Just a few shots in the dark:
Is external contamination a possible cause? I'm just thinking that if the pump/motor is in a sandy, dusty or otherwise "dirty" area you may be transferring that stuff to the seal and causing a failure.
Is the motor running at the rated speed for the pump? I'm not sure how tight these tolerances are but in theory you would be able to run the motor shaft so fast that the seal fails from excess friction and heat.
Could other nearby items or other environmental issues be raising the seals ambient temperature to a failure point? You mentioned a heater. Another possible cause may be direct sunlight overheating things.
I am in no way a "Pump Guru" but just thinking out loud. It may even be a few things that by themselves are "within tolerable limits" but coupled together are causing problems.
Is external contamination a possible cause? I'm just thinking that if the pump/motor is in a sandy, dusty or otherwise "dirty" area you may be transferring that stuff to the seal and causing a failure.
Is the motor running at the rated speed for the pump? I'm not sure how tight these tolerances are but in theory you would be able to run the motor shaft so fast that the seal fails from excess friction and heat.
Could other nearby items or other environmental issues be raising the seals ambient temperature to a failure point? You mentioned a heater. Another possible cause may be direct sunlight overheating things.
I am in no way a "Pump Guru" but just thinking out loud. It may even be a few things that by themselves are "within tolerable limits" but coupled together are causing problems.