Mystery: Blown Boiler -- House Covered in Ice
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?
If I understand what you are saying, this is a hot water, not a steam system.
HW will be filled with water,so if the water froze inside of a radiator(due to malfunction of the heating section), good chance it will break something. If the piping is copper, would be very suprised some of it is not split.
Some systems are open, but even if it was should not make a difference in this case.
It's possible that after the radiators broke, they either thawed enough that water flowed out onto the floors to cover them with the 1/2" layer of ice, or the water came from some other water pipe/fixture that leaked.
Must have been pretty cold then.
Correct, it's a hot water system, not steam. I'm not sure of the definition between closed and open systems. It would heat the water, move it through the system by the rise of the heated water, returned back down after cooled, had a reserve tank, and acquired additional (cold tap) water on demand.
Bear in mind that the ceilings, walls, doors -- everything was covered in ice through the whole house -- on all floors. Did the rads bust under steam pressure, or by ice expansion? Did the boiler steam up the whole place or did the broken rads do it?
There is a idea of what happened, but we'll take more stabs at it...
First look at the pressure relief valve on the boiler and see if it is functional. If ok, it was not a steam bomb.
Next I would look at the boiler make up water. If it is on, when the temp warms up you have water running out the broken pipes and radiators. Then at night, the temp drops again and you freeze the flooded house.
Are you familiar with glycol in your area?
The pipes are probably run close to a outside wall... and the radiators are often on outside walls. The home may have been maintaing 55F, but the walls were below freezing. The water in the radiators froze, burst the radaitors... but the system kept supplying water to the now broken radiators.
The other possiblity is the boiler quit heating, but even after the radaitors burst, unforzen water was still pumped to the now open radiators. The inside of the home was cold enough and apparantly sealed well enough to freeze a layer of ice across the floor.
At my work they installed 3 new process tanks that are something like 150,000 gallons each (about 30' diameter, 100' tall). They were about 1/2 full of water for leak testing after construction (welded in place). Well, it's around New Years and temps dipped into the sub zero range. The tanks didn't burst, but the valves at the base broke and the water slowly leaked out of a 2" valve for 2 days. Made a nice ice rink all around it and on the surrounding roads. Fortunately, with the ank being so large, there was little risk of complete failure because the outer layers of ice acted as insulation for the water in the middle. But the sounds of the ice sheets on the wall falling inside a hollow steel teel tank form 80' makes an interesting noise.
I'm suprised I guess that this was "a suprise" for the company that came to repair it. It very common for a burst pipe to fill a home with water.... and if cold enough... ice. Actually, once the water freezes on the floor in a tin layer, you now have a watertight surface, which can eventually form a bowl, that will continue to fill until the water source is exhausted.
It sounds like in either case, the system kept automatically refilling the boiler and trying to circulate the water.
The moral here is... in really cold weather, 55F may not be warm enough to prevent pipes and radiators from freezing. You can purchase devices that monitor hte temperature or other ciritcal data inside you home and call you if there's a problem. You can then go investigate or have a service company come out to check on the problem. That's where lock boxes with spare keys are handy... or having a home sercurity system the allows the secruity company ot dispatch a technician.
Well if you can freeze a radiator with the t-stat set at 55 and the boiler running you have a lot more problems. That would mean that the zone was not circulating and heating that radiator. When the room temp got below 55, we assume the radiator is hot. Then even with a window open and the room air at 0, the radiator would be way too hot to freeze.
Happens when the house is unattended. And the boiler locks out on a safety.
I've seen walls with a hole in them from a section of a cast iron rad poping off becuse of the force the ice exerts on it.
The best we can figure, the following happened... note that the iron supply and return lines were intact:
1. House Unattended, Stat at 55. A -5F cold snap hit the area.
2. One theory is that the main water supply froze. The boiler could have run low on water -- then supply thawed, cold water filled the unit and shocked the system. The boiler likely cracked spewing steam. The concentration of ice was found on the basement ceiling near the boiler. Otherwise, not sure of how it failed.
3. The house then became a sauna -- possibly up to a week. Steam continued to filter out and up, until it condensed on nearly every surface (upper floor ceilings, doors, furniture -- anything).
4. The boiler finally gave up for some reason. This unit was really old -- if I remember correctly, it was the original 1931 model with the late 50's / early 60's natural gas conversion. The relief valve was replaced after a failure New Years 1991 (high temp, high pressure, very hot radiators).
5. How the unit gave up is a mystery. It was a simple system with spring-loaded reliefs. Could it have had a safety lockout with its age? Maybe the moisture flooded the pilot and the thermocouple cut the gas?
6. Then the place became an ice palace. The extreme cold froze the remaining water and the tops were blown out of 2 rads and left a pool of water/ice at both carpets. That had to been a LOT of pressure!
Since then, the house was gutted, updated with forced air, sheetrock instead of plaster, etc. The place stayed relatively unchanged for over 75 years so it was a bummer to see it during the cleanup. I'm told that it had a total remodel and is now for sale. I'd like to get back to see it one last time...
Lessons learned about the heat setpoint. I'm not sure if the system could have handled glycol per code, since the pressure/overflow went to the drain. For its age, it was pretty efficient at its job (the banging wasn't as bad as steam).
Propylene glycol specifically for boilers is used by anyone who does not want frozen pipes and radiators.
We put it in the fire hydrants here too. Yes, right on the water main.
It is in your ice cream too.
If the boiler had cracked, then the rads wouldn't have had enough water in them to freeze and blow out the tops.