Wish to run my Room Air-Conditioner on solar during day time

[Mike90250]

The TXV valve or orifice tube is either inside or just outside the evaporator coil. It's nowhere near the compressor.

and if you splice it, it's going to leak. A unloading valve needs to be inside the compressor, or it's too vulnerable to damage or leaking. (moving parts - the electric solenoid and valve) with expensive refrigerant and pricey repair costs, all should go into the compressor can.

Well, you can put it anywhere you want, but not on my rig.

[NeilTheCop]

The TXV valve or orifice tube is either inside or just outside the evaporator coil. It's nowhere near the compressor.

[Mike90250]

A random thought, possibly impractical.
If a PWM controlled normally closed high pressure solenoid valve was put in as a bypass to the orifice tube/TXV valve. This valve could be opened before the compressor starts, meaning that it's spinning but not compressing and drawing a lower than normal start up current. When the compressor is up to speed, or about a second later the pulse width is changed so that it gradually closes the bypass solenoid and loads the compressor. This bypass could also be opened to dump any residual pressure in the high side of the system when the compressor stops.
I bought an Arduino so I'm mad keen to apply it to everything I can

That would all have to be built into the sealed compressor can (which has the motor in it)

[NeilTheCop]

A random thought, possibly impractical.
If a PWM controlled normally closed high pressure solenoid valve was put in as a bypass to the orifice tube/TXV valve. This valve could be opened before the compressor starts, meaning that it's spinning but not compressing and drawing a lower than normal start up current. When the compressor is up to speed, or about a second later the pulse width is changed so that it gradually closes the bypass solenoid and loads the compressor. This bypass could also be opened to dump any residual pressure in the high side of the system when the compressor stops.
I bought an Arduino so I'm mad keen to apply it to everything I can

[Raj]

If it were me, I would forget about the solar panels and charge controller and buy something like an Outback 3500 to 3600 watt inverter/charger, FX or Radian with a MATE3 and a 48 volt 500 AH battery bank. Run A/C on grid and charge the batteries while the grid is up. Automatic transfer to inverter when grid goes down. Batteries might give you 6 to 7 hours of downtime if the A/C is cycling at 50%. Solar could be added later.
Probably looking at 7 to 8 thousand dollars US. But then again, that's a lot of money for air conditioning.

Rick

[SunEagle]

hi, what is soft starter vfd?how does it work and in what senerio can we use it?

Actually there are both Soft Starters and VFD's.

The soft starter use electronics to slowly raise the voltage of a motor so that it "ramps" up to speed instead of immediately going full speed. The soft start function limits the "inrush" current being drawn by the motor to a level much lower than a normal start which could be 6 to 8 times the motor current rating.

A VFD (variable frequency drive) allows you to start a motor at full speed or slowly ramp it up to full speed. It also allows you to change the speed while running based on the process requirements. It can also allow you to run the motor at a fixed speed different then the motor rpm rating. One issue with the VFD is that if you run it too slow the motor will begin to heat up and cause an issue.

Both of these motors starters require a constant voltage source to start and run the motor. They as well as capacitors will not help you to run your AC system just using solar panels.

[jomolu]

Real simple, you need batteries. Not going to happen without them.

hi, what is soft starter vfd?how does it work and in what senerio can we use it?

[Johann]

Which way is cheaper? to increase the panels size by 5 X the need wattage or just buy 4 automobile 12 volt battery which cost about $80 each have 500 amps crank power?

I don't know so I am asking if this would be possible.

Instead batteries or even with conjunction of batteries, could someone use super capacitors with it that could give the instant high power/amps a compressor needs ? You see folks on u-tube starting their cars just on super capacitors or they use them with conjunction of a small battery. Super capacitors may not be cheaper than a battery, but may have a potential to last longer.

[inetdog]

Just keep in mind that not all mini-splits are inverter units (which can very efficiently drive the compressor at lower speeds with correspondingly reduced power consumption.)
On the other hand, with very few exceptions (such as unit ACs designed for 48V DC power) all of the inverter units are found in mini-splits.

[ZoNiE]

You really are better off buying an inverter Air conditioning unit and selling your non-inverter unit to recoup "some" cost or keeping it to run when on Genny. I'd bet in your neck of the woods, you can get them pretty cheaply as minisplits are the norm where in the US they are the exception. I have seen them as low as $300 US in Malaysia.

You should also put in a properly sized battery bank as discussed previously to handle the load, and provide enough panel wattage or genset to ensure you fully recharge the batteries or keep them charged while under the load of the Air conditioner unit or they will have a short life.

If you have a dry desert heat, consider an evaporative cooler. Look them up on wikipedia if not familiar with them. All they are is a large fan and a small water re circulator pump. Use much less power than an AC unit. They do NOT work when the humidity is high, they just make it worse (Swamp cooler). They are also pretty easy to make.

[SunEagle]

I know exactly what you are saying.
As soon as power is disconnected or lost to the AC or fridge, such unit will start to equalize pressure without power and this will take 1-2 minutes after that 2 minutes or so there would be no head pressure present at the compressor.
Now if you talk about a 80 ton (960,000BTU) trane unit, that is a different story and power is required to go through a shut down procedure on it.
Most 5,000 BTU AC's do not have a time delay build in. On the other hand a 18,000 BTU and fridges may have a time delay build in so the compressor may be able to start but with an 5 minute delay ( a $5 delay timer will do this). That is why I mentioned in my previous post ''that a time delay may be needed to power an AC unit'' and this was to protect the AC compressor. AC compressors are designed for an 15 minutes on cycle and 15 minutes off cycle to repeat it over and over again, so some cycling will not hurt the compressor and motor as long as there is no head pressure.

Exactly. The problem is knowing when the head pressure has been reduced enough for a safe start. An intermittent power source is not "time reliable" so an "on delay" timer would have to be installed to keep the compressor from starting too soon after the power comes back on. Still depending on how many times the power goes out may add up to a lot of more starts for that compressor over a period of time and shorten it's life.

[paulcheung]

An UPS that can start the Air condition unit will cost thousands Dollars, What is wrong with a set of cheap batteries? The UPS use batteries too, they are to be change every two to three years and will be quicker in this situation.

[inetdog]

Would it help somehow getting a compressor started with the battery boost. I think the cheaper PC type ups are mostly offline switching ups so it would not help a compressor during startup. Is that correct?

Unlike a hybrid off-grid system with generator support, a UPS will pretty much either switch off the grid source (which is actually the SPS) and use only the batteries (normal consumer UPS) or will constantly provide DC from the AC input to drive the output AC inverter for a seamless transition when the "grid" goes down (many commercial units).
In the case of the latter, you would have to look at the surge capability of the inverter portion of the UPS, which might be enough to carry through motor starting. But the UPS output power would always be coming only from its output inverter and not from a combination of UPS inverter output power and SPS power.
Look carefully at the specs and maybe contact the manufacturer for a more complete curve of surge power versus time.
You could hope that the UPS would also brown out gracefully under overload instead of shutting down completely as the SPS would.

[nomadh]

I was thinking if an extended outage I'd move some food and drinks to the mini fridge then just be careful. If the power drops then unplug it for a few min. Same with a small ac system. If there are clouds then hopefully it isn't so hot and then the ac wont matter. I would also consider a small pc type battery backup ups. I think that could let a compressor get through intermittent clouds. Would it help somehow getting a compressor started with the battery boost. I think the cheaper PC type ups are mostly offline switching ups so it would not help a compressor during startup. Is that correct?

[Johann]

There are two types of cycling. The normal way when a set point like the AC or fridge thermostat is satisfied and the compressor comes to a stop. This is ok and the equipment is designed for that type of operations.

Now when the power goes out in "mid cycle" for an AC or fridge the compressor has not gone through it typical operation of shutting down by relieving the pressure. So when the power comes back the AC or fridge compressor now starts under a much higher load which puts a strain on the equipment. Especially if the cycle of power being on - off - on is very short. Better for the equipment if the power has been off for a while allowing the compressor to release some of the pressure it built up while it was running before it starts up again.

Does that clear up what I have tried to say?

I know exactly what you are saying.
As soon as power is disconnected or lost to the AC or fridge, such unit will start to equalize pressure without power and this will take 1-2 minutes after that 2 minutes or so there would be no head pressure present at the compressor.
Now if you talk about a 80 ton (960,000BTU) trane unit, that is a different story and power is required to go through a shut down procedure on it.
Most 5,000 BTU AC's do not have a time delay build in. On the other hand a 18,000 BTU and fridges may have a time delay build in so the compressor may be able to start but with an 5 minute delay ( a $5 delay timer will do this). That is why I mentioned in my previous post ''that a time delay may be needed to power an AC unit'' and this was to protect the AC compressor. AC compressors are designed for an 15 minutes on cycle and 15 minutes off cycle to repeat it over and over again, so some cycling will not hurt the compressor and motor as long as there is no head pressure.