Window AC + furnace mod = Cheap central air?

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DrPizza

Administrator Elite Member Goat Whisperer
Mar 5, 2001
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Also, OP, I haven't given it a ton of thought, but you may need/want an exhaust fan to aid getting the hot air from the back of the air conditioner up the chimney. An alternative, at least for this summer, might be to put a window air conditioner in a basement window (if you can), and put the furnace blower on a timer to distribute the cooler basement air to the rest of the house (just have to remove the cold air return to allow basement air into the furnace's blower.)
 

Shawn

Lifer
Apr 20, 2003
32,237
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it definitely won't cool a whole house. if you want to be cheap just get one and cool a single room
 

iGas

Diamond Member
Feb 7, 2009
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Originally posted by: RedSquirrel
Originally posted by: Rastus
Ducts for heaters and ducts for heaters+a/c are not the same. Heater ducts will corrode and leak due to condensation if A/C is blown through them. Also a window A/C isn't powerful enough to cool down an entire house.

Hmm never thought of this. The real central air units have a condenser unit that goes in the furnace which catches all the moisture before it hits the ducts.

Probably better off to just save up and do it the real way. :p I have all winter to save up anyway.
Ducts for heaters are the same ducts that are use for AC. Duct work for Heating on a furnace and AC are design by the CFM of the blower/fan. Therefore additional fan on the windows ac unit will increase the friction ratio on the duct works (translate to slightly noisier noise transfer).

Condenser & evaporator on window unit is in the same package therefore it must be hung in a window or wall exposing the evaporator to the outside air so that heat can exchange, other wise heat is just cycling in the house.

Central air conditioning employ indoor/outdoor condenser & evaporator or roof mount package design. And, ductless split is use for efficiency for room AC.
 

Red Squirrel

No Lifer
May 24, 2003
67,194
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Originally posted by: DrPizza
Also, OP, I haven't given it a ton of thought, but you may need/want an exhaust fan to aid getting the hot air from the back of the air conditioner up the chimney. An alternative, at least for this summer, might be to put a window air conditioner in a basement window (if you can), and put the furnace blower on a timer to distribute the cooler basement air to the rest of the house (just have to remove the cold air return to allow basement air into the furnace's blower.)

Actually I never explained but that was my plan. There is a window right accross the furnace room and it's a slide window so I could install it properly in the window and just need to duct the cold air into the intake of the furnace. I'm guessing those AC units have their own intake so I could let it take the air from in the furnace room so it passes through it's coils then is fed through the furnace intake. Now only thing is I did not notice if the thermostat on that furnace enables to make just the blower run.

As for the condensation that could become an issue maybe though, or do the window units condensate outside?

This is how I imagine it would work:

http://gal.redsquirrel.me/imag...ghetto_central_air.PNG

I'd shut off all the vents except for the rooms I want to cool, if this does not work then I could just install the unit in my room.
 

iGas

Diamond Member
Feb 7, 2009
6,240
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Originally posted by: EricMartello
Central Air units are rated in "tons", and the rule of thumb is 1 ton of cooling capacity per 500 sq ft. 1 ton is about 12,000 btu...but there is more to it than that. There are in fact A/C units that have that kind of cooling capacity, but they are not "window mount". They are designed to be mounted permanently in a cutout within the wall.

As long as you can isolate the compressor portion of the A/C outside of your building, it is feasible for this to work. You could buy the foam laminated with foil ducting material to make a ghetto duct which goes into the return side of your furnace. The fan would then circulate the cool air through your house...the condenser is part of the A/C unit that will be outside. On central AC units, the condenser/compressor is a separate, self-contained unit which is installed outside.
I'm not sure which desert you live in and may be insulation is lacking in the calculation, but AC is calculated by R-value of insulation, air pressure test, surface area of windows/exterior doors, skin area of house vs. volume, outside temperature, and humidity.

Rule of thumb pending newer well insulated home to poorly insulated older home IMHO is between 1200 sqf/tonne to 350 sqf/tonne.

In well insulated buildings with solar paneling walls & roofs the load calculation can be almost 1200 sqf/tonne, and in older poorly insulated, drafty, large area of singe panel windows I have seen load calculation as low as 350 sqf/tonne.

1 tonne = 12000 Btu.

Duct insulation is R-6 to R-8 on the supply lines, and return need not be insulated, unless they are in uninsulated space such as attic/outside walls (R-4 for return line).

 

iGas

Diamond Member
Feb 7, 2009
6,240
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Originally posted by: RedSquirrel
Originally posted by: DrPizza
Also, OP, I haven't given it a ton of thought, but you may need/want an exhaust fan to aid getting the hot air from the back of the air conditioner up the chimney. An alternative, at least for this summer, might be to put a window air conditioner in a basement window (if you can), and put the furnace blower on a timer to distribute the cooler basement air to the rest of the house (just have to remove the cold air return to allow basement air into the furnace's blower.)

Actually I never explained but that was my plan. There is a window right accross the furnace room and it's a slide window so I could install it properly in the window and just need to duct the cold air into the intake of the furnace. I'm guessing those AC units have their own intake so I could let it take the air from in the furnace room so it passes through it's coils then is fed through the furnace intake. Now only thing is I did not notice if the thermostat on that furnace enables to make just the blower run.

As for the condensation that could become an issue maybe though, or do the window units condensate outside?

This is how I imagine it would work:

http://gal.redsquirrel.me/imag...ghetto_central_air.PNG

I'd shut off all the vents except for the rooms I want to cool, if this does not work then I could just install the unit in my room.
RedSquirrel,

It is a novel idea to save money with ghetto ideas, but there are time you must succumb to logic. Go for ductless split heatpumps/AC if you want to save money, or splurge and go for central AC/heat.
 

Capt Caveman

Lifer
Jan 30, 2005
34,547
651
126
Originally posted by: zerocool84
Originally posted by: Uhtrinity
Originally posted by: Sea Moose
Originally posted by: Iron Woode
I doubt it will have enough capacity to cool much of anything.

this is why central air units are rated in 22,000 BTU range as opposed to 8,000 BTU for window mounts.

This. Those window units are very crap, and will not cool your entire house. They will struggle to cool a room.

I have a large window unit rated at 22,000 btu. Been running it for almost 5 years and works great. Only paid ~$250 for it at Sears on clearance.

I have one too. Loud, takes forever to cool, and doesn't pump enough air. They are good for rooms but that's about it.

22,000 btu should be enough to do a floor, you'll need some fans to aid it though.
 

Kanalua

Diamond Member
Jun 14, 2001
4,860
2
0
I worked in a small two story office building, and they cooled the entire place using a window A/C unit and a/c ducting. Worked great! Like said above, you do need a powerful A/C, and one the has a side throw vent, not a top throw...

Only pain was every once in a while the duct connecting to the A/C would fall off...too much moisture for most tape holding the duct to the side throw...
 

Raduque

Lifer
Aug 22, 2004
13,141
138
106
I once had a similar idea, but on the condenser/compressor side. I used 5" dryer ducting (two hoses) with a ghettoed enclosure around the back of the unit to exhaust hot air outside the enclosed porch that the back end vented into. It worked surprisingly well.
 

Sea Moose

Diamond Member
May 12, 2009
6,936
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Originally posted by: MikeyIs4Dcats
Originally posted by: Rastus
Ducts for heaters and ducts for heaters+a/c are not the same. Heater ducts will corrode and leak due to condensation if A/C is blown through them.

you're an idiot. ductwork is all sheet metal. The only difference may be if the duct is insulated or not, but in many many homes duct doesn't get insulated.

Bullshit
 

Sea Moose

Diamond Member
May 12, 2009
6,936
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Originally posted by: DrPizza
Actually, something that I think Sea Moose is overlooking - OP lives much closer to the North Pole than Sea Moose thinks. The air conditioning demands in a climate 100 miles north of the US border are far less than the air conditioning demands where seamoose lives (doesn't have a central furnace.) The worst the OP will probably experience is a couple of days in the high 80's. And, living on the frozen tundra called Canada, I'm going to guess that his house is very well insulated. I've been in very well insulated houses in this area (western NY) in the summer when it's 85 outside. The owners typically brag about how their house AC only cycles on about once per hour. And, I've been in upstairs apartments of houses that have virtually no insulation - those window AC units work their asses off.


In my opinion, OP, go for it - what have you got to lose? Spend a couple hundred on a new window air conditioner at wallyworld. If it doesn't work, you're only out $100 (sell it used on craigslist for $100 less than you bought it during the first "heat wave" you experience up in the Great White North.

This is why i said, consult with your local hvac professional. THey will have the right equations for the local ambient temperature. Where i am from we have to work with 40degreecelcius days. So we use 170watts per square metre. If your in a cooler climate, you may only need about 100watts per square meter.
 

Red Squirrel

No Lifer
May 24, 2003
67,194
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Originally posted by: Sea Moose
Originally posted by: MikeyIs4Dcats
Originally posted by: Rastus
Ducts for heaters and ducts for heaters+a/c are not the same. Heater ducts will corrode and leak due to condensation if A/C is blown through them.

you're an idiot. ductwork is all sheet metal. The only difference may be if the duct is insulated or not, but in many many homes duct doesn't get insulated.

Bullshit

I never seen insulated ducts here. It's just sheet metal, kinda looks like aluminum but think it's just steel.

I've seen insulated dryer hoses though. Hoses for vents going up in the attic usually have some kind of foil on them, I'm guessing that may be insulation.
 

Evadman

Administrator Emeritus<br>Elite Member
Feb 18, 2001
30,990
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I don't have a heater in my house, I just have a 2.5 ton A/C unit. In the winter, I go to the breaker and flip the hot and neutral wires so the pump spins in reverse. That way, instead of cooling my house the unit warms it up.
 

Iron Woode

Elite Member
Super Moderator
Oct 10, 1999
30,854
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Originally posted by: Evadman
I don't have a heater in my house, I just have a 2.5 ton A/C unit. In the winter, I go to the breaker and flip the hot and neutral wires so the pump spins in reverse. That way, instead of cooling my house the unit warms it up.
:confused:
 

Sea Moose

Diamond Member
May 12, 2009
6,936
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Originally posted by: Evadman
I don't have a heater in my house, I just have a 2.5 ton A/C unit. In the winter, I go to the breaker and flip the hot and neutral wires so the pump spins in reverse. That way, instead of cooling my house the unit warms it up.

WTF - i have to go now, but when i get home tonight i will give you many reason why this is wrong.
 

Red Squirrel

No Lifer
May 24, 2003
67,194
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Originally posted by: Evadman
I don't have a heater in my house, I just have a 2.5 ton A/C unit. In the winter, I go to the breaker and flip the hot and neutral wires so the pump spins in reverse. That way, instead of cooling my house the unit warms it up.

Wait, if that works, wonder if you can make a microwave cool off something very fast. Like if you have a hot soft drink you want to cool off, just put it in and set it to reverse :p
 

Bignate603

Lifer
Sep 5, 2000
13,897
1
0
Originally posted by: MikeyIs4Dcats
Originally posted by: Rastus
Ducts for heaters and ducts for heaters+a/c are not the same. Heater ducts will corrode and leak due to condensation if A/C is blown through them.

you're an idiot. ductwork is all sheet metal. The only difference may be if the duct is insulated or not, but in many many homes duct doesn't get insulated.

I didn't realize that all sheet metal was the same :roll:

Some types of sheet metal will corrode easily, others won't.
 

Sea Moose

Diamond Member
May 12, 2009
6,936
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Originally posted by: RedSquirrel
Originally posted by: Sea Moose
Originally posted by: MikeyIs4Dcats
Originally posted by: Rastus
Ducts for heaters and ducts for heaters+a/c are not the same. Heater ducts will corrode and leak due to condensation if A/C is blown through them.

you're an idiot. ductwork is all sheet metal. The only difference may be if the duct is insulated or not, but in many many homes duct doesn't get insulated.

Bullshit

I never seen insulated ducts here. It's just sheet metal, kinda looks like aluminum but think it's just steel.

I've seen insulated dryer hoses though. Hoses for vents going up in the attic usually have some kind of foil on them, I'm guessing that may be insulation.

The ducts are insulated internally if they are solid. <-- They use fibreglass blanket

Flexible duct looks like its made of aluminum foil are also internally insulated. <-- They use either fibreglass or white fluffy stuff (some sort of wool blend)
 

Sea Moose

Diamond Member
May 12, 2009
6,936
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Originally posted by: Bignate603
Originally posted by: MikeyIs4Dcats
Originally posted by: Rastus
Ducts for heaters and ducts for heaters+a/c are not the same. Heater ducts will corrode and leak due to condensation if A/C is blown through them.

you're an idiot. ductwork is all sheet metal. The only difference may be if the duct is insulated or not, but in many many homes duct doesn't get insulated.

I didn't realize that all sheet metal was the same :roll:

Some types of sheet metal will corrode easily, others won't.

All duct has to be insulated, condensation will build up and eventually leak onto your gyprock ceilings and will stain through to the otherside.

Pour yourself a cold glass of water and set it on the kitchen counter. Does the outside of the glass condensate? Yes it does. This is because the cold water inside the glass is cooling the air below dew point. Same as your ac duct.... and that condensated moisture has to go somewhere....

Fuck i got to go
 

Iron Woode

Elite Member
Super Moderator
Oct 10, 1999
30,854
12,353
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Originally posted by: Sea Moose
Originally posted by: Evadman
I don't have a heater in my house, I just have a 2.5 ton A/C unit. In the winter, I go to the breaker and flip the hot and neutral wires so the pump spins in reverse. That way, instead of cooling my house the unit warms it up.

WTF - i have to go now, but when i get home tonight i will give you many reason why this is wrong.
dude, I am pretty sure he is not being serious.

but this is ATOT so nothing is out of the bounds of reason.
 

Red Squirrel

No Lifer
May 24, 2003
67,194
12,025
126
www.anyf.ca
Originally posted by: Iron Woode
Originally posted by: Sea Moose
Originally posted by: Evadman
I don't have a heater in my house, I just have a 2.5 ton A/C unit. In the winter, I go to the breaker and flip the hot and neutral wires so the pump spins in reverse. That way, instead of cooling my house the unit warms it up.

WTF - i have to go now, but when i get home tonight i will give you many reason why this is wrong.
dude, I am pretty sure he is not being serious.

but this is ATOT so nothing is out of the bounds of reason.

lol had to be a joke. You can't "reverse" AC, because it already reverses + and - 60 times a second, so swapping the wires is only going to shift the phase by 180 degrees.

Though think heat pipes sort of have a reverse function on them, so guess if you could make an AC go in reverse, maybe it would work same way? :p
 

xSauronx

Lifer
Jul 14, 2000
19,586
4
81
Originally posted by: RedSquirrel
Originally posted by: Iron Woode
Originally posted by: Sea Moose
Originally posted by: Evadman
I don't have a heater in my house, I just have a 2.5 ton A/C unit. In the winter, I go to the breaker and flip the hot and neutral wires so the pump spins in reverse. That way, instead of cooling my house the unit warms it up.

WTF - i have to go now, but when i get home tonight i will give you many reason why this is wrong.
dude, I am pretty sure he is not being serious.

but this is ATOT so nothing is out of the bounds of reason.

lol had to be a joke. You can't "reverse" AC, because it already reverses + and - 60 times a second, so swapping the wires is only going to shift the phase by 180 degrees.

how the fuck do you know that but still start a thread like this?
 

DayLaPaul

Platinum Member
Apr 6, 2001
2,072
0
76
Just hose down the roof of the house like we used to do when we couldn't afford to run the A/C.
 

IEC

Elite Member
Super Moderator
Jun 10, 2004
14,323
4,904
136
Originally posted by: xSauronx
Originally posted by: RedSquirrel
lol had to be a joke. You can't "reverse" AC, because it already reverses + and - 60 times a second, so swapping the wires is only going to shift the phase by 180 degrees.

how the fuck do you know that but still start a thread like this?

/thread