Temperatures lower than control set point.

[WeekendWarrior]

During my first smoke, I noticed my temps were running kind of low, I ended up cranking the temp to 250+ for the last 6 hours trying to get it up to 200.

I noticed how you auto tune your PID's, and wanted to try the same technique to see how my smoker was calibrated.

I got a 9x12 aluminum pan and filled it with 7 lbs. of river rock as I didn't have a brick or sand and figured it would work OK.

Foiled the bottom and smoker box as normal.

Placed 24 oz. of water in a disposable bread pan and placed it on the bottom.

Put a shelf on the top rack position and placed probe 2 there.

Put a shelf on the 2nd from top position and placed the rock pan and a probe on there.

Started it at 200 degrees, and started plotting once it topped out and the temp started to fall.

Plotted the temp every 5 minutes for 2 hours.

Max temp hit was 196, low was 165, average was about 183, 17 degrees below set temp.

This would seem kind of low considering the temp is set on 200.

Turned it off, and weighed the water, just to see how much was used, it was 22 of 24 ounces, so 2 ounces of water was used.


Next, I refilled the water to 24 ounces again, closed it up and turned temp to 225.

Waited until temps started to drop and started plotting again at 5 minute intervals.

After 2 hours, High temp was 219, low was 196, average was around 207, 18 degrees below set temp.

Again this seems kind of low.

Looks like it is running around 18 degrees below what the set temperature is.

Has anyone else plotted their temperatures without a PID?

Can the knob be moved and calibrated some how, or do I have a defective temp control unit?

Attached are the readings I plotted.

 

[DiggingDogFarm]

See my post here....
http://smokinitforums.com/index.php?topic=1832.msg10821#msg10821

 

[WeekendWarrior]

Nothing appears to be even close to the stock temperature sensor in the unit, so I don't think it would be that.

I suppose the stock sensor could be mis-calibrated.

I am just thinking that the dial isn't calibrated to the scale as it seems to be consistently 18 degrees on average below what the set temp is.

I can try it again using 250 and see if it even reaches 250.  I would guess it would run 225 to 245, and average around 232 degrees.

I did find a post on how to adjust the dial.

http://smokinitforums.com/index.php?topic=1219.msg5104#msg5104

Not sure I want to try that until I hear from support who I emailed about this just a bit ago.

 

[DivotMaker]

Hey Bruce,

First - what are you using to measure temperature, and where is the probe placed?  This can make a significant difference.

If you are confident that you are getting accurate box temps, then it's possible your dial is calibrated wrong.  Here's how to adjust the dial:

http://smokinitforums.com/index.php?topic=1219.0

I hate to ask this, but are you sure there's nothing covering the temp probe in the smoker (cardboard)?  We've seen this before.

 

[WeekendWarrior]

I have a dual probe maverick which I've calibrated to my accurite instant read thermometer, using both an ice bath and boil test.  1 probe is +1 degree off, 2nd probe is +2 degrees off.  They read higher than the accurate instant read pen.

I've tried several places to measure the temperature, 1 rack above, 1 rack below, and on the rack.

Built in probe seems to be OK.  Here's a couple of pics.

 

[DivotMaker]

Bruce, have you tried adjusting the dial? 

 

[DivotMaker]

One other thing, Bruce.  It sticks in my brain that you tested the temp at the vent hole with your instant read thermo during your cook, and it was reading correctly (or, as close as it will with the analog setup).  The air temp at the vent should be a pretty accurate picture of the box temp.  So, the low readings are centered around your Maverick.  You think it's possible your Maverick is off, and not the smoker?  Did I read it right about checking the temp at the vent?  Also, have you tried putting the Maverick box temp probe side-by-side with your instant read probe in the vent hole? 

 

[WeekendWarrior]

Well I did the knob adjustment and ran a 2 hour test at 200 degrees.

I placed probe 1 on the top shelf, the 7 lbs of rock on shelf 3, and moved the 2nd probe down to the 4th shelf, which is close to the built in probe.  Both probes  were placed dead center.

Numbers look much better now, maybe just a touch high, but much better than before.

Top shelf temp ranged from 187 to 217 for an average of 203.

4th shelf temp ranged from 185 to 234 for an average of 212.

 

[DivotMaker]

That's great, Bruce!