installing a 36000 btu airco offgrid

robocop · October 2016

to everyone

I am planning to install a 36000 btu an inverter airco in my living room. I live in the tropics.

Thinking of a solar dc inverter included possible installation of the household current and charger included for future battery.

then what type of dc inverter shouldl I buy and solar panels.

I think I should start with a dc inverter , 12v 0r 48 v input ??

It is for day time use only.

Which is better the airco with the dc inverter installed or with a separate dc inverter.

i think when there is no sun I can still use it on household current

So it should be a hybrid system which I can covert in a on grid in the future.

Hoping you wil understand as I am reading now about solar sysems to know about this foeld.

Thanks for reading

Robert

t00ls · October 2016

for an air conditioner that size you would definitely need a 48 volt system for offgrid use.
that being said, if you have electric grid coming into the house, then a hybrid system would be the way to go.
although at 36000 btu you would not be able to run very long during the day without having some solar to recharge the batteries during the day.
the first thing you would need to do is figure the loads that will be on the inverter in watts, that will tell you how much solar panel wattage you will need.....and you will have to have enough solar wattage to be above what the loads are.you will also need an inverter that covers the loads as well as whatever the surges for electric motors starting
so if the air conditioner and whatever other loads you have on the inverter use 2200 watts, you would be best to get an inverter that puts out at least 3000 watts....not 2500 as you may fall short even though it would be over the wattage being used....and the fact that starting at 3000 watts is where most inverters start incorporating 48 volts
the batteries would need to have at least 600 amp hours.......usually the minimum is 400-450, but again, an air conditioner that size will need some pretty beefy batteries
hope this helps

BB. · October 2016

Please open one thread about your installation/questions (new thread for different set of questions is fine)... Otherwise, you get answers in both and hard to move forward... Here is my post (I will delete the other thread). -Bill Moderator B.:

If your unit is a 16 SEER, there are other mini-splits that have ~25-30 SEER--If you are going solar, you should look at very high efficiency units. Also, insulation of the home/office (shading of windows/walls, etc.) is also very important too.

I am a little confused as to your needs... If you have a location where they allow/give you a good billing plan for Grid Tied Solar (net metering plan)--Grid Tied solar is going to be the cheapest, more reliable, least maintenance, and lowest ongoing costs.

If you need an off grid (battery based) or Hybrid (GT/Off Grid capable)--It will cost you about 4x as much as an equavalent GT only system (batteries are expensive, and need replacing every ~5-8 years or so, and you need new inverter/charge controllers/electronics every ~10+ years).

If you are simply looking to save money--Then doing as much conservation as possible will save you the most money. Going with off grid solar while you have utility power is, going to cost you more--Or at best, break even.

If you live in a region with fairly regular afternoon power shortages--You don't need to install solar (you can, if you wish), but a battery bank sized for 6 hours power outage and using utility power to recharge the bank (and you can add solar panels now, or later as you wish).

For sizing an off grid/solar power (or even GT system)--We really need to understand your loads... For example the typical AC system of that size may use 2,000 Watts running (inverter types do not usually have much/if any/surge current) and if you are well insulated, you may average 50% of that... So, just to make some quick math for off grid solar (give you an idea of size/cost of system). Using rules of thumb for a nominal full time off grid sysetm:

2,000 Watts * 0.5 duty cycle * 8 hours per day = 8,000 WH per day
8,000 WH per day * 1/0.85 AC inverer eff * 1/48 volt battery bank * 2 days storage * 1/0.50 max discharge (for longer batt life) = 784 AH @ 48 volt battery bank

Nominal solar rate of charge is ~5% to 13%, with 10%+ recommended for full time off grid:

784 AH * 59 volts charging * 1/0.77 panel+controller eff * 0.10 rate of charge = 6,007 Watt array nominal (based on battery bank sizing)

Need to know where the system will be installed--but say you have a minimum of 5.0 hours of sun per day (non-winter or equatorial installation):

8,000 WH per day * 1/0.52 off grid AC system eff * 1/5.0 hours a day minimum = 3,077 Watt array minimum

Now--Another way to look at it.. A minimum size battery bank and most power is supplied by solar power:

2,000 Watt max load * per 1,000 Watt AC inverter per 100 AH at 48 volts = 200 AH @ 48 volts minimum (day time loads)
200 AH * 48 volts * 0.85 AC inverter eff * 1 day storage * 1/0.50 max discharge = 4,080 WH per day (battery only) (or only about 1/2 of your daily load)

So--The absolute minimum would be a 3,077 Watt array and 200 AH @ 48 volt battery bank (day time/sunny day only)..If you have utility power, this would be possibly an OK minimum system where solar+utility share the loads/charging.

Your thoughts? I am just really guessing here... I do not live in an area that needs/uses AC (or at least, not very much).

-Bill

installing a 36000 btu airco offgrid

Comments

Categories