There are three steps to the charging process. Make sure you read and understand all three stages before starting the charging process.

1. Pumping the solar fluid in.
2. Getting the air out.
3. Pressurizing the system (this page).

CAUTION: You must cover the solar collectors when charging the system! Uncovered collectors will heat the fluid to extremely high temperatures which can cause steam venting and serious injury.

This is not optional: protect yourself. Cover the collectors.

By this stage, you have filled the solar loop with an antifreeze solar fluid mix and pushed the air out of the pipes. The pressure in the system is at least 10lbs/in², the inlet and outlet valves are closed and the pump is switched off. It is now time to pressurize the system.

Pressurizing the system

Start by switching on the pump and cracking open the filler valve. Allow the pressure in the system to rise to at least 35lbs/in² (aim a little higher), then close the valve again and turn off the pump.

The pressure gauge may bounce all over the place when you open and close valves, so give it a minute to settle down and for the system to stabilize. Open the drain valve a bit to allow the pressure to drop to 35lbs/in² with the solar fluid at 60°F. If you're using cold solar fluid, aim for 30lbs/in².

When in operation, you will see a wide range of pressure values: on a cold night, it may drop to 15lbs/in²; on a steaming hot day it may rise to 40lbs/in². Overall, the system should operate at around the 30lbs/in² mark. If you notice that pressure falling slowly over time, you may have a leak which you will have to find and fix.

Now you just need to finish up.

• Get your pliers and rags.
• Tighten the charging valves very tightly and remove the hoses.
• Install caps on the charging valves and tighten those very tightly, too.
• Once you're sure the system is stable and has no leaks, install caps on the filler and drain ports.
• Label your expansion tank with the date of installation, type of solar fluid, the percentage mix of glycol, the initial pressure and the details of any professionals involved in the installation.
• Label all the main lines with ID tags indicating what they are for and the direction of flow.

You should also put together a user manual for your system. This may seem a little obsessive but it is part of your investment in your home and the future. The more information you put in this manual, the less you will have to remember and the easier future use and maintenance will be. Keep everything together in one book and place it with the system, not in a filing cabinet somewhere. The manual should include:

• The installation schematics.
• List of model numbers and types of all major equipment parts.
• Operating instructions.
• Warranty documents for all the equipment.
• Storage and expansion tank information.
• Pump details.
• Solar fluid details.
• A description of how the system works.
• Controller information.
• Maintenance information.
• Manufacturers' documentation