AC compressor reduction/replacement

A

andytruck

Observer
I have been at this for a few years with each camper I own. I want an AC unit that will run off a 2200watt inverter gen, and run at altitude, and fit. The 9,000 btu Polar Cub will work low, but not well over 4,000 or 5,000 feet ele, so that is not an option. Let's say for discussion that a bigger generator is not even an option, because this is the point and many others also want to run AC on little gen.

I have two thoughts.
#1. Why can't I just replace the compressor in my existing AC roof unit with a smaller compressor that will run on the little generator anywhere?
I'm happy to buy a $99 window unit to get a compressor. Will this work?
I have a 13,500btu unit I can put on, but compressor too big.

#2 I havent figured a way to make a window unit work, there is just nowhere to place it.
I would not mind making ducts on a $99 window unit and placing it remotely (under the truck, on the bumper etc) but would like to see how others have done it. I know there are ducted units out there, but at ten times the price is also not an attractive option.

I'n not looking for silly answers or trolls please.
 
A

andytruck

Observer
you've trolled with links to slightly related but not specific topics. There are portable units out there but have nothing to do with replacing a compressor..
 
luthj

luthj

Engineer In Residence
Have you considered a variable frequency drive for the compressor? In theory you could just reduce its speed, and thus reduce power demand.

Reducing the evap fan speed will generally reduce the head pressure and thus electrical load.

Swapping compressors is doable. Nothing too hard. You just need a unit that will fit, recharge gear, and some brazing.

You could hack Up a window unit into a mini split thing?
 
Ozrockrat

Ozrockrat

Expedition Leader
Replacing the compressor with an AC one is possible (in theory) as long as you match the size and also handle the airflow for the condenser. Finding one that handles 134a could be a challenge.

Also check out how the Starcool (I think that was the brand) that Sportsmobile used to build into their rigs. It included an 110v AC compressor into the existing engine driven air conditioning system. I had one in my Sportsmobile but it didn’t work that well.

Another alternative is an inverter type mini split unit.
 
shade

shade

Well-known member
andytruck said:
I have been at this for a few years with each camper I own. I want an AC unit that will run off a 2200watt inverter gen, and run at altitude, and fit. The 9,000 btu Polar Cub will work low, but not well over 4,000 or 5,000 feet ele, so that is not an option. Let's say for discussion that a bigger generator is not even an option, because this is the point and many others also want to run AC on little gen.

I have two thoughts.
#1. Why can't I just replace the compressor in my existing AC roof unit with a smaller compressor that will run on the little generator anywhere?
I'm happy to buy a $99 window unit to get a compressor. Will this work?
I have a 13,500btu unit I can put on, but compressor too big.

#2 I havent figured a way to make a window unit work, there is just nowhere to place it.
I would not mind making ducts on a $99 window unit and placing it remotely (under the truck, on the bumper etc) but would like to see how others have done it. I know there are ducted units out there, but at ten times the price is also not an attractive option.

I'n not looking for silly answers or trolls please.
Click to expand...
Have you considered a soft start system for your current unit?

https://www.microair.net/collections/easystart-soft-starters
 
A

andytruck

Observer
Soft starts don't work. I did try a new soft start capicator, it did not help, and reading it seems nobody has had success.

"Have you considered a variable frequency drive for the compressor? In theory you could just reduce its speed, and thus reduce power demand."
I dont know what that is or how it would help? Just to help with the start-up spike, or all the time? does it just supplement the gen somehow?

Yes, I'd like for it to be as simple as just replacing the compressor. Will one from a fridge work? Can I just put a smaller one in? Do I need to reduce the fan speed to the cooling fins of the condenser as one guy said?
I have a perfectly fine roof AC unit, but the compressor needs too much power to run off the little gen. A smaller compressor would fix this.
I have a manifold gauge set and coolant, though I do not know the details after that. I became an expert on vehicle ACs recently.
 
luthj

luthj

Engineer In Residence
A VFD is basically like a dimmer for lights. It allows the compressor to run slower, thus using less power. Many also have a soft start, which can really reduce startup surge. You would need to wire the compressor to run through the VFD. The fan can run through the VFD as well. The electronics will need regular power bypassing the VFD.
 
A

andytruck

Observer
"In my application" is what I am talking about, see OP.
So, with a VFD, which are about $75 or so, it just goes inline with the alternating current power feed to the compressor motor? (no other AC components). Does this work, and who has done it? No harm to the compressor running slow or on less power? I guess instead of 120VAC it would be getting 80 or 90 or something? There is no chance to burn out the motor windings or anything? If it is just as simple as slowing down the compressor motor, then there are thousands of post on AC/generators in vane...

The Amazon link seems to be for a 220 power. Maybe this one? I stopped buying from Amazon because of his hate for America, but is fine to look. no politics pleeze
 
Last edited:
shade

shade

Well-known member
andytruck said:
"In my application" is what I am talking about, see OP.
So, with a VFD, which are about $75 or so, it just goes inline with the alternating current power feed to the compressor motor? (no other AC components). Does this work, and who has done it? No harm to the compressor running slow or on less power? I guess instead of 120VAC it would be getting 80 or 90 or something? There is no chance to burn out the motor windings or anything? If it is just as simple as slowing down the compressor motor, then there are thousands of post on AC/generators in vane...
Click to expand...
Good luck.
 
A

andytruck

Observer
I think they are all 3-phase, aren't they? If just one then a simple dimmer switch would work. When I added the soft start capacitor there were many wires like a 3-phase, more than just two to the motor... There was the capacitor, then another can that was a little smaller than the capacitor - I think one for the starting, and the other for continuos running.

I am doing a non-google search and not finding anyone who has tried this yet...
 
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