Stand alone Split unit?

[sinistral_leo]

Hi Ya'll,
I am setting up an off grid homestead in TX in the very near future.
I have the specs for the main solar system all set from my energy audit, without Air Conditioning...
My question is, can (or how can) I run a stand-alone system for the Air Conditioner so that the Air Conditioner only comes on with its own 3 or so panels are making enough for it's own invertor? (i'd probably have one 12V battery just for voltage regulation/stability)

My thought process is:
I don't want the Air Conditioner sucking so much power from my main system that my fridge doesn't make it through the night.
I can get by with the Air Conditioner on only when the sun is out.
I work full time, So it would be nice to know that when it is hot and I'm not there, the Air Conditioner is on for my dogs.

I tried searching for this, but I'm not sure what the term is. I don't need specifics because I don't even have the Air Conditioner yet. Just proof of concept.

Thank you in advance.

 

[BentleyJ]

Your question is difficult to answer based on the stated goals and lack of AC specifics.
How many sq ft need to be cooled and what is the heat load on the room, is the insulation adequate? How many tons is the AC unit. The best choice here would be a high eff. variable speed mini-split system. Maybe even one that can operate on DC.

I don't think 3 solar panels is going to run an AC unless its quite small and you can accept operation only during a 2-3 hr period during peak solar conditions. Also not sure why it would be advisable to install a second system rather than use the same investment to upsize the main system so you can have a higher level of comfort.

 

[Hedges]

You can enable/shed loads at various battery SoC.

With my Sunny Island, two relays can be programmed for two different SoC. I presently have 30% SoC disconnect all loads. I could have 80% SoC disconnect heavy loads like HVAC and dryer.

Some SCC also have an output that could enable a power relay or thermostat circuit.

With enough PV, A/C can run all day long. Load shed would turn them off in evening while leaving enough battery for other loads.

 

[Q-Dog]

Here is one way to do it.

DC Solar Air Conditioner Heat Pump | Solar Air Conditioning | Solar Heating | Manufacturers

 

[Rednecktek]

Something like Signature Solar's Hybrid A/C systems? They also make a 1-ton unit if that's more your size.

 

[sinistral_leo]

Here is one way to do it.

DC Solar Air Conditioner Heat Pump | Solar Air Conditioning | Solar Heating | Manufacturers

Yes, Or any mini split and I can add my own inverter/SCC.

 

[sinistral_leo]

Also not sure why it would be advisable to install a second system rather than use the same investment to upsize the main system so you can have a higher level of comfort.

I'm not sure. I can add this system to any AC for under $1000
but adding a 1 ton minisplit to my main system would add 15,000 W/hrs of batteries and 3000W of solar panels.
So it would double my current setup...

I'm new to this and don't have any experience. So I'm just asking.

 

[BobR]

You might be able to make a simple system with something like this.

I'm not sure. I can add this system to any AC for under $1000
but adding a 1 ton minisplit to my main system would add 15,000 W/hrs of batteries and 3000W of solar panels.
So it would double my current setup...

I'm new to this and don't have any experience. So I'm just asking.

You might be able to come up with a separate 12v system with something like this.

 

[LeoThomson]

If you make a system large enough that can produce enough in winter, you will most like have way more than you know what to do with in summer even if you do run your air conditioners.

If you don't a simple timer might help, turn the airco on in the late morning and off again a couple of hours before the sun sets. However there are better solutions proposed here and you could even look into home automation.

 

[sinistral_leo]

If you make a system large enough that can produce enough in winter, you will most like have way more than you know what to do with in summer even if you do run your air conditioners.

If you don't a simple timer might help, turn the airco on in the late morning and off again a couple of hours before the sun sets. However there are better solutions proposed here and you could even look into home automation.

It is my understanding that winter would only affect the number of panels needed. Not the battery capacity or inverter...

 

[Hedges]

Yes, Or any mini split and I can add my own inverter/SCC.

"During the day the ACDC12C can run exclusively on solar power with no AC power or grid connection when solar is strong enough. The maximum speed/capacity will be based on the level of available solar power available. If also connected to AC power source, the unit can run at full speed whenever needed, and will add in just enough AC power, if/as needed, while still primarily using available solar DC power."

That is the special feature, a VFD implementing MPPT.

Ideally, such a unit, or a mini-split with speed control, would be configured as a variable dump load. With some overriding "comfort" and "SoC" limits.

It is my understanding that winter would only affect the number of panels needed. Not the battery capacity or inverter...

Winter has more hours of darkness.
It may have more or less load. Electric heat? A/C needing to run through the night?

Having other power sources would make it easier to right-size a system. I have A/C, grid, PV, electric heat, gas heat. I have not automated it yet, but would like to use electric loads when sufficient power available, in the event grid is down switch to gas heat as needed to maintain SoC. For now that is manual.

 

[LeoThomson]

It is my understanding that winter would only affect the number of panels needed. Not the battery capacity or inverter...

You are partially correct, solar panels are cheaper than batteries so it makes sense to increase solar panels (if possible). But you can also add more storage, or even both.

Just try things out, put your solar panels in a corner and allow room to grow in case you do decide you want more after getting experience with it after a couple of years. Same for batteries...

 

[sinistral_leo]

You are partially correct, solar panels are cheaper than batteries so it makes sense to increase solar panels (if possible). But you can also add more storage, or even both.

Just try things out, put your solar panels in a corner and allow room to grow in case you do decide you want more after getting experience with it after a couple of years. Same for batteries...

No matter how much sun is out, the draw of my appliances are the same. therefore, the same battery requirements.
If there is less sun the only option is more panels...

 

[LeoThomson]

No matter how much sun is out, the draw of my appliances are the same. therefore, the same battery requirements.
If there is less sun the only option is more panels...

True, as long as you can charge the battery to the required capacity each day.

 

[sinistral_leo]

"During the day the ACDC12C can run exclusively on solar power with no AC power or grid connection when solar is strong enough. The maximum speed/capacity will be based on the level of available solar power available. If also connected to AC power source, the unit can run at full speed whenever needed, and will add in just enough AC power, if/as needed, while still primarily using available solar DC power."

That is the special feature, a VFD implementing MPPT.

Ideally, such a unit, or a mini-split with speed control, would be configured as a variable dump load. With some overriding "comfort" and "SoC" limits.



Winter has more hours of darkness.
It may have more or less load. Electric heat? A/C needing to run through the night?

Having other power sources would make it easier to right-size a system. I have A/C, grid, PV, electric heat, gas heat. I have not automated it yet, but would like to use electric loads when sufficient power available, in the event grid is down switch to gas heat as needed to maintain SoC. For now that is manual.

Oh, I like that VFD feature.
As far as winter, I have gas heat. no electric needed.

 

[sinistral_leo]

True, as long as you can charge the battery to the required capacity each day.

I feel like we are beating a dead horse here. Charge my batteries with what? Oh. THE PANELS!
The panels aren't the problem. The massive draw from the air conditioner is.

 

[sinistral_leo]

You can enable/shed loads at various battery SoC.

With my Sunny Island, two relays can be programmed for two different SoC. I presently have 30% SoC disconnect all loads. I could have 80% SoC disconnect heavy loads like HVAC and dryer.

Some SCC also have an output that could enable a power relay or thermostat circuit.

With enough PV, A/C can run all day long. Load shed would turn them off in evening while leaving enough battery for other loads.

Thank you.
This is probably the best route.

 

[SilverbackMP]

Oh, I like that VFD feature.
As far as winter, I have gas heat. no electric needed.

All higher efficiency minisplits these days are VFD (but don't have the MPPT).

 

[Rednecktek]

Oh, I like that VFD feature.
As far as winter, I have gas heat. no electric needed.

Gas heat doesn't need a fan? Or like a catalytic heater?

 

[Vigo]

I think the signature solar unit is the easy button because it doesnt require you to implement anything externally. If you do decide to implement something externally there are many many options. For example, i have my large ac running off a contactor controlled by my inverter’s dry contacts. I also have various things on timers and am going to put some of those things on voltage monitoring relays as well which is just a variable voltage window switch with delay timers. REALLY nice inverters allow you to trigger things off calculated SoC or other variables as well. To get that level of finesse outside of the inverter requires a coulomb meter with a shunt and some programmable outputs to control based on SoC. You can daisy chain multiple allow/disallow switching devices in series to control a contactor if desired. Cars used to do that before everything was computer controlled. So you could create a situation like IF time between 9-3, AND battery voltage above X, THEN contactor powering ac turns on. Etc.