If you enjoy HVAC mysteries, here's one for ya.
In the past, I've consulted this site as a mere homeowner with an interest in HVAC (I've always enjoyed discussing the trade). Thanks to referrals to have a tech properly repair items, many problems were fixed properly. I didn't think of the forum when my Dad's house exploded...
So here's a fun challenge. This happened in the Akron, Ohio area over the Winter months. My Dad was away from home for a couple weeks out of town. The Stat was set at 55F.
Setup: Hot water boiler with radiator heat -- original, early 1930's coal-burner converted to natural gas in the early 60's. House design: small, 2-bedroom Cape-Cod. Now for the interesting part...
After a cold snap, my Pops returned to the house to find the entire house covered in a 1/2-inch thick layer of ice and the boiler frozen solid - from the basement, all the way up to the second floor.
We had an HVAC specialist on the case, who had been a family friend for over 50 years. He never saw anything like it. Newer guys had theories too.
Here's another factor: two of the cast iron radiators had sections blown-out:
(the rad is upside-down, showing a top section missing).
So what do you think happened?