Window AC + furnace mod = Cheap central air?

[DrPizza]

Originally posted by: Sea Moose

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)

Sorry to burst your bubble, but of all the ducts I've seen in this area, I'd estimate that less than 10% are insulated. The vast majority of the homes are older, and 30+ years ago, I don't think ANYONE in this area had central air. Typical summer: maybe 10 days in the upper 80's/low 90's.

 

[alkalinetaupehat]

Originally posted by: DrPizza

Originally posted by: Sea Moose

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)

Sorry to burst your bubble, but of all the ducts I've seen in this area, I'd estimate that less than 10% are insulated. The vast majority of the homes are older, and 30+ years ago, I don't think ANYONE in this area had central air. Typical summer: maybe 10 days in the upper 80's/low 90's.

Current house I'm renting has a sort of fiberboard and 2x4's for the heating ducts, I really doubt running cold air through that is a good idea. Oh and I do believe that a house I worked on a while back had ductwork without internal or external insulation. Not saying that's smart but eh, so it was.

OP, given your winter pics you have on your blog, I'd say suck it up and save for central A/C. Go get an estimate and don't put your ductwork at risk just for a month or two of A/C. Very interesting idea though, just not something you want to do with your house.

 

[iGas]

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

Some older AC or conversion ductwork do not have insulation on supplies or return line.

 

[iGas]

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.

Sheet metal for ductwork are all the same galvanize metal.

Light gauge sheet metal are allows to be use in residential only, while industrial must employ heavy gauge sheet metal, and some are requires to be spiral or aluminium/stainless steel by engineered design.
.

 

[iGas]

Originally posted by: Sea Moose

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)

I'm not familiar with solid duct with internal insulation. Solid duct with external R-6 or R-8 insulation is common in my area.

 

[MrDudeMan]

Originally posted by: DrPizza

Sorry to burst your bubble, but of all the ducts I've seen in this area, I'd estimate that less than 10% are insulated. The vast majority of the homes are older, and 30+ years ago, I don't think ANYONE in this area had central air. Typical summer: maybe 10 days in the upper 80's/low 90's.

My house was built in 2001 and all of the ducts are fairly heavily insulated, so maybe it's a mixture of geographical area and construction date.

 

[Fritzo]

A thermocouple usually engages the furnace....how would you get around that?

 

[Uhtrinity]

Originally posted by: Capt Caveman

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.

This unit easily cools the front half of my house ... about 700 SqFt. Due mostly to the layout I use small 8,000 BTU units for the 2 back rooms. In fact I run the the 22,000 Unit on energy saver at 73 - 75 degrees and it still keeps the front half cool. If I crank it to max it gets too cold. if it wasn't for that single hallway to the back this one would easily cool all 1200 SQFT. It is a Kenmore and it isn't loud at all.

 

[BUTCH1]

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.

A few points, yes central split systems will always be more efficient than a window unit but 22K BTU is 22K BTU, it CAN cool more than one room with assist from small box fans. We had a summer cabin in Maine and used a 25K, mounted in wall unit like this and it worked fine. Now a proper split-system would have been far more efficient but at $500-600 for the wall unit vs $3000 for a proper split system installition there is a huge cost savings. In a location where you would be using AC on a daily basis the efficiency of the split system would more than pay for itself but in a limited-use scenario a wall-mount (or window shaker) will do. OP, keep in mind that these larger units (above 13K BTU) will need a 220V outlet to run so include the cost of hiring a electrician to install this in your calculations..

 

[DrPizza]

A lot of furnaces have a setting for fan only, so thermocouple isn't necessarily a concern.

And 220 V circuit is simple to run yourself - no more difficult than a 110V. If the OP is planning to do some of these things himself, I doubt he'd waste his money to hire someone to do such a simple task. Besides, compared to the difference in cost between central AC, and the OPs idea, the cost of an electrician is insignificant.

 

[BUTCH1]

Originally posted by: DrPizza
A lot of furnaces have a setting for fan only, so thermocouple isn't necessarily a concern.

And 220 V circuit is simple to run yourself - no more difficult than a 110V. If the OP is planning to do some of these things himself, I doubt he'd waste his money to hire someone to do such a simple task. Besides, compared to the difference in cost between central AC, and the OPs idea, the cost of an electrician is insignificant.

Simple?, you need to tap into fuse panel ,install breaker in panel, run cable through attic and drop into interior wall, install outlet box. Not rocket science but if a mistake is made and a fire ensues don't expect any insurance co, to pay off on work not done by a professional licensed electrician..

 

[Red Squirrel]

Originally posted by: BUTCH1

Originally posted by: DrPizza
A lot of furnaces have a setting for fan only, so thermocouple isn't necessarily a concern.

And 220 V circuit is simple to run yourself - no more difficult than a 110V. If the OP is planning to do some of these things himself, I doubt he'd waste his money to hire someone to do such a simple task. Besides, compared to the difference in cost between central AC, and the OPs idea, the cost of an electrician is insignificant.

Simple?, you need to tap into fuse panel ,install breaker in panel, run cable through attic and drop into interior wall, install outlet box. Not rocket science but if a mistake is made and a fire ensues don't expect any insurance co, to pay off on work not done by a professional licensed electrician..

Ha, the fuse pannel happens to be about 5 feet away from the window I would put the AC in. This is almost sounding more like a "worth a shot" idea. Everything is working in my favor. I've ran electrical wiring before, but never did from panel and never dealt with 240v but I'm sure I can find some books around that will show me how. Probably at home depot or something. In fact I *could* run it off the dryer plug which is right there, but not sure what the code is for those big plugs, don't know if you can "chain" them the same way with 120v just because the applications normally use up most of the amps so probably best to have a dedicated one.

But first I need to ensure my furnace thermostat has a setting to run just the blower. I never even noticed what kind of thermostat is in there, I think it's one of those higher tech programmable ones so I'm sure it can do that.

Another thing I was even thinking is just installing a big vent on the intake so I can make it take the cool air from the basement, then in winter I'd close that vent so it takes from the normal vent. That would probably be even more cost efficient then using an underpowered AC unit to slowly cool the house down. Not sure how much a blower uses, I'm guessing no more then a few amps.

 

[iGas]

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[iGas]

Originally posted by: RedSquirrel

Originally posted by: BUTCH1

Originally posted by: DrPizza
A lot of furnaces have a setting for fan only, so thermocouple isn't necessarily a concern.

And 220 V circuit is simple to run yourself - no more difficult than a 110V. If the OP is planning to do some of these things himself, I doubt he'd waste his money to hire someone to do such a simple task. Besides, compared to the difference in cost between central AC, and the OPs idea, the cost of an electrician is insignificant.

Simple?, you need to tap into fuse panel ,install breaker in panel, run cable through attic and drop into interior wall, install outlet box. Not rocket science but if a mistake is made and a fire ensues don't expect any insurance co, to pay off on work not done by a professional licensed electrician..

Ha, the fuse pannel happens to be about 5 feet away from the window I would put the AC in. This is almost sounding more like a "worth a shot" idea. Everything is working in my favor. I've ran electrical wiring before, but never did from panel and never dealt with 240v but I'm sure I can find some books around that will show me how. Probably at home depot or something. In fact I *could* run it off the dryer plug which is right there, but not sure what the code is for those big plugs, don't know if you can "chain" them the same way with 120v just because the applications normally use up most of the amps so probably best to have a dedicated one.

But first I need to ensure my furnace thermostat has a setting to run just the blower. I never even noticed what kind of thermostat is in there, I think it's one of those higher tech programmable ones so I'm sure it can do that.

Another thing I was even thinking is just installing a big vent on the intake so I can make it take the cool air from the basement, then in winter I'd close that vent so it takes from the normal vent. That would probably be even more cost efficient then using an underpowered AC unit to slowly cool the house down. Not sure how much a blower uses, I'm guessing no more then a few amps.

Fan only is a mode that call "summer" mode on furnace.

It is possible to have return air from the basement to help cool the house for a short period, but the it is not effective enough to ease the heat or humidity in the air. And, heat rises therefore the top floor of the house will always is hotter than the basement.

 

[vailr]

By using a dehumidifier + a large box fan, you still can be comfortable indoors, even though the uncooled summertime air temperature is fairly warm: >80° F. Of course, it depends on the geographic location + average humidity level.

 

[Red Squirrel]

I just set our furnace here so the fan runs constantly. Surprisingly it makes a big difference. The AC hardly runs and the house is staying cool. It's a really hot day today too so it's a good test. It's about +27. I may be on to something once I get in my own house.

Just not sure how big that offset is in terms of electricity usage. Maybe it comes up to the same thing in the end.

 

[us3rnotfound]

Originally posted by: RedSquirrel
I just set our furnace here so the fan runs constantly. Surprisingly it makes a big difference. The AC hardly runs and the house is staying cool. It's a really hot day today too so it's a good test. It's about +27. I may be on to something once I get in my own house.

Just not sure how big that offset is in terms of electricity usage. Maybe it comes up to the same thing in the end.

Yep, we do that at our house too, haven't really calculated the savings, though it seems to do a much better job.

 

[MrDudeMan]

I use a 3000CFM air mover to get the cooler air from my basement up the stairs into the first and second floor air spaces. It drastically changes the temperatures in both areas for quite a while. I only have to run it for about 5 minutes once in the morning and that plus open windows and fans will keep the house cool the entire day. We haven't turned our AC on yet this year (well once just to be sure it was working).

The house actually stays quite cool without doing this, but I've got the tool so why not use it? Plus it's fun anyway.

 

[BUTCH1]

Originally posted by: RedSquirrel
I just set our furnace here so the fan runs constantly. Surprisingly it makes a big difference. The AC hardly runs and the house is staying cool. It's a really hot day today too so it's a good test. It's about +27. I may be on to something once I get in my own house.

Just not sure how big that offset is in terms of electricity usage. Maybe it comes up to the same thing in the end.

They sell homes now were they are mostly enclosed in the ground, cuts heating/cooling to nil..

 

[roboron]

Old thread... I know...

By using a dehumidifier + a large box fan, you still can be comfortable indoors, even though the uncooled summertime air temperature is fairly warm: >80° F. Of course, it depends on the geographic location + average humidity level.

TRUE! Dehumidification is a LARGE part of the goal in many/most cases... it's about the "comfort index". You can be comfortable at 27°C and 30-40% RH, but uncomfortable at 23°C if the RH is 70%.

BUT... don't let the dehumidifier exhaust its heat into the living space... it will very nearly defeat the purpose by driving up the temperature.

I just set our furnace here so the fan runs constantly. Surprisingly it makes a big difference. The AC hardly runs and the house is staying cool. It's a really hot day today too so it's a good test. It's about +27. I may be on to something once I get in my own house.

Just not sure how big that offset is in terms of electricity usage. Maybe it comes up to the same thing in the end.

Furnace fan/blower can use around 600-1000 Watts... and some (25-45%) of that power is also dissipated by the fan motor, which sits in the airflow... heating the air (unless it's an ECM brushless blower motor, which are nearly 100% efficient).

In my first house (Missouri, USA, 850sqft), I took an old (olllld... from late 1960's) 1-piece 1.5t aircon unit, split it in-two, moved the evap coils indoors, plumbed new refrigerant lines between the two units, and used it as a central air for about 5 years without much problems before I moved.

You do need a evap. unit condensation drip pan with drain of course. I actually made an attic-mounted air handler (from weatherproof plywood, painted insides), with cool-air drop ceiling vents... natural convection airflow. Return air was a single, main hallway ceiling vent with filter. Used insulated flex ductwork to the vents.

Was it perfect? No... but it cost me less than $200 to build... DIY is wonderful. I had to do plenty of reading beforehand, but it was time well spent. Typically ran 18°F difference return air to cooled air.

Right now I'm building a small dehudifier/cooler from a 15+ yr old portable dehumidifier. Separated the the coils, uses separate fans, 12" to 6" duct reducers on both sides of both coils. It sits in our attached garage (split-level house), sucks return/moist air from basement (living space), runs it through cooling/evap. coils (condenses humidity there), dry/cool air blows back into house... uses all well-insulated flex ducting. May blow into furnace/central air return duct, and force the furnace blower ON when it's running to ensure circulation. Heated air from garage-located condenser coils exhausts into garage, condensate drains into garage floor drain.

During winter I can flip the flex duct hookups, and use it as a small heatpump... taking latent heat from garage, pump it indoors, help heat the cool basement and reduce run-time of main central heatpump w/gas furnace backup.

Requires about 6.5Amps at 120V, providing about 7000BTU (2KW) of heat movement as a heat pump, and 20-25pt of dehudification/day.

Lucked out, didn't even need to break refrig. lines... had plenty of slack, just moved cooling coils on top of unit.

Odd mix... I'm actually a 'lifer' electronics design engineer... HVAC just happened somehow.