Plumbing in a window AC Unit to simulate central air

Number_35

Number_35

Joined
Jul 7, 2014
Messages
5,169
Location
Winnipeg MB CA
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.
 
  • Wow
Reactions: JC1
I truly haven’t a clue on what size blower is needed (nor how to calculate) to move 1200 cfm through ductwork but I do know the blower in our furnace is huge.

My experience with window units is they often don’t really get a space comfortable but are better than a fan alone
 
You are in Canada so maybe it will help a bit if the house is small. It will likely run 100% of the time and I hope they have a floor drain for the condensation.

In a small house on a tight budget I’d get a couple regular window units and put them…..in the windows.
 
Our house is small so 3 ton central AC or 36,000 BTU. At the same time there has to be enough airflow to reach 1200+ cfm across the evaporator, and in our case also a 4” MERV 13 filter…no clue on how to calculate but seems like a powerful blower is needed…
 
RhondaHonda said:
You are in Canada so maybe it will help a bit if the house is small. It will likely run 100% of the time and I hope they have a floor drain for the condensation.

In a small house on a tight budget I’d get a couple regular window units and put them…..in the windows.
Click to expand...
The house is a post-war 1-1/2 storey. I would guess 1100 to 1200 ft^2 between both levels.

Our cooling season is short but intense, with high humidity. I found it difficult to sleep before we had AC.
 
John105 said:
Our house is small so 3 ton central AC or 36,000 BTU. At the same time there has to be enough airflow to reach 1200+ cfm across the evaporator, and in our case also a 4” MERV 13 filter…no clue on how to calculate but seems like a powerful blower is needed…
Click to expand...
Interesting! Our house is c. 1250 ft^2, and our 1-1/2 ton central AC is completely adequate.
 
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.,,
 
BigCahuna said:
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.,,
Click to expand...
This happened to us in 2008. We were at Disney and came home to a heat wave, in May. Condenser wouldn’t start. My buddy was a building mgr and told me we’ll go to the plumbing supply and buy the part. Get me the model# of your unit. And you could have been electrocuted even with the power cut off to the unit, you have to discharge the capacitor.

Not only did I not know that, but I rocked the condenser in anger when it wouldn’t work. Could have broken the line set. So stupid.
 
John105 said:
And you could have been electrocuted even with the power cut off to the unit, you have to discharge the capacitor.
Click to expand...

Usually when you're replacing the capacitor, it's precisely because it's incapable of holding a charge.

Typical capacitor wiring causes them to discharge themselves anyway:

1688393127786.jpg
 
Number_35 said:
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.
Click to expand...
I vote C
Mount on the main floor depending on home maybe the second floor.
Agree again on #5 Better off to buy new, Energy Star 12,000 btu are a dime a dozen for less than $500 including the portable type that can be moved room to room.
Heck, Amazon has some 12,000 BTU LG for $380 right now
 
Google says Winnipeg is currently 69 degrees and 48% humidity. It says its supposed to get to like 77F and I presume it will get the humidity down to low 40's.

12000 BTU is about 1 ton of cooling. Its small for the house but will drop it a few degrees which is probably all you need there in reality at those temperatures.

Your correct in the way he is doing it is the least efficient. He has to push the air past the coil and through the ducts. However if he does get it ducted properly in and out, deals with the condensation, and runs the furnace blower it will work to some degree. How much - not sure.. It would be more efficient to put it in a window and set up a couple box fans. I personally would not mess with the ducts.
 
Number_35 said:
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.

Thoughts? Thanks.
Click to expand...
Please go out of your way to get pictures of this once it's completed.
 
My father did what you described in a raised ranch but

1. We never had central ac
2. He mounted in a window that was directly across from the furnace
3. He shut off the gas to the furnace then hotwired the fan, he ran some simple sheets across cloths hanging rope that we already had there for cloths washing

This setup was great for a variety of reasons
1. Living room was nearby in the basement
2. Basement always gets too humid in the summer so this kept us from running a dehumidifier
3. Felt just like central air because you got the natural cool of the basement plus the AC Combined

From experience the old AC seem to blow more air, blow colder air and dehumidify better than modern ac

I don’t know why but our old 5000btu unit cooled a lot better than the 6000btu that replaced it

My worry is that your friend is going to overload/overheat the unit, get a ton of mold and a flood
 
They would probably be better off just using it like a regular window unit then using the existing furnace fan to circulate the air if it has a forced air heating system. Obviously if it doesn't have a forced air heating system, this won't work.
 
are ductless mini splits going to replace central AC with ducts someday?

What surprises me is the efficiency, but I don’t think we know the longevity at this point yet
 
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