Locating an outside temperature probe

[Brian B-P]

Under a raised solar panel makes sense for all the reasons given, but the panel absorbs sunlight and turns most of it into heat, so I suspect that in sunny conditions it's warmer under there than in the surrounding air.

I don't think there's any location which is ideal for measurement accuracy and at the same time practical.

[Mike Lewis]

I ended up sitting the sensor on the platform that holds the propane tanks, in between them, as a test. In that spot the sensor is shielded from the sun and gets ventilation from beneath. It seems to be giving accurate readings, so I'll secure it in place with Velcro and wire. Thanks for the responses.

[padlin]

wouldn't the propane bottles retain the days heat?

[gbaglo]

One way to determine how full a propane tank is, is to pour boiling water over it. Beads of sweat will form on the tank where the now hot metal comes in contact with the cold propane inside, indicating the level of propane.

[Mike Lewis]

I have a propane tank cover, so the tanks shouldn't get hot from the sun. If propane is flowing at a good clip, like when the furnace is on, it should cool the tank in use. How much, I don't know. I think having the sensor in its current position is good enough for my purposes.

[LeonW]

We have the sensor zip-tied and Velcroed to the center post that holds the regulator in the propane storage area. The readings are reasonably consistent with what we measure in the tow vehicle and hear on the radio.

[Mike Lewis]

Originally Posted by padlin

wouldn't the propane bottles retain the days heat?

Now that I think about it, I see what you mean: not just sunlight hitting the tank, but the propane absorbing the ambient temperature during the day and re-radiating it at night. Well, at this point I'm just going to locate the sensor between the tanks and see what happens. It seems to work okay for others.

[gbaglo]

This is from Canadian propane site:

"The propane inside a container is in liquid form with a vapour space above the liquid. Propane turns to vapour (gas) when it is released from the container. Liquid propane can cause severe frostbite if it comes in contact with your skin or eyes. Keep your head away from the valves on your tank or cylinder. A sudden release of propane liquid/vapour from the pressure relief valve could result in serious injury".

If the liquid propane "warms" up too much some will be vented from the container.
Given that liquid propane can cause frostbite, I don't think it retains heat.

[Brian B-P]

Originally Posted by gbaglo

This is from Canadian propane site:

"The propane inside a container is in liquid form with a vapour space above the liquid. Propane turns to vapour (gas) when it is released from the container. Liquid propane can cause severe frostbite if it comes in contact with your skin or eyes. Keep your head away from the valves on your tank or cylinder. A sudden release of propane liquid/vapour from the pressure relief valve could result in serious injury".

As usual with safety warnings, there's lots of drama and not much information there. What they don't mention is that the reason for the chilling is that the liquid absorbs heat to become vapour. That's happening slowly in the tank as you use propane, so it chills the liquid and the tank. Wait a while after you stop withdrawing propane, and it warms up to the ambient conditions. Release it to the air in a big gush, and you get lots of cooling - keep your hand in that (because you're an idiot, perhaps) and you get frostbite.

Originally Posted by gbaglo

If the liquid propane "warms" up too much some will be vented from the container.

By "warm", we mean the 140 F (60 C) required to get the propane to the 250 psi relief pressure.

Originally Posted by gbaglo

Given that liquid propane can cause frostbite, I don't think it retains heat.

Sure it does. Add heat, it warms up. A full propane tank has the mass of the same tank half-full of water... which is a bunch of mass, so it takes time to cool down.

Remember, liquid propane doesn't cause frostbite - it's not any colder than the stuff around it. Converting it rapidly to vapour - which is not happening at all in the closed tank - is what makes stuff cold.

[gbaglo]

That's why we keep you around Brian.

[Eddys]

I've located ours under the front window rock guard about 4" down from the top, centered left to right. Attached by heavy duty Velcro - easy to remove for battery change. Stays shaded and out of the rain. Works for me...

[MyronL]

After reading these posts and last evenings' off the wall readings I moved my remote sensor from inside my box to between the tanks.

[Mike Lewis]

This morning was chilly, so I turned on the trailer's furnace and watched the outside thermometer, thinking the cooling propane tank might make the temperature go down. It didn't. I went outside and felt the tanks; the tank being used was perceptibly cooler than the other one, but just barely. There is about a one-inch air gap between the temperature sensor and each tank, so I guess that's enough to keep a cooling tank from affecting the thermometer. So I'll leave the sensor in its new location.