The outdoor units of heat pump systems are factory-charged with the appropriate quantity of refrigerant to allow for the indoor unit and a specific pipe run. No additional refrigerant charge or adjustment is needed if manufacturer's installation instructions for the pre-charge pipe length is followed. Extra refrigerant may only be needed when pipe runs exceed the manufacturer's parameters. Refrigerant charging must be carried out in accordance with CAN/CSA B52 Section 8: Maintenance of System. The following procedures should be followed if extra refrigerant charge/adjustment is needed:
- Work should only be completed by contractors with the appropriate training and certifications.
- Only use manufacturer's specified refrigerant.
- Pressure test refrigerant line set using dry nitrogen and triple-evacuated with vacuum pump per manufacturer's instructions. Vacuum shall be held at 500 microns or less for a minimum of 15 minutes in each of the three vacuum cycles, and valved off to check for pressure changes that indicate contamination or leaks. Each evacuation shall be alternated with nitrogen under pressure. Pressure test refrigerant lines only at pressures lower than the pressure rating of service valves (typically 300-400 PSI), or per manufacturer's specifications).
- Measure the additional pipe run length and accurately calculate the amount of refrigerant required according to the manufacturer's instructions.
- Weigh in the required amount of refrigerant by mass, using electronic scales.
- Keep the charge lines as short as possible.
- Leak test the pipework before charging, by partially opening, then closing the cylinder valve to pressurize the connecting pipework.
- Charge using liquid refrigerant from the cylinder.
- Check for leaks using the bubble test solution.
- Ensure that the cylinder and unit are at the same height to prevent gravity transfer of the refrigerant.
Any system that is charged with refrigerant or lubricant must be labelled appropriately. Labelling must be done in accordance with CAN/CSA B52 clause 5.11: Marking and Labelling and must include the following:
- Refrigerant type
- Date of service
- Lubricant type
- Refrigerant charge (total including any additional charge)