Head Pressure

[slonergan82]

Hello im new to the Refrigeration trade just wanted to know how you can tell if you are not condensing buy looking at your head pressure?
This might be a dumb question but I havent been to trade school yet.

Scenero

adding gas to sys with sight glass flashing couldnt get it to clear and head press was climbing ... 404 head press around 300 still flashing.

[y7turbo]

was the condenser coil dirty?

[slonergan82]

nope it was clean

maybe non condensables?

[slonergan82]

When you set head pressure you set it between 90- 110 degrees right? Which means it is warmer than ambient so it will give off its heat correct? But how do you know what temperature it is saturated?

[skpkey9]

Denending on how high ambient temp is and how hot box temp is, it is very possible for 404 to exceed 300 psi . On a start up I've had it hit 350psi but once box temp is under control your pressure will fall. maybe its just under a load.. would need more info for a better answer.

[skpkey9]

your sat temp is pressure converted over to temp.

using a pt chart

[slonergan82]

So if 404 is at a head of 220its saturation temp is around 100 degrees if at a higher temp at the same pressure then it is superheated correct? and if lower than 100 degrees it is sub cooled? so pressure and temp only relate at saturation ?

[skpkey9]

Superheat" is the term used to describe the difference between the vapor point (ie. temperature at which the refrigerant evaporates at a given pressure) and the actual temperature of the refrigerant exiting the evaporator coil.

Better yet Read this

http://hvac-talk.com/vbb/showthread.php?threadid=54493

[markettech]

Hello im new to the Refrigeration trade just wanted to know how you can tell if you are not condensing buy looking at your head pressure?
This might be a dumb question but I havent been to trade school yet.

Scenero

adding gas to sys with sight glass flashing couldnt get it to clear and head press was climbing ... 404 head press around 300 still flashing.

You were adding it in a liquid state, right??!!

[slonergan82]

Ok. Thanks alot for all your help.

[Crazy4thenucks]

Dont forget, R-404 is a blend type refrigerant and must be added as a liquid, or you'll end up with the refrigerants used to make up the 404 seperating, if the conditions are right, "glide" . And remember, dont charge liquid straight back to the compressor throught the suction line, or you may damage your compressor. You have to meter it.