I have a model CG 6-SPDN boiler built in 1994 for my hot water radiant heat (radiators) and will be using it also for radiant floor heating in an addition I am building. It has been running fine without any issues, however, a few weeks ago, it started acting differently.

The boiler seems to try to maintain the "system" temperature all the time, even if no zones are calling for heat. I even turned off the thermostats - and even disconnected the wires from the zone control to the boiler. Once the water temperature drops below 160F, it starts heating. It then heats until the temperature reaches about 200F and then turns off. The temperature limiter in the boiler (the little wheel) is set to 170F. The only way to stop this is to turn off the power to the boiler.

The next issue is that the boiler temperature is dropping by maybe 1-2 degrees a minute, so it starts firing up again about every 30 minutes. Is that normal that the temperature drops that quickly? is there some insulation missing or can I add insulation somewhere?