homemade ac unit

so i might have a very tight space to work with in the future, with not much space to vent out hot air. so instead i've decided i'll study up a bit and build my own ac unit or air chiller.

right now my knowledge on ACs is pretty lacking so this is an open request for any links to threads on here of people that have made a cooling system from scratch or something along those lines.

i know you're thinking it's a waste of time, and that i should just go buy one, but i invested all my money in my avatar. maybe i'll buy a cheapo at goodwill and take it apart and upgrade it or something.

i'm just compiling reading material right now, and as time goes on i'll absorb as much as i can and build one of the best design.

i thought it'd be cool to make something like this and i'll post pics of the process and finished product.

so please throw me any reading you have on keeping a temp low or how an ac works or how to build one. i don't want wiki links or something i'll be able to google mine in a couple seconds. so share with me something you think i wouldn't know, or couldn't find with a quick search.

i have a general idea in my head, and as i read up i'll sketch up some designs and post em here to get some constructive criticism.

heat is going to be my biggest problem so i'm going to be taking this kinda seriously.

fortunately it'll only be a couple lights, so it doesn't have to be super industrial.

so an optimal ac unit or chiller unit would be:

-cheap to make(i've got a carpentry background)
-easy on the ears, not loud.
-easy on the electricity, pulling barely any amperage.(for the sake of other stuff i'll have on the circuit)
-chill the room without being fed a cooling agent every day.


if there's any points i missed please fill me in. anyway give me your feedback, if it's cheaper and easier to buy, you'll have to convince me. besides i would love to build one just for the experience and knowledge.

and a bonus is all you guys that wanna tag along will learn a boat load, and the forum will have a nice guide to ACs.

here's my questions so that we can get this collaboration started:

-i'm thinking a maze of walls that the air has to weave around, and these walls(made of copper pipes?) would be cold all the time because of a cooling agent running through them, and that would keep the air cool.

-would radiator fluid through some copper pipes do the trick?

-what's the cooling agent used in most ac units?

-is it possible to have a cooling unit without moving parts? a completely static cooler would be ideal because it'd be the easiest to make and maintain. unfortunately it seems like i'd need at least a pump for the fluid in the maze idea.

-what about a maze made out of thick concrete? would it keep the air cool effectively or would the stone just warm up after a couple hours and be useless?

~~~~~~~~~~~~~~~~~~
i'll find the answers to those one way or another and post my thoughts here. if you have some answers/questions/input i'm very open to suggestions.

link me to any useful threads!

First of all how big of any area are you trying to chill and how many degrees cooler are you trying to achieve? I also have been giving this a little thought. Most a/c units run on R22 and frigs on R134a. Some coolants are very dangerous to u and the ozone and should be handled carefully. A/C units cool the air using a compressor and two coils filled with the coolant. One coil gets cold and the other gets hot. Fans are used on both coils, one to cool the hot side and one to push the cold air out into the room/duct. I think that if you ripped apart an old frig and used the parts you could make some thing to chill water for sure and I think it would be ok for a small grow box/closet to cool the air. I think the easy thing to do is just find a old though the wall unit somebody is throwing out and fix it. I would love to here others thoughts on this as well.

dmakk777 said:

First of all how big of any area are you trying to chill and how many degrees cooler are you trying to achieve? I also have been giving this a little thought. Most a/c units run on R22 and frigs on R134a. Some coolants are very dangerous to u and the ozone and should be handled carefully. A/C units cool the air using a compressor and two coils filled with the coolant. One coil gets cold and the other gets hot. Fans are used on both coils, one to cool the hot side and one to push the cold air out into the room/duct. I think that if you ripped apart an old frig and used the parts you could make some thing to chill water for sure and I think it would be ok for a small grow box/closet to cool the air. I think the easy thing to do is just find a old though the wall unit somebody is throwing out and fix it. I would love to here others thoughts on this as well.

Click to expand...

yeah getting an old one and fixing it up can be free if i do it right. whats the most common problem in a broken fridge?

hey with a bank roll like that just buy one, find a used one on craigslist in your area

Take an entire car air conditioning system from a junkyard. Condenser, compressor and everything. Hook it up to a good sized AC electric motor on a belt, a high speed electric drill or a circular saw or something might work, whatever you use it will need some torque to spool that compressor. Wire it up with a resistor and capacitor (look it up if you arent sure how to) to have a duty cycle that will keep the room at the temp you want it. Ought to work pretty good it might make a little noise but it wont be too bad..

Between a used AC system and a used saw and some basic electrical stuff should run you less than 100 bucks.

I have put some thought into just that.

Assuming you have a mini or micro grow (if you are doing big just go to costco and buy a window A/C) you could pick up one of those mini fridges. Most of them have a compressor that is quiet and pulls little power. Many have the cooling coils just hanging out inside the Freezer area. The easy way is remove the door and attach the fridge to the end of your grow cabinet. (fridge area to the inside)
The least amount of room would require that you cut the back panel (that includes the compressor and condensing & evap coils) off the rest of the insulated box. Mount the panel with the cooling coils inside the grow cabinet and the compressor and condensing coil on the outside. Careful when cutting it apart so you don't cut the refrigerant lines or wiring. This even gives you a temp control for inside the grow cabinet. Add an exhaust and a circulation fan, lights and your favorite clone.
water add some grow time and smoke.

The cost of a mini fridge at wallyworld is less than $100.

Good luck

methias said:

I have put some thought into just that.

Assuming you have a mini or micro grow (if you are doing big just go to costco and buy a window A/C) you could pick up one of those mini fridges. Most of them have a compressor that is quiet and pulls little power. Many have the cooling coils just hanging out inside the Freezer area. The easy way is remove the door and attach the fridge to the end of your grow cabinet. (fridge area to the inside)
The least amount of room would require that you cut the back panel (that includes the compressor and condensing & evap coils) off the rest of the insulated box. Mount the panel with the cooling coils inside the grow cabinet and the compressor and condensing coil on the outside. Careful when cutting it apart so you don't cut the refrigerant lines or wiring. This even gives you a temp control for inside the grow cabinet. Add an exhaust and a circulation fan, lights and your favorite clone.
water add some grow time and smoke.

The cost of a mini fridge at wallyworld is less than $100.

Good luck

Click to expand...

sounds good but i've left the door open on a fridge for a while and eventually the compressor or some mechanism inside breaks and it doesn't produce cold air anymore. but yeah taking apart an old fridge or ac unit, or getting a small new one seems like the best approach. pictures will come in time, still tossing it around in the head.

Hey mikov, I'm working on an proof of concept right now that should be finished this weekend (have to chase down a sheet of copper). If it works I'll post it here or start a thread. If you are looking for a cheap route, the salvaged mini-fridge is the way to go, can't build anything better cheaper period. If you just want to experiment then there are a world of ideas: evaporative cooling, ammonia absorption cooling (propane fridge), typical freon systems (well not freon anymore), TEC (peltier effect), etc. Good to see you didn't electrocute yourself

I don't have any pics of how I did it but I used an old drinking fountain that was removed from a school to make a water chiller. It was the type that cools the water before pumping it out to be consumed.

I just took it apart without disconnecting the refrigerant lines which involved some creative cutting of the drinking fountain and then placed a second pump in the reservoir that would pump the res water through the chiller and back into the res. Most of them use 1/4 inch compression fittings on the water inlet line and this particular one had the same fittings on the outlet side that went to the valve on the top. All I had to do once it was taken apart was mount the pieces to a board outside the grow area so the fan that cools the condenser core (hot part) wouldn't heat up the grow room and connect some hose to the lines using brass fittings I got from Lowe's.

I plugged the pump and chiller into a timer that turns them both on twice a day for 30 minutes at a time and adjusted the thermostatic switch on the chiller so that the chiller only turns on if the water is over 70 degrees.

I got the fountain for free and already had an extra pump so I only bought some hose and fittings for about $12-15.

I thought about using it to make an A/C unit but ended up doing the chiller instead. To make an A/C unit out of something similar you'd just have to cut the refrigerant lines on either side of the tank that houses the coiled copper line and splice in something that serve as an evaporater core (cold part) and install a fan to blow air across it. I did the chiller instead of this option becuase I don't have a vaccuum pump anymore to suck the system down before charging with new refrigerant.

It's crucial to an A/C units' operation for the lines to free of leaks and there can be no air in the system, only refrigerant. You have to put it under a vaccuum to remove the unwanted air and it's a good idea to let it sit under vaccuum for a bit to make sure there aren't any leaks. If it holds vaccuum, it'll hold pressure, typically. So if it holds, you're good to go and you can get r134A refrigerant at hardware stores and auto parts stores. Harbor Freight sells vaccuum pumps pretty cheap too as well as gauges and anything else you'd need if you decide to do something similar.

I used to work at an Auto Electrical and Air Conditioning shop so I have a little experience with A/C. I don't claim to be an expert and I haven't worked on automotive A/C systems in about 10 years but if you have any questions, feel free to ask. I'd be happy to try and answer them for you.

ScrogThis said:

Hey mikov, I'm working on an proof of concept right now that should be finished this weekend (have to chase down a sheet of copper). If it works I'll post it here or start a thread. If you are looking for a cheap route, the salvaged mini-fridge is the way to go, can't build anything better cheaper period. If you just want to experiment then there are a world of ideas: evaporative cooling, ammonia absorption cooling (propane fridge), typical freon systems (well not freon anymore), TEC (peltier effect), etc. Good to see you didn't electrocute yourself

Click to expand...

hah well i have yet to get in the breaker box and do it, but like i said i'm going to be get super smart on it before i do anything. i also wanna calculate exactly how many amps i'll be pulling. with one 600 watt and a small ac unit, a small pump, and a fan or two it might not be too much. well below 20 amps, probably below 10, and i think each breaker can take 21 or something to that extent so i might just plug it into a current circuit until i have the time to mess with it.

and sick i'm looking forward to your concept. throw a link on this thread if you start a new one for it. if you get too lazy to finish it that's cool, i'm going to draw some plans up after class today.

Dezracer said:

I thought about using it to make an A/C unit but ended up doing the chiller instead. To make an A/C unit out of something similar you'd just have to cut the refrigerant lines on either side of the tank that houses the coiled copper line and splice in something that serve as an evaporater core (cold part) and install a fan to blow air across it. I did the chiller instead of this option becuase I don't have a vaccuum pump anymore to suck the system down before charging with new refrigerant.

It's crucial to an A/C units' operation for the lines to free of leaks and there can be no air in the system, only refrigerant. You have to put it under a vaccuum to remove the unwanted air and it's a good idea to let it sit under vaccuum for a bit to make sure there aren't any leaks. If it holds vaccuum, it'll hold pressure, typically. So if it holds, you're good to go and you can get r134A refrigerant at hardware stores and auto parts stores. Harbor Freight sells vaccuum pumps pretty cheap too as well as gauges and anything else you'd need if you decide to do something similar.

I used to work at an Auto Electrical and Air Conditioning shop so I have a little experience with A/C. I don't claim to be an expert and I haven't worked on automotive A/C systems in about 10 years but if you have any questions, feel free to ask. I'd be happy to try and answer them for you.

Click to expand...

sounds like getting it to be pressurized and air free could be hard. so the evaporator core is what will get super cold and need the fan blowing on it? so i assume this is the part that breaks down if the ac stops producing cold air. what usually causes it to break down? loss of pressure?

sounds simple enough, i doubt i could keep any air from getting in when i disconnect the vaccum to try and get the whole circuit closed up. there will have to be a split second or two where i have to take off the vacuum and attach the copper wire. how can i pressurize it and close the line at the same time? otherwise sounds like i could do it.

Heh, I won't show it to you then, it's finished just haven't gotten the pics up. It's not working but it's finished... fried the power supply, too small. Too complicated for you to build anyway!

Kidding, here are some drawings, have to edit the build pics; make 'em smaller, take out the nekkid chicks, etc. More later.

Mikov, there are many things that can cause a system to break down but typically it is loss of refrigerant due to a leak someplace.
The evaporator core is the part that gets freezing ass cold and yes that's where you'd want a fan to be blowing to cool the air in your room.
Just keep in mind that you'll also need a fan blowing on the condensor core because it gets HOT. I have my condensor core mounted just outside te grow room with the original fan blowing across it. It can get hot enough to burn the shizzle out of you be sure it's not in your path of travel or anything.
As far as not getting air in the system without having a vaccuum pump, not sure how you'd do that.
I like what scrog this has going there. Very creative.

My neighbor is in the process of moving out and he wants to get rid of two a/c units. The kind that fit into the window with a little skirt to seal around the edges.

I have considered buying it and using it this winter to pump cold air since the house(or ambient temps) will be a little higher. I currently have tapped into my central a/c, but haven't run it since I harvested. I know I would have to catch the condensation drip, but how would it affect the air quality? I assume the exhaust is just warm air? If so, it could actually help keep the house warm.

Sorry, don't wanna hijack this thread. Just a thought on the matter based upon my current situation.

budlover13 said:

My neighbor is in the process of moving out and he wants to get rid of two a/c units. The kind that fit into the window with a little skirt to seal around the edges.

I have considered buying it and using it this winter to pump cold air since the house(or ambient temps) will be a little higher. I currently have tapped into my central a/c, but haven't run it since I harvested. I know I would have to catch the condensation drip, but how would it affect the air quality? I assume the exhaust is just warm air? If so, it could actually help keep the house warm.


Sorry, don't wanna hijack this thread. Just a thought on the matter based upon my current situation.

Click to expand...

Someone told me when I asked but I don't remember the reasoning behind it. Those window ac units have written all over the boxes and inside the instructions that the exhaust is NOT to be directed into any garage or living space. Again, I don't remember exactly why but that's what they all say on them.

no worries mate you're not hijacking.

what if i have a fully enclosed room? the condenser core and evaporating core would have to be in the same area. could i just insulate the condenser core to keep the heat from going into the grow space? or would that cause problems?

so a core is going to be super hot, and the other super cold, and if the air blowing across them goes in the same enclosed space they'll just cancel each other out? i really hope i'm wrong about this. i won't be able to vent the hot air anywhere, what could i do? please tell me i can insulate it. i'm trying to make a grow room with no venting available.

Mikov said:

no worries mate you're not hijacking.

what if i have a fully enclosed room? the condenser core and evaporating core would have to be in the same area. could i just insulate the condenser core to keep the heat from going into the grow space? or would that cause problems?

so a core is going to be super hot, and the other super cold, and if the air blowing across them goes in the same enclosed space they'll just cancel each other out? i really hope i'm wrong about this. i won't be able to vent the hot air anywhere, what could i do? please tell me i can insulate it. i'm trying to make a grow room with no venting available.

Click to expand...

I'm afraid I don't know how to accomplish this with a typical AC system. I believe the experimental deal that 'scrog this' as come up with would work in your case though, if I'm understanding it right.

Don't know when the new power supply is going to show up, thought I'd get started with this post and not leave you hanging. I don't have the switches and such done, waiting on the supply to hook it all up. The drawings are close, available tools and materials predicated some modification.

The idea is a thermal electric cooler using a peltier device. Keep in mind it's just a working prototype. Cons: not very efficient, expensive, draws a lot of power - Pros: portable, works well for a small space, can be used as a heater by reversing polarity.
Same concept as the portable warmer/coolers for camping or the desktop mini-fridges, they use them in wine storage also.

I'm using a 62mm TEC with two big cpu heat sinks, they have five heat pipes surrounded by aluminum fins and a passive sink as well. Both small fans ended up on the hot side, salvaged a small 110v fan for the cold side. Basically it's an insulated box enclosing the cold side of the TEC and a big heat sink on top cooling the hot side with fans to move all the air around.

It connects to the 4" fresh air inlet on my cabinet via dryer duct so it can be positioned where ever it's handy. It works by drawing air from the room and cooling it as it passes over the fins in the box. The big heat sink on the outside is needed to keep the hot side cool. The device is limited by the difference in temperature between the cold side and the hot side (deltaT). In other words if the maximum temperature difference it can create between the two sides is 65 degrees and the hot side gets up to say 165 degrees then the cold side will be 100 degrees. Conversely if you cool the hot side to 100 degrees then the cold side will be 35 degrees. In my testing it looks like 10-15 degree reduction in ambient air temp is possible in a small space.

That's enough for tonight, here's a few pics of the construction.

well below 20 amps, probably below 10, and i think each breaker can take 21 or something to that extent so i might just plug it into a current circuit until i have the time to mess with it.

Click to expand...

There are no 21 amp breakers, a circuit breaker is a safety device intended to interrupt the current path should the circuit become overloaded or shorted. Just because you have a 20A breaker doesn't mean the circuit can handle that much current, someone may have replaced a 15A with a 20A for example (happens all the time, I've seen lamp cord used to add outlets). Look at the wires in the breaker panel, 14GA aluminum wiring was/is typically used for 15A circuits in older and manufactured housing. Usually 12GA copper is used for 20A circuits in newer housing. These aren't rules, just typical. If you have small aluminum wiring on a 20A breaker, pushing that capacity could result in a fire. See if you can borrow or rent an amprobe or ampmeter with the inductive (clamp style) pickup then simply clamp the probe around the wire connected to the breaker with everything on and read the actual load. Trust me a fire will wreck your weekend, be safe.

Arrg! Killed another thread... didn't mean to hijack the thread, let me know if anyone is interested in details on the cooler/heater build.