Oven observation today.

So I have been using an apartment sized electric range oven in my shop for duties such as coatings. It's been a great tool! I love having burners and oven. But I was always a little suspicious of the temp accuracy. So today I drilled a hole in the door and placed a lead thermometer (also had my non trustworthy IR gun handy). Turned on and was surprised that temp seemed low, very low. It was cycling on and off at about 300°-325° While set to 400°. So I cranked it up and finally got 400° at setting of 525°. But then it started climbing. Eventually I had backed it down to 400° on the knob and had a stable 400° on the thermometer. So, what I learned from this is that just because the oven is cycling on and off doesn't mean that it is actually at the set temp. The oven needs to heat soak for about 30 minutes in my case.

My little convection toaster oven is the same and I learned by placing an oven thermometer in there which I still use to know when it reaches temp

If your oven takes 30 minutes to get to temperature, it sounds like there is something wrong with the oven

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Originally Posted by Grmps

If your oven takes 30 minutes to get to temperature, it sounds like there is something wrong with the oven

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Have you tested yours to see how long it actually takes to settle on set temp?

I have 2 countertop convection ovens and my home oven that come to temp in less than 10 min.

1 trick with coating in ovens is to cover the bottom with a heat retaining material (I use ceramic BBQ briquettes, others use firebrick or pieces of steel) this doesn't speed up innitial warm up time but it greatly increases recovery time after you open the door.
I use 2 of the hanging oven thermometers to initially set the oven to the right temperature 400* then I mark the dial on one and oven on the other (digital oven).

Due to the configuration, placement, and type of thermostat used in lower end ovens their temperature readings are all off and directly affected by the surrounding temperature. Many people have their ovens hooked up to a PID teperature controller.

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Originally Posted by Drew P

So, what I learned from this is that just because the oven is cycling on and off doesn't mean that it is actually at the set temp. The oven needs to heat soak for about 30 minutes in my case.

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That is consistent with almost every oven, learned that in some baking classes. If you really want to cook at the proper temp the preheat cycle is needed for at least 30 minutes. You can also put bricks or baking stones inside to soak up the heat and help maintain even temp during cooking. Convection ovens are typically 25f lower than what the dial says.

Cool. Yeah I figured it was common knowledge lol. But it was news to me. I like the heat retention stones idea. I had thought about placing a thick steel plate above the heat elements to block the IR off the hot element and even out the temps but haven't tried it yet.

All of this is why I wired mine with a PID
it doesn't have a fan so the wiring was simple
it is small enough not to need a fan
I can do about 200 bullets at a time which, at my age, is fine and dandy

Attachment 204567

"Nuff said!"

OS OK nailed it. A lead thermometer is used for LIQUID material. Buy a $5 over thermometer like this one. ^^^^^^^^^^^

You may be more familiar with this configuration like grandma used [hers wasn't made in China :)]

Taylor 3506 Oven Dial Thermometer Walmart #: 552230722 $2.34

At this price, I bought 2 to confirm they agreed with each other

http://i.imgur.com/v13pXhA.jpg

`Grmps...that's what I used for a long time but it gave up the ghost so Dragonheart turned me on to the other type.

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Originally Posted by Grmps

You may be more familiar with this configuration like grandma used [hers wasn't made in China :)]

Taylor 3506 Oven Dial Thermometer Walmart #: 552230722 $2.34

At this price, I bought 2 to confirm they agreed with each other

http://i.imgur.com/v13pXhA.jpg

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Ditto here. For the price as cheap as it is can't understand why more people don't follow suit. I mean we sink a lot of $$$$ into our craft ,but this simple cheap device has saved my bacon more than once. Lol - CASTER

I'm sure there's a lot of things at Walmart that I need to buy. Just don't know they are there!

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Originally Posted by OS OK

`Grmps...that's what I used for a long time but it gave up the ghost so Dragonheart turned me on to the other type.

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OVEN GUIDE THERMOMETER - Accurate from 100¼F to 550¼F. Easy to read zone guide references Hangs or stands. Contains non-toxic mercury free fluid. Large, easy-to-read face. Durable stainless steel. Dishwasher safe. NSF listed

Taylor 5921n Taylor Five Star Commercial Oven Guide Thermometer $10.50 definitely higher quality

Hard for my eyes to see through the glass:(

Yes, a PID temp controller is the way to go. I have a convection counter top oven with a fan and just wired the PID with a relay in place of the temp control and drilled a small hole through the side of the oven just above where the tray of bullets is an stuck a thermocouple sensor in there.
Works great. Maintains the temp with in 5 degrees or so as long as the door is kept shut.

lsippell PID's are great, I would recommend wiring the fan directly to a power source. With the PID frequently/rapidly flipping the heat on and off the fan will burn out before it's time and having the fan on full time keeps the air circulating and temperature even

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Originally Posted by Grmps

lsippell PID's are great, I would recommend wiring the fan directly to a power source. With the PID frequently/rapidly flipping the heat on and off the fan will burn out before it's time and having the fan on full time keeps the air circulating and temperature even

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The fan on mine is a separate circuit. Stays on constantly when the timer control is turned on. The timer control also turns on the PID. The way I wired it was to replace the temp controller with a solid state relay powering the heating element when told to by the PID.

I love these PID's. I use one to control my melting pot and another warming block of aluminum that I rest my molds on.