Solar collector t&p valve excessive tripping
I have a new 4x10 solar collector with a t&p valve installed on it and a new 82 gallon solar water heater with its own t&p valve. This is an active system and the collector t&p valve cycles open about every 10 minutes and dumps steaming water to the ground. The tank t&p valve does not cycle. The pressure in the system goes to about 70psi and drops to about 55psi when the valve cycles. The city water pressure is about 55psi and a expansion tank is pressurized to 55psi. The thermometer attached to the line at the tank coming from the collector indicates a high temp reading of 180 degrees just before the t&p collector cycles and drops as the cold water entering the tak is picked up by the circulating pump.Any help would be appreciated.