Evacuated tube refers to the glass tubes in a solar collector which are connected to a metal or absorber pipe. Each of the tubes is air tight and is properly sealed to avoid the escape of heat in the process of convection and radiation collection from the sun. The number of evacuated tubes needed to increase the performance of a solar collector usually ranges from 16 to 20 tubes. If there are some broken evacuated tubes, they should be replaced, although a solar collector can still function well with broken tubes.
Step 1 - Remove the Broken Tube
Locate the tube which is broken or the tube that you want to replace. Before removing the tube, you need to make sure that the evacuated tube is not hot. One effective method of removing the heat from the evacuated tube is to circulate water or other working fluid inside and outside of the interior part of the evacuated tube. The fluid or the water will absorb the solar energy gathered by the solar collector which makes the tube hot. The absorbed energy will be carried to a part of the solar collector where it will be stored or put to practical use.
If the evacuated tube starts to cool down and the temperature is now manageable, slowly remove them from the manifold box of the solar collector.
Step 2 - Secure the End of the Evacuated Tube
If you are replacing more than one evacuated tube, you should mount them to the solar collector one by one. With the first tube, you have to use the rubber cap to be put at the end of the evacuated tube. The rubber cap will serve as a cover preventing the heat inside the evacuated tube from escaping. Do these to the other tubes as well before attaching them to the manifold.
Step 3 - Insert into the Manifold
After you have covered the end of the tube with the rubber cap, use the silicon grease and apply it to the top of the evacuated tube which is the copper section. Insert the evacuated tube into the manifold after applying the silicon grease. The purpose of the silicon grease here is to clean the cover part and serves as a lubricant which makes it easier to insert the evacuated tube into the manifold box. In inserting into the manifold, see to it that the tube is fitted properly or else the energy will just be wasted.
Step 4 - Secure the Rubber Cap
With the use of the Jubilee screw clamp, secure the rubber cap which was placed at the end of the tube. You need to clamp the protected rubber cap to stay in place. Make sure that the tube is held securely in the box or in the frame of the solar collector. Check all the evacuated tubes if they are covered. You can only remove the cover before you start using the solar collector. Apply the same steps to the remaining evacuated tubes.