Keggle, Thermometer, Thermowell - Temperature Issue

[phillc]

I am getting my equipment together in eager anticipation of my first All Grain brew. Tonight, I filled my HLT with water, and fired up the propane burner. I watched with baited breath as the temperature on the thermometer rose at a rate I couldn't believe. Could it possible heat 65 degree water up at that pace, I thought? I was pretty excited! I let the thermometer rise to about 150 degrees, and then I cut the heat and proceeded to test the water temperature with another thermometer. 80 degrees. I then flowed some out of the ball valve at the bottom and tested that. 80 degrees.

What I see happening is that the actual metal surrounding the thermometer is heating up from the propane flame and giving a false reading. It is not in direct contact with any flame, but the heat that creeps over the side is heating it up. I am bummed. I really wanted my slick thermometers to give me a constant, accurate temperature reading from near the bottom of the vessel without having to climb up a ladder and test it all the time!

Has anyone else dealt with this issue?

Link to construction pictures:
Picasa Web Albums - Phill - Brewery

Pictures:

 

[phillc]

The other picture wouldn't show up in the initial post:

If it still doesn't show up, here is the plain English URL:
http://lh3.ggpht.com/phill.corm/SPS6wpOsaPI/AAAAAAAAAZM/L8FPKSMEiYU/s912/IMG_0061.JPG

 

[Fett327]

It seems like you put your thermometer right on top of a hole where the flames could get to it. Its plain as day in your picture. The small hole in the keg below your thermometer is where most of the heat is coming out of and giving you a false reading.

I would suggest that maybe you can switch your thermometer with your ball valve and that things would be ok. But then again by the end of your boil you could end up with a really hot ball valve.

 

[Funkenjaeger]

It seems like you put your thermometer right on top of a hole where the flames could get to it. Its plain as day in your picture. The small hole in the keg below your thermometer is where most of the heat is coming out of and giving you a false reading.

I would suggest that maybe you can switch your thermometer with your ball valve and that things would be ok. But then again by the end of your boil you could end up with a really hot ball valve.

Yeah... maybe you could get a piece of metal welded over that hole?

Regardless of the hole though, the side of the keggle is always going to end up a lot hotter than the water, because stainless is a bad heat conductor. I usually hose down the outside of my keggle after flameout to dump the heat, and even 1/3 of the way up the keggle walls it immediately steams off the water for quite a while of spraying.
One would hope that your thermometer is designed to determine the temperature at the tip of its probe, rather than at the point at which it's bolted in place... If that is not the case, then even if you cover that hole I bet it's still going to read high.

 

[Fett327]

BTW, after looking at the pictures in the link that you posted, i gotta say, that is an AWESOME setup that you and your buddies built. Looks really well put together too.

 

[jds]

You could try to plug the hole with something like a big wad of aluminum foil as a test. If the foil wad keeps your thermo temperature closer to the liquid temp, then you've found the problem, and can make a more permanent fix.

 

[sigmund]

It appears the thermowell is what is causing your problem. If your thermometer was in direct contact with the water, you'd probably be ok, but since you don't have that contact, your thermowell is getting hot and causing the false reading. You could switch locations as stated earlier or go with a direct contact thermometer and eliminate the thermowell.

 

[phillc]

Thank all of you for the quick replies. I have not responded because the email notification didn't fire...

It seems like you put your thermometer right on top of a hole where the flames could get to it. Its plain as day in your picture. The small hole in the keg below your thermometer is where most of the heat is coming out of and giving you a false reading.

I would suggest that maybe you can switch your thermometer with your ball valve and that things would be ok. But then again by the end of your boil you could end up with a really hot ball valve.

Good suggestion. I noticed that also when looking at the pictures, I will try to cover it up.

Yeah... maybe you could get a piece of metal welded over that hole?

Regardless of the hole though, the side of the keggle is always going to end up a lot hotter than the water, because stainless is a bad heat conductor. I usually hose down the outside of my keggle after flameout to dump the heat, and even 1/3 of the way up the keggle walls it immediately steams off the water for quite a while of spraying.
One would hope that your thermometer is designed to determine the temperature at the tip of its probe, rather than at the point at which it's bolted in place... If that is not the case, then even if you cover that hole I bet it's still going to read high.

These thermometers are designed to be used in large scale commercial boilers. I am not sure about how they are mounted in said boilers, however... I would hope that the temp would be taken further down the tip, but I am sure that there is some unavoidable cross over. I may research to see what a proper, intended installation for these thermometers looks like.

BTW, after looking at the pictures in the link that you posted, i gotta say, that is an AWESOME setup that you and your buddies built. Looks really well put together too.

Thank you very much!! I am very proud of it and absolutely can't wait to get the wrinkles ironed out and use it for the first time. I will be sure to post some pics here of the finalized rig, and of the first brew.

You could try to plug the hole with something like a big wad of aluminum foil as a test. If the foil wad keeps your thermo temperature closer to the liquid temp, then you've found the problem, and can make a more permanent fix.

That is a great idea. I am going over to my buddies house tomorrow to add one fitting and weld the MLT shelf, which is currently just tacked on. I will try that this week. I may just have my friend fill that hole while I am over there... I have the same setup on both the HLT and the boil kettle. I will post the results later in the week.

It appears the thermowell is what is causing your problem. If your thermometer was in direct contact with the water, you'd probably be ok, but since you don't have that contact, your thermowell is getting hot and causing the false reading. You could switch locations as stated earlier or go with a direct contact thermometer and eliminate the thermowell.

I agree. I actually considered filling the area inside the thermowell with water, and then inserting the thermometer into that. The water, instead of the air, may provide a better medium to transmit the temperature inside the keggle to the thermometer instead of the metal outside, or the super heated air inside. The air may be acting as an insulator. The disadvantage to this would be ease of use. Right now I can disconnect the thermometers in seconds to prevent damage during transport/cleaning.

 

[phillc]

Oh, I forgot to mention. If you noticed that plate chiller in my picture gallery:

It was an awesome deal. 30 plate 316 stainless, oxygen free furnace copper brazed. $101 shipped.

Link: DudaDiesel.com Biodiesel Supplies

I have not seen a better price anywhere...

 

[BrewBeemer]

phillc; great posting and something i'm going to look into, one of those plate chillers. Thanks for sharing.

Weld up those skirt holes and try adding a longer skirt material inside the keg skirt to see if this will help prevent any heat from getting below the kegs skirt then out and up the outside of your kegs skirt which is rather short to begin with. A quick fab from scrap tin material for a quick test may be worth a try and possible surprise.

 

[phillc]

I had my buddy TIG weld up the holes at the bottom of the keggles last night. I will probably be doing a test tomorrow evening and I will post the results in case anyone is curious.

I have my pyrex sight glass tubing ordered, which is the last component I need. Great price for custom lengths from a guy on eBay. Some cleanup, a test run with water, work out any leaks/issues I find and then I am ready to brew!

 

[BrewBeemer]

I would add a piece of 12" wide sheetmetal around the keggle base flange allowing a deeper pocket for the burner heat from spilling out and up the side of you keggle. A giant worm drive hose clamp or two connected together, a cheap test. Watch the flame tips of your burner in the dark or at night as you might be overpowering causing this outside keggle overheating problem. Might want to think about adding a motorized mixer to maintain a even HLT water temp.

 

[phillc]

I would add a piece of 12" wide sheetmetal around the keggle base flange allowing a deeper pocket for the burner heat from spilling out and up the side of you keggle. A giant worm drive hose clamp or two connected together, a cheap test. Watch the flame tips of your burner in the dark or at night as you might be overpowering causing this outside keggle overheating problem. Might want to think about adding a motorized mixer to maintain a even HLT water temp.

Good suggestions. Have any details/suggestions on a motorized mixer?

 

[phillc]

In case anyone is interested, the welded holes in the kegs solved the issue, and the first brew on Saturday went great.
I updated the pictures here:
Picasa Web Albums - Phill - Brewery
You can see the whole system in the pictures from brew day.