Calculating superheat

[fairbank56]

  Ok, I've been doing some extensive reading about how residential HVAC works and how to determine if your system is operating properly. There's a lot of inaccurate garbage on youtube (yeah, I know) but I had been viewing some of this guys videos and he seemed to know what he was doing until I came across this one.

 

http://www.youtube.com/watch?v=sVvJbjWTiOY&feature=c4-overview&playnext=1&list=TLil43F4xsQn8

 

  Seems to me, he isn't using the sliderule calculator correctly. He is supposed to be seeing an 18° superheat and according to how he is using the calculator, it's about right on but according to his gauge readings, it's actually 4°. His suction line temp is 61° and vapor temp is 57°. Am I missing something?

 

Eric

[fairbank56]

  Ok, nevermind, I misunderstood what he was saying. He never did give the suction line saturation temp, just the pressure which was around 68psi which is good for his required superheat.

 

Eric

Edited July 2, 2013 by fairbank56

[smasher711]

I watched about 15 sec of the video and noticed that there is no water around the unit, Why do I bring this up? If you are going to get your Freon level right on the money by checking with Super heat and sub cool there are a couple of things you would want to check first, Evap coil clean ? If you have a thin layer of dust on your evap coil fins the Freon is not going to absorb heat properly and this will throw everything off right outta the gate. Check it. Of course put a new filter in , I use the cheap ones , they are not real restrictive and do a decent job, just be sure and change them about every 30 days for low to the ground return vents or 3-6 months for returns that are in the ceiling. Might as well give the blower wheel a gander with your insp. mirror, if there is  Dust built up in the cups of the fins will not move air well. And last wash the outside unit. Nowdays with the higher efficiency units a TXV valve installed will call for different charging procedures  and if you are a home owner I highly recommend calling a licensed Technician to help out , you could ruin a very expensive unit by trying to save a few bucks