'm doing now
That way I will have a winter and summer dryer, the benefit being drying the clothes will help heat or cool when needed.

So you're planning basically to replace the electric heating elements with the the AC condenser?

Yes, and direct the coold discharge into the house.

I think your idea is really good.

However, I suspect that a 1Ton HP is over-sized.

I say go with what you have, and adjust what needs adjusting.

Good luck on your project.

-AC_Hacker

P.S.: a clothes dryer is essentially a de-humidifier. Maybe more good could be piping all your dryer air through a dehumidifier instead. They are already set up so that humidity in the air (clothes) will freeze on the evaporator coils, and a built-in sensor detects when sufficient frost has built up and a frost removal cycle starts, and the frost from the air (water from your clothes) drains into the little bucket. Then the de-humidifier returns to moisture removal cycle. There is even a sensor, such that when sufficient moisture has been removed from the air (AKA: "your clothes"), the machine will stop.

What ac hacker said. Use your 1 ton unit to be a big dehumidifier. Retrofitting a conventional electric dryer would be simple. Use the dryer blower as is to move air. Rig the condenser upstream from the electric heating element and let it find its way to the clothes. Rig the evaporator downwind from the blower, and recirculate the exhaust air back towards the condenser. The waste heat generated by the compressor will concentrate in the air loop and aid the evaporation process.

The dryer doesn't need to reuse it's own heat since it will be used in summer only, out in the garage where it will be 80 to 100°F with 15 to 50% humidity.

The heat pump discharge will produce up to 18,000btu, if the dryer only uses 2/3 of that it's still over 3kw worth of heat.
If doing it this way makes the dryer take a little longer that's fine since it will be helping to cool the house.
This design goes against conventional design by actually helping cool the house. Every other design puts off heat.

Ok but you do understand that water evaporates at a nonlinear rate versus delta T right? Most all dryers cycle around 160 to 175 degF exhaust temperature so they don't take 3 hours to dry a load. You know what happens to heat pump performance at these condensing temps right? If you're doing an airside pump and dump, you may be better off just preheating your dryer suction air. Let the electric element finish the job downwind from the condenser.

I know gas and electric dryers can get that hot but it does not appear necessary on all but heavy denim.
The electric dryers converted to run 120v across the heating element don't get nearly that hot and dry light weight clothing just fine.
My flirI7 shows the discharge on my air conditioner being about 125 to 135°F which is hotter than my 120v dryer. So I don't see why it wouldn't work great on all but the heaviest clothing.
I also have the advantage of very low humidity that most of the country does not have.
Probably won't work as well if the air going into the heat pump condenser coils starts off at 80 to 100%.

If I really need it I can put the heating element on a switch say for denim.
Then run the whole thing off my 30 amp garage 120v welding circuit.

I have some thoughts on this :)

I've looked at the commercially available units (there's one on the US market), at heat recovery ventilators, energy star dehumidifiers over 100qt/day, at high drying efficiency PTACs and hospital sized AHUs.
Also I have an electric dryer vented indoors (thanks to stupidity of the previous homeowners).

my thoughts are to do this:

dryer vent --> some kind of easily cleanable (and GOOD) filtration, probably down to MERV8
filtered air into an HRV to bypass thermal energy around the dehumidifier (so that the head pressure doesn't blow it up), and to lower the air temp to the evaporator for better performance-->into the dehu to dry and heat the air, back to the HRV to pick up the thermal energy, then into the dryer - air is just a working fluid.

like this (horrible drawing):
http://ecorenovator.org/forum/attach...1&d=1523513518

the problem with the unit on the market is cost (wow they cost a lot) and apparently dust fouling of the heat exchangers. they offer a heat pump only mode, as well as heater assisted mode (heat up with heater then switch to heat pump once the water is evaporating, instead of waiting for compressor waste heat to raise the temp of the water/clothing mix).

a major advantage (aside from not using resistive heat to dry clothes), is the lack of conditioned air being exhausted (and replaced) from your house. assuming a dryer moves 200CFM for 45 minutes, that's a lot of hot humid air infiltration in texas, or cold dry air infiltration in canada.

That's exactly what I was not going to do.
Discharging the waste heat and dust/lint outside and cooked air inside solves a lot of problems.

exactly, wow! ;)

I would argue that the waste heat isn't waste heat, but rather money being wasted. yes, the lint is a problem, and im not quite sure what cooked air is. the other issue is air infiltration. 100% of the air you exhaust must be replaced (an issue with a standard dryer as well) by unconditioned air, which then needs conditioning.

I would think the lint could be handled by a couple of extra wire screens, perhaps a minisplit style screen, and depth loading filter after.

one of the issues with portable AC units is they generally attempt to use the condenser to evaporate the water that was condensed on the evaporator side - both to increase efficiency, and to avoid the need for a condensate pump and drain hose. not sure what yours does, but if it does evaporate the water it will hinder the drying process.

if your exhaust air is adequately dry, have you considered a "hot box" with a drying rack in it, instead of a dryer? longer drying times mean the clothes tumble longer, which probably increases wear on your clothes. if you were using the AC unit for comfort, then you get dry clothes purely as a byproduct, instead of running the AC for drying? that may be semantics though.

Use concentric ducts. A dryer duct inside a stove pipe works pretty well. Make sure to slope the duct so the condensate will drain.

Cooled, not cooked.

The rig is going out in the garage. No air infiltration into the house.
Didn't I put all this in original post?

not with adequate specifics -
how many hoses on your portable 1 ton air conditioner, and where is it taking the air from that it's heating and cooling? most I've seen have no hoses for the side that "conditions" air, and one for the side that exhausts hot air and evaporated water.
assuming yours is like the one pictured, where will you place the unit?


it sounds like you're conflating the rate of heat production with energy consumed/released into the house. if that's not the case i apologize.

if you're venting a single-hose AC into the garage, you will be de-pressurising your house, and pressurizing the garage. this will lead to infiltration from the garage into the house, which is a bad practice. I assume you'd be ducting directly to the dryer and then the dryer to the outdoors? in that event you've built part of a recirculating heat pump dryer by virtue of depressurizing your house and bringing hotter, more humid outdoor air into the house to replace it, some of which through the hole you made into the attached (?) garage.

I put in the original post that the whole thing, which means the air conditioning unit and dryer are going out in the garage and that I was going to duct the cool air into the house and the hot air out of the garage.

I intentionally didn't specify if I was going to run open loop or closed loop. Because I don't know if I want to put 2 holes in the wall. But I will most likely run closed loop

I did not mention that the garage is an addition. It is completely sealed off with an exterior door and storm door and exterior stucco wall.
The garage is unfinished and very drafty. There will be virtually no pulling air pushing air from the garage to the house.

Hi

Your invention is Awesome. Is it available in the markets right now?
Best wishes
Cheers

Yeah it's available.
You go buy a used electric dryer and a portable A/C unit with at least a single discharge duct for the hot exhaust and put them together.

Hey,
Thanks for the info
cheers

Could you provide a sketch of what you're going to do with the setup? I'm confused as to how (not what) you're going to use the portable AC.

The pushing or pulling air comment refers to unwanted air leakage like you get from running any normal dryer, a single duct portable A/C or a bathroom fan from inside your house.
Running closed loop mean the intended movement of air.
There will be lots of intentional movement of air between the garage and house through the A/C unit, but little to no undesirable or unwanted air leakage or air infiltration.

that's what I was hoping you could elaborate on. There's something I think i'm missing in your plan that might be clear to me if you drew it out or explained it in detail.