Ultra Boiler and 60s Outside Temps

I just had an Ultra boiler installed; it went on a few nights ago and worked splendingly. But now I am trying to figure something out.
The boiler has an outside temperature sensor designed to shut it off at 70 degress, which is not in the summer. But I am looking ahead to Fall and Spring in the Northeast, when outside temps can be in the 60s. What to leave the boiler set at? Because I have tried the heat when the temp has been in the mid-60s outside, and the boiler display immediately shows code 6, "Burner off because limit achieved," even with a water temperature in the 70s. My questions, for those who have experience with these boilers and can answer me without losing me in a maze of jargon: In that situation, would the pumps just run ad infinitum? Or would the targtet boost kick in after a few minutes, nudging up the limit until the system went on (assuming it doesn't hurt anything to have the pumps moving cold water around)? What thermostat settings for such days have you found work best?
I had thought 67 was a good "fail safe" setting, but now I am not so sure. I could try for 60, but that seems a bit cool (bearing in mind that when the temps are in the 60s, insulaiton allows passive solar heating to work), What level works best? I want a setting that, for the Spring and Fall, I can set it and forget it.
Thanks in advance.

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