Jump to content

Dome thermometer off by 30-40F


Random Pointer
 Share

Recommended Posts

Before using Kamado Joe, I use Broil King Keg, and the dome thermometer is always about 20F higher than the grate level.

 

My KJ Classic II dome thermometer shows a lower temperature, when it shows 230F on the dome, it is around 250F on the grate. I found it strange. I thought it was because of the deflector radiating heat to the grate temperature sensor (Flame Boss).

 

I cooked pizzas today, I put the deflectors on the x ring, put the grate, and a pizza stone on the grate. The temperature difference is about 30F. I detached the sensor from the grate, and clip it to the dome thermometer sensor. KJ dome thermometer shows 30F lower than the digital thermometer. It varies between 30F to 40F.

 

I calibrated the thermometer using boiling water, I used both thermometer. The digital thermometer as reference, and adjusted KJ thermometer. They both showed 212F (or very close).

 

I am quite puzzled. Is the dome thermometer defective? I am considering replacing it with other thermometer, and see how it behaves. I can accept some variances, but 30-40F is too much.

Link to comment
Share on other sites

If I’m understanding your post, you should be fine now that you’ve calibrated your KJ thermometer. I haven’t had to do anything with mine yet, as reads the same as my digital, but from what I’ve read, it’s a good idea to test and recalibrate the KJ thermometer using the boiling water method every year.

Link to comment
Share on other sites

After it showed a lower temperature than the grate, I calibrated the thermometer. It was fine, so I thought it was because of the heat deflector radiating the heat.

 

Today, I was curious and clip the digital thermometer sensor on the KJ sensor probe. I was surprised to see the gap from another sensor just two inches away.

 

Link to comment
Share on other sites

6 minutes ago, John Setzler said:

you can calibrate the dome thermometer on your KJ.

I did. It is fine up to 212, but the higher the temp, the thermometer started to diverge. I will talk to KJ support to see what is going on.

Link to comment
Share on other sites

2 hours ago, Random Pointer said:

I did. It is fine up to 212, but the higher the temp, the thermometer started to diverge. I will talk to KJ support to see what is going on.

 

diverge from what?  If you are trying to make your KJ dome thermometer match a probe temp, GIVE UP NOW!  It's not gonna happen.  See this pinned post at the top of this forum section:

 

 

 

Link to comment
Share on other sites

On 7/27/2021 at 12:21 PM, John Setzler said:

diverge from what?  If you are trying to make your KJ dome thermometer match a probe temp, GIVE UP NOW!  It's not gonna happen.  See this pinned post at the top of this forum section:

 

I clip the probe thermometer to the dome thermometer. I know that the dome temp and the grate temp will be different, but I want to know if I can trust my dome thermometer. 

 

This picture shows how I attached the probe thermometer to the dome thermometer. 30F difference between these two probes is not right.

 

I replaced the KJ dome thermometer with a Tel True dome thermometer that I had laying around, and the difference is less than 5F. Much better.

 

image.thumb.png.454ef6dbc54f93819c3cbba42c527620.png

Link to comment
Share on other sites

6 hours ago, John Setzler said:

@Random Pointer you can trust your dome thermometer if it reads close to 212 in boiling water.

 

Did you solder that alligator clip on there?  That can damage these probes in multiple ways.  

 

No, the probe is slid into the alligator clip. It has a special round tube handler where I can push the probe in. 

 

Three different thermometers show similar temp, (Maverick, Flameboss, and Tel-True), and KJ is the outlier. Maverick and Flameboss probes are attached to the dome thermometer probe.

 

I retest the KJ thermometer with Maverick just now. I watched the pot starting to boil, KJ thermometer climbed in unison with Maverick. At boiling point, they are in agreement. Up to 212F, KJ thermometer is properly calibrated.

 

The same probes showed different temperatures on the dome when I cooked pizzas, 40F gap. 

Link to comment
Share on other sites

8 hours ago, Random Pointer said:

 

No, the probe is slid into the alligator clip. It has a special round tube handler where I can push the probe in. 

 

Three different thermometers show similar temp, (Maverick, Flameboss, and Tel-True), and KJ is the outlier. Maverick and Flameboss probes are attached to the dome thermometer probe.

 

I retest the KJ thermometer with Maverick just now. I watched the pot starting to boil, KJ thermometer climbed in unison with Maverick. At boiling point, they are in agreement. Up to 212F, KJ thermometer is properly calibrated.

 

The same probes showed different temperatures on the dome when I cooked pizzas, 40F gap. 

 

Believe it or not, that is normal. 

Link to comment
Share on other sites

I just accept the fact that the dome temp is going to somewhat lower than the grate temp. I know its about 20-30 degrees off and thats the way it is. On longer cooks it tends to even out

 

I dont stress about it if I want a super accurate grate reading then I will clip a probe to it

 

This isnt heart surgery

 

 

Link to comment
Share on other sites

10 hours ago, Buttburner said:

I just accept the fact that the dome temp is going to somewhat lower than the grate temp. I know its about 20-30 degrees off and thats the way it is. On longer cooks it tends to even out

 

I agree that the dome temp vs the grate temp will be different. I am not worry about it.

 

However, this is not about dome vs grate. This is dome vs dome.

 

10 hours ago, Buttburner said:

I dont stress about it if I want a super accurate grate reading then I will clip a probe to it

 

My original post is about digital thermometer probes (Maverick, FlameBoss) clipped at the dome thermometer probe. The tip of the probes were about two inches apart, and they were different about 30 to 40 F compared to the KJ dome thermometer probe. The higher the temp, the wider the gap. KJ thermometer always showed a lower temp.

 

I used a Tel-True BBQ thermometer (made for Kamado style cooker), clipped the digital thermometer probes the same way, and the difference was only about 5F. I think it is much more reasonable. I am sticking with that thermometer for now, and I will test the thermometer with another thermometer clipped in with my next few cooks.

Link to comment
Share on other sites

The dome thermometer is a bimetel coil devise that works by expanding and contracting with heat changes. If you calibrate it at 212 degrees it will be accurate at 212 if you calibrate it at 250 it will be accurate at 250. Clipping a thermal couple probe to the thermometer is a good idea. Maybe some one will make a thermal couple one to replace the coil one we now use.  

Link to comment
Share on other sites

On 8/3/2021 at 8:26 AM, len440 said:

The dome thermometer is a bimetel coil devise that works by expanding and contracting with heat changes. If you calibrate it at 212 degrees it will be accurate at 212 if you calibrate it at 250 it will be accurate at 250. Clipping a thermal couple probe to the thermometer is a good idea. Maybe some one will make a thermal couple one to replace the coil one we now use.  

 

Yep - something like this. Search for Hyperbbq AT-01

 

I don't see many/anyone actually selling it though.

 

 

 

Hyperbbq-at-01.jpg

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Loading...
 Share

×
×
  • Create New...