DIY Powder Coat Oven heating element too hot?

[hotrod56]

I got the idea from watching a Youtube video about taking on an old fridge and making a powder-coating oven (mistake). Got it all set up and upon testing (400 degrees), I see that the inside sheet metal is blue, well after cooling down. This usually means that the metal was too hot. Is this an issue and should I put another layer of sheet metal in there between the heating element and the floor of the oven? The oven heats up to 400 degrees in 15 minutes, dimensions: 34.5"x21.5"x14", the thermocouple is 3/4 up from the bottom, the inner tub is 19-20g sheet metal - bare metal - no paint or galvanizing, burner - 3200 watts, 220v, Rock wool - 3".

Thanks

PXL_20230114_235642498.jpg

[hotrod56]

This picture is of when it was cooled after the test. This is not hot.

[weldguy]

Wow, that did get hot! Ya I would put a thicker piece of steel under that element and space it off the floor a little if you can. Cool build though. Love being able to do my own powder coating!

[J-SIG]

This picture is of when it was cooled after the test. This is not hot.

I would move your thermocouple up higher, or at least see what your temp is a part height!
You may be getting hotter than 400 above before burner shuts off!
Also what do you have under the bottom? Can it handle the heat? If it can you shouldn't have a problem for quite a while!
I have a old 250 gallon fuel oil barrel we made into a oven that uses 2 oven burners and is insulated with 1" high-temp Insulation!
Takes about 30-45 minutes to get to temp but only about 1-2 to return to 400deg F after putting parts in!
I use a "Turkey pot" thermometer at the top to check temp, about 3.5' above burners!

Jeff

[hotrod56]

Rockwool is directly under the steel floor - it's touching the steel. I did check the temp around the heating element and it is in the 500s. I used double 14g wires (high temp) to each leg of the heating element (4 wires total). Could this be pumping too much-unrestricted electricity to the element? Is there a way to set the PID to slow everything down?

[Plasma-art]

The heating element is just a big resistor, it takes the amount of electricity its designed for at a certain voltage.
As long as you are using the voltage it is designed for you are fine on that part.

Adding some more distance between the element and the steel should give less direct heat transfer.

[J-SIG]

Rockwool is directly under the steel floor - it's touching the steel. I did check the temp around the heating element and it is in the 500s. I used double 14g wires (high temp) to each leg of the heating element (4 wires total). Could this be pumping too much-unrestricted electricity to the element? Is there a way to set the PID to slow everything down?

Sorry read the Rockwool part after I posted!
Haven't checked the temp close to burners and haven't checked into PID's yet!
I'm using regular burner controls for ovens 1 for each burner so I can have them
come on and off at the same temp!

Jeff

[acourtjester]

The PID is the way to go it does not just blast the amps to the element. It starts to pull back as the temp get near the set temp. I use 2 large stove top elements in mine. Its about the size of a 55 Gal drum inside.

powder coat oven (4).jpg

[hotrod56]

It is controlled by a PID. One thing I just found out is that the element is a broiler element. I just read somewhere that a broil element is hotter than a regular element. If this is true, go figure.