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DayCreek Journal

October 21, 2000

Down in the Trenches

Pictured here are both sets of collectors, copper pipes and the trench.

Now that the collectors are up, light can be seen at the end of the tunnel. (The question is, is it daylight or an oncoming freight train.) This last week was spent trenching in one inch pex tubing from the bridge to the two banks of solar collectors. I thought about renting a machine to do the job, but since the distance wasn't extremely long I decided to use pick ax and shovel.

After the trench was dug, I needed to find a way to insulate the pex tubing that would soon be run in the trench. The best method I found was the Steve Krug (Owner of Next Step Energy) method of building a insulation sandwich out of 2" foam board. First, a six inch strip of foam board is cut lengthwise. Next comes two pieces of 1" foam board that are glued to the bottom board forming a channel for the pex tubing. Finally, another six inch strip is secured on top to complete the "sandwich". The foam board has an R factor of R10, which is excellent when it comes to pipe insulation.

Here's a view of the copper pipes from the collectors, the pex tubing and the foam board "sandwich".

The one inch pex tubing is manufactured by Durapex. I first learned about Durapex through Menards. Menards is a regional home improvement center that sells a wide variety of plumbing supplies and as luck would have it, began selling Durapex product this spring just as I started piecing together the supplies for this system. I had to special order the one inch tubing since Menards only stocks the 1/2" and 3/4" tubing. After receiving the 1" tubing, I realized that the tubing would not except other manufacturers fittings, so I called Durapex directly and explained my situation. Durapex has been extremely helpful in supplying me with the necessary fittings and tool to finish the job. If you are planning on a radiant floor system or any other flexible tubing project, I highly recommend them. You can learn more about their products by going to their web site: I have used their tubing in the sand bed, in the concrete floor and now for the connection from the collectors to the mechanical system.

Balancing the Heat Supply
Because the system incorporates two sets of collectors, there needs to be a way to balance the output from the collectors. If there are two sets that are identical, it is not too difficult to do. All that is required is to run two identical lengths of pipe between both sets, each representing 50% of the fluid flow.

This system has two factors that could skew the balancing act. The first being that there are two different manufacturers of these collectors. One set of collectors has ten tubes running inside of each collector, while the other set has eleven. This means there is more resistance (ten tube collectors) in one set of panels vs. the other. Secondly, the easiest way for me to connect both sets together was to use "T" fittings sideways. This configuration causes less resistance to one set of collectors versus the other. To help balance the flow of the two sets, a full port valve was installed on the set of panels with the lowest amount of flow resistance. This will add controlled resistance and balance the output flow. It at least sounds good, so hopefully it will work.

Things are getting exciting now that we're getting closer to a production system. The next projects on the list are sweating in all the mechanics of the system and installing a shunt load that will dump excess heat during the summer months. Once the system is up and running, I will describe the working system in detail.

Stay tuned over the next few weeks for the (hopeful) conclusion of the system.