"Geothermal" Energy -- The Free Kind

#1

This is more of a general post and not specific questions about my pistons.

Here is my situation:

  1. Oldish home
  2. gas furnace/AC (located in basement) for first floor and basement
  3. heat pump (located in attic) for top floor.
  4. Both units controlled by Nest thermostats
  5. On very hot days (89 degrees+), the upstairs (especially the master bedroom) gets hot. The AC runs but cannot keep up.
  6. The floor plan is somewhat open and the AC from the top floor just runs down to the first floor.

This is what I have done so far.

  1. At 2:30 AM, I have webCore check the daily forecast. If the high temperature will be over 85, I start the basement unit fan. This brings cooler air from the basement up to the first floor.
  2. When the temperature drops below 85, I shut of the fan as the AC unit upstairs can keep up once the sun starts setting.
  3. I currently have the upstairs unit ā€œprecoolingā€ the upstairs to 70 at 4:30 AM and 69 at 5:30 AM to get ahead of the heat load that I know will come as the sun switches to that side of the house in the afternoon.

Some things that I have tossed around.

  1. Temperature sensor near the basement unit to that I can take advantage of any temperature differential from the basement to the first floor.
  2. Temperature sensor in the attic. I think that on sunny winter days, I may be able to capture some attic heat and move it into the house.
  3. A piston to switch from heat mode to cool mode based upon the temperature forecast for the day. No need to run the AC in the house on a cloudy day that is 72 in the morning if the temperature is dropping to 65 later that day.
  4. Eliminate the Nest schedule totally and just use Pistons to set the set points and mode.

Any thoughts on this subject? What have you done that has worked for you?

Iā€™m using the simple event logger with google sheets to see how successful my attempts will be.

#2

Another idea.

Door sensors on the upstairs bedroom doors to remind me to close them if they are open on hot days (or open them if closed on cold days).

#3

Be careful drawing air from your basement. The warm air that will be replacing the nice cool air has more moisture, so you might start getting condensation on your basement walls and floor. ā€¦and with moisture comes mold. Just be aware. Iā€™m in Michigan and that nice cool basement air does sound mighty tempting!

#4

I hadnā€™t considered this, but I have a dehumidifier running and draining to the sump.

Thanks for the reply!

#5

I am a huge fan of letting webCoRE be the brains and logicā€¦ Youā€™ll always get more control and options, and there is no limit to the complexities you can create. Normally, I only use the third party software if I cannot get webCoRE to do something. (which is quite rare, actually)

It sounds like you have mapped this out quite well. I think you are on the right track!

As far as heat goes, I have a certain room that used to get overly hot when compared to the other rooms in the house. I ended up buying a ā€˜Vornadoā€™ fan and installed it high up (since heat rises). This fan is not like a typical fan. It blows air up to 70 feet away in a tight tunnel-like movement. So I have it aimed to blow the hot air down & out into a colder room. My house feels much more balanced now.

Here is one model:

You may also be able to place the fan low aimed up and INTO the room to force colder air into the hot room as shown here:

temp
temp.jpg1221Ɨ1363 131 KB

Just keep in mind that this fan is designed to really MOVE air from one area to another. You wonā€™t feel a steady breeze in most areas of the room like normal fans, but as you walk in front of it, you will definitely feel the power of it. In general, you will not want to spend much time directly in itā€™s path, so plan accordingly. (My eyes actually dried out after 20 minutes, so I had to re-position the fan a bit)

This type of fan also works well if you place it in front of an AC vent to push the cold air where you want it.

Also note, this fan is not a smart device. I have mine plugged into a Smart Outlet so I can use webCoRE or Alexa to toggle it when needed.

IF [RoomA:Temp] is greater than ([RoomB:Temp] + 2)
Then turn on fan
#6

Here is a my temperature chart. Yellow is outside temp. Greens are upper level, browns are lower.

primlim%20HVAC%20control
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The first two days (orange circles), I hadnā€™t done much. Then I just started with changing my NEST schedule and turning on the lower level HVAC which essentially brings cooler air from the basement up to the first floor. This also results in lower temperature differential and the upstairs air doesnā€™t ā€œrunā€ to the first floor as much as you see on the third day (orange circle).

This eliminated the spikes of 77 and 76 degrees upstairs in the master bedroom.

By the fourth day (blue circle), I eliminated the NEST schedule and used WebCore to program the set points. I started at three hours before sunrise (fan running), then 2 (a pre-cooling temp), then 1 (a lower pre-cooling temp). This actually made the master a little chilly and I received a reprimand. :stuck_out_tongue: However, the first and second floor actually matched temperatures for most of the day.

By the 6th day, I had tweaked things a bit more with the pre-cooling temperatures and I was able to invert the temperatures (pink circles - cooler upstairs than down).

The purple arrows are spikes caused by late day sun striking the thermostat. One of these days, Iā€™ll move that thing (Iā€™ve been saying for years.)

I noticed that the systems did not need a full three hours to get to my ā€œpre-coolingā€ temps. So, Iā€™ve updated the times for those to operate. No need to get things cool too early. That is just a waste of energy. Tomorrow, I have the first pre-cool temp set for 80 minutes before sunrise, then 40 minutes and then sunrise.

Here is the current piston. More to comeā€¦

hvac%20piston
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#7

Beautiful analysis and tweaking! A visual graph with a few days of data is so helpful when making adjustments. Keep up the good work!