i have a restriction on a 3 toh heat pump,had a nother tech thinks it is a low charge,i hace a unit that has 2 floaters,one at the cap tubes,the outher is about 10 inch back of the cap,the first one 10 inch back is frosting up fron there and starts freezeing up into to the evap,what do you think,this schoud be a easy one
Actually if you just grab the liquid line and feel the temp. A low charge will be passing hot gas along with liquid and be hotter than expected. A restriction will be colder than expected. Adding charge isn't a good first approach. Actually even putting on the gauges is somewhat down the line.
You can't have hot gas and liquid in the line together. If it was saturated meaning there is no subcooling, vapor and liquid would be in the line at the condensing temperature. Low charge would drop the head pressure reducing saturation temperature and line temperature. A restriction would back up the liquid in the condenser increasing subcooling and reducing line temperature. Without knowing the saturation temperature in the condenser you would just be throwing darts at guessing whats wrong without checking the suction for low or high superheat. I do agree that a small loss of charge could reduce the subcooling in the condenser raising the liquid line temperature but only if small enough not to drop the head pressure.
Just put a little gas in it. If the suction pressure changes you will know what to do. Suction goes up, short of gas, no change, restricted. Quick and easy. Hell, you don't even need to check superheat, subcooling. Ya don't even have to know what superheat, subcooling, saturated is. Most a/c guys don't! It's not complicated.