Weil Mclain Gold GV Series 3 circulator problem

tvincent

I have the above mentioned boiler with 5 zones controlled by zone valves. I have noticed that the system supply pipe on my boiler is always colder than the return pipe. When there is a call for heat and the boiler is not running, it sounds like the "bypass circulator" is running at a low RPM and the "System Circulator" is doing nothing. When the boiler fires up, it makes a rushing water noise for about 30 seconds. Is it possible someone mis-wired the circulators, causing the bypass circulator to operate as the system circulator? Is the bypass circulator only supposed to be on when the burner/fan is running?