Wednesday, October 06, 2010

Solar Sundays Part VII- Lots of Copper!

Taking advantage of the T-shirt weather of October, I decided to focus on the solar hot water system until it is finished. The last few days have been all about copper- cutting, cleaning and soldering together the network of tubing that will carry fluid through the solar collectors. Each of the 9 collectors has around 45 pieces, so I set up a little assembly line for the process. I'm building the collectors in 4'x8' modules with threaded fittings on the ends to connect each one to adjacent units in the system. Thus, I needed a way to ensure proper alignment between adjacent modules so that the union fittings would line up perfectly. For this, I built a simple wood framework on sawhorses to act as a jig/table for assembling each module.The vertical spacing is achieved with stop blocks at either end of the first riser, and I cut another block of wood to use as a gauge of the riser tube spacing. Before any of the fittings were soldered, I checked the assembly for squareness, length and spacing.
Starting from the 'jigged' end (you can see the stop block in the top of the photo), I soldered the first 5 tee fittings, leaving the final 3 fittings loose for the next step. Likewise, I soldered the opposing 5 fittings at the other end of the assembly.Next, the partially-soldered assembly was rotated 90 degrees on the table, and the previously finished (already soldered) module was set to the left of it. Then, the stubs and a union fitting were installed between the two modules. The unsoldered fittings of the module-in-process are towards the union of the two modules, such that they can be brought into perfect alignment before proceeding. With the union in place, I soldered the remaining tee fittings on both ends, but not the union itself.Before soldering the union in place, I separated the two modules and attached Sharkbite end stop fittings at three of the corners, plus a pressure-testing assembly at the fourth corner. The module was pressurized to check for leaks. Once this was done, I removed all the Sharkbite fittings, reconnected the modules at the union fitting and soldered the union in place. Now the modules can be disassembled and reassembled to one another using the threaded union fittings.
Meanwhile, I installed insulation in the collector frames. I opted for 2" of insulation using a bottom 1" layer of XPS foam and a top layer of 1" polyisocyanurate.
To test fit the system while building the modules, I temporarily installed them as I went. Here is a closeup showing the union fittings in place. Holes bored in the vertical frame members allow each unit to be inserted into place. Next step- installing the heat transfer plates....


Anthony said...

how did the insulation work out using the two different types? I used 2" blue poly insulation and in melted at the top during the summer in my collectors. So i m going to replace it and add the 1/2" polyiso on top of it like you did. so thats why i'm asking.

Shawn said...

I haven't installed the glazing or connected the plumbing yet, so can't give you any results...but I have no doubt that the double layer insulation system will work just fine. FYI- I used 1" of XPS on the bottom and 1" of polyiso on top.

good luck,