Airconditioning questions

[Nismo280zEd]

So I just put another can of charge in my 03 Subaru WRX, blowing pretty good about 50 degrees or so. Unfortunatley when dead summer hits, the A/C system on my subaru can not keep up with the rate at which the sun heats the car. I have a wagon, so there is a larger volume of air and a larger surface area for the sun to heat up. I have tinted windows, going to upgrade to a better tint this summer to try an help the system a bit.

 

At anyrate, I'm still learning the ins and outs of HVAC systems. General idea, there is a medium in the system, gets compressed, then is allowed to expand, as it does this is gets cold. (I know it's more complicated than this, but general idea)

 

My question is how do commercial freezers work without freezing up the thermostat?

 

Also, what determines the lowest temperature you can achieve? The pressure differential? Greater pressure differential yields colder result upon expansion?

 

What can be done to achieve lower temperatures in an automotive A/C system? When the hundred plus heat comes again my system just can put out 50 degrees. I'm looking more at 70 degrees till the cabin ambient temp gets around 100 then it'll start to drop cooler. (This process takes about 25 min sometimes, looking to improve this.

 

Many questions I know, and not easy to answer. Just want to learn more.

-Ed

[Mike kZ]

50* is kind of high, are you sure it's full? All my cars get from 39* to 42*

 

http://www.aircondition.com/

[cencalz]

Yes your partially correct. The lower the pressure after expansion the colder the media. Also the type of media. For example Ammonia will will have a colder temperature then Freon at the same pressure. The pressure is the key. At 30PSI Ammoniais 17 degrees F and 134 about 35 degrees F.

[Nismo280zEd]

50* is kind of high, are you sure it's full? All my cars get from 39* to 42*

 

http://www.aircondition.com/

 

Thanks for the link, been reading the articles.

 

Honestly, I'm not sure if it's full. I only have the little cheapo gauge you get with the combo pack of refrigerant. I saw autozone had a basic gauge set for about 50 bucks. I'll probably pick that up once I get some other issues fixed first.

[mgjim]

Thanks for the link, been reading the articles.

 

Honestly, I'm not sure if it's full. I only have the little cheapo gauge you get with the combo pack of refrigerant. I saw autozone had a basic gauge set for about 50 bucks. I'll probably pick that up once I get some other issues fixed first.

 

 

I put an a/c system in one of my MGB's. I think I am a pretty clever guy, had a good vacuum pump and set of gauges, even brought in a commercial a/c engineer to assist but could still not get it right. Not until I took it to a professional auto a/c place and pull out my most useful tool (my check book) did it blow cold. I had nothing wrong in the design or construction of the system, the guy said it was just in how it was filled up (loose nut at the wheel). Instead of spending the $50 on a cheap set of gauges, now is probably the time to take it to someone who has done a few hundred and knows all the tricks. Good Luck

[Nismo280zEd]

I put an a/c system in one of my MGB's. I think I am a pretty clever guy, had a good vacuum pump and set of gauges, even brought in a commercial a/c engineer to assist but could still not get it right. Not until I took it to a professional auto a/c place and pull out my most useful tool (my check book) did it blow cold. I had nothing wrong in the design or construction of the system, the guy said it was just in how it was filled up (loose nut at the wheel). Instead of spending the $50 on a cheap set of gauges, now is probably the time to take it to someone who has done a few hundred and knows all the tricks. Good Luck

 

Honestly, if I wasn't a college student I would gladly drop it off and let somebody else deal with it.

Unfortunately I am, and I work full time to make ends meet. This combination allows me little spare funds and even less spare time.

I put a can in last summer and worked good enough, put another in this summer and it works better than last.

 

I was talking to an engineer my father works with who knows alot about HVAC. He suggested adding another coil, this is what Porsche did to improve the A/C in the weak system of the 911. It was also suggested to try an electric compressor. This would eliminate one variable from the complex system allowing the compressor to run at optimum efficiency at all times regardless of engine speed. My wallet just doesn't allow for either one at the current time though. It's a good learning process though as I'm swapping in a maxima a/c system into the Z, can never know too much!

-Ed

[akuma-z]

I was talking to an engineer my father works with who knows alot about HVAC. He suggested adding another coil, this is what Porsche did to improve the A/C in the weak system of the 911. It was also suggested to try an electric compressor. This would eliminate one variable from the complex system allowing the compressor to run at optimum efficiency at all times regardless of engine speed.

 

I am not aware of any electric a/c compressors designed for 12V systems. Everything I have ever seen has been for hybrid electric cars that operate at much higher voltages. I guess it doesn't matter how the compressor is driven since load will still make it to the motor either way, only this way it is redirected through your alternator.

[Nismo280zEd]

I am not aware of any electric a/c compressors designed for 12V systems. Everything I have ever seen has been for hybrid electric cars that operate at much higher voltages. I guess it doesn't matter how the compressor is driven since load will still make it to the motor either way, only this way it is redirected through your alternator.

 

Most boats, marine application run electric compressors. Check out west marine

[jasper]

Buy the guage set.

Compare your guage readings to the diagnostic

s in a good ac book. It realy isn't that dificult.Just make sure you have GOOD airflow through the condensor. IE; fan working properly, fins not dirty/restricted.

Sounds like your low on freon, the guages won't lie........

Edited March 28, 2010 by jasper