red8174

Hi. Looking for some suggestions. I recently moved my Hot Springs - Grandee tub and refilled it. I am now having a problem where my no-fault PDR heater will work for about 20 minutes and then trip the internal limit in the heater. It does not trip the high limit on the control board. If I turn off the 30 amp heater breaker for about 15 minutes and then turn the breaker back on, the heater will reset itself and then come on again for about 20 minutes before going off again on the heater's internal limit. I have remmoved the filter, verified that the circulating pump is running and I appear to have good flow through the heater. There is good suction at the filter intake, and I have disconnected the water lines at each connection one at a time to verify that I am getting good flow and don't have a restriction somewhere. I have removed the heater and verifed that there is nothing clogged and have made sure that I don't have any air lock problems. Both the heater and the circulating pump were replaced new in 2008. I am at wits end as to whether I have a heater problem or a flow problem. I would lean toward a heater problem but everybody says these heaters either work or don't work and my logic says that is could be a flow problem but it shouldn't take that long to trip the internal limit if it is a flow problem. Any suggestions or ideas would be greatly appreciated. Thanks!