Rebuilding a 31 Year Old Suncatcher Copper tube, Aluminum Fin Collector

This is a story from from Doug on rebuilding his solar water heating collector after 31 years of service. This is interesting from two points of view:

Doug goes over some good techniques for rebuilding old collectors that may be helpful to you.
This is another data point for collectors that use copper tubes and aluminum fins, and how they do with respect to copper - aluminum galvanic corrosion.

It appears that the corrosion problems were minimal and easily cleaned up even after 31 years of use in a collector that had some rain leaks for at least part of that period. Pretty nice to see this 31 year old collector rebuilt to serve for many more years!

Thanks very much to Doug for providing this!

The collector rebuild details from Doug...

Gary,

Last May I refurbished the collector that I have been using for 21 years. It has welded aluminum sides and back, it's a 31 year old Suncatcher by Solar Unlimited Inc, Huntsville AL. They were fairly common around here, three friends also have them, all show moisture inside from rain. This is a before pic showing the moisture inside the collector.

Water in solar collector

The collector label says it weighs 168 lbs-but that's dry, and this had working fluid in it, and rain soaked insulation. Lots of fun moving it up and down my 24' 7/12 back slope to mount on the 12/12 front slope.

The collector is 39 sq ft. I bought it used 21 years ago, and have had it working on my roof for that time. Needed new roofing, as my 21 year old Celotex asphalt shingles were starting to curl, oddly, just on the north slope.

I was stumped at first as to how to take the tempered glass off without nicking it- it was well sealed into a recess. Finally figured out it was sealed with solvent release butyl. So, I soaked all ~30' of glazing edge with mineral spirits, and gradually got it to release- but what a cleanup job.

The collector had 2" of dense fiberglass blanket in it, wet from rain coming in around the glazing. I removed all the FG, and put in 2" of polyiso, four 1/2" layers, one middle layer just strips to leave an air space to reflect radiant heat. I taped all joints with aluminum tape.

Saw some corrosion as it has aluminum fins on copper tubing, the corrosion was just where the FG was staying wet and in contact with the tubing. Fortunately, it was just superficial, cleaned up nicely, and pressure testing showed no leaks. Repainted the absorber, lots of cleaning, sealed the box really well, leaving one small vent hole where water cannot get in, and reassembled to reinstall.

Doug

Doug has contributed several of his renewable energy projects to Build It Solar -- here are all of them:

Gary July 22, 2011