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paulstef

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Reply with quote  #1 
Anyone ever built a ground temeprature probe that measures temperatures down to 10feet?

I would like to measure in 1 foot steps.

I have a very long steel peep of about an inch diameter and I thought I could try to screw this into the ground. The lower end would need to be closed and formed like something screwlike.

The sensors would be inside the steel pipe. Don't know with what to fill the pipe, maybe just earth.

My main question is:

Steel is quite a good conductor of heat. So would the steel pipe represent the same temperature gradients as the surrounding earth? Or would the measurement be altered because the upper end of the pipe is subjected to the very cold outside temperature?

Garage_Hermit

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I am currently installing one of these - under a concrete slab.  It is two feet under the top of the slab and well below the frost line.

I have opted for a simple alcohol thermometer, fixed to a piece of electrical flex, inside a 40-mm-dia PVC pipe.
If U R considering using sensors, U want to make sure that the sensor will emit OK through that much earth - mine would *NOT* [frown]

Also, bear in mind the battery-changing process - it could get to be quite a pain...

I should tend to think that a steel pipe would be a bad idea - unless it were stainless, it would soon corrode.

Also, like U say, it would probably give incorrect readings anyhow, given the conduction effect.

Just curious why you would need such a fine temperature record ?
Once U R below the frost line, the earth temp should not vary much at all, so unless U R very rich [redface] it sounds like a bit of overkill, IMO !

G_H

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gbwillson

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Hi Paul-

Are you running an experiment where you need the detail of the temps at various depths? Once you are below the frost line, the soil normally remains in the 50 degree range. Below is frost line depth map.

Greg

http://sqfoot.com/pdf/US_Map_Frost_DepthAVG.pdf
paulstef

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I live in Canada, the frostline, when I look at maps from Canada it's like a huge range, something like 3 feet difference. could be 5 feet or 8. Then also, don't have different soils have different thermal conductivity and therefore the frostline would vary with different soils? 

It's out of curiosity AND for a possible future ground loop for a heatpump.

I did not think about using wireless sensor but wired. There are many sensor ICs which I could just seal in epoxy and then bury. The question is how to dig the hole. :-)
Garage_Hermit

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Neat, Paul !

I did not think of *wired*, for that matter [redface]

Ground-source heat pump, now that's the way to go !

G_H

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paulstef

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I finally found the time to do it, was easier than I thought. Improvements can certainly be made. Now we will seem to be getting the hottest winter ever here, middle of december and it's raining??

SolarInterested

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Thanks for posting your video. It would be interesting to see some of your data too.

Mike

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paulstef

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Reply with quote  #8 
The initial data is at the end of the video. It's been a month since I installed it and there hasn't been much change since then, it's way to warm for this time of the year.

I want to know what the frost line is here...

One thing I already noticed is when there is heavy rain with air temperatures just above the freezing point it seems to soak the ground down to 10ft because it got colder (about a degree) one to two days after the rain and then temperature went up again.
Garage_Hermit

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Great video, *very* smart thinking !

Congratulations !

G_H

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SolarInterested

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Quote:
Originally Posted by paulstef
The initial data is at the end of the video. It's been a month since I installed it and there hasn't been much change since then, it's way to warm for this time of the year.

Thanks I should have said future data. Don't complain about the warm winter, I'm at 53° latitude in Alberta and it's -10°C with snow.

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