Hot water zone

I’ve been searching the internet and came across this site. I’m at my mother in law’s and she recently had a new indirect water heater installed. She was complaining that the water was too hot, so I went down to turn down the temperature and couldn’t figure out how. The water heater is a Weil-McLain 45-s2. There is no dial or digital control on the tank, but a temperature transducer that is wired out the top of the tank directly to the Taco pump relay. It appears that the circulation pump is running continuosly and circulating through her gas fired boiler with the temperature around 170f. The Honeywell temperature control/mixing valve also appears to be stuck. I removed the screw and was still unable to turn it in either direction. She plans to call them tomorrow, but I was wondering if this installation could be correct and if not, what she should ask to have remedied by the installer. Thank you!