Final answer:
Before connecting a manifold gauge set to a heat pump system, you should first ensure that the system is off and that the refrigerant pressures are at equalized.
Step-by-step explanation:
Before connecting a manifold gauge set to a heat pump system, you should first ensure that the system is off and that the refrigerant pressures are at equalized. This is important to prevent any damage to the gauge set or the system itself. To achieve equalization, you can wait for a sufficient period of time for the pressures to stabilize or use a refrigerant recovery machine to remove any remaining refrigerant from the system. Once the pressures are equalized, you can proceed to connect the manifold gauge set to the heat pump system.