There are five possible reasons for the receiver shutting down. 1. There is a problem internally with the receiver. 2. There is a problem with one or more of your speakers. 3. There is a problem with one or more of your speaker wires. 4. There is a problem with the speaker wiring done on your system. 5. The unit is overheating. No ventilation. First, check the wiring at every speaker terminal at the back of your receiver and at the back of your speakers. A single strand of speaker wire crossing from one terminal to another would be enough to cause the amp to shut down or go into PROTECT. If you do not find any problems with any of the wiring, you should disconnect all speakers from your receiver. If the receiver continues to go into PROTECT, the problem is in the receiver. Please submit a case on the Contact Us page. They will be able to assist you. However, if it turns on, the problem is elsewhere. Begin reconnecting one speaker at a time. Eventually you will connect a speaker that will cause the receiver to shut down. At this point you have found your culprit. On the other hand, it may just be overheating. You must have at least 2 - 3 inches of space between the top of the unit and any shelf or component above the unit. The unit should not be inside a sealed compartment when being used. The unit must be able to breath. There are very powerful amps in these receivers. If they run too hot, they will shut down. An external fan can help this.