Plumbing in a window AC Unit to simulate central air

[SC Maintenance]

You're kind of stating that both occur: pull air in from the outside AND recirculate the interior air?? Modern window units do not pull air from the outside, except as noted that a few might have a lever to open up to outside air.
EDIT: o.k., maybe your wording is just a bit confusing. They use outside air on the condenser, but it is not "pulled in" to the inside room.
https://hvac-boss.com/cooling/does-a-window-air-conditioner-pull-air-from-outside/

A diagram might be helpful.

They typically have two fans run off a common shaft. The outdoor fan circulates air across the condenser. The indoor fan pulls air from the room across the cooling coil. Indoor and outdoor air never mix - the unit is sealed on the inside.

 

[Number_35]

I did a little bit of poking around on the 'net to try to understand how window AC units work.

@doitmyself and @bullwinkle are correct; the outside air is cooled, and heat from the inside air is transferred to the outside (without inside and outside air mixing).

So, that means the outside of a window unit has both an intake and exhaust side - and therefore, if my friend proceeds with his plan to install a window unit in the basement, he should try to separate the ducting for the two sides (intake and exhaust) of the "outside" of the unit.

If the entire outside half is connected to the outside by a narrow duct, the hot exhaust air will mix with the incoming outside air, badly reducing the efficiency, correct?

He would be better to run ducting out from the exhaust side, and let the intake side draw in air from the basement, correct?

 

[FZ1]

Bad Idea! You are right. Get a free estimate to repair the existing unit or get a new window unit. Depending on local electricity costs, one may save money to buy a 15/16 seer. Your friend needs to shop various electricity sellers for lower KW pricing. .02

New window units about $200 at WM. Buy 1 or 2 and stick 'em in the windows.

 

[Number_35]

New window units about $200 at WM. Buy 1 or 2 and stick 'em in the windows.

I know, I looked earlier today and found same ... but the lure of "free" is pretty strong sometimes.

 

[andrew_j]

I know, I looked earlier today and found same ... but the lure of "free" is pretty strong sometimes.

I love giving away free inefficient appliances to people who have no idea how much energy they will consume trying run our old chest freezer and AC units. They think they scored but not need to burst their bubbles , they can when they open their power bill (NH has highest rates of USA)

 

[alarmguy]

I would have the existing unit checked out , to find out whats wrong with it before I start doing all sorts of Frankenstein work to it. I have a 18,000 BTU window unit that stopped blowing air. Did some research online and found out the biggest cause of unit failures was the capacitor. Not being an expert, I took a shot and bought one online. Was less than $50. I took the old one out , and replaced it with the new one. Crossed my fingers and turned it on. The unit fired up, and has been in action for 4 years now. I'm not saying this is your problem, but there are was to find out what wrong with it on the cheap.,,

Capacitors and Contactors are the #1 failure reason of central systems... other than low freon and a broken fan. 2 dirt cheap parts that repair people make a lot of money on, some will convince some to replace the unit for a massive profit.
You did a good guess. They do wear out in time, in many cases it's worth it to replace both at the same time but not necessary as you found out in your case.

 

[alarmguy]

This makes me realize I don't actually understand how window AC units work.

Do they draw in hot air from inside, cool it, run a fan to blow air across the evaporator to inside, and then exhaust the original air outside?

No, that other post is wrong. The air cooled is the existing air in the home recirculated through the cooling coils, our new home is a super efficient home so the system does have a damper near the house air intake that will mix in a small amount of fresh air because the house is so airtight.

 

[alarmguy]

I did a little bit of poking around on the 'net to try to understand how window AC units work.

@doitmyself and @bullwinkle are correct; the outside air is cooled, and heat from the inside air is transferred to the outside (without inside and outside air mixing).

So, that means the outside of a window unit has both an intake and exhaust side - and therefore, if my friend proceeds with his plan to install a window unit in the basement, he should try to separate the ducting for the two sides (intake and exhaust) of the "outside" of the unit.

This is incorrect, there is no exchange of air between the inside and outside.
It is correct that the heat from inside the home is transferred to the outside by means of freon. The coils outside "evaporator coils" transfer heat from the freon to the outside air.
The coils inside (condenser coils) remove the heat from the air using a fan inside and transfer that heat via freon to the evaporator coils outside which then the fan blows over the outside coils removing the heat.

(you very well may saying the same thing*LOL*) ok, bye

 

[repairman54]

I can't wait to see the final product of the Red-Green HVAC installation.
''If they don't find ya handsome they'll sure find you handy''.

 

[CDX825]

Easier to just fix the central air. Probably something simple like a run capacitor or bad contactor. Window air conditioners are not efficient and trying to duct one is just going to make it worse.

 

[bullwinkle]

I know, I looked earlier today and found same ... but the lure of "free" is pretty strong sometimes.

Honestly, the hardest part of this rig job would be getting the heat outside-the fans & motor on a window A/C are just barely strong enough to move air over the coils, and on most window units the condensate just drips off the case outside (or gets thrown everywhere like my GE/Haier ones). I had one that had a hose fitting to collect it, but it clogged often enough to be a pain. Shame you're not local, I could at least tell you what you needed to fix the original system.

 

[FZ1]

I know, I looked earlier today and found same ... but the lure of "free" is pretty strong sometimes.

They need to get a free estimate of what's wrong and the cost to fix the central. Does the condenser fan run ? Does it run but not cool, etc.etc.?

 

[Number_35]

They need to get a free estimate of what's wrong and the cost to fix the central. Does the condenser fan run ? Does it run but not cool, etc.etc.?

Good questions - they live out of town, and I have so much going on right now that I can't get out there to do a basic assessment.

However, my friend has decided against running the big window unit in the basement - he is going to try to find a way to install it in a window. (And as I type this, I envision the opposite of what he had proposed - if the AC unit is too big for an existing window, he might build a stand for it outside a window, and install a plywood shroud from the cold side of the unit to the window.)

 

[97prizm]

The AC has quit working at my friend's daughter's home.

I don't know whether they were running central AC or a window unit.

My friend has picked up a large used window unit at no cost.

I helped him load it into his van, and asked whether there was a window large enough to accommodate it.

He replied that he doesn't need one - he plans to install it in the basement, with the cold air output plumbed into the existing ductwork, and the hot exhaust air ducted outside.

I doubt this will work properly.

Concerns:

1. The unit's blower fan will not be powerful enough to exhaust the hot air - an inline booster fan will be required.

2. The cost of the sheet-metal work would be prohibitive.

3. The footprint of this installation would be large.

4. Condensation would have to be gathered in a pan and emptied regularly. The exhaust ducting would have to make allowance for this.

5. This unit will be very expensive to run (1170 W/10.9 A on 120 VAC, SEER 10.8, 12,600 BTU/hr) plus the cost of running a booster fan and the furnace fan.

My preferences would be:

A. If the existing broken system is central, repair or replace it.

B. If the existing system is a window AC, replace it with a modern SEER 18 (or better) unit.

If required, run a dehumidifier as well.

C. If this old free unit must be used, cut a hole in the wall (properly framed with a header, etc.) and install the AC unit as it was designed to be installed.

Thoughts? Thanks.

A window fan won't have even close to the volume to move air through ductwork. All that will happen is the Window A/C unit will burn out then be back to square one.

 

[FZ1]

Good questions - they live out of town, and I have so much going on right now that I can't get out there to do a basic assessment.

However, my friend has decided against running the big window unit in the basement - he is going to try to find a way to install it in a window. (And as I type this, I envision the opposite of what he had proposed - if the AC unit is too big for an existing window, he might build a stand for it outside a window, and install a plywood shroud from the cold side of the unit to the window.)

That sounds better.

 

[Owen Lucas]

Terrible idea, it's the residential equivalent of this.

View attachment 164617

Someone get this guy a fin comb!

 

[Rmay635703]

Good questions - they live out of town, and I have so much going on right now that I can't get out there to do a basic assessment.

However, my friend has decided against running the big window unit in the basement - he is going to try to find a way to install it in a window. (And as I type this, I envision the opposite of what he had proposed - if the AC unit is too big for an existing window, he might build a stand for it outside a window, and install a plywood shroud from the cold side of the unit to the window.)

All the places I’ve lived have some form of window available in the basement, dig one out if needed, makes a better basement anyway

 

[Bladecutter]

Getting a couple hand tools onto the home A/C unit will at least help them understand if its a sub $100 fix, or if they actually have a big failure, like a loss of refrigerant or a failed compressor.

If the capacitor is the problem, then that might be a sub $20 fix (that's the cost of the one on my Trane unit).
Heck, last summer the a/c stopped working one afternoon, and I went to take a look at what the problem was, and it turned out that a couple of earwigs had gotten themselves trapped in the contactor plunger.
Once I scraped the bugs out, the a/c unit started working once again.
So that was a no cost fix to my problem.

But, someone has to take a look at the thing to get to the bottom of the problem.