Camper AC considerations.

[MadElectrician]

Obviously, this is a topic. Something I have found in my research. An AC unit is rated at its maximum draw, which is when the compressor is running. The rest of the time it draws far less current. From my research online, this is usually from half the time to nearly always. But I presume this is in a dwelling, and not a camper. My custom build will include very well insulated walls with a radiant barrier aluminum skin and 2" of R10 foam board. It will essentially be a walk in cooler with a sofa. In considering solar, I'm guessing my compressor will work 1/4 to 1/3 of the time. This brings me into the 400W 600W range, although I am planning closer to 800 just to be safe. I will also have a propane generator, but I just don't want the noise when I can help it. Other considerations. I have an LG dual invertor window unit that costs amazingly little to run and will freeze out a penguin. This of course is all theoretical. I'd like to hear from people with real world experience cooling their campers. What is your setup (BTUs) and what have the power demands been?

 

[snoobler]

In my leaky 4 season 5th wheel (slide out seal is shite - otherwise good), 15000 BTU unit runs max power all the time and can barely maintain a 15-20°F delta with the outside.

Yours should be way better.

 

[MisterSandals]

An AC unit is rated at its maximum draw, which is when the compressor is running.

I am not sure how your AC unit is rated but the maximum draw should be within the first second(s) of starting. This locked rotor (aka startup surge current) amperage can be 5x the running amperage.
If you are sizing an inverter to run your AC, it'd be wise to get your locked rotor amperage figured out.

EDIT:
>>LG dual invertor window unit

Hmmm, maybe this ramps up gently. I'd be interested to hear the numbers.

 

[Hedges]

In my leaky 4 season 5th wheel (slide out seal is shite - otherwise good), 15000 BTU unit runs max power all the time and can barely maintain a 15-20°F delta with the outside.

In the shade? Or with the sun beating down on it?

 

[Bob B]

Go to Youtube and do a search for RV split system.

I'm seriously considering taking the one off my roof and installing a mini split instead.....much more efficient and easy to start ... compressor regulates speed.

 

[MadElectrician]

I am not sure how your AC unit is rated but the maximum draw should be within the first second(s) of starting. This locked rotor (aka startup surge current) amperage can be 5x the running amperage.
If you are sizing an inverter to run your AC, it'd be wise to get your locked rotor amperage figured out.

EDIT:
>>LG dual invertor window unit

Hmmm, maybe this ramps up gently. I'd be interested to hear the numbers.

A locked rotor is something else. That's when the rotor is prevented from moving. The max amperage draw on the panel is the initial startup current - the absolute most it draws. That's my whole point. You cannot calculate long term power requirements using the advertised draw because much of the time it's only running a fan. I guess one could measure it and track it.

 

[MadElectrician]

In my leaky 4 season 5th wheel (slide out seal is shite - otherwise good), 15000 BTU unit runs max power all the time and can barely maintain a 15-20°F delta with the outside.

Yours should be way better.

Sound like you should be looking on a camper insulation forum. Spray foam perhaps.

 

[MadElectrician]

Go to Youtube and do a search for RV split system.

I'm seriously considering taking the one off my roof and installing a mini split instead.....much more efficient and easy to start ... compressor regulates speed.

Most are more than I need and expensive. Very nice systems for sure.

 

[snoobler]

In the shade? Or with the sun beating down on it?

Full sun. Pinon Pines and Juniper/Cedar in the area rarely get tall enough to shade

 

[Hedges]

Full sun. Pinon Pines and Juniper/Cedar in the area rarely get tall enough to shade

I figure the sun is depositing significant energy on the skin, maybe more than what the warm around outside does.
Reflective paint helps, of course. How about an awing, tarp, etc. to shade the trailer? (or PV panels, but I find it pretty hot under them.)

 

[snoobler]

Oh yeah. This desert dweller is all too familiar with the effects of our star. It's white, but it doesn't help much. We do have some hard-mount window awnings that should make it more tolerable.

Shown here before they were removed for transport:



That 4' deep slide is a monstrosity.

 

[MadElectrician]

Oh yeah. This desert dweller is all too familiar with the effects of our star. It's white, but it doesn't help much. We do have some hard-mount window awnings that should make it more tolerable.

Shown here before they were removed for transport:

View attachment 25387

That 4' deep slide is a monstrosity.

his is a reason I will be building mine from scratch. I plan to boondock and good insulation makes a world of difference. I'm also doing an aluminum skin with an air gap to block the sun's radiant heat. I'm a fat guy so I take my AC seriously.

 

[tazmann]

Make sure to insulate the floor also, I did not on mine and on 108 degree days the floor was hot, roof AC ran full blast to keep it 82, 5000 btu window air was a joke. This was with rig sitting in sun

 

[MadElectrician]

Make sure to insulate the floor also, I did not on mine and on 108 degree days the floor was hot, roof AC ran full blast to keep it 82, 5000 btu window air was a joke. This was with rig sitting in sun

There will be no place that does not have 2" of R10 foam and spray foam in the gaps. I figure the most efficient way to use power is to not need it.