diy solar

diy solar

3 Ton AC unit how much energy?

I'd start by buying a clamp on ammeter that accumulates power and make sure you know what the requirement actually is. You'll need to spend a lot of money to implement what you're trying to do, figure out how much it will save you on your power bill and how long it will take to break even.

You could install a grid tie inverter and let the utility company start your A/C, then if your array is producing power it can run or supplement the A/C draw, or maybe you can sell the power back if the A/C is not on. Not sure where you live, but A/C is likely a seasonal thing, you're going to spend a lot of money trying to support a device that may not run all the time. When I looked at our power requirements the cost of batteries made it impractical to go that direction so I went grid tie.

The other possibility is if your utility offers hourly pricing, you could use your house as a thermal battery. Run your A/C all night when the power is really cheap and get the temp really low in the house, then turn off the A/C all day. That can work well if you have a newer house that's insulated and your family won't move out and leave you.
Well my unit is an all in one. So it’s used everyday whether its the heater or AC. But of course the power consumption is the heater. And my fear is, I just bought (32) 3.2V x 320AH LIFEPO4 batteries so I was hoping I could make it work. But I can’t sell back to the utility where I’m at in Texas. But will a grid tie inverter help? How would I make the utility be the surge and the remainder run off the Solar system?
 
Well my unit is an all in one. So it’s used everyday whether its the heater or AC. But of course the power consumption is the heater. And my fear is, I just bought (32) 3.2V x 320AH LIFEPO4 batteries so I was hoping I could make it work. But I can’t sell back to the utility where I’m at in Texas. But will a grid tie inverter help? How would I make the utility be the surge and the remainder run off the Solar system?
Your house will use all the power the array is producing first, if it needs help it will draw power from the grid. That's all handled by the inverter. Too bad you can't sell back to the grid. Since you already bought the batteries, your best bet might be a hybrid system that is grid tied and can use batteries.
 
Nothing wrong with capacitor. Read up on what LRA spec means. It is not starup surge current. It is much lower then typical startup because LRA spec is at lowest AC voltage and increased copper wire loss due to hot compressor. Also when rotor is not truely locked but rotating at a very low rpm allowing low frequency rotor induction current pickup the run and starter windings draw more current. How much power do you think it takes to take a rotor mass from zero rpm to 93% synchronous rpm speed in a very small amount of time and what does that have to do with a locked rotor situation.

For air conditioner compressors run capacitor is a compromise between startup and run power factor improvement. The start capacitor boost + softstarters temporarily increase starter capacitor value by about 5x during spin up to increase startup rotational torque for full 360 degree rotation angle. This must be mated with a voltage ramp soft starter otherwise the peak current will be higher for a shorter startup time.
I service a LOT of ac equipment each year… I assure you… if your startup current is double the LRA… you need service.
 
Well my unit is an all in one. So it’s used everyday whether its the heater or AC. But of course the power consumption is the heater. And my fear is, I just bought (32) 3.2V x 320AH LIFEPO4 batteries so I was hoping I could make it work. But I can’t sell back to the utility where I’m at in Texas. But will a grid tie inverter help? How would I make the utility be the surge and the remainder run off the Solar system?
You can actually power the whole house off the batteries/solar with grid assist, but you would have to run everything through the inverter and it would have to be a hybrid type unit that does not back feed the grid. You basically set it up as off grid, but have grid feeding into the inverter. If the solar/battery cannot handle the load, the grid kicks in. Once the sun goes down and the batteries get low, the grid will either power your loads or charge the batteries (which will power your loads). A lot of people use this setup off grid and use a generator in place of the grid, but it is basically the same concept.
 
Simplest analogy I can think of. A locked rotor is like a transformer (be it a transformer with a lot more leakage inductance then normal power transformer) with a short circuited secondary winding.

A startup surge on induction motor is like above but instead of short circuited secondary it has an out of phase voltage applied to its secondary. This is worse than just a shorted secondary and effectively increases the applied input voltage increasing the primary side current compared to just a shorted secondary winding.

Mechanical loading on induction motor only makes startup surge worse. Copeland scroll compressors have the highest startup surge current of any air conditioner compressors I have measured. I have checked several models of various btu sizes, all typically about 180% of LRA rating.

Attached is an Emerson 'SecureStart' starter cap boost-soft starter graph from their unit's data sheet which is on a 3.5 ton Copeland scroll compressor with a LRA rating of 104 amps. Not my graph. I have verified 180 amp startup surge current on an actual unit.

SecureStart chart.gif Copeland scroll compressor copy.png
 
The AC unit has added much more usage that I was anticipating making my electric bill at an uncomfortable monthly amount.
Keep in mind whatever you spend on the solar stuff is money you could just put towards the bill.

You should do an ROI estimate first.

If you spend 5 grand just to save $40 a month 7 months out of the year (or whatever your numbers are) that's a whole lot of years you could just pay the bill with that money.
 
You said 6 to 7 hours, but is that run-time of the compressor? Or just how may hours thermostat has A/C enabled?

If your utility bill jumped when you started using A/C, the difference will give you average consumption throughout the month. Which may or may not make it easy to estimate kWh/day.

If you can do grid-tie net metering, all that matters is average kWh over an entire year (except if you have time of use pricing, or will be forced on that when you get net metering.)

Starting the motor an providing 100% of power from PV/battery is the most difficult approach.

Zero-export is one way to offset consumption with PV and not do net metering.
A grid-tie inverter connected to compressor side of relay would only operate when compressor is enabled (and has to wait 5 minutes before connecting.) That's a way to do a bootleg system that never exports, if sized no larger than what A/C draws.

Keep in mind whatever you spend on the solar stuff is money you could just put towards the bill.

You should do an ROI estimate first.

If you spend 5 grand just to save $40 a month 7 months out of the year (or whatever your numbers are) that's a whole lot of years you could just pay the bill with that money.

DIY GT PV costs about $1/watt in hardware (assume labor is free). Amortized over 10 years, it delivers power for $0.05/kWh. Over 20 years, $0.025, or $0.03/kWh if inverter needs replacing.
So net metering (assuming same buy/sell rate) breaks even in about 3 years if utility rates are $0.15/kWh.
Other systems costing more or harvesting less than 100% of available power will be less favorable.
 
well with my medical situation I just don’t wanna leave my dad with an atrocious electric bill for life if my heart gives out. I’m only 30 and have heart failure (which is why I still live with my dad and not alone) so that fear is In the back of my head. I make good enough money to dump the money on what I need to now and I eventually want to move everything over to the off grid system so my dad would only have to pay the minimum $40 electric bill for off-grid systems (stupid law where I live) but what if I do a setup like how Will did with 2 inverters going into a panel? And let both of them take the hit from the initial surge?
 

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You should do an ROI estimate first.

I don't think there is anything wrong with calculating ROI, but I don't list that as the most important factor.

It might not make financial sense to spend $10,000 to save $500 a year, but if you can also say "I don't have an electric bill" there is a personal satisfaction value that needs to be added.

Kind of like buying a sports car instead of a more practical sedan. But hey, I can go 0-60 way faster! :p
 
I don't think there is anything wrong with calculating ROI, but I don't list that as the most important factor.

It might not make financial sense to spend $10,000 to save $500 a year, but if you can also say "I don't have an electric bill" there is a personal satisfaction value that needs to be added.

Kind of like buying a sports car instead of a more practical sedan. But hey, I can go 0-60 way faster! :p
That's fine but if the point is saving money it's important.

OP explained and I definitely feel the reasoning is sound enough to not care about roi.
 
ROI was not a factor for me either!
I am so old, no possibility of adequate time remaining to recover the investment before my warranty expires.
We just need electricity (stupid hurricanes & drivers shearing off power poles @ 3AM)
Yes, we can run the noisy, stinky Diesel generator, so long as fuel is available.
Would rather just borrow Photons from the Sun, instead.
 
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