Capillary tubes are a fixed metering device commonly used in small commercial refrigeration applications like prep tables and small reach in cooler boxes. It is simply a length of small copper tubing that changes the high pressure liquid refrigerant into a spray of low pressure liquid. Cap tubes are used because they are less expensive than TXV or piston type metering devices.
Cap tube systems are used to store already refrigerated products. If non refrigerated products are placed in a cap tube refrigeration system it could take up to 24 hours for the box temperature to drop down to the proper temp.
For example: A small sandwich shop has a small walk-in cooler where they store the deli meat and sandwich toppings. The removes the product from the walk-in, that is need for the afternoon lunch crowd, and places it in the cap tube system box. The box only needs to maintain the product temp and not drop the temperature.
Cap Tube Characteristics:
Want to learn some more? Watch the video here.
by Ron Walker
Cap tube systems are used to store already refrigerated products. If non refrigerated products are placed in a cap tube refrigeration system it could take up to 24 hours for the box temperature to drop down to the proper temp.
For example: A small sandwich shop has a small walk-in cooler where they store the deli meat and sandwich toppings. The removes the product from the walk-in, that is need for the afternoon lunch crowd, and places it in the cap tube system box. The box only needs to maintain the product temp and not drop the temperature.
Cap Tube Characteristics:
- If the condenser pressure rises, so does the evaporator pressure and vice-versa
- The longer the tube the smaller in inside diameter of the tube - "Longer must be larger, smaller must be shorter"
- Sizing is critical - a difference in just .005" can double the refrigerant flow to the evaporator
- Cap tube systems do not respond well to load changes
- The refrigerant charge is critical - a 10% undercharged system will not operate properly
- Use your gauges only as a last resort
- Make sure the thermostat is set properly and operational
- Check to see if warm product was put in the box within the last 24 hrs
- Remove any product and place ice or something else cold to the box
- Check door gaskets and frequent door openings
- Check for dirty condenser
- Bad condenser fan
- Has anyone else serviced the box recently?
- The most common problem is a plugged cap tube
- Usually within the first few inches after the filter drier - small flakes of desiccant usually plug the beginning of the cap tube.
- Remove and replace drier
- Cut off the first few inches of cap tube
- Evacuate
- Weigh in system charge
Want to learn some more? Watch the video here.
by Ron Walker