cap-tube !

[next life]

If the capillary tube was to long, Does this affect the temperature?
I am working on cycle using gas R404a and I want to get to -30 c ,
The length of the capillary tube 3 meters (48) and the maximum temperature reached it is -15 c
The pressure of the gas in the suction line 2.2 bar (30.2) psi
In your opinion, what is the problem?

[Rtic]

2.2 Bar is way too high, but we need a more information really to help you out; such as the orifice size of the cap, the high side pressure, more info about the appliance etc.

However, for very low temp refrigeration such as -30, I wouldn't recommend capillary. You say that you are “working on cycle using gas R404a and I want to get to -30 c”; was the system designed to work at these temps, or are you building the system yourself (if you are consider a system using a TEV).

[The Viking]

The way to size capillary tubes is not by temperature or pressure.

Get your superheat right and the rest will follow. (Longer cap tube = higher super heat, shorter = lower)

[next life]

yes i build the system by my self , the cap-tube is (0.048 " Diameter ) i cut a 50 cm from the cap-tube , now its a 2.5 m , the low side pressure is 3 bar and the high side 7 bar , the temperature is -5 !!
and thank you for replay

[next life]

" The way to size capillary tubes is not by temperature or pressure.

Get your superheat right and the rest will follow. (Longer cap tube = higher super heat, shorter = lower) "
i didnot understand
could you please speak in details

[xxargs]

Measure temperature short after end off capillary tube in evaporator and measure temperature on suction pipe outlet short after evaporator (few cm) and temperature differences between points calls superheat - if 3-5 degree C fine.

If almost zero, you possible flooding compressor with liquid refrigerant, > 5-6 degree C, evaporator starving of liquid refrigerant.

if you have OK Superheat but still to warm in box - check air circulation inside box, check if insulation on box or put in bigger machine and evaporator.

if you can download data-sheet on your compressor - you can see cooling capacity in different temperatures on evaporator side and assume evaporator temperature at least 5-10 degree lower than air temperature in yor box under running if not using active air circulation trough evaporators surface inside box.

most classic refrigerator have around -10 degree C on evaporator under compressor running to hold temperature around +2 - +5 degree C in box.

[mikeref]

One has to select a Capillary tube's internal diameter and the length of that tube by the compressor displacement...temperature required, and refrigerant used on your kit. There are charts out there for Cap tube selection.

This thread reminds me of a + 2 degree C Coffee shop display cabinet down town.