1st time planning to power window ac unit (midea 8k btu U shaped ac)

[Scrugs]

Hi all, I am finally ready to start purchasing solar and want to start small. Then get the 18k inverter later. First project is to power a window ac unit, it is a midea U snapped ac unit (8k btu) specs are below. Your help in design and specifying the solar equipment would be much much appreciated. The initial though is to purchase mounting (Integra rack ir3o mounts), aptos 370 watt biracial panels, some type of inverter… , battery , and wire it all up to power the little unit.

I like to plan very well, before spending $ and making mistakes. all I ordered so far is the kuman kw47 power usage monitor ( $12 ) to see actual power consumption and to be able compare to attached data sheet specifications of the window unit.

Next steps, determine how many aptos 370 watt solar panels to purchase and how many integra rack or 30 mounts, wiring, battery and inverter to purchase.

Ideally these items would be able to be used with the eg4 18k ( once I am more comfortable with understanding solar, then I would go for a big system).
( so this is a requirement of the little project, design such that can use the same equipment for the big system or as much of it as can be used )

as I go along I will share what ever I learn here and track the progress of the project.

Your comments and review and experience and knowledge will be a large part of my training

Appreciate you and thank you in advance for help and ideas to move forward.

Chad S

 

[Scrugs]

Here are some photos the midea 8k Btu window unit. I purchased it about 2 years ago. I assume the data sheet that I found today is still same or very close as I purchased the unit 2 years ago.

 

[Scrugs]

I think the next step is to determine the power consumption and peak power consumption. Of course I am doing learn as you go.

Chad S

 

[Scrugs]

Update: I just purchased the power monitor and plugged in the AC unit, then set the AC unit for highest fan speed and coldest temperature setting. The power monitor (kill a watt ) reads: 410 watts, 115 volts, 4.9 amps,
The specifications state 710 watts, but I get 410 watts.

Before changing the settings, it was in auto mode and was reading in the 370s ; it did not break 400 watts in auto mode.

 

[Scrugs]

What options do you see for inverter and battery or no battery ?

 

[areoseek]

Options are endless man. That unit is so small and has a variable speed compressor so little to no surge. You mentioned an 18. That's crazy huge. Oversized inverters are usually a waste due to the standby power and lower efficiency when you don't utilize all of it.

Look into the eg4 6000xp's
you can expand them indefinitely and as long as you dont desire grid export, they're an awesome, more cost effective option than a 12k or 18k.

Three 6000xps rather than an 18 k gives you more $$ for batteries. Like I said, they're expandable so you can start with just one for now, and scale up as you need, both with solar and additional solar.

If you go this route:
Grab 7 or 8kw of solar so you can run two strings and max out the 6000xp and then double it for the next, and again and again, and so on.

This way you don't waste 6-800$ on a small AIO that you'll immediately grow out of the second you get more solar.

As for how many batteries, take your desired run time and your usage and do the simple calculation.

Get as many as you can afford while they're cheap and before more tarrifs get added.. 48v will keep you with current available tech and is the most efficient.

Stick to 16s batteries(51.2v) avoid 15s. They can't be mixed.

The server rack batteries are an amazing option because you can just keep growing, starting with as little as 1.

The power pro eg4 batteries are super cool too, and they mate right up to the 6000xp if that's more your jam. They're a bitch to move though. 300lb

Good luck, and great job wanting to do it right. You'll save lots of money by researching your head off for a few days. This forum is an invaluable resource

 

[ChrisG]

I would use the manufacturer specs to make sure you're covering when the compressor is running. Depends on temp, house efficiency, insulation, etc. Can make some assumptions, say the unit runs 12 hours a day @710 watts = 8.5 kWh. Assume the standard of 5 solar hours per day for the panels to absorb you need enough panels to cover 1.7kwh for 5 hours to make up the 8.5kwh (need 5 Aptos 370w panels). This also assume optimal sun conditions, no shading, no clouds.....ever. You will also need at least a 10kwh battery to store this power to run the AC outside of the 5 peak solar hours.

Knowing the weather is never optimal, I would double everything I said above if not more to run this AC.

 

[zanydroid]

The power monitor (kill a watt ) reads: 410 watts, 115 volts, 4.9 amps,
The specifications state 710 watts, but I get 410 watts.

This is a fine starting point and enough for just this AC. Looking more broadly, here are some places to improve methodology.

Kill-a-watt does not analyze surge (though this appliance does not have it) like a clamp meter with surge measurement can, and it doesn’t show timeseries data like an Emporia Vue would. It also can’t handle 240V. Which Vue and Clamp meter can handle.

or no battery ?

No battery requires more engineering prowess, you need to decide whether the cost savings of going from zero to one battery are worth the complexity.

Kind of a meme, but IMO in the U.S. successfully going batteryless with an inverter is more of a flex on how clever you are than a good cost savings measure.

Batteryless with a hybrid heat pump will raise the hackles of the forum faction that thinks it is silly to pay a premium for a hybrid and have solar panels that can only power the hybrid. Which is a ding against how much you can flex on people as a DIYer or engineer

 

[zanydroid]

BTW I also like how you're proceeding in this project carefully and methodically.

The 6000XP and 18kpv question, I think is also determined by what level of code compliance you want to hit. For some reason it seems that a lot of Texas members are not that bothered with UL9540. Yet, I just looked on Upcodes for Texas residential code, and it has largely the same text for R328 as California does.

For grid tie system, you can also consider MidNite One (is promised to be 9540 compliant to same tier as 18kpv). This is an All-in-one.

For fancier off grid alternatives, you can look at Rosie, or Victron, these are modular inverter/chargers to which you would need to add a separate SCC. 6000XP will easily beat these in price/performance and while being in the same equivalence class wrt code compliance.

 

[zanydroid]

I'll add that going battery less and going without an interconnection agreement is a recipe for even more problems. With batteryless you need some kind of fallback power source, or a very large system.

The hybrid heat pumps can legally achieve this drawing from grid power without an interconnection agreement.

 

[ChrisG]

Agree with @zanydroid but check your local requirements. For my area in the U.S., a 6000xp works perfectly fine and is compliant with it's UL listing as we are not allowed to have an interconnect or sell back to the grid.