Capillary table for R404A

The R404A Capillary Table allows the refrigeration technician to orient himself on the diameter and length measurements that the capillary tube must have in a given equipment.

The selection of the capillary that works with R404A refrigerant depends essentially on the evaporator temperature required and the power or cooling capacity of the system.

It is highly recommended to select the capillary based on the cooling power value, and not necessarily on the electrical power in HP of the compressor motor.

However, selection tables are included below that take electrical power as a reference, because for some compressors the exact information on cooling capacity is not available.

Basic Rules for Selecting Capillaries with R404A Gas:

Capillary tubes rely on both their length and diameter to determine their overall restriction.
A percentage change in diameter can change flow more than an equal change in length.

The restriction can also be changed by lengthening or shortening the tube.
The longer the tube, the slower the flow.
There comes a time when going to extra-long lengths, to increase restriction and reduce flow, is not only uneconomical but often useless.

Then, as the tube length decreases, the flow slowly increases until the critical point is reached, where the flow rate increases more rapidly with each reduction in length.
If the length is further reduced, a point is reached where further decrease in length results in ever increasing flow.
When the tube is so short that even small changes in length will cause large increases in flow. This is due to the fact that the length no longer affects the flow and the tube now begins to act more like an orifice than a capillary tube.

As a general recommendation, keep the pipe no shorter than 5 feet and no longer than 16 feet. As with all general rules, there are of course exceptions, but for daily operation, staying within this range will eliminate many problems.

Capillary tables according to the electrical power of the compressor:

The compressor’s electrical power is the maximum energy that the compressor motor can use or consume to perform its work. In practice, it is the most commonly used parameter for capillary selection, although it is far from being the most precise.

Why is it not necessary to use HP for capillary selection with R404A?

Because depending on the performance of the compressor model, the manufacturer and other aspects, it may happen that motors with the same electrical power HP, have different cooling capacity.

		The temperature of the condenser
LBP	-23,3 °C -10°F	54.4°C 130°F
MBP	-6.7 °C 20°F	54.4°C 130°F
HBP	7,2 °C 45°F	54.4°C 130°F

Information Source: Tecumseh

HP		Diameter in	Length m
1/2	LBP	0,036	1,7
1/2	LBP	0,036	1,5
3/4	LBP	0,042	2,5
1	LBP	0,050	2,6
1 1/4	LBP	0,050	2,0
1 1/2	LBP	0,050	1,5

Application Reference Table

What is cooling capacity and how does it relate to capillary with 404A?

Cooling capacity is the amount of heat that the system can extract from the equipment’s evaporator, using a given compressor model and capillary dimensions.

It has a lot to do with the amount of coolant that the capillary allows to pass, depending on its diameter and length.
Cooling capacity is the most appropriate parameter for capillary selection, because it is not so closely related to the model type and efficiency of the compressor.