...to make damned sure that power is not accidentally applied to any component in the system without operator knowledge. For example, if in the heart of winter, I never shut off the circs, or any feed and return lines.
'Cleaning' is on the 'dry side' so depending upon your situation, you sure don't want a heat call or a timer to turn something on when you are in a compromising situation.
Every install I've ever done has the circs or zone valves operating independently from the boiler. The boiler is merely a heat generating device, and no, I don't rely on the minimum of 140 water temp to start anything.
I am always active by thermostat, not by water temp. I've seen way too may freeze-ups that end up costing tens of thousands of dollars, so I for one DO think outside the damned box.
I like the 'system' to be smart enough to remain pumping even if the burner has failed for any reason, flowing/moving water will never freeze. Of course a total loss of power is a deal breaker without a back-up generator.