AC Hacking a Figidaire 5000 BTU

[lrrowe]

I am not sure what a "long length" is and just maybe I am in that category. But my original trials last August produced good, unscientific (meaning no data obtained other then temperatures) results. I have since added a few more feet and maybe another bend or two in the rear installation. I cannot wait for the first real trial of this new design.

Final setup with first test.


Final set up with AC unit to be under trailer.

[daveesl77]

Going along Martin's idea trail, last week I remembered that I had two 6" 120v inline duct fans in my garage. I pulled them down and they will work perfect I think for the extra push on the air supply. I have a 12v marine blower which puts out a ton of air, but haven't figured out how to quiet it down yet. The computer fans in the ductwork work ok and I may end up just sticking with those for the 12v side of things. This week I'm building the supply/return box for underneath the floor. Just haven't quite got the full design figured out so I can easily switch it over from open, screened access for times I don't want AC or heat to AC/Heat insertion. I got the aluminum box made, insulated with foam board. Once I get it all figured out, I'll post photos.

And Bob, I like the 6" (I assume) drain pipes for ducting! I wish I had thought of doing it that way last year before I actually built in my ducting system. Would have made life a lot easier.

dave

[lrrowe]

Thanks Dave,
I hope these 6" pipes work. And if I see flow issues, I will look into fans as you and others have done. I do not have to worry too much about the inside noise given where the pipes are.

[steve cowan]

Thanks Dave,
I hope these 6" pipes work. And if I see flow issues, I will look into fans as you and others have done. I do not have to worry too much about the inside noise given where the pipes are.

That looks great Bob.I just used 4" insulated flex duct to hook mine up and get good air flow.I ducted mine into the back wall because I didn't want to cut a hole in the side but I can't fully close the hatch which is not a big issue.With the 6" pipe should be great flow.

[m.colley]

Thanks Dave,
I hope these 6" pipes work. And if I see flow issues, I will look into fans as you and others have done. I do not have to worry too much about the inside noise given where the pipes are.

The 6" ducts should make quite a bit of difference and be quieter at the same time. Let us know what you find out.


Martin

[m.colley]

Going along Martin's idea trail, last week I remembered that I had two 6" 120v inline duct fans in my garage. I pulled them down and they will work perfect I think for the extra push on the air supply. I have a 12v marine blower which puts out a ton of air, but haven't figured out how to quiet it down yet. The computer fans in the ductwork work ok and I may end up just sticking with those for the 12v side of things. This week I'm building the supply/return box for underneath the floor. Just haven't quite got the full design figured out so I can easily switch it over from open, screened access for times I don't want AC or heat to AC/Heat insertion. I got the aluminum box made, insulated with foam board. Once I get it all figured out, I'll post photos.

And Bob, I like the 6" (I assume) drain pipes for ducting! I wish I had thought of doing it that way last year before I actually built in my ducting system. Would have made life a lot easier.

dave

I did a little research here at work and pulled the specs on our 6" duct fans. The 6" fan is rated as 240cfm @ 3000rpms and pulls .41A @ 110V.
Knowing that the average 5500 btu window ac is rated for approximately 240cfm or so the above duct fan would move the same amount of air as the unit moves, which could be a little bit of overkill. Without knowing how many CFM's of air your losing to static/friction losses from the plenum box and flexible duct I'd would probably put a speed controller on the fan and experiment.
I may have to see if I can find a donor AC and do a few experiments, checking for friction loss and cfm loss. Knowing how much air to that we'd need to make up would go along way to getting the same cfm's that the unit is rated for without feezing up.


Martin

[lrrowe]

Thanks Dave,
I hope these 6" pipes work. And if I see flow issues, I will look into fans as you and others have done. I do not have to worry too much about the inside noise given where the pipes are.

The 6" ducts should make quite a bit of difference and be quieter at the same time. Let us know what you find out.


Martin

I will do Matin. I am headed to a TearJerkers event at VA Beach in mid April. In a way, I hope it is warm, opps hot enough to test them then. I too used a used $25 5000 BTU unit. If it works, I will keep my eye out for a better quality unit to save and use when the current one kicks the bucket.

[capnTelescope]

Hey Bob, could you put up a pic of your plenum box, from the side that mates to the A/C? I'm a little bit stuck on how to do that.

[lrrowe]

Hey Bob, could you put up a pic of your plenum box, from the side that mates to the A/C? I'm a little bit stuck on how to do that.

Sure will. But it is a rented storage bldg and I can get to it within a few days.

[Socal Tom]

Just a reminder to folks that I'm using 5 inch ducts with no fan and no icing problems.
Tom

[m.colley]

Just a reminder to folks that I'm using 5 inch ducts with no fan and no icing problems.
Tom

Thats good to hear Tom, you may have found the sweet spot for airflow without the freezing. Are you using flexible duct of some type? How long are your runs of duct?

Martin

[Socal Tom]

The ducts are 5" OD designed for a portable AC unit. Stretched out they are 60" long. I also have my vents hook up parallel to the coils. I believe this also helps ( I copied the pet cool design). If you return aims directly at the coils then moisture is concentrated in one spot, making. That area more likely to ice up. Once the ice forms it just grows to cover the whole cool. If the air comes in parallel to the coil the the air has to turn to pass through the coil? The turn helps dry the air, and spread the load across a larger surface area. Studies I found online generally supported that theory.
Tom

[capnTelescope]

Final setup with first test.

and that got me all motivated to go out to the shop and do something.

I think one of the main things that kept me from going forward was no plan. So I decided to do a mockup in cardboard. I like cardboard. It's free, sturdy, very easy to work on the table saw, wood glue works great, and it's free.

First, I cut 4 pieces to form a surround, taped them together and test fitted. Oh! you gotta take a hunk out for the electrical cord, and take about a quarter inch off the bottom for it to fit. Done.

Next, I wanted to separate the return air from the cold . I needed to also leave room for my duct starter collar. That got me to here:

Cold air comes out of the opening at top right, and needs room to fit the starter collar. That's why the angle on the partition.

Next, I laid out the return intake and cold air ports to be roughly centered over the coils and the blower opening, respectively:


Next, more tape and add collars:

Needs a little better job of measuring for the surround. Just add more tape, for now.

Another view:


Taking a look at the condenser coil on the back, the fins are getting pretty bent up, and the A/C hasn't even hit the road, yet:


Anyone have a suggestion on how to protect this? I'm thinking heavy-duty screen.

This setup passed the Bare Minimum Performance Test with flying colors. It ran for about an hour without freezing up, all while blowing cold air out the top and sucking in room air at the bottom.

[Shadow Catcher]

Protecting the very delicate fins, (which can be fixed with a fin straightener) grill, hardware cloth, expanded metal, on a bit of a stand off, washers or whatever, might be the trick similar to this which I used on the water heater heater.

[lrrowe]

CaptnTelescope,
Your mock up is pretty much what I did.
I am trying to get to my storage bldg today.