bill1
Master of the Pit
- Apr 25, 2015
- 1,889
- 872
couple more ideas Keith:
1. The short PitBoss controller probe sat in a bit of a recess so its tip was ~.25" inch from the wall. This taller one may have it's sensing tip too close to the back wall??? For the typical single-wall smoker, the wall is cooler than inside cooking air, because its cooled by room air on the outside. But for this double-wall design, it could be that the inside wall is hotter than the air inside...it is conductively connected to the fuel pot after all. So if you space up just the rear of the new sensor's mounting plate with a bike spoke or bobby pin it should then angle inwards at the top, away from the rear wall...does that give you a lower reading, thereby comparing better with your other (independent) probes? Of course be careful that sliding in a rack doesn't then damage the probe.
2. It's harder than it sounds to get a true pan of boiling 212F water. But even though it will be a little less, all the water an inch below the surface should be very equal in temp. It sounds easy to loosen the chamber's 2 mounting screws and pull out that probe by ~6". If you stick it, and all your reference probes, into a near boiling pan of water on the closest rack/grate, how close do they read?
3. Although it's not expecting too much of modern Chinese manufacturing methods to produce wound resistors at 1-2% accuracy (in this case within 20ohms of 1000ohms,) that doesn't mean you get 1-2% accuracy in temp with these RTDs. (Even if you use an "absolute" scale like Kelvins or Rankines.) Instead, the RTD is measuring temp by a small amount of resistance change with temperature, so I'm afraid 20F errors are not uncommon. A lot of temperature controllers let you correct for the fact that two different RTDs will measure the same temperature differently. You might want to ask RecTec if that isn't possible with yours? A lot of controllers have features that aren't really spelled out in the manual so don't expect the first person who answers the phone to know about these "hidden features". (Think of it like being the only person who knows to order Animal Style fries at In-N-Out Burger.) If not, at the price of these probes, you can afford to buy a few, and use the one that's the most accurate...a lot of electronics have this sort of variation and get sorted this very way so you pay a premium to get the "just right" one.
4. You sounded like you might have thought that the recent colder temps might be making your machine less temperature-stable and to have more inner spatial variation in temp. These double-wall units aren't usually too hot outside...you might want to try slipping a cardboard box over the thing so only the air entry at the bottom and the exhaust pipe at the top is exposed. Corrugated cardboard is a amazingly good thermal insulator and can really help with winter temps. If nothing else, it acts as a wind block, and cold gusts can cause hot and cold regions in a cooker you don't have in the summer. The factory box is probably too small (with the handles installed) but maybe a shortened hot water heater box?
1. The short PitBoss controller probe sat in a bit of a recess so its tip was ~.25" inch from the wall. This taller one may have it's sensing tip too close to the back wall??? For the typical single-wall smoker, the wall is cooler than inside cooking air, because its cooled by room air on the outside. But for this double-wall design, it could be that the inside wall is hotter than the air inside...it is conductively connected to the fuel pot after all. So if you space up just the rear of the new sensor's mounting plate with a bike spoke or bobby pin it should then angle inwards at the top, away from the rear wall...does that give you a lower reading, thereby comparing better with your other (independent) probes? Of course be careful that sliding in a rack doesn't then damage the probe.
2. It's harder than it sounds to get a true pan of boiling 212F water. But even though it will be a little less, all the water an inch below the surface should be very equal in temp. It sounds easy to loosen the chamber's 2 mounting screws and pull out that probe by ~6". If you stick it, and all your reference probes, into a near boiling pan of water on the closest rack/grate, how close do they read?
3. Although it's not expecting too much of modern Chinese manufacturing methods to produce wound resistors at 1-2% accuracy (in this case within 20ohms of 1000ohms,) that doesn't mean you get 1-2% accuracy in temp with these RTDs. (Even if you use an "absolute" scale like Kelvins or Rankines.) Instead, the RTD is measuring temp by a small amount of resistance change with temperature, so I'm afraid 20F errors are not uncommon. A lot of temperature controllers let you correct for the fact that two different RTDs will measure the same temperature differently. You might want to ask RecTec if that isn't possible with yours? A lot of controllers have features that aren't really spelled out in the manual so don't expect the first person who answers the phone to know about these "hidden features". (Think of it like being the only person who knows to order Animal Style fries at In-N-Out Burger.) If not, at the price of these probes, you can afford to buy a few, and use the one that's the most accurate...a lot of electronics have this sort of variation and get sorted this very way so you pay a premium to get the "just right" one.
4. You sounded like you might have thought that the recent colder temps might be making your machine less temperature-stable and to have more inner spatial variation in temp. These double-wall units aren't usually too hot outside...you might want to try slipping a cardboard box over the thing so only the air entry at the bottom and the exhaust pipe at the top is exposed. Corrugated cardboard is a amazingly good thermal insulator and can really help with winter temps. If nothing else, it acts as a wind block, and cold gusts can cause hot and cold regions in a cooker you don't have in the summer. The factory box is probably too small (with the handles installed) but maybe a shortened hot water heater box?
