A heat pump’s refrigerant charge has a huge impact on its efficiency, reliability and running cost. Both overcharging and undercharging cause problems, so getting it right is one of the most important parts of a quality install or service.
Why correct charge matters
Too little refrigerant and the system can’t move enough heat, efficiency drops and the compressor can overheat. Too much and you risk liquid floodback, high pressures and compressor damage. Either way, running costs rise and lifespan falls.
Getting the charge right
- Always start from the manufacturer’s specified charge on the data plate
- Account for pipe-run length — long runs need additional charge per metre as specified
- Verify with superheat and subcooling readings, not just pressures
- Weigh the charge in for accuracy using scales
Signs of incorrect charge
Poor heating performance, unusual compressor cycling, frost or ice in the wrong places, and high energy bills can all point to a charge problem.
FAQ
How do I know if a heat pump is low on refrigerant? Look for reduced heat output, abnormal pressures, and superheat/subcooling readings outside the expected range. A leak test should follow.
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