Portable air conditioning running on solar

[warewolff]

So I'm looking at energy efficient portable air conditioners. Next to the RV roof mounted a/c's, they are extremely efficient. For example, this 14,000BTU unit supposedly pulls less than 10 amps. Contrast this with near 20 amps for most of the similar spec'd rooftop models. I have an 860amp battery backup, or approximately 10kWh, and 1.2kW of solar on my roof. I don't think I'll have a problem running this unit a few hours a day on high to knock the interior temps down from 90 to 70.

Any opinions?

[EastCoastCB]

Originally Posted by warewolff

So I'm looking at energy efficient portable air conditioners. Next to the RV roof mounted a/c's, they are extremely efficient. For example, this 14,000BTU unit supposedly pulls less than 10 amps. Contrast this with near 20 amps for most of the similar spec'd rooftop models. I have an 860amp battery backup, or approximately 10kWh, and 1.2kW of solar on my roof. I don't think I'll have a problem running this unit a few hours a day on high to knock the interior temps down from 90 to 70.

Any opinions?

Mini Split. that is all.

[warewolff]

Originally Posted by EastCoastCB

Mini Split. that is all.

Can you post or link me to pictures of this install in your rig? And what is the advantage to this vs a portable unit minus space savings? It seems more costly and more complicated for comparable efficiency.

[EastCoastCB]

Originally Posted by warewolff

Can you post or link me to pictures of this install in your rig? And what is the advantage to this vs a portable unit minus space savings? It seems more costly and more complicated for comparable efficiency.

SomewhereinUSA's rig is up and running man. Check his out, he's running two of em. Mines under construction. If you wanna see a bus dissected click the link at the bottom of every post I make.

Mini split on a camper-

https://www.youtube.com/watch?v=IHDT5ZEpKkw

Maybe up in NY those portable units are ok. I'm in FL, and here those portable things aren't worth a damn.

[warewolff]

Originally Posted by EastCoastCB

SomewhereinUSA's rig is up and running man. Check his out, he's running two of em. Mines under construction. If you wanna see a bus dissected click the link at the bottom of every post I make.

Very cool, thanks for the link. I have got to get on following more of these builds but have been so busy with my own I get tunnel vision.

[cadillackid]

I own what would be considered the top of the line portable unit.. its called a CLimax and is an inverter type variable speed unit.. it is an excellent unit when the temps are somewhat tepid but if your interior is 90 and its a hot one like 90 outside.. good luck..
that unit Chokes in high temperatures...

the condenser coils arent big enough to handle the heat load.. and their energy useage goes way up... the R-410A refrigerant needs a large condensor area as it tends to condense slow.. the higher the temperature the slower it condenses and if you cant remove the heat away from the refrigerant you cant move it away from the room...

theres a reason that a 12,500 BTU mini split has roughly 2.5X the condensor coil area that a portable unit does... R-410A needs it.. and minisplits have it... yes they are larger but they work Much better at a Much better efficiency
-Christopher

[warewolff]

Any thoughts on this 9,000BTU Pioneer mini-split? I know I'd need some mounting brackets but my bus is 95 degrees today, fully insulated with elastometric roof paint and I won't make it through the summer.

[cadillackid]

firstr off dpmt mess with 9000, get the 12000... a minisplit running flat out is very inefficienct.. they want to run at 30-80% of capacity to be efficient and effective at humidity and heat..

they sre sold under any number of various nameplates... 95% of them are made by the same 3 chinese manufacturers.. and for some reason all of them are located in the same geographical area so it may be all those companies collude I have no idea...

mitsubishi and daikin are the only ones I know that use different manufacturers.. and daikin may not on their consumer grade mini splits..

the big thing is make sure it has lots of airflow wherever you mount the outdoor unit...
-Christopher

[warewolff]

Originally Posted by cadillackid

firstr off dpmt mess with 9000, get the 12000... a minisplit running flat out is very inefficienct.. they want to run at 30-80% of capacity to be efficient and effective at humidity and heat..

they sre sold under any number of various nameplates... 95% of them are made by the same 3 chinese manufacturers.. and for some reason all of them are located in the same geographical area so it may be all those companies collude I have no idea...

mitsubishi and daikin are the only ones I know that use different manufacturers.. and daikin may not on their consumer grade mini splits..

the big thing is make sure it has lots of airflow wherever you mount the outdoor unit...
-Christopher

A Mitsubishi getting into 12kBTU+ and I'm looking at thousands into my a/c... This 12kBTU Toshiba looks pretty enticing though.

[cadillackid]

Originally Posted by warewolff

A Mitsubishi getting into 12kBTU+ and I'm looking at thousands into my a/c... This 12kBTU Toshiba looks pretty enticing though.

yeah mitsi is too pricey.. I never use them... I have 3 cheap chinese ones that I modified the H*LL! out of in my house and have had running since 2009 and they work just fine... had a couple issues at first but none since about mid 2010.

toshiba, panasonic, gree, grunaire, etc are all similar.. some use sanyo compressors others toshiba..

I never wouldve thought any mini would last in a bus due to the vibrations and thin copper pipes but somewhereinusa has been doin it for awhile and they work great
-Christopher

[EastCoastCB]

Originally Posted by warewolff

A Mitsubishi getting into 12kBTU+ and I'm looking at thousands into my a/c... This 12kBTU Toshiba looks pretty enticing though.

Go with a $500 chinese system, they're all the same pretty much.

[cadillackid]

Originally Posted by EastCoastCB

Go with a $500 chinese system, they're all the same pretty much.

yep this!!! like I say ive had 3 modified chinese ones in my house since 2009.. i use them for heat and cool and they work just fine.
-Christopher

[warewolff]

10 or 11 amps/hr is nothing, even on the Chinese systems that are not energy star. However I'm having some difficulty crunching the numbers. THIS 24kbtu mini split has a rated capacity of 6800w, a rated power consumption of 2465w, and running current of just 10.76 amps.

Now ... I can find a 3kw inverter, but a 7kw inverter is going to be tough. Being I'm not an electrician, can anyone explain these numbers to me? if A x V = W, 10.76amps x 230v = ~2.4kW. I would imagine a 3 or 4kW inverter could handle the startup surge. Am I very mistaken?

So even if I go with the lower number, 230/240v at 3kW, I'm looking at about a $1500-2500 investment if I go on the cheap, between the chinese mini split and the inverter? Jeeze... I thought this'd be easier.

[cadillackid]

capacity is deemed by the amount of heat it moves.. that efficiency is determined by a lot of factors, theres no real startup current because these units are running internal inverters with soft start compressors...

my "24k" btu unit slowly starts up adding more and more power.. I see it reach a maximum of 2600 watts when im overloading the CFM of air across its indoor coil in heat mode.. in cool mode I rarely see it pull more than 1800 or so..

-Christopher

[warewolff]

So do I need an inverter with this unit? If so what specs should I be looking for?

It looks like I can get a 12k btu unit and a 240v 3kW inverter like THIS for under a grand.

Or I can get a 110v unit and maybe not even have to upgrade my inverter. Right now I have a Magnum 1500w, 2200w peak unit. For the most part I haven't seen my power consumption in the bus go over 3 or 400 watts and a 12k BTU unit like THIS uses less than 10 amps at 1180 watts. I assume the 1180 figure is peak, on high. I just might be alright ... Thoughts?

[warewolff]

Just an update and solution:

I was looking at thousands of dollars to go for a 230/240v unit and also a comparable inverter. I found a 22 SEER Pioneer 9k btu ac/heater for $810 shipped on ebay. It's highly efficient and will only pull ~650 watts total at full load. The best part about it is that it's 120v, meaning I can use my existing 1500w Magnum inverter and still have headroom even running my fridge, televisions, and computers. I'm very happy. All running comfortably off grid on my 1.2kW solar array and 10kW battery backup.

I'll be installing it in the next few weeks. Follow my build thread for updates.

[cadillackid]

9k is gonna maybe keep you from sweating profusely ti just sweating... 650 watts is a pipe dream at full load.. as i mentioned either in previous post or another thread.. mini split inverter units running at full tilt are VERY INEFFECIENT.. they are designed to be most efficient at 30-80% or so of their capacity...

I have 3 of them in my house connected through temperature and energy monitors.. since I hacked the computer protocols in them i can limit them to 85% of capacity so they are always in their efficient range when i choose to...

minisplits are a great way to go in a bus, but as with all HVAC gear it should be sized appropriately for the job at hand...
-Christopher

[warewolff]

I checked the specs. This is a high SEER unit, which is why it's so expensive. 665 maximum cooling watts, 790 maximum heating watts. Christopher, I'm not trying to be argumentative but do you honestly believe it will draw higher than that at full load? Keep in mind it's rated as a 22 SEER unit. Most are 13-17. That means it draws 30% less power than a 15, which is probably what you have installed in your home. 15 is the norm. That's why this 9k btu unit is pricey at over $800. I spent hours poring over energy specs on the various units and found that most of them are inefficient. I can pull just over a kW more on the inverter before I'm redlining it.

I do believe you that the 9k unit might not cool enough. I figured worst case scenario I could wall off my bedroom and make it as airtight as possible so I have a space to cool off, leaving the rest of the bus with fans. I'm concerned about energy consumption as I'm completely off grid and don't want to stress my inverter/batteries. As for the the comparable 12k unit ... it's selling for $100 dollars more at ~$910, which is not the issue. Manufacturer states that the 12k btu unit at the same 22 SEER rating pulls, MAXIMUM, 960 watts for cooling and 1120 watts for heating. I could make it work, but it's going to be tight with my solar array. Again, those specs are direct from the manufacturer and generally I find my appliances never reach the maximum stated power consumption.

Also you stated yourself that there is no surge as the inverters are internal. So I shouldn't have to worry about overhead space, right?

Thoughts? I trust your opinion ... just wanted to present all the facts.

[cadillackid]

My units are 21 seer from 2009 which is the most I could get they were brand new then.. in my hvac lab downstairs I have a Fujitsu which claims to be 26 seer but I have yet to take it out of the box.
they aren't supposed to draw more than their rated load but they will run over capacity ..
there is no surge current so you don't need a honking large inverter to account for that .
Mine are rated at 12000 btu but actual capacity is 5000 through 14500 as listed in the book. Since I can manually command my units capacity I have watched useage vs commanded capacity .. and once I reach 80% or so I am at around 1050,watts.. this is 90 outside and 75 inside and 55 wet bulb .. now when I then command 100% my usage jumps to 1450 watts or so... you can see the loss in that I've jumped over 35% power to gain 20% command ..
granted it's not truly scientific but enough so that I force my blower speeds and temperature deltas so that the unit never commands above 80%. You have a chance of attempting that by never turning your indoor fan on high as it will always have a cold enough cool temp to stay at low command .. unless your bus is so hot that it runs flat out all the time...
I don't know what. Linage you are going to live in or if you are going to let the unit run all day where it stands a chance of running 50% capacity as a maintainer .. or if you want to let the bus boil when you are not in it and then expect it to cool down.. the latter scenario is where you will waste efficiency ...
I don't pretend to know how to live off grid as I'm the opposite . I am an in grid city boy type that only lives off grid when lightning hits the power lines..
all I know is what my experience and experimentation on hvac design have brought... I built a computerized zone system in my house from scratch that has features which high end commercial buildings don't yet use...

If all you have for power source is solar and a small inverter then 9k may be all you can run.. but for efficient operation calculate your climate, heat load, and methods of how you plan to run the unit and what temperatures and humidity levels you want in the bus and also how much insulation and how dark and cave like you want the bus ( less windows less heatpoad)..
if your design shows that much of the time your unit runs flat out then you may be more efficient to run a bigger one ...
it's something to think about
Christopher

[warewolff]

Thank you. Really appreciate the response. It helps to know you are running a 21 SEER unit. If you don't mind my asking, have you ever checked the specs on your units to see what the manufacturer says the max wattage consumption is? Then you can compare that with what you're actually seeing and put an end to my obsession. I'd be curious to know if the specs are actually inaccurate, low balling, or if maybe the units are little more efficient today.

My bus is pretty heavily insulated now with 1 1/2" through all the walls and floors but I think what's happening is the sun is beating down through the remaining windows (I've got 6 in the front open and 2 in the rear), heating up the bus like a greenhouse as the heat can't escape through the insulation. Adding insult to injury, the compressor on my fridge is blowing hot air, the 12 solar panels are absorbing heat that I would assume is transferring into the roof at least a little, and the charge controller/inverter/battery array are giving off heat. Temp today was 98 degrees in the bus. I couldn't even work. This is with reflective elastometric roof paint too. Once I frame the windows I'm going to design window inserts to reflect the sunlight / insulate the bus, but that's a few weeks down the road. Hopefully that will help a lot.

I think I will spring for the 12k unit. Maybe we can meet up sometime and you can share these hacks with me. I might have to add another set of batteries in series but I think I'm close to being able to handle leaving the a/c on all the time. Worst case scenario I can set it to the low setting and close the bedroom door. Voila, problem solved. While I definitely have the headroom on my inverter I am just worried about topping the batteries off before night time. Pulling a 1kWh load with a total available incoming of less than 1.2kWh is like trickle charging an 860aH battery bank.

Anyway, thanks. I'm going to buy the 12k unit and see how it goes.