120V vs 230V mini split on a small travel trailer?

wankel7 · October 2018

Trying to figure out the best way to go with using a mini split on my travel trailer. It is a smaller unit....the box is 18X7 and total length is 21'.

The highest quality 120V mini split I have found is the LG. Their 9000btu unit is Energy Star rated, 17 seer / 12 eer and has the largest BTU range.... 1,023 - 13,785. They claim 710 watts (80F indoor temp and 95F outdoor temp). Their 27.5 seer / 15.6 eer 230V unit claims 575 watts under the same conditions. So 20% less power.

Obviously, going to a 230V MS opens up a much higher seer / eer rating for the MS. But going to 240V in my small RV adds more expensive boxes. The options I have found is the Conext SW2524 ($1200 + $200 for the control panel) with does split phase...120v and 230v from the same inverter. Or the Victron auto transformer which takes 120V and transforms it to 230V....$560.

My battery bank is going to be on the small end for a MS....4 100ah LifeBlue LiFePO4 batteries for around 2600 watts of storage in a 24V bank. So, if I want to run the AC after the sun dips down maybe a 240V unit is worth the complication it brings. Not sure on the solar yet but somewhere between 800 - 1200 watts. I have room for 1200 watts but would like to have less for weight and cost.

Thoughts?

LG 115V 9000 btu 17 seer LSN090HXV
https://www.ecomfort.com/manuals/MegaEngineering.pdf
Page 42 shows the power consumption (The PI column is Power Input)

LG 230V 9000 btu 27.5 seer LA090HYV1
https://www.ecomfort.com/manuals/ArtCoolPremierEngineering.pdf
Page 26 shows the power consumption data.

One note....I learned DB is dry bulb...air temp measured with a thermometer. I know there are higher seer MS but I just focused on these two for easy comparison.

mcgivor · October 2018

The SEER rating can be misleading because it's a calculation based over changing seasonal conditions, EER ratings are said to be a more accurate for comparison, ultimately it would come down to the actual draw from the battery bank during useage. The current draw of the MS is a useful for calculation purposes, say for example the 575W/240V uses 2.4A, the battery current would be 24A approximately at 24V, multiplying that by the actual run period in hours will give the Ah capacity needed. Granted it's a simple estimate because the actual duty cycle will be dependent on insulation along with reduced current demand if inverter based as the set-points are met, but it's useful as a guide. This comes down to the battery capacity available, the use of a MS with such a small capacity is not feasible even assuming there are no other loads, my opinion naturally, the PV should be capable of both charging along with supporting loads as required, remembering the inverter's self consumption is important, just under 1Kw per day in the case of a SW 2524. Even in a perfect situation with panels angled to reap maximum harvest the system as described is too small. Again just an option.

wankel7 · October 2018

Can you help me how you determined the 1000 watt self consumption rate of the SW2524? I am guessing you determined that through usage?

Are you able to see the watts going into it and the watts going out to determine the efficiency?

Estragon · October 2018

At ~40w (1kwH/day ÷ 24hrs = ~40w), that seems to me to be on the high side of normal for an inverter of that size. The manual likely specs it.

IIRC, my Outbacks are ~30w no-load idle per specs, confirmed as about that with trimetric and Midnite Classic Wbjr shunt. I try to avoid constant small loads on the big inverters at night so they can use search mode (~6w), or turn them off entirely.

Dave Angelini · October 2018

Is this an offgrid application in a hot place where someone will be there?

In my opinion with tons of experience in mini-splits and offgrid, this is the most important thing you have to be able to answer. The next thing is you will need lots of room for an array.

Is this temporary and all the info you can post will get you reasonable answers.

wankel7 · October 2018

Dave Angelini said:

Is this an offgrid application in a hot place where someone will be there?

In my opinion with tons of experience in mini-splits and offgrid, this is the most important thing you have to be able to answer. The next thing is you will need lots of room for an array.

Is this temporary and all the info you can post will get you reasonable answers.

Hi Dave

This will be in a small single axle travel trailer....we move around a lot. If this AC idea works we will gravitate towards hot places that are not very humid. The most I can cram on my roof is 1200 watts....6 200 watt panels.

So, 1200 watts on the roof in good sun should be good for 900 watts assuming a 25% loss.

With the MS running at 710 watts that leaves 290 watts to charge the batteries and run the 12V side of the trailer. Not much excess. My loads are light though a few LED lights here and there and a DC compressor fridge that uses around 3.8 amps (50 watts) with a 50% duty cycle.

My 2380 watt battery bank that I am able to take down to 10% soc leaves me 2,142 watts to play with.....and it would take nearly 8 hours to recharge at 290 watts per hour. The huge variable though is the variable speed compressor. If it all works out maybe the average wattage I see is in the high 400s....if that is the case 1200 watts on the roof works. It is pretty frustrating that I am unable to find any YT videos that take a deep dive into MS power consumption. Maybe I am searching with the wrong words?

The other option is to spend the extra money now and a 230V MS and the supporting electrical equipment to make that happen.

It seems like the highest the 9000btu would draw is 810w so I could run it with a 1000 watt genny.

If I pull the trigger on this I will be sure to update.

Dave Angelini · October 2018

Can't comment without answers...

wankel7 · October 2018

Dave Angelini said:

Can't comment without answers...

"Is this an offgrid application in a hot place where someone will be there?"

It is a small travel trailer that we do not take to RV parks. While we adventure for the day a small dog will be there.

"Is this temporary and all the info you can post will get you reasonable answers."'

The installation of the ODU and IDU will be fixed. The ODU will go on the tongue. The IDU on a wall above a window on the left side of the trailer. I am planning on running the line set inside of the trailer and having the lineset exit at the ODU.

Dave Angelini · October 2018

The concept of how a mini-split could work in this situation would require someone to be there and monitor the power.
As the temperature differential (programmed to actual room) increases the power will go up past your limited and fixed array.

There will be no warranty for a mobile application. A compressor of this quality probably will not like the jarring motion and shock either.

The reason I asked about temporary is I have helped folks who were/are building homes install a trailer/split 20 feet from the ODU. They then change the lineset back to the home when they were ready. The trailer worked but once in the home with R19+ walls and R30+ ceilings the performance really was amazing. They also were tracking 2KW of solar and had normal size home batteries.

To make this work you would need to run a genset when you return if you are in summer places like the south east and west. Seems like a lot of work if this is just for a year or two.

wankel7 said:

So, 1200 watts on the roof in good sun should be good for 900 watts assuming a 25% loss.

So, 1200 watts on the roof in good sun should be good for 900 watts assuming a 25% loss.

You are leaving out the conversion loss of the CC and the inversion loss of the inverter. Your panel loss may be more with a fixed array at non optimum angles and possible shading.

Sorry to paint this non rosey picture but that is my take. I do wish you luck with whatever you end up doing.

wankel7 · October 2018

If I was able to have battery storage of 4800 watts / 200 ah @ 24V....would that change your thoughts?

weejub · October 2018

New here, but was thinking about doing the lowest BTU Mitsubishi with a utility trailer camper.

Have you also considered something smaller like the Dometic Cool Cat?

I am starting to plan out a 4x4 Mercedes Sprint build.

littleharbor2 · October 2018

weejub said:

New here, but was thinking about doing the lowest BTU Mitsubishi with a utility trailer camper.

Have you also considered something smaller like the Dometic Cool Cat?

I am starting to plan out a 4x4 Mercedes Sprint build.

The only way that this makes sense would to have all solar panels freestanding. If you have the panels hard mounted on the roof you need to keep the Sprinter in the sun. We all know how hot a closed up vehicle sitting in the sun will get. If there is no shade available where you are dry camping you would need to create your own shade with some sort of pole and tarp setup.

I don't have any photos but I have done the pole and tarp setup with 1/2" emt conduit and 1/4" nylon rope. It works great and is super easy to set up. You can drive a 1/2" wooden dowel into the top of the emt and with some eye screws create the guides for the rope.

wankel7 · October 2018

weejub said:

New here, but was thinking about doing the lowest BTU Mitsubishi with a utility trailer camper.

Have you also considered something smaller like the Dometic Cool Cat?

I am starting to plan out a 4x4 Mercedes Sprint build.

The highest seer lowest btu Mitsu unit is 6000btu at 33.1 seer. It is pretty amazing when you look at the power use. For example 105F dry bulb outside air temp / 71F indoor temp wet bulb it is using 360 watts....the unit is producing 5500 btu. So , it won't take much solar to keep this thing running. This unit has a BTU range of 1700 to 9000 BTU. So if it uses 360 watts at the temp I posted....can you imagine what it uses when it ramps down to 3000 btu? 200 watts and still cooling would be my guess. You could run this thing with a 1000 watt generator. I am not sure if you have looked at them but the Honda weighs 28 lbs and is 49 or 50 DB at full throttle.

You can find the power numbers on page 135 of this document.
http://meus1.mylinkdrive.com/files/M-Series_Engineering_Manual.pdf

Check out this group on FB - Second Life Batteries (Re-Using EV Batteries on other projects) and search for Chad. He is using the 33 Seer 9000 btu mini split in a Sprinter. He separated the compressor and condenser. He is using a Conext SW2524 I think for the 230V and is using two Tesla modules...so almost 10000 watts of battery storage with 120 lbs of batteries. An amazing build.

The efficiency of the Cool Cat is pretty bad.

Photowhit · October 2018

wankel7 said:

The efficiency of the Cool Cat is pretty bad.

That's an understatement, with a 2500 btu at 480 watts an EER of 5.21, you should just throw it out of consideration. My window air conditioner a 5200 BTU, EER of 11 using 475 watts!

https://c.shld.net/assets/docs/spin_prod_786785712.pdf

Photowhit · October 2018

wankel7 said:

The highest seer lowest btu Mitsu unit is 6000btu at 33.1 seer. It is pretty amazing when you look at the power use. For example 105F dry bulb outside air temp / 71F indoor temp wet bulb it is using 360 watts....the unit is producing 5500 btu. So , it won't take much solar to keep this thing running.

Well I'm not Santa Clause, and I can NOT tell you it will work.

I can do the basic math for you and tell you about my experiences.

Math, 360 watts at the unit = about 400 watts at the battery bank (before other energy draws) so if you want to run this day and high, (...you don't want to fry the puppy...) That's 400 x 18, that is giving a generous 12 hours running at 50% capacity and shutting the compressor down. I don't know if the fan will turn off or what the idle energy draw is. but 400 watt hours x 18 = 7200 watt hours, if you are getting 900 watts on an array that is not properly oriented to the sun I'd be surprised, about the max you can get from a fixed array properly oriented, is about 7 hours of solar insolation, 7 x 900 = 6300 watt hours. All this before other energy users and other system losses (other than the inverter).

You could go with a a flat solar array above the items on the roof, and another flat panel array on the non-door side of the camper and get a large enough array to charge a "...4800 watts / 200 ah @ 24V..." battery bank and likely have enough daytime power to charge and run the air conditioner.

The other option is to take advantage of lithium's ability to take a strong charge and have a larger battery bank and do a strong charge for an hour or 2 each evening after you start drawing off the battery bank. I would think this is the most cost effective.

I've run a window AC on a minimal system, well insulated cabin, thick walled (6") and well insulated roof and floor. 10 x 16 maybe half again as much cubic feet as I had a high roof. It was built in the shade, had double pane windows. I ran a window air conditioner in the evening for 4-5 hours to sleep on 4 GC batteries (about 5 KWhs similar to your smaller battery bank in usable energy drawn down to 40-50% each night) It was charged with a well oriented 1000 watt array the first year and up to 1600 watt array 4 years later. With the added array it gave me more run time during the day and less load when starting to cool down for evening sleep (I worked 2nd shift at the time) With everything going for me, I couldn't really run it around the clock.

120V vs 230V mini split on a small travel trailer?

Comments

Categories