O.K....I know the end of December is winter in most of the country but not here... It seems to me that regardless of the temperature selected, the compressor is running until that lower temp. is reached. How does the AC work if you select a temp just a little lower than the air temp? Does it mix outside air to warm the output? If so, it doesn't matter what temp you select as far as energy efficiency is concerned. The compressor will just run until the inside temperature is met. Correct or please inform me. Thanks, Don
Just run it in Auto AC all of the time and adjust the temp for your comfort with the steering wheel controls. Let the system work as it was designed. The compressor is electrically driven and will cycle only when needed.
The A/C compressor uses a variable speed direct drive electric motor. Speed is dependent on the required cooling. The amount of outside air mixed in depends on the recirculation setting and a dealer setting for outside air mix. Normally some outside air is mixed-in even on the recirc setting, but the dealer can override that setting if you wish. Tom
It seems to me that regardless of the temperature selected, the compressor is running until that lower temp. is reached. What is your exact question because your post is not making alot of sense? : The system controls cabin temp. If the temp selected is LOWER than cabin temp the compressor will run to cool the cabin. Your "Regardless" infers the temp selected could be either higher or lower. If the temp selected is HIGHER than cabin temp the system routes hot water into the heater core like any other car to warm the cabin and of course the ac compressor does not come on. How does the AC work if you select a temp just a little lower than the air temp? Does it mix outside air to warm the output? Got nothing to do with air temp. It has to do with cabin temp. If its 40F in the cabin and you call for 30F in the cabin..the ac will come on. If you call for 50F it routes hot radiator water into the core. If you call for cool it turns on the ac compressor. There is no mixing of outside air unless you have the system set for re-circulate. And it does no calculation of mixing outside warmer air to warm the cabin except for the fact that outside air re-circulated will eventually affect cabin temp which is what it references too for temp. If so, it doesn't matter what temp you select as far as energy efficiency is concerned. The compressor will just run until the inside temperature is met. Correct or please inform me. Even though the compessor is not run off a belt on the engine like most cars and is electric there is a very small mpg hit in summer in Florida being that its so damn hot down here in the dos. It drains the traction. Traction must be re-charged. Its been in the eighties all week here in Tampa. I've owned my 07 seventeen months now and have never turned the heat on once. But I think its a 1-3 mpg hit in the summer. But you do not want to run a real hot cabin on the Prius as the traction battery might overheat. First sign is the battery vent fan comes on. Its a bad thing.
Unlike the crap air-conditioner in a normal car, the Prius air conditioner runs only as hard as it needs to to maintain the selected temperature in the cabin. In crappy old fashioned systems the compressor speed is determined by the engine speed so in stop go traffic it struggles to cool enough but at highway speeds it runs too fast so cycles on and off to maintain temperatures between an upper and lower value. It is more efficient to slow the compressor than to over cool then shut off. The Prius air-conditioner compressor will run constantly when needed but only as fast as it needs to, Isn't your Prius clever?
Thanks all especially Patsparks who seemed to be able to decipher my question. I was wondering ONLY about cooling the cabin. If the cabin was at 85 and I selected 80, the cooled air coming out of the vents seems warmer than if I had selected 65 degrees. That could only mean that the compressor was putting out different temps of freon or mixing air IF it wasn't variable speed.. In 'normal' cars forgetting about engine speed, the compressor is always putting out freon as cool as possible and then it shuts off when a selected cabin temp is finally reached. So its' load on the engine is constant whenever the compressor solenoid engages regardless of selected inside temp. Thanks everyone. Don
Hi Tiger..., That is because the system is a proportional control system. If the difference between the set point, and the actual cabin temp is high, the system will run the compressor at a higher speed, and thus cool the air out of the condensor more. You feel this at the vent. As the cabin temp reduces, the compressore speed is reduced in proportion to the difference between the cabin temp and the set point. In this way the temperature in the cabin is reached, and not skipped by , or overshot. It also accomadates varible conditions - like turning into the sun and getting a much greater heat load.
