Look! There goes a BTU into the Floor!

The Northern Lights. This image was taken looking towards the NNE from the front porch of the cabin.

I returned on Saturday afternoon after spending a couple of days at home in Illinois. Weather-wise, things looked ominous for the week. The forecast called for mild temperatures, but very little in the way of sunshine. I had only a couple of days of work left before the system was ready to test, but would the sun cooperate? Only time would tell.

The first thing I checked when I returned was the pressure. I was still losing air pressure after all the checking that I did. So, I went around one more time with the soap bubbles with the system charged at 70 pounds. I found one very, very, slow leak from one of the unions and cranked it a bit more and the bubbles went away. At this point, I decided to stop worrying about minuscule leaks and finish the installation.

I finished mounting the second PV panel on Saturday and called it a day. Later that evening, Sundae (the cat that adopted me) and I were treated to quite a show. At around 8 p.m. I noticed that the sky to the north was brighter than normal. The more I watched the horizon, the brighter things got. It was the Northern Lights.
The Northern Lights. This photo was taken looking towards the NNE from the front porch of the cabin.

As the night progressed, things got better and better. At around 11 p.m. there were hints of red in the sky. Since I happened to have a manual 35mm camera without all the fancy auto junk, I was able to shoot a whole roll during the course of the show. It was quite a sight to see. After midnight the show came quickly to a close, but what a show it was!

On Sunday, I finished up the wiring under the bridge where the two pumps are located. With the sun shining at midday, I decided to do a quick check of the pumps and discovered that one of the pumps did not power up. After close inspection, I noticed that one of the motors did turn as freely as the other. So after a phone call to Steve, we made arrangements to meet on Monday to exchange the pump. I spent the remainder of the afternoon installing pipe insulation on the return side of the system.

Monday I met Steve, exchanged the pumps and installed the new pump in the afternoon. The forecast still looked ominous for the rest of the week, but as luck would have it the skies cleared Monday night and the forecast was revised for mostly sunny skies on Tuesday.

Yikes! Now I had to rush to get my hoses and fittings together to fill the system bright and early on Tuesday. After a quick run to the hardware store Monday evening I was ready for the fill on Tuesday. I had a used 3/4 HP jet pump that I purchased for the cistern last year that I planned on using to fill the system.

As promised, I was greeted to a clear, sunny morning on Tuesday. The first step was to flush the system with water. There was sure to be some residual gunk in the system from all the sweat connections that were made. The jet pump was connected to the fill side of the system and I started pouring 5 gallon buckets of water into a large tub. 45 gallons later, I was starting to get a return flow of water out of the system. As the hoses belched out a combination of water and air, I started seeing lady bugs coming out of the hose! Those dang lady bugs must have gotten into the solar collectors before they were raised. I counted about 50 or so of them floating in the tub, some of which were still alive! I left the jet pump on for about 10 minutes and then started draining the remaining water out of the system. Since most of the underground tubing still had water in them, I got out the air compressor and blew out the remaining water. It was now quickly approaching 10 a.m. and I was getting concerned about the collectors producing steam. I quickly opened up the 5 gallon buckets of nontoxic antifreeze into the tub and started filling the system.

After getting about 20 gallons of the antifreeze into the system, the jet pump started having convulsions. The viscosity of the antifreeze was a bit too much for the jet pump and eventually the jet pump overheated and shut down! Now what? I left the pump off for 10 minutes and tried again. By now I had enough water with the antifreeze that the pump started working again. I started getting a return flow back in the tub, so I knew the system was almost full. I figured I had about another 15 minutes or so to get all the air bubbles out of the system. The pump overheated again and shut down. By now the sun was surely starting to heat up the collectors. I turned on the system pumps and tried to circulate what fluid was already in the system. I could hear air gurgling in the system, but I did notice there was heat going into the floor.

I called Steve in a panic explaining the situation. (I can’t believe the guy is still talking to me after all the phone calls and emails I have sent him.) Steve said to leave it running and see what happens. The one thing for sure you don’t want to do is leave the system stagnant.

So, for the next hour I alternated by running the system pumps and the jet pump, slowly ridding the system of any air bubbles. By noon, the system was up and running. The temperature going into the floor was about 120 degrees, while the return temperature was about 85 degrees. After months of work, there were BTU’s going into the sand bed under the floor!

By 2 p.m. I noticed the pumps were slowing down. There was a very thin layer of cirrus around, but not enough to make a real impact on the sun’s intensity. By 2:30 p.m. the pumps had quit completely. I checked the voltage from the PV panels, and although they weren’t running at full power, they were clearly still producing power. I also knew the collectors were still hot, so I wasn’t able to take advantage of the heat they were producing. After fiddling around, I determined that the PV panels were just a bit too small for the system. I disconnected one of the pumps from the system and the other pump started running with vigor.

So, for now half of the collectors are producing heat using one of the two pumps. Two 75 watt PVs are on order and by next week the larger PVs will be installed. With 150 watts of power, the two pumps should run just fine.

A final paragraph or two
I hope I haven’t board you to tears by now regarding this project. It has definitely taken me longer to finish this project than I had imagined. I have great respect for homeowners who have built these systems for their own heating needs or contractors who build them for a living.

It won’t be until the spring of 2002 that I can report on the advantages or disadvantages of using the sand bed to store the heat. It’s just too late in the season now to get much heat out of the floor and the walls aren’t up yet. Next fall the walls will be up and I will have the advantage of charging the sand bed in August of next year. If by chance the sand bed doesn’t perform as well as I would like, I have the option of using the tubing in the concrete floor to heat the house. By installing both sets of tubing before the floor was poured, I have left myself options for redesigning the system if required.

It is such a thrill to actually witness the system in action. I literally watched the system for hours. Looking at the thermometers and feeling the temperature of the pipes I could see that heat was getting dumped into the sand bed. Wow! Think about it. Here is a system that runs by itself when the sun is shining. To think that we live in a era where solar power can be used to greatly reduce our dependence on nonrenewable energy. Why aren’t we using it more?