Rooftop RV A/C in a building???

[Tford]

I figured there’s enough expertise out here to explore this. So I’ve got a Dometic A/C I’ve pulled off my Escape roof…… and I’ve got a shop that could use some cold air! You’d think someone would have done this on YouTube by now but maybe I haven’t typed in the right search to find it. Yeah, I know this unit is way too small for the size of my shop, but cold air blowing from anywhere would extend my time out there in the summer with my big shop fan moving things around as well. I’ve got a separate little framed shed that holds my big air compressor, so there’s a lower roof structure that would hold the unit down flat, and I’m pretty sure I could cobble a bit of solid smooth 90° ductwork to send the airflow into the shop about 7-8’ off the floor. Metal shop building has radiant barrier insulation that at least knocks the sun hit metal panel temps from 120° down to ambient air temperature (which at 102° ain’t no bargain!). 120 VAC is right there, but how do I get around the 12V thermostat? If it was a stand alone roof unit with the controls ON it I could just extend that wiring into the shop wall. I reckon Dometic probably has an answer to this in the form of other units with the controls on them…but I figured there’s a wealth of knowledge here with these units and this kind of stuff in general to ask!

[Centex]

Check the schematics / instructions for your Dometic unit.

I believe (I could be wrong yet again) you'll find that like most 'residential' HVAC units, it provides the required low voltage power for the wired remote thermostat via internal electronics powered by the AC's main 120volt source.

IOW, your trailer thermostat gets whatever low voltage power it needs from a connection to the AC unit, not a connection to the trailer's separate 12VDC system, therefore may lend to the same when installed in your shop.

Have Fun!

[Tford]

…you’re absolutely right, the 110 feed goes into the control box and the thermostat wires come out of there…

[Centex]

That issue 'solved', go for it and keep us posted!

[splitting_lanes]

I’d suggest doing a manual J load calculation to get an estimate of how much cooling you need. This tool is pretty easy

https://www.loadcalc.net/

[Tford]

I’ll need WAY more insulation to even think about the actual amount I’d need, I just wanna stay out there till 2 PM in August!��

[hugh]

Originally Posted by Tford

I’ll need WAY more insulation to even think about the actual amount I’d need, I just wanna stay out there till 2 PM in August!��

Yeah, agreed. Even an undersized unit would help drop the humidity substantially! Sounds like a fun project.

[Selkirk]

Just for reference, there is a portable building located across the street from my office at a used car lot. It's about 250-300 sqft with 8' ceilings with an abundance of window area. I suspect it's not particularly well insulated. This building is cooled with two RV-style AC units on the roof....I'm guessing 13000-15000 btu each, based on their size.

Also, I would think that the old Dometic unit would require at least a 120V 20A circuit. Something to check.....

[Rockhead]

On my trailer barn I installed regular window unit 15000 btu. Works just fine and easy to get to to clean the coils as needed

[Tford]

Oops! Nope, the Dometic control box is fed by a separate 12v power source. So I’ll need to figure out how to wire in a switch or thermostat….maybe powered by a couple batteries?

[hugh]

Originally Posted by Tford

Oops! Nope, the Dometic control box is fed by a separate 12v power source. So I’ll need to figure out how to wire in a switch or thermostat….maybe powered by a couple batteries?

Maybe just wire in a 12V power supply? I bet it doesn't need much current, so almost anything would work. Something like this?


https://www.amazon.com/dp/B0875WMYCX

[Centex]

Originally Posted by Tford

Oops! Nope, the Dometic control box is fed by a separate 12v power source.

Darn, wrong again

[Tford]

Not to fear! A Rube Goldberg setup on some scaffolding (so I could get below it), Romex extension cord to control box and 12V battery to thermostat (I’m an old car guy, there’s always a battery around!) and it blows hi/lo on fan and cools as well! Test phase successful! Now the actual work putting a platform on my attached compressor room room and cobbling up some ductwork for filtered return air and blower!
I’ve got a 5A 12V supply I’ll try hooking up to the thermostat tomorrow….