non-condensable gas

[mallmk13]

hi
how can you tell that system is runing under non-condensible gaz. basically what are the symptoms?
mallmk13

[nh3wizard]

High discharge pressure

[Cofreth]

Liquid refrigerant temperature measured are much higher than it's saturation temperature corresponding to the pressure.Abnormal high pressure.

[Electrocoolman]

Hi Mallmk,
I see you've double posted this thread....so do you want to delete one.
As to your question...A non condensible in a system will generally cause high head pressure....this is a because as it does not condense (unlike refrigerant) it will tend to collect in the condenser and vapour space in the liquid receiver (if one is fitted).
As a consequence of this, the effective area of the condenser is reduced and so the system is unable to get rid of the heat. This will cause the head pressure (and consequently the whole system pressure i.e suction pressure as well) to rise.

The compressor will have to work harder....drawing more current. The system will trip on HP (if protected), the compressor might well trip out on temperature or current.
The rise in suction pressure will adversely affect you cabinet temperature.

Do you follow all this....it should be a logical thought process.

[lana]

Hi there,

non-condensable and excess refrigerant show exactly the same symptoms.

High discharge pressure and High sub-cooling.

By performing a test you can know which fault it is.

NON-CONDEMNSABLE TEST:

Pump-down the system and make sure the low pressure setting is low enough to evacuate the refrigerant from the evaporator. Turn on the condenser fans and let them run for at least 30min. If there is water cooled condenser then let the water flow.
Measure the air (water) inlet temp into the condenser and record it. With this temp go to the refrigerant pressure-temp table and find the corresponding pressure in gauge (not absolute). Now compare this pressure with the system discharge pressure.

If P(discharge-system) >> P(from table) then you have non-condensable.
If P(discharge-system) = P(from table) then you have excess refrigerant.
Remember : this test will not work unless the receiver and condenser are at the same place with the same temp.

Hope this helps.
Cheers

[US Iceman]

Hi Mallmk,

In the future please only post your question in one area. When you have multiple posts you have different areas where the questions are responded to and it makes it harder to follow the comments. Thanks.

how can you tell that system is runing under non-condensible gas.

You check this in a similar manner as if you were checking for subcooling using the pressure/temperature charts for the specific refrigerant in the system.

basically what are the symptoms?

High discharge pressure & high motor amps are the first things you will notice. The non-condensable gases cause the total pressure (non-condensable gas + refrigerant pressure) to increase. This is why you can bleed the non-condensable gases out of the system and the discharge pressure comes down.