Frozen boiler piping

steamer45

Received a call to inspect/evaluate the damage to a hydronic system from frozen piping. System has been in operation for approximately 20 - 25 years in a 100+ year old home, it is a cast iron Utica boiler w/ Effikal flue damper/standing pilot/Grundfos pump/4 W.R. zone valves. I replaced the L.W.C. approximately 1 year ago (transformer failed) and one zone valve operator 3 months ago. System has been operating properly & as designed up until approximately 2 weeks ago when it was discovered that it had failed, resulting in 10 to 12 frost breaks in the finned tubing. Breaks are located on both 1st. & second floors. There is no record of a power failure from the utility company or from a next door neighbor (usually inspects the home if owners are away, didn't on this occasion). Have not inspected the boiler for failure as yet, but all appears in order. When the damages was discovered, the system was heating, flowing water thru multiple breaks at temp. creating massive humidity.
First question is, what is the burst/breakage threshold of 3/4" copper finned tubing, 3/4" type - M copper is 2000 lbs. if I remember correctly?

mattmia2

Maybe the time between cycles was long enough to freeze in some vulnerable location stopping flow in that zone or zones and then other stuff in the zone stopped heating and froze from the lack of flow while the boiler was working fine.

JUGHNE

Did any of the domestic piping freeze?

Just from the weight, IMO, fin tube copper seemed thinner than type "M" pipe.

Jamie Hall

mattmia2 said:

Maybe the time between cycles was long enough to freeze in some vulnerable location stopping flow in that zone or zones and then other stuff in the zone stopped heating and froze from the lack of flow while the boiler was working fine.

That would be my guess, particularly if the owner had the heat turned down.

In answer to your pressure question -- annealed 3/4 inch copper can be as low as 400 psi working pressure and even hard drawn can be as low as 1300 psi. Water freezing in the pipe can get well over those pressures.

EBEBRATT-Ed

as @JUGHNE mentioned, baseboard tubing is thinner than even "M" copper tubing.

I don't know if the mfgs do this to save $$$ or to increase heat transfer.........maybe both!!


If the split is not too bad or too numerous you could braze then with silfoss

steamer45

Here is an update regarding my "frozen boiler piping" situation. There is a single break in a first floor zone wrapping around the south side of the home. It is located immediately at the inlet of the finned tubing, where it is connected to a 3/4" copper elbow. This location is at the corner of the living room and a bay window approximately 4' deep X 6' wide, all thermo-pane glass. This section of baseboard is the second in line after a 12' section (this has a "bulge", directly under windows, but no break in it) along the west wall of the "parlor". It continues into another 12' section along the east wall of the living before dropping thru the floor into the open basement and on to the boiler.
The north side of the first floor has a similar layout, first is a 6' section of base-board in the front entryway (double wood doors, 6' w. X 8' tall - no damage), then into a 12' section along west wall of dining room (no damage), dropping thru floor and turning east , then up thru floor into a 6' section in dining ( no damage), on into a 4' section in a powder room off kitchen (no damage) dropping thru floor into basement, into 6 - 8' sections of finned tubing only, suspended between floor joists spread across kitchen floor, then returning to boiler (no leaks, no damage).
The second floor S. side is laid out similarly, supply pipe extends up thru west wall from basement, enters a bathroom baseboard, then 1st. bedroom, then closet. then second bedroom, then stairway landing where it drops down east wall into basement.
Bath has no damage, bdrm #1 (S.W. corner, window on each wall, 8' section of finned tubing under each window, 2 breaks along S. wall, 1 on W. wall). Closet has no damage, B.R. #2 has window on S. wall with 4' finned tubing under it - leak at end of finned tubing, E. wall has no window but has leak in finned tubing midway across room).
The N. side zone is laid out similarly, supply extends up thru W. wall into B.R. # 3, pipe stays above floor, running thru bare cabinet along both W. & N. wall (finned tubing under W. & N. window/no damage), thru closet (no damage) into B.R. # 4, into finned tubing under window (2 breaks) over to E. wall (1 bulge damage) into stairway landing & down to basement. Stairway landing has full wall windows, approximately 18" above both returns w/ no damage in either run.
I tested the boiler function by the following process: Relite pilot (manual valve had been turned off when the damages were first discovered) detected what appeared to be a bit of air in the line (flame did not ignite smoothly, took a few seconds before it stayed burner properly). My first thought was the gas supply had been worked on by the utility and air had entered, however, there is no record of any work having been done, plus, the system was heating when the damages were discovered. Pilot stayed on, burned properly. I then connected a "by-pass" between the boiler supply & return piping, refilled the boiler to a sufficient level to allow circulation. I then activated the power supply to the system, turning up each wall thermostat individually and found that all components on this system operated perfectly, zone valves opened, end switches activated the flu damper, after opening it activated aqua-stat relay, pump started & burner lit up, detected circulation thru each zone. Cycled this process multiple times for each zone, everything operated perfectly - no failures!
I still can not up with a definitive answer for how this occurred. Clearly the leaks are caused by frost damage, yet not all are in the most likely sections. The basement of this home is very wide open ( block wall dividing N. & S. sides with 2 door way openings) 10' ceiling. House is old enough to have a brick (2 row) foundation wall, therefore quite leaky with infiltration. Yet, no damage to any piping in the basement or up side walls, including the domestic water system.
If one or more zones failed, the others should have kept the home from freezing to that extent. I am leaning toward an electrical failure (tho the utility provider verifies they show no record of any outages - Home has a "smart meter"). One thought is the flue damper did not open sufficiently to trigger it's end switch, which would keep the flame from activating. Then again, the zone valves would be open and the pump operating, so that should have kept water flowing, preventing a solid freeze ( I have experienced a home so cold the water was slush - could actually here it moving thru the piping, still didn't freeze solid). Weather conditions around this time were not excessive, no extremes, nothing that would have alerted attention. House was unoccupied for approximately 2 weeks after a son had left for school, stats set to 50 deg.
No solid answers!!!

Jamie Hall

And you'll probably never get one. However, a thought. Just one pump? I'm looking at the single actual break you mention, and the damaged piping beyond it. You mention an elbow at that location. Then keep in mind that water is lazy. Very lazy. And will always take the path with the least resistance. Now consider that section of pipe: as I read your description of the damage, that is directly under a big window -- and has a bulge in it, indicating that it froze. How could this happen with the boiler going and the circulator running? If any other zone was calling at the same time -- dismayingly easily. That nice big window chilled off the section of pipe and it started to get ice on the perimeter of the pipe (remember -- all those nice fins to cool it off?). As that happened, the flow through the pipe dropped, bringing less heat. The ice got thicker... and so on until the flow stopped and all the water was going through another path. Pipe froze, and it broke at the stress riser where the regular pipe joined the baseboard.

Speculation? Certainly. But... plausible.

steamer45

Hey Jamie, thanks for the reply. Yes, at this point, any explanation is plausible. One leak is at the turn from 3/4" soft copper riser (type-K) from basement, thru an elbow, into the inlet or leading end of a section of finned tubing, approx. 14' long, wrapping around a first floor bay window. One leak at the inlet, nothing along the remainder. There are multiple additional leaks on the second floor zones, some under windows, others along solid walls, 15' from any windows. No rhyme nor reason!

mattmia2

The space where the floor plat and rim joist meet is frequently poorly sealed and a good place for some cold, windy weather to freeze a pipe through let's say forced convection.