[RE-wrenches] Air Conditioning energy usage

[larry at starlightsolar.com]

William,

The LRA of an A/C system is the peak current demand. The inverter must be sized for that and all other potential loads if using a single inverter. For that reason, we have almost always used a dedicated inverter for an A/C systems and leave the primary inverter for all other loads. That way the A/C will start no matter what other loads are on the primary inverter. 

Install a hard start capacitor unit (sometimes now called soft start) if it is not factory equipped with one. Using Li-ion batteries is also recommended due to voltage sag using LA. Otherwise, you may want to size a LA bank larger for the additional current demand while starting.

We have been doing separate inverters for 120V RV A/C’s and 240V mini splits this way for years and it has been trouble free. 

Larry Crutcher
Starlight Solar Power Systems





On Jun 23, 2021, at 9:30 AM, William Miller <william at millersolar.com> wrote:

Friends:
 
In the old days when a client suggested they might want to run air conditioning equipment on an off-grid system we would just laugh.  Now I find I get that request more frequently and clients are willing to pay to acquire enough system capacity to run AC equipment.
 
This means I need to size off-grid installations appropriately for the loads.  I have a job pending with a 5 ton AC unit.  I cannot find real-life energy specs.
 
I do have a new, fairly efficient 3 ton unit at my grid-connected home and I do have energy monitoring.  On a real hot day recently we used a little less than 11kWh in this unit.  The max power draw was about 2.5 kW.
 
Here are my questions:  
 
1.   Can I linearly extrapolate my usage to a 5 ton unit?
2.   Do any of you have real-life, measured energy data on modern AC condenser units that you would be willing to share?
 
Thanks in advance!
 
William Miller
 
Miller Solar
17395 Oak Road, Atascadero, CA 93422
805-438-5600
www.millersolar.com <http://www.millersolar.com/>
CA Lic. 773985
 
 
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