Customer had installed new WiFi thermostat and after that boiler had a code for LOP, boiler had 7 PSI in boiler and was in lockout, fed water into boiler raising pressure to 11 PSI, reset code and boiler fired up, had customer turn on heat for first floor, circulator and boiler came on let run until supply and returns got hot, customer felt radiators upstairs and began to get hot. Customer had turned power off to boiler to change thermostat and is very possible water got drained from usage while boiler was off and with it locked out could feed water into boiler. Tested system and everything operational. We are due to do servicing in a couple weeks we will check again to make sure boiler is not losing pressure. Mail invoice to customer.