What Suction Pressure do i need?

[Mish]

Hi all

I was wondering what suction pressure i should be looking for will trying to achieve a room temperature 0 degrees celscius.

The system runs on R22 and feeds 2 T.E.Vs and 2 coolers.
The charge in the system is approx 20kg


If anyone can help that would be great!

[Gary]

Start here:

http://www.refrigeration-engineer.co...ad.php?t=19701

[Mish]

Thanks Gary but i will explain my problem a little more

When doing my refrigeration course i was taught if i dont know the weighted charge a system holds, fill it until the sight glass on the liquid line is full, no bubbles or flashing etc.

Due to a very hot couple of weeks here in the UK we had a sub-contractor in our factory helping out. The system in question had lost its charge, after the leak was repaired he re-charged the system.
Now whilst charging he said he noticed the room set point was 0 degrees C. But while having a suction pressure of 3.5 bar he was reluctant to put more charge in until the sight glass was clear. Saying that while having this suction pressure we would never achieve the set point. He has not been back since.

Now do i reclaim some of the gas put into the system, alter the set point to something more achievable or check the superheat, i am however reluctant to alter the superheat until im sure thats the cure.

[Brian_UK]

Do not touch the TEV, it is not at fault.

Read Gary's link.

[taz24]

Hi all

I was wondering what suction pressure i should be looking for will trying to achieve a room temperature 0 degrees celscius.

The system runs on R22 and feeds 2 T.E.Vs and 2 coolers.
The charge in the system is approx 20kg


If anyone can help that would be great!

R22 at 0 deg C is about 5 b so if you have evap at -10 deg C then back pressure will be about 3.5 b.

taz.