tankless on boiler popping relief

tim_20

my dispatcher has a tankless coil that keeps dripping or discharging the relief valve usually wneh the burner shuts off. going by in am to look at i know there is no flow control valve on it and it is rated a 3gpm he also states relief is a 150 lb relief any ideas? i know one of our other guys replaced last year. could water hammer be a cause??  thanks tim