temperature measure of storage tanks

[zadwit]

What type of temperature measurement device can I use to measure the water temp of my two propane storage tanks. I have a small indoor outdoor digital thermometer but the lead is only 4 feet long so it has to remain by the tanks. I need something with leads that are 60 feet long . My tanks are in a shed outside, so to measure the temp, I have to go outside, around the building and into the storage tank room and look at the digital thermometer. If I could locate some kind of digital thermometer with a 50 or 60 foot lead that will work on the temp range of 40(f) to 200(f) that would be great........

Thanks in advance

 

[Hansson]

I use a wireless digital roast termometer.
(broken link removed to http://www.clasohlson.se/Archive/Images/Products/Hi/346723_X_2007-06-29_102320_460.jpg)

do not cost much

 

[Kipstr]

Go and check this out http://www.accentshopping.com/product.asp/P_ID/149655 Just add wire

 

[Nofossil]

Ditto on the wireless barbecue thermometer. I've seen them used to good advantage. Home Despot sells them, among others. You can also splice in extensions to standard (inexpensive) indoor/outdoor thermometer leads if you're OK with soldering little bitty wires. Can't do that with thermocouples, but all the indoor/outdoor units I've seen use thermistors and an extra 60' would be no problem.

 

[deerefanatic]

I'd go for thermocouples and just order them with 60' leads..... Ok, I'm an overkill lover............ I admit it.

Actually, those Wireless BBQ devices look pretty neat.....

 

[VtRv]

Are the probes going inside the tank or do you attach them to the exterior of the tank. I hope this isn't a silly question but I'm in the process of setting up my storage using a 500 gallon LP tank and need to figure out how I'm going to measure the water temprature. Whats the recomended locations for temprature readings? I was thinking right at the to and one near the bottom.

 

[Nofossil]

Are the probes going inside the tank or do you attach them to the exterior of the tank. I hope this isn't a silly question but I'm in the process of setting up my storage using a 500 gallon LP tank and need to figure out how I'm going to measure the water temprature. Whats the recomended locations for temprature readings? I was thinking right at the to and one near the bottom.

There are some compromises involved. The exterior of the tank is OK, as long as the tank is really well insulated. Any exterior temperature will be lower than the average temperature of a slice across the tank at that level.

Ideal would be a vertical thinwall well about 1/3 of the way in from the edge / end, with sensors every few inches.

However, perfection is not necessary. There is only one critical control decision that depends on tank temperature: "Is the tank hot enough to provide usable heat right this minute?"

A second slightly less critical question that depends on tank temperature is "How full is my tank as a percentage of maximum capacity?"

Neither question requires a lot of precision, and you can adjust your interpretation of the measured temperatures based on experience. The answer to the first question is based on the temperature at the top of the tank - easy to measure fairly accurately.

The second question feeds into deciding if you should build a fire, or how much more wood you should add to an existing fire. In order to answer it, you need to know how much stratification you have and where the thermocline is. This requires at least another couple of sensors at different heights.

 

[ManiacPD]

I use one of these and it works great.

http://www.partshelf.com/maet73.html

Paul

 

[WoodNotOil]

Are people using meat thermometers putting them in the water directly or are they in a dry well of some sort?

 

[ManiacPD]

Mine are attached to my send and return (hot & cold) lines with pipe clamps and then I put pipe insulation over it. The hot probe is within 2-3 degrees of the T&P;gauge on the boiler.

Paul

 

[zadwit]

I currently have my temp probe taped to the top of the tank and the tanks are well insulated. I'll try the wireless digital temp guage if I can find one here in Fairbanks...or else I'll order one.
My EKO-60 and 1000 gallons of insulated storage seems to be working pretty well. I feed the heated water thru a heat exchanger and then into my oil fired boiler so in order to use the heat from storage, I must have a zone valve open and a circ pump running. Not the best setup, but as long as I keep the tanks above 170(f), my oil boiler never runs. The circ pumps go and heat the house and shop fine.
Next is to install the 45 superstor DWH I bought a few weekends ago.
I't early winter yet here in the interior of Alaska, but it was -7 last night, about 11 hours of dayslight, highs in the 20's during the day, but the cold wx is around the corner.
Thanks to everyone for ideas and advice. I could not have assembled this project without the help and insight from the group.!
Thanks again, Mark

 

[chuck172]

An eye opener:
With a temp. sensor located about 5" from the top of my 500 gallon storage tank, I would heat my storage up to lets say 190*
It would hold that temperature for a while telling me my insulation is sufficient.
This year I added another temp. probe down about 4" off the bottom. Both probes are immersed.
The bottom temp would rise to the top temperature. The entire storage tank would be at about my target temp. (190*)
Now, the bottom temp would begin to cool much more rapidly than the top. After about 12 hrs., I would have about a 10 or 15 degree difference.
The top temperature would hold, dropping only a few degrees.
After a day or two, I would have a 25* difference in the stratification.

 

[in hot water]

sensors do fail from time to time.

Put a copper well onto the pipe, or into the tank is even better, pinch the end closed, then insulate it. I squirt some heat transfer paste into them also. Now you have a way to install, remove or replace the sensor if need be. Put a couple wells in every location, make them long enough to reach outside your insulation jacket. This is the bottom of my 500 gallon tank.

On top I had an extra connection so I used a well that goes down into the fluid. My control has 6mm sensors, so 3 will fit inside a 1/2" copper well.

When the pump into the tank is running the tank temperature will be fairly consistent from top to bottom. When the pump is off the warmer temperature will rise.

Vertical tanks will stratify more, up to 40f depending on how tall.

I like those Azel dual temperature gauges also. They record high and low temperatures which is helpful to see what goes on when you aren't watching

hr

 

[chuck172]

That's exactly what I do. I have 3/8 copper tubing pinched to be used as a well. That goes to the bottom. I have another short one near the top. I use the conductive paste. I guess I can pull the long probe to any height and take readings.
This stratification is very interesting.
The water in the tank cools from the bottom to the top. Much more quickly than I first thought with the one high probe.

 

[Nofossil]

An eye opener:
With a temp. sensor located about 5" from the top of my 500 gallon storage tank, I would heat my storage up to lets say 190*
It would hold that temperature for a while telling me my insulation is sufficient.
This year I added another temp. probe down about 4" off the bottom. Both probes are immersed.
The bottom temp would rise to the top temperature. The entire storage tank would be at about my target temp. (190*)
Now, the bottom temp would begin to cool much more rapidly than the top. After about 12 hrs., I would have about a 10 or 15 degree difference.
The top temperature would hold, dropping only a few degrees.
After a day or two, I would have a 25* difference in the stratification.

What I suspect is happening is this:

You get your whole tank up to temp - excellent. It sits for a while, and heat is lost out the sides. As that happens, the layer of water against the sides is cooled and slowly sinks. By the time it gets to the bottom, it's a fair bit cooler that it was. This cooler water pools at the bottom of the tank, creating the stratification that you're seeing.

Better insulation will reduce the rate at which this happens, but it will always happen to some degree. Note that this stratification is a GOOD thing. The water at the top is still 190 degrees, and ready to provide heat. If you draw water from the bottom to add heat, you're drawing water that's cool enough to provide efficient heat transfer.

All good - this is the way it should work.

 

[DaveBP]

nofossil

What I suspect is happening is this:

You get your whole tank up to temp - excellent. It sits for a while, and heat is lost out the sides. As that happens, the layer of water against the sides is cooled and slowly sinks. By the time it gets to the bottom, it’s a fair bit cooler that it was. This cooler water pools at the bottom of the tank, creating the stratification that you’re seeing.

Better insulation will reduce the rate at which this happens, but it will always happen to some degree. Note that this stratification is a GOOD thing. The water at the top is still 190 degrees, and ready to provide heat. If you draw water from the bottom to add heat, you’re drawing water that’s cool enough to provide efficient heat transfer.

All good - this is the way it should work.

Well put and in a very concise nutshell.

 

[zadwit]

I've had my system up and running for a year now and it works great. Even at -50(f). I can go about 3 days between firings at -40 however I feel better if the storage tanks internal temp is higher than 180. Also I install a superstor 45 and pull hot water from the tanks to heat the superstor45. In the summer, I fire the boiler about every 5 days and this provides all the hot water I need for laundry each day, 2 to 4 showers, dishwashing etc.....I could probably go a week but I would rather use wood to heat the water than oil. The one thing I need to do is install an electric heater in the tank room for when I go away in the winter for two weeks which happens a few times each winter. This is just to keep it all from freezing up.
In the Fairbanks area there is political talk fo outlawing wood burning outdoor boiler, mainly the types that smoks so much......My EKO-60 runs so clean that you can't tell when it is running. You have to sight a tree behind the chimney exhaust and then all you see is heat waves......

The roaster thermometer works well. It is wireless, purchased at Lowes I think or Home Depot, anyway the probe is taped to the top of the storage tank and the reciever is taped to the EKO-60 so I can see what the tank temp is without having to go out into the cold and into the tank room...
the one thing I may work on is more insulation for the tanks.....I currently have two layers of 2" foam and I know I need more insulation. I have taped all the seams
up but still loose heat into the room. All in all a very good setup....

 

[jebatty]

I use a 2 input, K-type thermocouple, digital thermometer; one input on the top of the tank, and one on the bottom. It can read either F or C, and also provides a T1-T2 output to see the differential. These are quite inexpensive on eBay. Search "digital thermometer" and you will find these and many others. Also search on K-type thermocouple, and you will find thermocouples with the proper plugs to fit the thermometer with leads from 3' and on up, although a wireless roast thermometer likely is better for longer distances and/or an outdoor tank. My tank is inside. Cost is around $35 incl s/h.

If you do this specific search on eBay you will quickly find an example: "Scientific Digital Thermometer"