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[RSI]

I am starting to experiment with different ways to try getting the reading as close as possible to water temp. (probes are 1/4" diameter)
I have always just used the foil tape with the peel off backing and put all the way around pipe and sensor and then insulate.

I started out yesterday but did not insulate any yet. I am using a short section of 1" copper pipe for all sensors. I did one with the usual foil tape. I had a roll of the thinner more plastic like foil tape (IPG 698) so I tried that to see how it would compare.
I didn't have any thermal paste to test but had some ox gard compound that supposedly will transfer heat somewhat so I tried that just attaching with electrical tape.

If you have any suggestions to try, I will try it out and see how it compares. I am going to keep making changes till I get bored of it or run out of ideas.

You can see how they compare here: www.my-thermometer.com

[wreckit87]

Are thermowells out of the question?

[RSI]

Not out of the question but not usually worth the trouble to put in. Also, not very easy to get them that mount in a 1" line and don't screw up the flow.

[RSI]

btw, I just put some insulation around the sensors so will see after a cycle how much it does. I only had an old ratty piece of pipe insulation handy so may not work the best. Will have to remember to bring some insulation home for this.

[Radio Tech1964]

What I did in the past and what I will do here as soon as I can save up for the equipment is mount the sensor directly to the PEX using a bit of white heat sink grease with wire ties then wrapped with foil tape and a piece of the insulation left over from some PAP underground. Seemed to work really well for me at the other house.I will update when I get this home in monitor mode 

[MD20/20]

Get something you can calibrate to correct and dispatch the difference betweeen probe reading and actual temp—-then you can be happy!

[RSI]

I can do that but I am looking for the best method since it is something that a lot of people here do with various different stuff.

I have always recommended the foil tape and insulation method which so far has been best. I am sure there are better ways though.

Also a simple calibration offset for the sensor does not work because when the temperature difference between the water in the pipe and the air temp increase so does the amount it is off. 

[heat550]

I have adjustable meat thermometers I calibrate with my spendy touch temp checker .. It runs pretty Dang close I have meat thermometer just taped to the copper like resting on copper and cheap black tape . And web cam pointed at it I can know temp anywhere there's internet. Had it for 3 years now works great .. slow internet can screw with me a bit .

[Fourced]

I used 1"x1/2x1" T's with a short well. The well just bearly protrudes into the flow path. I also have a 1/4" air fitting I drilled out to fit the probe(per a conversation with RSI) that would put the probe right in the water, but I have not tried that one yet.

[RSI]

That should react real fast if you can get the probe right into the water. I might eventually do something like that just so I have an exact correct reading to compare to. The problem is I only have about a 8" of copper in the house before it goes into the plate exchanger. If I put a tee in then there would not be much area left for sensors to get a comparison.
I do have some pex-al-pex before that but it is before the valve and don't really want to mess with that.

[RSI]

I tried wrapping foil tape around a sensor to build up the diameter and then shaved one side to the sensor would sit against the pipe. I was thinking that would get a better connection to the pipe but it doesn't work as well as just putting tape around the whole works. I also did another with just tape around it and they are usually tracking exactly. I have seen a few times that they are off by 0.1F but that may just be due to changing water temp as they are being read.

I still didn't get around to getting any thermal paste. I am kind of hoping it doesn't do much because it is easier to not deal with goop on the sensors. I will have to try it though.

Also, I have some copper foil tape on the way so that will be interesting to see how it compares to the aluminum tape.

[mlappin]

When attaching to steel or copper pipe I scuff it up good with a scotch brite pad, then place a little thermal paste on the tube, lay the sensor in it and wiggle around to get it on the pipe, then wrap with a minimum of two wraps of foil tape, Then insulate if desired. I’ve found no real use in that if at the back of the stove.

[atvalaska]

Supply house  and get u a well...plumb that is ...only way I was able to get good  ACRUATE  numbers  do it rite once imo ..I've been down all  them other roads to no where  ! 1/2 or 3/4   cheap to     https://www.supplyhouse.com/OMI-121371A-OMI-1-2-Aquastat-Well

[Fourced]

This is what I used. Installed in a 1" T.
https://rover.ebay.com/rover/0/0/0?mpre=https%3A%2F%2Fwww.ebay.com%2Fulk%2Fitm%2F223213701417

[greasemonkoid]

I turned down a well in the lathe, the threaded portion, and used a parting tool to cut a brass male/male uponor connector in halves, soldered the well into the half connector and used the typical rehau pipe and sleeve to connect it to the tee in the main line. It might have stood a chance at being accurate, but the well doesn't really protrude into the flow as I wanted to avoid that. I'm using it for differential temperature measuring only for a couple of unit heaters in series, it was a clean way to put a mechanical gauge in a pex line.