I Took the Plunge - New Oven

[34by151]

Are you saying that electric ovens are vented to outside as well?

Yes all ovens need to vent
The powder gives off a gas that needs to be removed
Not venting can lead to issues with the coating
Lots have a poor door seal which is enough of a vent
Gas ovens need a bgger vent but hey all need to vent

[adbuch]

Are you saying that electric ovens are vented to outside as well?

Yes all ovens need to vent
The powder gives off a gas that needs to be removed
Not venting can lead to issues with the coating
Lots have a poor door seal which is enough of a vent
Gas ovens need a bigger vent but they all need to vent

Thanks for that! I will check out the plans I was going to use for my oven build and see if the vent is included.
David

https://www.powdercoatguide.com/2014/09 ... BmS-OW6PxU

How to build a powder coating oven.jpg

[34by151]

From memory that same guy converted to gas not long after finishing the oven, though that first build is well published on the net

I think it was all detailed on the caswell forum
https://forum.caswellplating.com/forum/ ... -questions

or the powder by the pound forum
https://www.powdercoatingforum.net/forums

Most have a poor door seal (not air tight) that does the venting.
So for electric often no extra vent is needed.
Electric will need a fan to pull the hot air fromthe top and move it to the bottom
Gas does not need the fan as the gas burner is already doing that.
Gas oven will need a bigger vent to releve the positive pressure inside the oven.
For the seals use a high temp RTV sealant. Dont use a flame prrof sealant as they will harden and come off like chalk. You can see the RED rRTV in my oven pic

[34by151]

Not th one I wa slooking for but close
https://www.powdercoatingforum.net/foru ... oven-build

[Joe Jones]

Triple mast! I SALUTE you, sir! If I put a triple mast on my little Toyota, I think it might tip over if the weight was slightly off center.

I did ask the local forklift salesman if it was possible to add side shifting to the blades. He said, "Yes, for about 1/4 of what you paid for the forklift"

Joe


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[Joe Jones]

So ... as I understand it, the electric oven needs a vent simply because the air inside expands and the pressure needs to go somewhere. I think a simple 1" pipe or so would suffice. Or does it need to be a "stove pipe" ?? If it is just for the gasses that come off of the powder, I can't imagine that I need a 'YUGE escape route for the gasses and HEAT.

Joe

[rdj357]

As for heating in stages - the reason I want to do this is the same reason you have an accelerator on your car and not an on/off switch. I can use more BTU/h to get to temp and lower BTU/h to maintain so that the heat can be better controlled and not have to have as much temperature swing.

You have only one thermostat because that's how it is designed. Many of the systems I'm installing today have multi-stage thermostats or communicating thermostats that operate variable capacity equipment. It's just much more efficient and much, much more comfortable.

[rdj357]

I've been an HVAC/R contractor since 1996.

That is interesting!

Again, you probably have it "figured out" but even you have to RIG something that works.

.....
Honestly Robert, if YOU put a package together that works well, and doesn't end up looking like it was built by the Three Stooges with Lucy and Ethel supervising the project, I'd certainly be interested, depending on the total price, of course. You could either sell the PLANS with a detailed and sourced shopping list of parts, and some comprehensive HOW-TO assembly instructions (or a video?) OR you could sell the parts and ship them out at a modest profit, but that seems less logical, considering how easy it is to get most anything delivered to your door these days.

So much going on. so little time...

Joe

I think you hit the nail on the head with your closing line; I just don't have time to add that to my plate.

I'm not sure 'rig' is the right terminology when a professional uses available parts and pieces to build a system. I agree that there isn't much commercially available in a complete package to DIY an oven. Regardless of what you call it, so far - so good! I've been know to rig a thing or two in my day!

[34by151]

So ... as I understand it, the electric oven needs a vent simply because the air inside expands and the pressure needs to go somewhere. I think a simple 1" pipe or so would suffice. Or does it need to be a "stove pipe" ?? If it is just for the gasses that come off of the powder, I can't imagine that I need a 'YUGE escape route for the gasses and HEAT.

You may find the door seal vents enough on an electric oven but a 1in tube would be more then enough

[SegoMan DeSigns]

Triple mast! I SALUTE you, sir! If I put a triple mast on my little Toyota, I think it might tip over if the weight was slightly off center.

I did ask the local forklift salesman if it was possible to as side shifting to the blades. He said, "Yes, for about 1/4 of what you paid for the forklift"

Joe


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I hate welding overhead This trailer frame is over 32' long

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I built the truck bed as well

[34by151]

As for heating in stages - the reason I want to do this is the same reason you have an accelerator on your car and not an on/off switch. I can use more BTU/h to get to temp and lower BTU/h to maintain so that the heat can be better controlled and not have to have as much temperature swing.

For those reasearching a build or building an oven,

The thermostat is called a PID Controller (look up the differences)
2 stage heating can be done with abasic PID controller like a rex c-100
3 Stage or more needs PID with ramp/soak features or a multistage option. These are a lot more expensive than a basic pid and the programming is not somthing id recomend for your first pid controller.

If you have a low thermal mass inside the oven some form of variable heat source would be of benifit.
Much easier to increase the thermal mass
IE the thicker the steel the more stable the temp but a longer rise time

I have tought of linking the PID to the variable output but its not really needed and allways have a more pressing project to work on.
One day maybee

As for my oven once im up to temp (204 degC / 400F) the gas will pulse about every 10mins for 15-30 seconds. If I shutdown the heater (door shut) it will stil be well over 100C inside hours latter

[rdj357]

As for heating in stages - the reason I want to do this is the same reason you have an accelerator on your car and not an on/off switch. I can use more BTU/h to get to temp and lower BTU/h to maintain so that the heat can be better controlled and not have to have as much temperature swing.

For those reasearching a build or building an oven,

The thermostat is called a PID Controller (look up the differences)
2 stage heating can be done with abasic PID controller like a rex c-100
3 Stage or more needs PID with ramp/soak features or a multistage option. These are a lot more expensive than a basic pid and the programming is not somthing id recomend for your first pid controller.
….

For most of those building ovens here I’d agree 100%. My larger oven is right at 1100 cubic feet so I need 2 burners to satisfy the load and have a relatively short preheat time. No point in not staging them appropriately for me as once that thermal mass gets closer to temp and the speed of heat movement into them slows, there is no point in short-cycling ~450,000 Btu/H. I am very familiar with PID controllers and while you’re correct about the basic terminology don’t be too quick to dismiss the ‘thermostats’ used in home HVAC/R today. They operate with similar algorithms to control electronic expansion valves and variable capacity compressors, variable stage gas furnaces, and/or multi-stage equipment and often times do so with adaptive ‘smart’ recovery. These aren’t applicable to oven technology but they were the comparison made to which I was referring.

Hope that helps clarify my previous post and makes it clear that multi-stage PID controllers are likely not needed for these smaller ovens.

[Joe Jones]

A simple PLUG n' PLAY modular system needs to be developed. Like a loaf of bread, how many "slices" will your oven have? 12? The you need 6 burners and 6 controllers, at 2 per. You're going to expand your oven from 12 to 20 "slices?" You need four more burner and controller sets.

SIMPLE.

Joe

[Joe Jones]

I hate welding overhead This trailer frame is over 32' long

PA190010.JPG

PA080018.JPG

I built the truck bed as well

Me too!

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[Joe Jones]

So I need to know ..

It is my understanding that the controller I bought ONLY turns the elements ON and OFF. It does not regulate the amount of power going TO the elements. So couldn't I use the controller to trip relays that would then handle the power to SIX or EIGHT elements, rather than four?

The temperature swings are critical, I guess. Okay ... It would seem that ONE element should stay ON, while the other three are added according to temperature regulation. ON 1, or 1 & 2, or 1,2 & 3, or ALL ??? That would seem to offer four levels of heat application. But this controller apparently ONLY turns all four ON or OFF.

Another question ... if the elements are turned ON and OFF during the baking process, that means they can produce more heat than what is required to maintain temperature in a 4x4x6-ish oven. So WHY couldn't the oven be larger, which would only mean the burners are ON for a longer period of time to put more heat into the oven?

Inquiring minds want to know!

Joe



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[Joe Jones]

One things is for sure ...

You haven't known stress, until you've cut a truck in half that you still owe $24,000.00 on, in the HOPES that you can pull off the conversion you drew up on graph paper!

If they came to repossess it, I'd have to say, "The front half is here. The rear half is over there!"

Joe

49379701408_620deb78d6_c.jpg

[34by151]

So WHY couldn't the oven be larger, which would only mean the burners are ON for a longer period of time to put more heat into the oven?

Its not how hot it can get but how quick you can get there the is important
The faster the rise time the better.

For the rest of your quiestion do some reading on PID controllers. I can then answer any questions you may have.
Im guessing that will be a light bulb moment for you.

[Joe Jones]

"I know something you don't know" doesn't help me.

So if I use propane burners to get it to temperature, will the electric elements MAINTAIN the temperature despite the oven being potentially larger than the 150 watt per cubic foot calculation? Someone said it should be closer to 500 watts per cu. ft.

It will do me no good to "read up" on PID controllers. I am not interested in becoming a HVAC pro, and I probably would not retain the information anyway. Is it a big secret? Can this controller I bought trip relays that can handle MORE than four burners, or does it need to control the burners directly?

What if the entire floor was heavy gauge expanded metal, and beneath that, a bank of Bar-B-Que propane burners all turned on to get to temperature very quickly, then shut off to allow the electric elements to maintain the temperature? Or maybe (two or four) propane burners running the entire time during the baking process, with the electric burners only there to pick up the slack on the temperature, assuming the gas burners could not keep the oven at 400 degrees, or whatever the correct temperature would be?

There will be two fans circulating the hot air the entire time after all. One drawing front center air and running it down the left wall, and the other drawing rear center air and running it down the right wall. So I am not seeing the difficulty in maintaining an even temperature with four electric burners running off of this controller.

I just want this to be a clean installation. I do not want to monkey rig the thing with torpedo heaters, and duct tape and bailing wire!

Apparently an oven much larger than 3x3x5 cannot efficiently cook powder coat with four elements running at 50 AMPS and 12,000 Watts. It is AMAZING that we can cook a turkey with only one element!

Joe


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[Joe Jones]

do some reading on PID controllers.

Assuming I do not have the time to research God only knows how many books on the topic, can you be a bit more specific about where I might find the information?

Joe


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[adbuch]

Its not how hot it can get but how quick you can get there the is important
The faster the rise time the better.

For the rest of your quiestion do some reading on PID controllers. I can then answer any questions you may have.
Im guessing that will be a light bulb moment for you.

That is good advise. There is a great explanation as to how these work (linked to below).
David

https://www.omega.com/en-us/resources/h ... oller-work
https://www.omega.com/en-us/resources/pid-controllers

pid controllers.jpg

[Joe Jones]

Okay, so a PID controller doesn't just turn the burners on and off. It regulates the amperage or voltage to the burner(s), to slow the ability to produce heat as the desired temperature is reached. This is demonstrated by elevator cars that rapidly move from the first floor to the fifth floor, but slow their speed as they approach the floor for a smooth stop. I understand the concept. This answers the question about using a PID controller to flip a relay. I guess that would not work, because the controller is rated for a maximum of 12.000 watts of power. Thanks!

Joe

[34by151]

The PID connects to an SSR (sold state relay)
You can have either on/off output or PWM (pulse width mudulation) output
PWM is the same way a switch mode PSU operates

IF lets say you want 50% output the PWM output would turn the SSR on and off thousands of time a second 50%on/50%on
If you needed 25% output it would be 25%on/75%off and son on

Here is a rex c100 with probe and ssr
https://www.ebay.com.au/itm/31381292143 ... ctupt=true

This is how it is connected

PID.jpg

In a simple terms the PID has feedback where a thermostat does not. So the PID adjusts the heater output for more when you have a a large temp differenc and less when you are close.

PID_Control.gif

The temp graph shows how a pid "tunes in" the temp. The settings in the pid are how good this is achieved

This is what a themostat does

ezgif.com-gif-maker.jpg

[34by151]

Apparently an oven much larger than 3x3x5 cannot efficiently cook powder coat with four elements running at 50 AMPS and 12,000 Watts. It is AMAZING that we can cook a turkey with only one element!

If your cooking a turkey it does not matter how quick the oven (time to rise) gets to temp and it not important how stable that temp is
For powdercoat how quick you get to temp is very important as is keeping that stable

As I have said the powder will flow at 180C and you need to cook it at 200C
You need to get the parts from 180 to 200 quick or you will have lots of orrange peel and bad adheason

This means a much larger heat source than a cooking a roast dinner

When you get to 200 you need to maintain that for the cooking time.
This means cooking it a a stable temp for 12-20 mins
The cooking time varies and is listed for each powder you purchase but its usually 15min

Keeping the temp stable is why you need a pid

I cant make it more basic than that
How and what you use for your heat sorce is up to you. Make it as complex as you want with as many types as possible it wont change the basics
You need a big heat source to get to temp quickly and to keep that temp spot on

[adbuch]

Here is the manual.
https://www.mpja.com/download/rex-c100.pdf

[34by151]

Simple way to setup the PID

1. Set P=0, I=0 and D=0
2. Increase P until the output starts overshooting significantly.
3. Increase D until the overshoot is reduced to an acceptable level.
4. Increase I until the final error is equal to zero.