I have a WM instantaneous NG boiler hooked into my radiant system. It actually works very efficiently and I am very impressed for the most part. I only have one problem that has been persistant since its instalation. Probably once a week during the heating season the computer controller gets tripped and gives an error message of E 03. If you hit the reset button, it usually just fires up again and does it's thing. It doesn't bother me too much except if we ever want to go on vacation, etc we have to worry about it going out. I had it serviced by a technician who changed out the thermo-couple. Last year I took the TC out and "brushed" it off and that weemed to help. When it does not come back on with the reset button, you can hear it go thru its cycle and try to ignite with the spark ingnition but there is a flash and then it goes out. Some kind of feedback loop? Experts please help.