Home made air conditioner?

lml999

Minister of Fire
Oct 25, 2013
503
Cape Cod, Massachusetts
Maybe I have too much time on my hands (not really...), but here's a challenge...

We have a good sized room (12x20) that experiences a lot of heat gain during the day. 80 square feet of south facing glass plus two skylights. I'm going to cover the glass with 90% sunblock screen material, which should cut down on some of the solar gain during the summer.

We also have an LCD tv and av receiver that generate some heat. I've thought about relocating the receiver, but that's challenging.

The two windows in the room are too narrow for conventional AC units. We run a large AC at the opposite end of the house, the closest location where I can mount a window unit.

For now, we're making do with the window AC units. At some point we'll invest in mini splits or perhaps a high velocity system...but that's a ways off.

The room has an HRV return feeding fresh air in. Typically that air is just a couple of degrees higher or lower than ambient inside air.

The HRV unit is in the basement, directly below the room in question, with easy access to the ducting.

So I'm thinking (which usually gets me in trouble...)

Can I cool the air being returned by the HRV?

One approach is to insert a cooling box inline that has a small water radiator and use either my well water supply or a ground loop with a solar powered pump to provide the cooling function. I have not done any testing of ground or well water temperature yet. The ground loop would be easier, as I would not have to deal with circulating house water through this setup.

I don't know if this would provide sufficient cooling to be worth it. I've done some googling and found people creating McGyver type cooling systems with copper loops going through buckets of water and ice and then looped on fans. That approach would require constantly adding ice...

I've already got the air flow, so I'm wondering how to condition it...

By the way, the other short term option is to use a portable air conditioner and exhaust it through the window or the fireplace. I haven't heard good things about those units...

Comments appreciated!
 
  • Like
Reactions: xman23

blades

Minister of Fire
Nov 23, 2008
3,519
WI, Leroy
basically what you are talking about was referred to as a swamp box. warm air through pipes with cold water cascading over pipes. in your case reversing - water in pipes air flowing around which is the same principal as a standard ac coil. old car radiator, pump, fan=basic supplies. Well water will be apx 50::F if you pump it out and back in (geo thermal ) eventually the surrounding earth will warm up and you lose the differential, unless you divert the water somewhere else. It is better to run the warm air in the pipes and mist them with a hi velocity fan and water. The combination of mist , fan & evaporation is more efficient and uses much less water. Biggest hurdle is what to do with the water that does not evaporate. this is a pretty slow air speedin the pipes to accomplish the heat transferance with alum. being the best for heat transfer. Used to have a building on the river using the swamp box to cool it in the summer- water drawn from and returned to river via a pump ( pricey running that pump).
 

brenndatomu

Minister of Fire
Aug 21, 2013
5,265
NE Ohio
What about using one of those portable AC units...I think the exhaust can be adapted to just about any window size...and they have gotten pretty cheap the last few years...not much more than a window unit.
upload_2018-7-13_13-37-53.jpeg
 
Last edited by a moderator:
  • Like
Reactions: sloeffle

begreen

Mooderator
Staff member
Nov 18, 2005
83,703
South Puget Sound, WA
What about using one of those portable AC units...I think the exhaust can be adapted to just about any window size...and they have gotten pretty cheap the last few years...not much more than a window unit.
View attachment 227846
Someone showed me a picture of a 5000btu unit the cobbled into their RV recently.
 

lml999

Minister of Fire
Oct 25, 2013
503
Cape Cod, Massachusetts
Save your money for the mini-splits. Get a nice fan. :)
Sigh...

I have no problem running the AC at the other end of the house and dealing with the imbalance. SWMBO, on the other hand, doesn't like it COLD in that end of the house... So...

If I stall long enough, the issue will go away and we'll pick up the conversation about getting the insert installed in the fireplace. 5 cords of seasoned oak and I have no place to burn it...
 

xman23

Minister of Fire
Oct 7, 2008
2,117
Lackawaxen PA
What about using one of those portable AC units...I think the exhaust can be adapted to just about any window size...and they have gotten pretty cheap the last few years...not much more than a window unit.
View attachment 227846
I have one, which we use in a single bedroom. I don't recall the size, but I think it was fairly large. I works but has a hard time keeping up with the heat of the day. Being the engineer I am, I got thinking about whats wrong. My theory is the condenser is within the unit. That's the part that would normally be outside. So the heat from the condenser is ducted and exhausted out your window. The problem, as I envisioned it, is the air to do this comes from the room your trying to cool. Creating a negative air pressure in the room. The air replacing it is hot air from the surrounding rooms. Based on this and the efficiency of the machine I theorized the room should get hotter. Must be something wrong with the calculations. A bit of rebuilding of the machine, creating a second duct should fix this design flaw. But as usual I have more idea's and plans than time.
 

fbelec

Minister of Fire
Nov 23, 2005
2,784
Massachusetts
swamp coolers don't work if it is humid. if you don't have the money for a ductless split pop a friedrich air conditioner thru a wall. i say friedrich because they are one if not the quietest wall or window units out there. and they last a long time. they are priced between a normal window air of good quality and a ductless split.
 

TillLindemann

New Member
Jan 22, 2020
3
Vienne
Sigh...

I have no problem running the AC at the other end of the house and dealing with the imbalance. SWMBO, on the other hand, doesn't like it COLD in that end of the house... So...

If I stall long enough, the issue will go away and we'll pick up the conversation about getting the insert installed in the fireplace. 5 cords of seasoned oak and I have no place to burn it...
Hey there, so I think that I have problem with my Air conditioner, so when I was on the job, I've comed at home and I felt that smell of aircon that was all over the place. So I've tried to fix it but I actually don't know how it works so I made it worse and it was over for me. Later when I tried to ask on different forums about this I found an article about aircon servicing that helped me to fix it fast and with high quality of their work.
 

Sodbuster

Minister of Fire
Sep 22, 2012
1,458
Michigan
We installed a window rattler in our bedroom and keep it at about 65 in the heat of summer at night, Good sleeping at it barely makes a dent in the power bill. I keep the central AC at 80 just to keep the humidity out. We also use some oscillating fans to stir things up.
 

peakbagger

Minister of Fire
Jul 11, 2008
5,442
Northern NH
The portable units are very inefficient. You have what appears to be a significant heat load. You would need a lot of well water to make a difference you also need to rig up a pump to drain the water that a portable AC unit condenses out of the air or get used to emptying out the tank frequently. Lets guess you need 10,000 BTUs per hour of heat removed from the room. A BTU by definition is the heat required to heat one pound of water one degree Fahrenheit (F). A gallon of water is roughly 8 pounds. Assume your well water is 45 degrees and you want the room to cool to 75 degrees. There has to a be difference in temperature between the water and the air so lets assume 25 degrees of cooling for each pound of water.

So lets do the math. Convert 10000 BTUS per hour to BTUS/minute 10000/60= 167 BTUs per minute. Divide by 25 and you need 6.68 pounds per minute or around 0.8 GPM through the coil. Your well needs to be quite large so that it does not heat if you are recirclating the water to it, otherwise you need to drain it somewhere. If you have big garden or orchard you amy already be moving that much water. You also need to pay to pump that water. Note that this is a very simplified approach as in addition to the cooling you need to cool the air, you also have some hidden cooling to condense the liquid in the air. This usually means its takes a long time to initially cool the room to dry the air out. I have seen articles about systems like this where water is essentially free, usually the water source is above the house like a spring so they dont need to pay to pump it.

The other water based cooling approach is evaporative cooling. The equipment used to cool is usually referred to as "swamp cooler". It only works in dry climates where the relative humidity is quite low. Water is trickled down pads that are kept wet all the time and the air is blown through them. The air cools down but gets damp. In places like the desert they can make a big difference but if you live near the ocean or in an area with lots of plants and trees, high temps have high humidity along with it. Not many swamp coolers sold in the Northeast or the Atlantic seaboard.

Cooling only minisplits are getting cheaper everyday. There are units that come with specialized connectors and piping that do not need a service tech to install. They typically are not super efficient and its questionable on their life span but usually much more efficient than a window unit.

If you could shade the windows from the outside with an air gap between the shade and the window it makes a big difference in cooling. Either that or sheets of Isoboard foil faced foam can be cut to fit in the window openings on the outside. Interior blinds are better than nothing but sunlight heat ups the blinds so it heats up the room.
 
  • Like
Reactions: ben94122