Geothermal HVAC Blog

Summer 2006

Well, this has been accomplished. I tested it yesterday. Now during the heating season, if my geothermal HVAC system calls for auxiliary heat or if the emergency heat is required, electric resistance heat run time will be tracked.

What will be displayed on the Live Data page are two variables at the Air Handler display. These two variables are daily run time and total monthly run time.

Now we can see during the course of the winter how much the system actually goes into auxiliary heat. This will also give us an idea of how much this is costing and a ball park as to how much power is being consumed. We will also be able to tie it in with the outdoor temperature, loop temperature, etc.

Ok, now I am looking forward to winter!

The 10 temperature sensor assemblies have been completed.

A twisted
pair wire has been soldered to each DS18S20 temperature sensor. Each pin and solder connection on the temperature sensor has been covered with shrink tube.

Each temperature sensor was then covered with 3:1 dual wall shrink tube. Each end was sealed to prevent moisture from contacting the temperature sensor.

The temperature sensor assemblies have been added to the 1-wire system. The temperature values can be seen on the live data monitoring page.

Once the grout material has been received, each sensor assembly will be placed in the copper tube and the copper tube assembly created.

At that time, all 10 copper tube assemblies will be bound together and placed in a sealed plastic bag and the temperature sensors calibrated. After calibration, the copper tube assemblies will be removed from the 1-wire system and the ground monitoring assembly put together.

The hole will then be bored in the ground and the ground monitor assembly placed and then connected to the system.

I have been thinking of creating another temperature sensor assembly and placing it in water to test to temperature sensor assembly should it come in contact with water.

Let’s monitor the temperature of the ground!

Well, I have been busy with my next project for my Geothermal HVAC monitoring system.

What else could I do with the system?

I am going to put temperature sensors in the ground! I plan on placing a temperature sensor from 1 ft below the surface to 10 ft below the surface.

I now have the temperature sensors, twisted pair wire, shrink tube, copper tube, CPVC pipe and connectors. I am going to start by wiring the sensors, placing them in the copper tubes and then placing them on the monitoring system to calibrate them. I will be adding to this post with materials, lists, plans, status, and other details.

Here’s the project:

I thought it would be neat to monitor the ground temperature at 1 foot intervals. There is no real value to this project accept monitoring the ground.

I have been curious that Geothermal Installers and other professionals claim that the loops can be as shallow as 5 - 8 feet.

Now, in my area the frost line is considered to be 42 inches. In the winter, when temperatures are below zero I would think that if it is near freezing at 42 inches, another 42 inches down it would be cold.

We shall soon see. Here is what I plan on doing.

• Part List:

  10 DS18S20 1-wire temperature sensors will be placed at 1 foot intervals starting at a depth of 1 foot.

  10 pieces of 1/2 inch copper tubing, each 3 inches long.
  10 pieces of 1/2 inch CPVC pipe, each 9 inches long.
  19 1/2 inch cpvc pipe union connectors.

• Twisted pair wire is soldered to pins 1 and 2 of the temperature sensors. Shrink tube covers the solder connections and pins to insulate them from each other.
• Each sensor assembly is covered with 3:1 dual wall shrink tube. This is done to protect the sensor from moisture.
• Each copper tube assembly will contain a temperature sensor assembly. A small piece of tubing will be placed in each copper tube assembly to run the 1-wire twisted pair through the entire monitor assembly. The bottom copper assembly will have a copper cap soldered to it. Each copper tube assembly will be filled with grout material used to seal vertical geothermal well shafts. This is done to improve the thermal conductivity of the copper tube assembly.
• In between the copper tube temperature assemblies will be a 9 inch piece of 1/2 inch diameter CPVC piping. The CPVC piping will be attached to the copper assemblies with union connectors. Each copper assembly’s temperature sensor wires will be connected to the twisted pair wire running the length of the entire monitor assembly. This connection will be soldered and then covered with 3:1 dual wall shrink tube to prevent moisture from entering the connection. Each one of the CPVC pipes will then be filled with low expansion foam. This is being done to help keep the temperature sensor assemblies isolated from the others.
• To prevent the 1-wire twisted pair from being accidentally cut, the wire will be placed in CPVC tubing at a depth of about 1 foot below the grass as it goes to the house to be attached to the WEL monitoring system.
• Creating the hole to place the ground monitoring assembly in place appears to be a challenge. At this point, I believe I will use a process which I learned as my ground loop was installed.
• I will use 3/4 inch diameter CPVC piping about 3 - 3 foot lengths. I will dig a hole about two feet deep and then using the 3/4 inch diameter CPVC piping and a high pressure nozzle on a garden hose literally pushing the 3/4 inch pipe in the ground.
• Each one of the 3 foot pieces will be connected using union connectors. When the entire length of 3/4 inch CPVC is in the ground, then the entire length will be pulled out. The ground monitoring assembly will then be placed in resulting hole.

I have been working on one of the last two outstanding issues with my monitoring system, the run monitor for the desuperheater. The last issue is the run monitor for the auxiliary heat unit of the Air Handler. The run monitor for the desuperheater has not been working when the heat pump is running. I could not verify that the water pump in the desuperheater was running either.

I connected a volt meter to the power wire leads on the desuperheater and on the heat pump when the units were active. The voltage I read seemed to fluctuate from 95Vac to 24Vac. This seemed odd since the desuperheater runs on 230Vac.

I talked with a Tech Rep from Trevor-Martin, the Manufacturer of the desuperheater. It seems that there were a few issues. It turns out that one of the sensors for the desuperheater was not mounted on a pipe. The sensor was lying on the bottom of the unit. It is possible that the sensor had vibrated off the pipe. There are three sensors in the desuperheater.

A white sensor which is for the anti-freeze function.

A blue sensor which shuts the pump off when the water temperature reaches 140 degrees Fahrenheit.

The red sensor does not allow the unit to turn on unless the gas in the line from the heat pump to the desuperheater is at least 125 degrees Fahrenheit.

The sensors are placed on the respective water/Freon pipes within the desuperheater. The sensor which was not attached to a pipe was the red sensor. When the red sensor is connected, one red wire is connected to one power wire coming in to the unit and the other is connected to a wire from the blue and white sensors. This sensor was removed so the power wire was connected to the wire nut containing the wires from the white sensor and the blue sensor. This will turn on the pump when the heat pump runs regardless of the gas temperature.

Once this was completed, the unit was tested and the run monitor on the desuperheater once again did not work. This then prompted me for the following test:

• If all the sensors were connected properly and the desuperheater pump still did not operate, it would indicate that the unit did not get the power required from the heat pump. This would verify the ac voltage readings from the volt meter.
• To test this, a pair of wires was connected directly from a 230Vac source to the desuperheater. The heat pump was activated and the unit worked!

The next step is to talk to my installer to see what can be done and/or talk with a Waterfurnace Rep. It seems that the terminals which the desuperheater is connected to in the heat pump would provide 230Vac according to the schematic. For some reason it doesn’t provide the needed power.

At least we are getting closer to resolving this monitoring issue. The next step is to get the run monitor for the auxiliary heat unit in the air handler working. This will be tackled in another post in this blog.

Yeah! The desuperheater run monitor now works…

Had to re-wire the power wires from T1 and T2 on the heat pump. T1 and T2 to CR2 black wire to the pump and the white pump wire. The power for the desuperheater is now sent to the desuperheater when the heat pump is running.

I had to talk with the manufacturer to get the proper wiring for the desuperheater.

I called my installer. He is going to check it out. I should hear back from him today. I am anxious to get this issue resolved and see the results on my live data monitoring page. I’ll update this post when I hear something

Well that didn’t happen. Glad I called the desuperheater manufacturer,