1 wire temp sensor location on tanks

[taxidermist]

I am getting ready to put my sensors on my 2-500gal propane storage tanks. I know I want top middle and bottom sensors, do I need just 1 for each and if so where have you found the best spot to place them for the best results? I know some run 3 across the top 3 at the middle 1or 2 at the bottom. All I want to know is how much hot water do I have and if I am mixing to much.


Thank you,
Rob

 

[timberr]

I have only 2 sensors, one on the top and the second about 1/4 the way up from the bottom. Both sensors are are on the center line of the tank. I can see the stratification well; are more sensors better? Maybe or Maybe not, to much info will drive me crazy. I can see the difference in stratification when I change the speed on circs. so I am happy with my 2 sensors.

Good Luck.

 

[WoodNotOil]

It really depends on how much information you want. To know if you have stratification and if the charging pump should run, you really would only need two (one top and bottom). If you had more like 5 (top,top/mid,mid,bot/mid,bot), you could better tell where the thermocline was. This would show you the volume of water that is at the top temp and the volume of water that is at the bottom temp. This would help in measuring the actual amount of btus stored. The only purpose of this is really to measure the effectiveness of your setup. It can easily run without extra sensors...

 

[twofer]

Just to add my two bits.

I ran with three sensors on top, two in the middle, and three on the bottom. The sensors were then equally spaced along the length of the tank. The reasons I did this are: ensure that tank is equally charged along the length and redundancy in case a sensor fails.

On a side note, I found that my tank does charge uniformly even without any sort of diffusion.

 

[taxidermist]

Thanks guys! I will start with 3 on each tank, Top ,Middle and bottom. I will put one on the supply from boiler and one on the return from the tanks. Maybe one on hx in and hx out. I will start there. I have some plumbing changes to make this summer so I could add more then.


Rob

 

[DaveBP]

It really depends on how much information you want. To know if you have stratification and if the charging pump should run, you really would only need two (one top and bottom). If you had more like 5 (top,top/mid,mid,bot/mid,bot), you could better tell where the thermocline was. This would show you the volume of water that is at the top temp and the volume of water that is at the bottom temp. This would help in measuring the actual amount of btus stored. The only purpose of this is really to measure the effectiveness of your setup. It can easily run without extra sensors…

One advantage to knowing more accurately where the thermocline is in the tank-- with a little practice you could get a sense of how big an arm load(s) it will take to top off the tank without overshooting the mark and having the boiler idling for a long time with all the extra wood in the firebox, or falling short of available heat storage capacity and not keeping the house warm until you can fire the boiler again.

You could get carried away with this (and I expect I will) but with top and bottom only all you know is that the tank is or is not completely filled with hot water and what temperature that is. Sometimes inquiring minds just gotta know more.

 

[jebatty]

I would go with 3 or 4 sensors: top, middle and bottom; or top, down 1/3, down 2/3 and bottom. The 4 sensors give a real good indication of tank charge, as the middle 1/3 of a horizontal LP tank is the bulk of the water. My 1 wires are fixed to the outside of the tank with aluminum tape and covered with insulation.

 

[dogwood]

DaveBP, Good idea about correlating the sensor reading with how much wood to load. Inquiring minds want to know if you think three sensors would give you enough info to do that, or should I be ordering four? Jim, what sensor do you have taped on? I've got to order some stuff tomorrow and might as well get the sensors too. Should I be scraping the paint off the tank under the sensor to ger a better read or do you think this wouldn't matter?

Mike

 

[jebatty]

I have the DS18B20 sensors. I taped them firmly to the steel, did not scrape off the paint. My top of tank reading gets to within 1 degree of the sensor on the boiler supply line as it exits from the boiler, so I think taping covered with insulation is getting good thermal contact. Ordered them from a Thailand supplier mentioned in the Data Logger thread, $1.60/each. They arrived in less than a week. It was "fun" soldering them to Cat E cable, with shrink tube insulators, and then encasing the whole sensor and lead connections in shrink tubing.

 

[Gooserider]

One factor I would consider is how hard it will be to add more sensors at a later date if you decided you wanted more data... This would mostly be a function of what kind of insulation / enclosure you had around the tank, and how hard it would be to get through that...

IMHO one can't have to much data, and the DOW sensors are cheap - probably be easier to put on a bunch before insulating the tanks, and then just ignore a few if you found that it was giving you data overload... IMHO this is one of the great advantages of DOW sensors, since you can have an effectively unlimited number of sensors on a string, you aren't limited to a fixed number the way you are with some of the other options, so it is not a big deal to put in lots of sensors anyplace you think you MIGHT want them, and then ignore the ones that turn out not to be all that useful.

Gooserider

 

[DaveBP]

Anybody with sensors on the outside of their tank use heat sink paste or other goop (silicone caulk?) to get better/quicker response?

Even better, anybody do this with adjacent sensors, one gooped and one not gooped to compare?

 

[taxidermist]

Anybody with sensors on the outside of their tank use heat sink paste or other goop (silicone caulk?) to get better/quicker response?

Even better, anybody do this with adjacent sensors, one gooped and one not gooped to compare?

Dave,

I plan on using the paste when I install mine. I read on the data logger thread of them using heat sink paste and getting better readings.

Rob