Arrived at location on 1/21/22 - Unit being used upon arrival. Reported tripped twice earlier intermittently. Last time was about 4 hours ago. From what Hatco told us last time seems like thermostat may be sticking intermittently will order and return. Returned to location on 2/3/22 - Replaced thermostat. Set to cycle between 180 and 190. Tested. Sys ops ok.