How to Fill a Hydronic System

Prepare

• 1

  Turn off all power to the boiler by turning the boiler switch off or by switching the boiler circuit breaker to the "Off" position.

• 2

  Close the gas valve to the boiler.

• 3

  Open all the return line bypass valves. System fill is done through the return lines, opposite to the normal flow of the water. Check valves that aren't bypassed will prevent the system from filling properly.

Fill Each Loop Separately

• 4

  Attach a length of hose to the first loop drain valve and place the other end in a drain or bucket.

• 5

  Open the inlet water valve. Water will flow up through the return line, through the loop, and eventually out the hose attached to the loop drain valve.

• 6

  Close the loop drain valve once a steady stream of water without air bubbles flows from the hose attached to the drain valve. Water will continue to flow through the inlet valve for a moment until the loop reaches the pressure set point of the inlet water valve.

• 7

  Move the hose from the first loop drain valve to the second loop drain valve.

• 8

  Repeat the process of opening the drain valve, filling the loop and closing the drain valve until each loop has been filled with water.

Finishing

• 9

  Close the return line bypass valves.

• 10

  Restore the gas and power to the boiler.

• 11

  Purge the system of air after it is filled.