Question on long distance soil temp testing

tcmtech said:

Sounds like you're in the same boat as me. I to have a large commercial application heat pump unit I picked up cheap years ago and my own excavator equipment as well.

The only downside here is not needing high powered air conditioning given the system I have could easily cool two large houses plus my 32' x 64' shop and my 14' x 20' workshed without breaking a sweat.
Heating wise where I would need it it would have a hard time heating one house. unless I added huge solar thermal collector systems to heat load my ground loops all summer to get enough energy stored to run with any efficiency in the winter.
But for that the numbers even at the full on DIY level just don't add up in my favor being I have near unlimited and free fuel for heating at my disposal through collecting and burning used oil or wood which I have been doing for the last ~15 years now.

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Curious as I have not checked geo data in your area but can you not just go deeper for a good geo loop? What is the ground water temp on average?
Also, IIRC, the wind blows there? I guess if you have other heat sources, wind might be too costly but that can work well to simply dump all wind genny heat to a resistive heater for radiant heating.

The reason I am doing radiant tubes in the whole shop is I then have a LOT of options. I like automation in which waste oil is easily automated. Wood can work too but not set and forget. In any case, I plan to use a water/water exchanger to eliminate any contamination concerns. The way things are getting done, I should have lots of ways to tune the system and if the geo system runs as designed, I may run it more.
I also plan to cool the slab in summer too. I hate to use the term "radiant cooling" because we know that won't really work but I want to remove extra heat gained by the slab from surrounding hot soil. I have learned that the slab can get to 90*. Just getting that back closer to dew point should significantly reduce cooling loads.

Nigel Goodwin said:

How many sensors and readings are you talking about?.

As you're doing this totally from scratch, it's something you want to get right from the planning stage.

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Well, geo field lines would probably need to jog about 300ft. I would probably have 5-7 sensors out there. Indoors I will have another 10 sensors or so with short runs only.

I realize I may not find a module that can digest all this in one unit but maybe? Eventually I have will have to walk into some type of PLC type device to module a few things based on these thermal inputs but for now, I just need to see the data. Is there maybe a down and dirty way to simply use some USB converter so I can review the data via a laptop? Maybe not ideal though.

What I need to work towards is bring all this data into a PC for logging so I can log other variables such as indoor/outdoor temp, RH, etc.

Also, in looking at that sensor, I am not sure +/- .5C accuracy is acceptable. 1 F can make a difference for me in terms of BTU calculations. I might like to see a resolution to .1-.2F

Perhaps go for a Raspberry Pi as the data gathering/collating engine. A Pi has a lot more processing power than an Arduino. An Arduino may still be good for controlling each temperature sensor though.

Am I correct in thinking that a wireless link to each temperature sensor is not possible because the temperature sensors will be buried underground?

Just to support what TCM said: it is vital for this project's success to get the high-level system design sorted.

spec

well, again, my thought process was to simply install down tubes at each required probe site and then install a home run conduit out to that location as an "if needed" deal. If I can find a way to run wirelessly on the cheap and easy, great, but I might need to get power out there anway in which if I run the 1 wire systems, I could run a 3 wire cable for power out, and signal back in. There won't be any additional electric lines in that trench to cause issues but I did hear the part about stacking capacitance.

fastline said:

I could run a 3 wire cable for power out, and signal back in.

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Thanks for information FL.

By the way, you can run power and data down two wires; three wires are not necessarily required.

There are two basic typologies for this kind of system:

(1) Circle
(2) Star

Star would seem to be the optimum choice in this case.

Would it be practical to physically have one interface unit (IFU) having one input connector for each temperature sensor?

If so, what would the absolute maximum length of communications cable that would be required from any one individual temperature sensor and the IFU? UPDATE 2016_11_20 Whops. I see you have alresdy stated this = 300 feet.

spec

PS: what State are you at? If you put it next to 'Location' on your user page it will show in the box at the left of your posts.

fastline said:

Well, geo field lines would probably need to jog about 300ft. I would probably have 5-7 sensors out there. Indoors I will have another 10 sensors or so with short runs only.

I realize I may not find a module that can digest all this in one unit but maybe? Eventually I have will have to walk into some type of PLC type device to module a few things based on these thermal inputs but for now, I just need to see the data. Is there maybe a down and dirty way to simply use some USB converter so I can review the data via a laptop? Maybe not ideal though.

What I need to work towards is bring all this data into a PC for logging so I can log other variables such as indoor/outdoor temp, RH, etc.

Click to expand...

You could either run it all direct from a PC, or use a micro-controller to read the sensors, and transfer the data to a PC - it really makes little difference.

As you're only talking about less than 20 sensors it's fairly simple to do.

My current PC based wireless monitoring I'm playing with would easily do 20 'as it is', as it currently uses 1 byte ASCII codes to identify each sensor (I'm using A, B, C and D for four).

Or as already suggested, a PI would easily do it - or an Arduino, or PIC based board.

If you go the one wire route then make sure to identify each chips ID number before installation.

Mike.

Nigel Goodwin said:

You could either run it all direct from a PC, or use a micro-controller to read the sensors, and transfer the data to a PC - it really makes little difference.

As you're only talking about less than 20 sensors it's fairly simple to do.

My current PC based wireless monitoring I'm playing with would easily do 20 'as it is', as it currently uses 1 byte ASCII codes to identify each sensor (I'm using A, B, C and D for four).

Or as already suggested, a PI would easily do it - or an Arduino, or PIC based board.

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What software did you use, or was it GoodwinSoft?

spec

spec said:

What software did you use, or was it GoodwinSoft?

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A program I wrote using Lazarus - here's a screen sample from November, with three sensors.