April 10 , 2002
"Bursting" into Spring
I hope this comes out legible as I am writing this after a very long work day. It is only Wednesday, but it feels like I've been up here for more than a week. Things started on an ominous note when I arrived up here last Saturday. I went to check on the house after moving supplies into the cabin and as I approached the house I noticed a humming sound. Now normally, a humming sound is a good thing once you are at the house because that means the solar collector pumps are running, but I was quite a distance away. The pumps were running, but much louder than usual. I ran to the back of the house and noticed I had no pressure in the solar heating systemalong with no fluid I might add. Yikes! I shut the pumps off immediately. So now the questions were when, why and what happened?
did it happen?
I had been up at the house during the month of February and the system was running just fine, but something must have happened between the end of February and now.
The 5 gallon bucket under the pressure relief valve was full, so I figured that I had another incident like last winter. (If you recall, last winter I had a leaky pressure relief valve.) It appeared that for some reason, pressure relief valves don't like the cold.
On Sunday, after installing a pressure tank for our well and cutting some wood for the walls, I finally got around to the solar heating system. Using an air compressor, I started to fill the system with air to see if I had any leaks. Well...I couldn't believe my eyeseither the pressure gauge was broke or I had one humungous leak.
I looked in the house, by the pumps and by the solar collectors. Everything appeared to be okay. But then I noticed something strangeon the return side of the one set of solar collectors there was a vertical dimple-like line about three feet from the ground running down the side of some insulation casing. (It's made out of plastic and quite susceptible to heat.) I started digging down below ground and I could smell glycol. (The glycol is nontoxic, not the same as in cars.) I dug down to the insulation trough and broke it open. I couldn't believe the size of the rupture!
So now I found the "leak" or in better terms, gaping hole. So there was the smoking gun, but who fired it?
did it happen?
By the looks of the tubing it appears that either a flaw in the tubing and/or excessive heat and pressure caused the rupture. The system is normally charged at 30 psi, so unless there was some kind of blockage, the pressure shouldn't have gone up high enough to cause the problem. The only way blockage could occur would be if the fluid froze. Considering that it didn't get much below zero°F this winter, the possibility seems nil to none considering the antifreeze is good to -50°F.
A second possibility could be that the pumps stopped working. This would cause the collector temperature to get really hot if there was little or no flow. As far as I can tell the pumps are working fine and if this was the case, I would expect to find the same scenario with the other set of collectors.
A third possibility is an out-of-balance flow to and from the two sets of collectors. I had put a ball valve on one set of collectors that typically receive more flow than the other. The ball valve may not have been set correctly allowing equal flow between the sets of panels.
A fourth possibility is the tubing (rated at 80 psi @ 200°F) has a defect. At this time, this is unknown. The ruptured piece of tubing is being sent to the manufacturer's engineering department for analysis.
Considering the tubing has been in operation for almost a year and a half, it appears to me that the tubing met a slow death. Over that period, the tube gradually melted until the combination of heat and pressure finally caused it to burst. The other set of collectors that had the same configuration of copper pipe-to-pex tubing appeared fine.
But not taking any chances, the new plan is to run 1" copper pipe a good 25' out from each set of collectors, with a new set of "T"'s that hopefully will help balance out the two sets of collectors. There's actually less fittings and 90° turns with the new design, plus the output from the collectors will have much longer run of copper before joining up with the pex tubing. This should help temper the fluid a bit.
So far this repair has cost me about 4 days in labor and about $300 in glycol, miscellaneous copper fittings and pipe. The majority of this is the cost of the glycol. The nontoxic stuff (propylene glycol) is quite expensive, but it's the only fluid available for solar and/or boiler systems that require antifreeze.
This has been quite a test of my wits that is for sure. Besides the failure of the system, I got into a traffic accident in La Crosse on my way back from the plumbing supply place. It wasn't anything major (thankfully), but it does make you wonder if someone is testing your commitment to this whole adventure.
Even though this week was "hell week", it was nice to take a few breaks while digging trenches to look up at the house and realize what a great place we have. I'm still smiling and by next week, the revised solar heating system should be up and running. I'll write on the progress next week.