12VDC Air Conditioner Installation

[dpearson]

Spring has sprung and grass is riz, and I wonders where the air conditioning iz. My 2011 Serenity came with no roof-top AC unit and I bought it with the intention of installing a 12V unit. I am thinking that it will be a 2 weekend project. This weekend I am going to deal with getting heavy gauge wire from the wiring jumble under the settee up to some convenient point in the roof.

The AC unit came with some 4AWG wire that looks like it will be almost exactly the right length. According to my calculations, 4AWG is a little light for the 45A load and will have around 6% drop in the wires. I would prefer a little less drop, but going to 2AWG would add quite a bit to the cost and wouldn't add that much to my run-time on batteries.

Challenge #1 is finding the path for the wire. Step 1 is to remove the back panel in the closet. Of course, a couple of screws are blocked by the medicine cabinet in the bathroom, so the real step 1 is to remove the medicine cabinet and then remove the box that it is mounted in. Oh, and even then you can't remove the back because the panel is clamped by the top panel in the closet, so you need to remove that too. But once you get there it reveals a collection of wires:

Interesting to discover quite a few wires that were not terminated:

There are extra power, cable and phone connections and a few wires that might be for controlling uninstalled options. No time to investigate, but worth remembering if I decide to add things later.

I managed to fish a small rope from under the settee up to the closet:


Now to find my helper to pull some wire.

 

[DiverBob]

What model and brand of DC air conditioner did you purchase. I’ve been looking into possible replacements for the installed Dometic as it draws ~160 amps at 12vdc.

 

[SSTraveler]

I too am very interested in your 12v AC installation and operating experience. I see from your other posts that you are installing the Kingtec K20D2, https://kingtecusa.com/2020/03/05/outside-vans-power-station-build-featuring-kingtecs-k20d/.

 

[dpearson]

I got totally stalled on this project. I summoned the courage to cut a hole into the interior ceiling cover and through the roof. Then I got that sinking feeling in the pit of my stomach when I realized that I had measured something incorrectly. It turns out that the gap between the ceiling cover and the roof was quite a bit larger than I was expecting and the cover extended quite a bit further forward than expected. This meant that the air conditioner would have to be quite a few inches further forward than originally planned. This was compounded by the problem of the shape of the depression in the roof to keep the air conditioner low down. My original calculation was that I would need to mount the AC on a 1" to 2" riser to allow it to clear the roof. Now it needed a 6" or 7" riser which meant the AC would stick way up from the roof. I started designing a mount for the AC that would align it sideways to allow it to fit down in the roof depression, but the complexity level mounted and I threw in the towel. So... no 12V Air Conditioner at this time. I picked up a Dometic Penguin and dropped it over my hole with a defeated sigh. It fits perfectly but it wasn't very satisfying.

With respect to the 12V Air Conditioner, yes I have a Kingtec K20D2. I tested it out in the workshop, and it kicks out cold air pretty nicely and draws around 40 to 50A on 12V depending on fan speed and a few other things. I am not giving up on it entirely. I have been noodling over a design for mounting it and may try again next Summer. In the meantime I am moving on to the next project.

 

[aksotar]

How big is your battery bank in that you can run 40-50 Amps p/hr to run your AC for hours in the day and still be able to have DC power overnight ?? Not to mention how much solar do you have in regards to charging your house bank... unless this is only meant to be used with the engine running and/or via shorepower...

 

[dpearson]

To be clear, I never finished the 12V air con. install, so it is a bit of a moot point. Just to make sure we are using the right units, it draws 40-50 Amps, which would mean 400-500 Amp-hours over a 10 hour period (overnight), which was my design goal.

The next project is to install an 800AH lithium battery bank, so when I get back into the 12V air conditioner project it should be able to run overnight on battery with no problem, but even a full day would be out of the question. There is around 150W of solar panel on the roof, but that is pretty meaningless at the power consumption levels we are talking about. However, the other big reason to use the 12V air conditioner was to be able to run on a small generator. The 12V air conditioner has both low overall power draw and any additional starting current is completely carried by the batteries. This would have meant that I could run the whole RV on a 1000W Honda generator that fits in the outside compartment behind the driver's door. The generator would feed a relatively constant 600-700W into the battery charger. The load would go up and down, but on average it would keep the batteries topped up. Lightweight, quiet and super efficient.

FYI, the Honda EU1000 generator is quite a bit quieter than the more popular EU2000/2200 models. It just doesn't stand a hope of running a 120VAC air conditioner of any size as it can't kick out enough starting current.

Cheers
David

 

[Briankeller]

Hello. I just purchased a Velit 12 volt roof AC. I have a 2200 watt inverter generator. I also purchased a 3000 watt converter. I’m using 2 awg wiring. I assume I can connect the converter to the generator, then to 300 amp Lifepo4 battter the the directly to my AC unit . Also I have an 80 amp fuse but unsure where To install it. Any help would be appreciated.

 

[Rocksnsalt]

Hello. I just purchased a Velit 12 volt roof AC. I have a 2200 watt inverter generator. I also purchased a 3000 watt converter. I’m using 2 awg wiring. I assume I can connect the converter to the generator, then to 300 amp Lifepo4 battter the the directly to my AC unit . Also I have an 80 amp fuse but unsure where To install it. Any help would be appreciated.

Besides the other things you mentioned, you’re likely going to need another battery if you want to run the AC unit for more than a few hrs without having to run a generator - which in some places are prohibited after certain hrs.

 

[Rick Michaels]

What model and brand of DC air conditioner did you purchase. I’ve been looking into possible replacements for the installed Dometic as it draws ~160 amps at 12vdc.

Hello,
I’m looking for a quiet AC unit & as you mention, one that draws <160 amps! I’m researching Houghton’s Quiet AC unit. I’m hearing theres a 14 dB reduction compared to the unit in my 2023 Wonder. Anyone familiar with Houghtons Quiet AC unit? If so, love to hear the compressor draw number and any other data.
Cheers, Rick

 

[Rocksnsalt]

Hello,
I’m looking for a quiet AC unit & as you mention, one that draws <160 amps! I’m researching Houghton’s Quiet AC unit. I’m hearing theres a 14 dB reduction compared to the unit in my 2023 Wonder. Anyone familiar with Houghtons Quiet AC unit? If so, love to hear the compressor draw number and any other data.
Cheers, Rick

I’m not sure if the quiet model, but I think there are a few Houghton install threads.
Search function is at upper right.