iced up evap coil

[wilks]

hi guys ,

say if the evap coil was freezing up ( cellar cooling ) room temp 12/13 oC , evap fan ok , stat is ok ( its starting comp when room temp raises above 13 ) the drain is clear , would an under charged system cause this?? the whole evap freezes and some suction pipework, why do under charged systems cause evap coil freeze ups ?

any help greatly apriaiciated

al

[PaulZ]

Hi Al
Evaps ice up for a few reasons. What is the suction pressure, is the condensing unit matched to the evap, is the evap dirty, is the air flow off the evap restricted.
If the system is undercharged you generally get ice build up on the first few rows of tubes as the suction pressure will be low.
If you are getting ice on the suction I would think there is another problem.
If you get all the operating conditions help can be given.
Paul

[taz24]

hi guys ,

why do under charged systems cause evap coil freeze ups ?

any help greatly apriaiciated

al


Think of the TEV, and imagine how it works?
All it knows is that it has to keep the suction superheat at the level it was set (say 6K)
So if the system is low on gas then the liquid in the evaporator will have totaly boiled off before it should do (say 1/2 way through the evap instead of 3/4 the way through)
From that point on the gas starts gaining temp and rises above 6K, The TEV thinks that not enough cooling is being done so opens up the valve.
The problem is there is no more liquid in the system so the valve just sits there fully open. Because the system is low of gas the pressure drops and the drop in pressure causes the refrigerant to boil at a lower temp.
This lower temp cause the first part of the evap (the bit with gas in) to freeze.
If you have a LP switch fitted it will slowly drop in pressure and temp untill it finaly fails.

taz.

[pacus]

pacus:can a three phase motor be run on single phase by changing the internal connections.

[taz24]

pacus:can a three phase motor be run on single phase by changing the internal connections.
Some can.
It all depends on the make.

taz

[wilks]

thanks taz , paul ,

when i washed out evap coil i started to get more reasonable low side pressure i was blocked up with all kinds ! being in a beer cellar !

[Electrocoolman]

Hey Pacus,
Start a new thread re your 3 phase motor