PEX in the Collector Loop

In a SHEM system, the pressure might build up and the collector temps could easily be over 200F even if the tank High limit is set to 180F.

I've heard somewhere that maybe the supply could be PEX. I'd say NO, because if the tank is 179F, the collector output might be 204F. Once the tank hits 180F, the pump will stop and the collectors will begin to drain back. This process can take a minute or two, and the water draining slowly inside the collectors continues to heat up and might even reach the boiling point. If that happens, the PEX in the collector supply could blow out because these conditions would exceed the PEX temperature and pressure ratings. No fun. We have heard of this happening in the field.

Do you think that if we were to to put a vacuum breaker on the tank and a 10 psi relief valve that the PEX would always operate under its rated temp and pressure?