After troubleshooting a heat pump system, the technician concludes that the check valve is defective. He connects a recovery system and removes the refrigerant from the unit. He then proceeds to unseat the old check valve and remove it from the system. He cleans the area where the new valve will be installed, places it into position, and brazes it into the system while not protecting the valve. After a thorough evacuation, he starts the system and notices that the new valve is defective.

What could have been the problem with the new valve?

The new check valve in the heat pump system likely became defective due to damage from excessive heat during brazing, which should have been mitigated by using a heat-absorbing gel or wet rag to protect the valve.

Explanation:

When a technician replaced a defective check valve in a heat pump system without protecting it during the brazing process, the new valve became defective. This likely occurred due to the sensitive internal components of the check valve being exposed to excessive heat, which can damage the valve seating or internal seals, rendering the valve inoperative. The proper procedure would involve using a heat-absorbing gel or wet rag to protect the valve during the brazing process, ensuring the new valve is not compromised by the heat.