Geothermal HVAC Blog

Link: http://www.duanesworld.net/duanesworld.net.geotherma.htm

I noticed back in early January that my Humidifer was not operating. Previous issues were that the humidifer was cycling very quickly on and off at times. I called my geothermal installer with the problem and was asked to do more troubleshooting. The humidifier finally quit and does not work now.

I called my Geothermal Installer. Not surprised that I needed to do some troubleshooting before anyone would be sent out to resolve the issue. I found that when installed, the 24 volt power was coming from the Bryant Air Handler not from a seperate transformer for the humidifier. I learned that the 24 volts was not present at the Air Handlers circuit board.

I relayed this information to my installer and due to other commitments, I was told to “sit tight", they’ll get back to me. Well, it is now near the end of February and no word from my installer. I have left numerous voice mails. I get the feeling that he doesn’t want to return my calls.

Needless to say that the humidifer is still not working. It is a really uncomfortable situation. Had I known the type of response I would get from my Geothermal Installer, I never would have had them install my HVAC system.

Link: http://www.duanesworld.net/duanesworld.net.sensors.htm

There is a new page for the ground temperature sensors. The page includes charts for the previous hour and meters which show the current temperature at depth. The page can be accessed directly at http://www.duanesworld.net/duanesworld.net.sensors.htm

Link: http://duanesworld.net/duanesworld.net.geothermal.htm

Great News ….. The ground temperature sensors are operating and looking good.

I am excited to see how they perform this winter and how consistent the ground temperatures are

As expected, I see the temperatures of the firs four feet fluxuating quite a bit. The sensors below four feet are fairly stable.

The only concern I have is that I may have made a mistake in construction and did not provide any earth or insulation inside the 1/2 inch CPVC piping down to the sensors. This will propbably be the next generation of sensors or a modification to be made in the spring of 2008. A little late in the season to change things now.

Stay tuned ……

I am happy to announce the ground temperature sensors are in place. There have been couple changes to the above plan.

First, there are now 11 sensors. The deepest one is at 11 feet. Each sensor is one foot lower than the previous sensor (1 foot to 11 feet in depth).

I placed 3/4 inch PVC in the ground for each sensor to the appropriate depth. This was to act as a sleeve to lower the sensor in the ground. I did this so that if a sensor needed to be replaced, I can replace an individual sensor without disrupting the others.

Each sensor was placed in a 3 inch piece of copper pipe with a cap at the end. Around each sensor, the tube was filled with fiberglass resin.

I used direct bury wire to each sensor individually. The wire was then sent through piece of 4:1 dual wall shrink tube and a 1/2 inch CPVC pipe. The CPVC pipe then connected to the junction box.

The junction box is a watertight fiberglass enclosure. The junction box is at a depth of about 12 inches below the surface. In the junction box, each ground sensor wire pair was soldered to a twisted pair which then goes back to the WEL unit. The solder connections were sealed with double wall shrink tube, liquid electrical tape or a combination.

For now, the ground temperature sensor readings can be viewed at the (real time data page)

Parts list for the final assembly of Ground Sensors:

• 11 – Length of 3/4 inch PVC pipe cut to 1 foot 6 inches short of desired depth.
• 11 – 3 inch pieces of 1/2 inch copper tubing.
• 11 – 1/2 copper pipe caps.
• Fiberglass Resin and Hardener.
• 1 – Watertight Fiberglass enclosure.
• 11 – 1 inch to 3/4 inch CPVC threaded reducers.
• 11 – 3/4 inch to 1/2 inch reducers.
• 11 – 1/2 inch CPVC pipe cut to 1 foot 3 inches short of respective lengths.
• 11 – 1/2 inch 90 degree elbows.
• 1 Roll of direct bury twisted pair cable (4 pair per wire).
• 4:1 Double Wall Shrink Tube (to secure 1/2 inch Copper pipe to 1/2 inch CPVC).
• 3:1 Double Wall Shrink Tube (for solder connections).
• 11 – DS18S20 Temperature Sensors (from (http://www.ourcoolhouse.com)

This was a fun project. And as usual, I found better ways of doing things after the fact, so I am thinking of a second generation ground sensor system.

Well, I am running into issues with deploying the ground sensors. Five of the 10 sensors which were originally assembled had to be replaced. Once replaced, these sensors seemed to operate well with all the existing sensors.

The next step was to place the sensors in a length of copper tube surrounded with bentonite (grout). This was not an easy task. Finding the right consistency of water and grout was a trick. Then during the drying process, the grout was compacted. I found that this is a difficult process to make sure that there are not air pockets left in the tubes.

Now the problem I am running into is the rest of the monitoring system. It seems that there is an issue which periodically causes the temperature sensors to register false readings, extremely high or no reading at all.

I checked the humidity in the crawl space which was very high. I started a dehumidifier to bring down the humidity level. The level is now about 50% and the occurrence of temperature spikes has been reduced. I have set the dehumidifier to 45% to see if this will eliminate the temperature spikes completely.

At first I thought it might have been caused by a bad temperature sensor again from the ground sensor group. All those sensors were already removed from the system.

I was hoping to get these sensors in before the start of winter (2006), but this may not happen this year.