Turning an air conditioner into a heat pump by turning it around
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- Опубликовано: 2 ноя 2014
- This describes and experiment where I turned my cheap 5000 btu air conditioner around to make it a heat pump. I show all the problems I ran into and how I solved those and that this works when the weather is 52 degrees or higher, otherwise, it frosts up the coils.
Don't try this at home unless you are expert in electricity and making modifications to appliances. 
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![Converting my A/C into a HEAT PUMP! [Adding TXV, RV & re-pipe]](http://i.ytimg.com/vi/qDQTVvDENZM/mqdefault.jpg)
Nice experiment! Midea makes 2 Reversible Window Heat Pumps: MAW08HV1CWT (8k BTU) & MAW12HV1CWT (12k BTU). According to User Manual: (Heat mode) If the outside temperature is below 39°F, the machine will shut off and display ‘LO’. I got a one at Coscto in 2022 (summer 2024 they have the U-shaped unit which is NOT reversible), but Amazon lists both units in stock. I installed it in a guest bedroom, and mainly use cooling, but have tested the heating function, and it works fine (takes unit 5 min to switch between modes).
For $379 on amazon www.amazon.com/Midea-Conditioner-Ultra-Quiet-Operation-Energy-Saving/dp/B0CVVQWGH2, that isn't much or expensive than a normal air conditioner, but it doesn't have a defrost mode so it can't be used below 41 degrees. The other unit I see from Rovsun www.amazon.com/ROVSUN-Conditioner-Function-Installation-Assistant/dp/B0CYT39Z2V doesn't say if it doesn't work below 41 degrees and needs 240 voltage.
Excellent experiment, I was fixing to try this myself, now I know the magic number, 52 degree limitation. Thanks for sharing.
Make sure you see my follow up video where I use an ardrino controller to do automatic defrosting. ruclips.net/video/wpsMVukBvG0/видео.html This is the system I use to heat my room today.
Add a solar thermal collector to warm the outside air before passing over the AC evaporator coils.
I used a window AC unit to make a 40 deg. walk in cooler for a flourist shop. Took me a while to figure out how to get it down to 40 degrees as it would only go down to 60 out of the box. Basically installed a small light bulb 12v close enough to the temperature sensor to fool it into thinking the air in the room was 20 degrees warmer than the actual room temp.
bypass the switch, no need for a bulb.
There are plug through controls for this you would simply bypass the thermostat in the unit and use the plug through settings to control.. People use them for all sorts of stuff like converting chest freezers into refrigerators and this kind of stuff like you did for the florist shop. These ones specifically can handle more amps than others and have very good reviews... www.amazon.com/WILLHI-Temperature-Controller-Thermostat-Improved/dp/B00V4TJR00/ref=pd_sbs_469_2?_encoding=UTF8&pd_rd_i=B00V4TJR00&pd_rd_r=D2DPPRKJEQY3BWSZW39H&pd_rd_w=iG3la&pd_rd_wg=aRnCe&psc=1&refRID=D2DPPRKJEQY3BWSZW39H
A small cheap device called a Coolbot will do this for you.
@@cpacker33 Yeah, well it was the mid 1980s so we did what we did and made it work. Now days it's usually a RTD sensor and you just need to add a resistor to fool the controls into thinking it's warmer.
The manual thermostat can be adjusted so it will run until the evaporator freezes up. It will then cycle off and on below 61 degrees.
To reduce or eliminate coil's frosting over, maybe you could use a solar thermal collector to bring solar warmed air to the air conditioner.
The outside air absolute himidity in the winter is dryer , with enough prewarming, you should be able to keep it above the frost point, maybe even above the dew point.
You can even gave the AC fan help pull air through the solar thernal collector pulling the heat out and improving the collector's efficiency. This could provide suplental heatibg during the day without frosting over.
Sure, one could do solar thermal right into the home, but it takes much larger thermal collector area to get a given volume of air flow to room temperature where as heat pump airconditiober concentrates the heat energy, and the airconditioner as a heat pump can have its output easilly get upto 120f.
You can modify the pcb in side and install a valve which will switch the outer heat into the room and the cold air out . The gas has to be removed and after the valve is installed, you can switch both ways by installing a toggle switch which would work both ways for cold and hot. If you to this way your fan would throw in the hot air into the room for more better and efficient temperatures.
It would need some sort of timer for defrost.
To add to what Workin Alday said would be to simply add a external circular high volume fan to blow into the outside evaporator coils. This will help your heat efficiency even more.
I did this conversion..the cold side froze over quickly..but it did generate substantial heat..
I wonder if you could fashion a separator device to possibly channel the cold out and a mix of indoor air to the intake side
I suspect that an air conditioner being used as a heat pump probably has a coefficient of performance (COP), not much different than standard heat pumps.
That is, a COP around 3 to 4 might be common in warmer winters. When the Cop is 4 and using 400 watts, you'd be getting 1.6kw of heat, pulling in 1.2kw of heat from the outsidr. As it gets colder outside, the COP can drop. When running with a COP of 3 and using 400 watts, you'll get 1.2kw of heat pulling in 800 watts of heat energy from the outside.
Yes this video was saying something like 300-400 watts in and 3000 or so of heat moved. Sounds rather high. Id like to find a chart depicting COP as a function of temperature as temps go from like 100F down to 32F. BTW they use Coolbots and Inkbirds(cheaper) to solve the icing problem when making DIY walkin coolers. Though I do like the idea of free solar heated air in the daytime
@@CharlesGwinn-ep9pb Fluid mechanics ltd makes a pretty unique heat pump. And they publush a graph that may give a snapshot of something similar to what your asking for reguarding COP At different temperatures. Search these term. Isothermal stirling heat pump cop. You'll find two interesting graphes. One for air temp, and another for differential.
And while you at it, you might like to look at their stirling heat pump and how they design the piston to get near isothermal performance.
I've played with the same thing on and off myself. I think that these units come with coils that have very little room between the fins to help their efficiency as an air conditioner. Turn them around and they work GREAT as a heat pump, but the frost closes up the tiny openings way too quickly. I haven't done it, but I think that with a much larger evaporator coil that has more space between the fins we could work around the icing problem a lot easier. Kind of kills the idea of this being a simple hack I suppose. But I also suppose maybe we could remove some of the fins ( I don't really know how, they are delicate and taking out more than every other one might do more harm than good ) to provide more air flow to allow more ice before the air stops flowing. Then maybe a flow sensing switch could turn off only the compressor once the ice builds up too much? Maybe with less fins, the ice would actually build up faster... I don't know.
I did create an arduino controller that would detect the ice over condition and turn off the compressor but keep the fan on to defrost it. I'll have to make another video on how I did that. I did use it as a practical heater and it did save me lots of money on heating my master bedroom.
I solved the frost issue by taping a styrofoam cooler over the coils. I ran a hose into the cooler from inside the house and blow a hair dryer into the hose. Works perfect.
@@richardcollins3861 Can't tell if you're joking or not as it is a possibly viable solution. Just depends how much power you're using to run the blow dryer I guess. Haha.
I was thinking just have it pull inside air into the evaporator but that also creates suction in the house pulling all of the cold air from outside in...
Might make a solar thermal collector to prewarm the air.
To overcome the freezing you need to get an insulated AC Cover, then while your unit is running direct a small portion of the hot air to the side that freezes up. This will keep it at optimal running temp all winter. Constant hot air, no freezing up. Hope this helps.
+WorkinAlday
This is the best advice I've heard yet. I should fashion a device which Takes the outdoor air temp into consideration to operate a louver which can adjust the air mixture running through the, now, outdoor coil. The electronics section should be protected or bypassed altogether or rerouted to the inside. You still have the problem of the indoor fan motor being unable to withstand excess moisture. Enjoy that compressor noise, at least the heat from the compressor can now be of benefit to you. You can find window systems for super cheap sometimes.
I am down a RUclips rabbit hole but this was a cool experiment and I love the suggestion above
This was a great explanation from the next auto play video that I thought applied and explained heat pumps vs ACs and why they need the defrost temp sensor. ruclips.net/video/dzA9jrfAvSM/видео.html
Hope you got it working well 🍻
I also think this is the most practical solution to solving the heat pump issues in cold weather and now wonder why this isn’t built into them 🤔
I want more elaboration on this topic . Could u please help us?
Yep, same results I see..Now if one were to address the freeze up issue with modifications such as very high speed fans..some geothermal modification...thanks for figuring the wattage! I personally refuse to use resistance electric heating BC its just so wasteful..I employed a $50 garage sale AC unit for mine using a light bulb to heat the thermostat in order to fool the AC unit into thinking it was above 70 degrees..then it came on..And yes, runs about ten minutes and freezes, mus be thawed and then..
Just run it on fan mode when it’s frozen over to make it defrost faster.
I know the fan mode blows air "inside" of house side, but does it also continuously blow air through the exterior coils?
@@qualicumwilson5168 yes
A lot of window units run the same motor and shaft to turn both fans
Great idea! i heated my hot tub with two submersible sump pumps, recycling the water. Though, sump pumps rate their heating capacity as inefficiency, the loss in electrical to mechanical energy was 15 percent. All the inefficiencies of the water pumps were slightly heating the water they were pumping! It took a week of pumping the hot tub, water back on itself, to raise the cold tap water to a 40 degree hot tub temperature. But once it was up to temperature, it was quickly back up to temperature the next evening after a dip. If you have a submersible sump pump, try running it in a barrel of water, in about a day, the water recycling gets warm to hot, depending on the pumps' inefficiency!
yes, I had an aquarium heated by the water cic pump..a fountain pump which really moved the water plus heated the tank..The fish LOVED the high speed water flow and grew tremendously! Like being in a stream..
Shame said developed countries such as the UK, where I live, make it so hard to actually find heat pumps on sale. People are single minded with gas appliances over here, until the stuff runs out.
I have some heat pumps that run as a dehumidifiers and during the eve my house goes to the low 50's, so the coils naturally ice. I have a few ways to deal with the issue:
First: Run a thermo sensor on the evaporator (cool side) and set it to switch the unit off once the evaporator gets to -5C or so. A Fridge thermostat works nicely.
Second: Run the unit with a variable duty cycle. Something such as 5 minutes on and 10 minutes off. This needs a digital timer to work properly.
Third: Wire a valve bypassing the expansion device. This will trow hot gas from the inside coil to the outside coil, effectively defrosting it in a few seconds. The cycle can be repeated every 5 or 10 minutes, but requires the unit to be re-gassed.
Whatever the case leave the outside fan running to help melt down the ice.
Susana Godinho
No air exchange from outside to inside or outside to inside. The unit uses the refrigerant to move heat from inside to outside in cooling. In heat mode it moves heat from outside to inside. The air in your home is recirculating in through the coil and then blown back into the space.
I did this all winter long only time it stopped was went temp got down to single digits I had a 500 watt heater to keep coil from freezing under 38 set it on a timer cheap heat solar could make it near free heat
I was thinking similar use one of those solar heat air exchangers for day time and heat lamp at night to cycle a set time after the unit shuts off and see how far you can get with the unit.
How did you bypass the thermostat?
In this example, I think I just disconnected the thermostat control and shorted it so it would always be on. See my other videos on how I use an arduino controller to use a relay to control the fan and compressor which allows me to use this DIY heatpump down to 40 degrees F.
1 W is equal to 3.41 BTU/h, helpful to know.
Not sure that works. 1000w would be 3410 BTUs..he is getting way more
Cool idea but you may have a problem with the electrical parts getting wet by the rain
Fan and Hvac dude . This is solved by making an awning cover.
I solved the frost issue by taping a styrofoam cooler over the coils. I ran a hose into the cooler from inside the house and blow a hair dryer into the hose. Works perfect.
this person is making a clever riddle. He is inefficiently using resistance heating of the air for the air condtioner to reclaim, so there is no advantage, and infact, now is paying for 1500watts as well as the power to operate the air conditioner. He probably made this post out of frustration to some of the ideas other posters have presented here to defrost the coils. Its all in teasing good fun, but lets remember, this youtuber is actually saving real money on his electric bill while he learns abpout aircondtioners and heat pumps and efficiency.
Instead of a blow dryer he should just use another reversed window unit of significantly smaller capacity as a defroster, and then another one for that one until the problem either goes away or becomes small enough to be solved by another type of very small heat source.
Ill start by defining terms: front is the intended inside and back is the intended outside part...
Confused here? lets begin with window ac in correct orientation, front inside.
well these window units draw air from the lower 2/3 of the front and cool it and push said air out the upper 1/3 of the front. and pump the heat to the back or outside coils.. So if its hot inside your home, in AC mode it pulls the heat out of the home to the back or outside of unit to be removed from the home.
lets now reverse the unit front is now outside.
So if its cold outside and inside and you desire heat inside the home, turning it around backwards would draw cold outside air into the front lower 2/3 of the front (thats now outside) and try to cool it even cooler. it would struggle to find heat outside to pump to the back (now inside the home) and now coils will frost over.
a crafty handy individual could duct or direct air from inside the home to front intake (lower 2/3 of front thats now on the exterior) where it would initially find cool air that in time gets warmer as the unit pumps the heat into the home from back of unit (now inside the home) this would solve frosting and essentially pump the cool interior air out through the front upper 1/3 of front (now outside) the thermostat wouldnt work and a crafty person could get a lizard habitat thermostat and plug ac into that.... also ducting or directing air to the front should be done with insulating material like styrofoam sheet and the proper metallic tape.
Do see my part 2 of this project where I created an Arduino controller which just lets the fan run in order to defrost the coils. This works very practically and I used this setup to heat my room. ruclips.net/video/wpsMVukBvG0/видео.html
this is fucking genius!
What if you ran the whole AC unit inside your house and just vented the cold air out? The coils should stay much warmer, and it should run much longer. There might be some moisture you have to deal with. But no Matt how cold it is out side it should work
It might be easier To do this with a portable AC rather than a window unit.
@@mjmbishop exactly my thinking when I bought a second hand portable ac. Just need a proper hose on top. I don't understand why ac market is so uncompetitive
To vent the cold air out you have to consume warmed air from inside thus creating negative pressure in the house and forcing cold drafts all over the house. Putting it inside and intaking out door air and discharging cold air again outside would result in the very same freezing up issue. Remember the window AC has totally separate cold and hot sides both has separate intakes and discharges. If you tried to use a portion of the heated side air to defrost the cold side then your decreasing the efficiency of the whole unit and thusly it becomes no better than the electric resistive heater.
@@eXTreematorIf your discharging the cold air out the window and the unit is inside think where did that air come from….. You literally put a vacuum on your house pulling outside air in to displace the cold air out.. the window ac or portable ac are separate between the cold side and hot side. The content creator was correct to mount it this way and use the window ac. If you use a portable and intake air from the house to discharge cold you increase draft in the house (negative pressure) if you intake outside air and discharge for the cold side you have the exact same issue of the cold side coil freezing up.
@@masterdebater8757 if it's a standalone small house then yes. Otherwise no. I actually tested all of this and works good enough. And i heat up my corner room like this with external thermostat when i feel it's too cold or start to feel sick. Of course all of which would be unnecessary if fucking j3v (youtube leftist dump) building owners had thermostats on radiators and everyone could adjust. You can make a loop to circulate only cold air from outside (a proper way to do it avoiding frezzing-at least protracting) but in big building it makes no difference (improves dehumidifing ability).
I'm just throwing this out there. Is your ground temperature above 52 degrees? If so a large pex loop underground filled with dilute ethylene glycol (Antifreeze) bathing the cold coil in its ABOVE 52 DEGREES heat, would be a great source of heat for your house, without frosting up (because there'd be no freezable moisture against the coils.
That might work, but would be really complicated and expensive. I did do a follow up video where I created an Arduino computer controller to implement an automatic defrost cycle that allowed me to create a practical heat pump from an air conditioner: ruclips.net/video/wpsMVukBvG0/видео.html
What of you just bathed the coil in antifreeze above ground??
If you want to make eco just use inplix handbooks
Babe go outside and Turn it on
So she can find a way to Fashion a box to the front part of where it pulls the air in from the outside and then stick a pipe on that and have that come in through that window or something you could probably solve the issue of it icing up and really cold temperatures
All you really need to make this work with the unit right side in is a defrost timer board and reversing valve from some old heat pump at the scrap yard. I am not sure what is available in your area but reversible window AC units are commonly available here and not significantly more expensive than a straight cool unit.
Post us a link I can only find 240volt units or fake/ false links to window AC's with resistive heaters inside.
Damn you should just get a reverse cycle air con.
If you find a 120 volt window AC that is also a heat pump please share it with us! As far as my research has taken me I have only been able to find 240volt units that have this function or false ad's or redirected links to window AC's with electric resistive heat cores inside them.... It is a shame none of the major brands are making these window model AC/heat pumps because they would sell to people like me that do not find a need for central air nor do we want the hassle or expense of these new split ac systems. Also if you could make that with VRF tech inside that would be great.
Not bad but it doesn’t work well
A 1500 watt resistance heater puts out 5000 BTU. So your 5000 BTU ac is putting out about the same.
Explain more plz
No he said it uses only 300w while running. He’s actually saving energy
You should make something that makes it where it pulls the heat that is coming into the room back through it because then it'll concentrate that heat and you really won't lose no energy and it would pull it through like a pipe or something and then you could have that where it pulls the heat in from the room that way it doesn't freeze up and it'll get twice as hot and you won't have to worry about it freezing up as easily
Ill start by defining terms: front is the intended inside and back is the intended outside part...
Confused here? lets begin with window ac in correct orientation, front inside.
well these window units draw air from the lower 2/3 of the front and cool it and push said air out the upper 1/3 of the front. and pump the heat to the back or outside coils.. So if its hot inside your home, in AC mode it pulls the heat out of the home to the back or outside of unit to be removed from the home.
lets now reverse the unit front is now outside.
So if its cold outside and inside and you desire heat inside the home, turning it around backwards would draw cold outside air into the front lower 2/3 of the front (thats now outside) and try to cool it even cooler. it would struggle to find heat outside to pump to the back (now inside the home) and now coils will frost over.
a crafty handy individual could duct or direct air from inside the home to front intake (lower 2/3 of front thats now on the exterior) where it would initially find cool air that in time gets warmer as the unit pumps the heat into the home from back of unit (now inside the home) this would solve frosting and essentially pump the cool interior air out through the front upper 1/3 of front (now outside) the thermostat wouldnt work and a crafty person could get a lizard habitat thermostat and plug ac into that.... also ducting or directing air to the front should be done with insulating material like styrofoam sheet and the proper metalic tape.
sorry I posted this first from my sons account then later posted from my account