wattage requirements

[chicagorich]

Im building a 4x6x3 oven i have two 3100 watt elements will this be enough to get it to 400 or should i make it smaller?

[dagobert]

It all depends

That's kind of a loaded question. It also depends on the type and amount of insulation you use, as to how much heat you can contain and build up.

Mine, for comparison, is 3 ft by 3 ft by 8 ft deep, and has 4 3200W elements running on a 50A contacter, and the walls are made of 26 gauge sheel metal (HVAC ductwork) boxes containing 4 inches of Knauff 850 degree hi-temp insulation.

I've had it up to 520 F and it still had room to climb, and my IR thermometer read the outside skin temp at 72 degrees (in an unheated garage during a night in the 30s).

[bzer1]

At some point it should make it to 400. I wouldn't want to wait that long myself. My oven is 3ftX3ftX5ft, and I'm using 4 2500w elements. The problem you will face with your setup is that it will take a considerable amount of time for an oven of that size to reach the required cure ranges. It will probably cost alot more to heat and maintain temps. It's kind of like using a 4 cyl engine to move a pickup truck...It will do it but you have to keep it pinned the whole time. This will lead to higher power bills and shorter element life. If I were building your oven I would double what you have.

[chicagorich]

Im a rookie when it comes to electrical

Mine is being made of 20 gauge galvanized steel, and with 3 5/8 of knauff insulation. I will be using my 220v with a 60 breaker that powers my tig welder to provide the juice. I will be using Viper56s wiring set up. I would add third element but i dont know if i have enough juice to power it and i dont know how to wire in a contactor. Can you post a pick of your wiring diagram? if its straight forward i may add a third element. But if my two elements can get it up to temp i wont bother. What do you think?

[Noob2PC]

So on a 30 Amp service, what would the max #/Watt elements you would use? 4 smaller ones or 2 larger ones? I would think that 4 smaller ones located on the sides would be more efficient. also rather than using a slow fan to circulate the air, would some vents on the bottem and the top creates enough air flow? yes, about ready to build my own oven.

[dagobert]

If you've got 220 on a 60A breaker available, you've got enough to run 4 3200w elements. At 3200w x 4 = 12800w/240V = 53.33A for the elements, plus .7A for the fan (using the same one he did) + .3A for a 40w oven light = 54.33 total Amps draw, and a 10% safety margin with a 60A breaker. I say that because that's what I am using in mine. Be sure to use #6 wire as your main to handle the load to the contactor, and at least #10 from the contactor to the elements wired with two elements per side, and use the wiring scheme from the guy in Texas instead that uses a contactor as a guide. (I believe his website is at www.powdercoatoven4t.com ) I could even shoot a cameraphone picture or two of mine and walk you through the setup, if need be. You'd be FAR happier with the performance of the 4 elements in the bigger space, I'd imagine, although I did find a LOT of other great ideas from Striver's design, too. I kind of used the best of both worlds, and you can probably improve on mine.

[Noob2PC]

I guess I will check the breakers and see which one my Oven is on now. If it is a 30A, what is the Max I can use? 7200 watts total right. That would be umm....4x 1800 / 3x 2400 elements I plan on a 4'W x 4'D x 6'H oven.

[chicagorich]

thanks dagobert

Thanks alot for the help, I already have the temperture control that viper56 uses. Will i still be able to use this piece? i hope so because it cost me 200 dollars. Heres a pic of vipers setup, i want to set it up just like this but what i dont understand is where i would set up the contactor. If you know how to use microsoft paint can you draw on the pic where the contactor would go and how it would be wired up. I dont mean to bother you but i would really appreciate the help. If you can snap me some pics of yours that might help to. Thanks again

[dagobert]

From the looks of it, the contactor is being replaced by Viper's temp control switch, which I believe he once said was only rated to handle 30A. To make the question simple, you wouldn't be able to simply "add" the contactor into that set-up. Where that has a fused switch and a temp control unit, mine has a double-pole contactor that carries the 240 volts across it, and the off/on action is controlled by taking power off one leg (one side of the two hot wires coming into the contactor) and running it through a 110V light switch to a 110V oven thermostat to a transformer that steps it down to 24 volts, which then switches the low power part of the contactor off and on. Put simply, it's apples and oranges. The difference is, my set-up is made to take full advantage of the 60A available from the breaker, whereas with Viper's you might want to consider changing the breaker and plug(s) to a 30A set-up. in all fairness, Viper's design IS a good one, but it is also designed for the size of oven that he built. Just like mine wouldn't be the best for a walk-in oven, his may not be the most efficent for the size oven you are wanting to build. but if you've already got the money invested in his set-up, you might consider building the oven smaller to match his in cubic feet, and changing the breaker and plug to match what you will be needing. But that's your call, of course. I'm not responsible for what you choose to build or not; I'm just offering my experience from what worked for me.

[chicagorich]

thanks

since i have the parts and im not that good with electrical i think i will just make the oven smaller, im going to go to 3ft tall 3ft deep and 5 or 6ft long hopefully it will work well. Maybe next year i will sell the one i will have and build a bigger one. Thanks for the feed back

[tinbender722]

Chicagorich

Get contactors with 110v or 220v coil and let the temperature controller that you have control the power to the contactors. I'm not an electrician by trade, but I can probably try to draw you a sketch if you need it.

[chicagorich]

ok

sure ill take as much help and feedback as possible.

[Pearl-Jam]

A magnetic motor starter works just as well for what you guys are trying to do. I have a well over rated #3 electric motor starter that the 220v power goes to . The therm. is connected to the 110v side of the coil. As heat is needed by the therm. it tells the coil to flip the magnetic switch on that then powers the heating elements. A low amp timer is also attached to the 110v coil side of the starter.
When the oven hits its cure temp, I set the timer, then the timer kicks the power off to the coil so the therm. wont kick the oven on. The oven can be turned off and on by either the therm. or the timer this way.The therm. is one for a commercial oven I got for $ 34.00 on e-bay , brand new. It can go to 600 deg. The timer you can get at any good electrical store for $ 25.00 . If you want a fan, rip one out of a house forced air oil furnace ( used ). They usually have a longer shaft, are 110v and have a metal ( high heat ) squirrel cage. Take a look at the pics of my oven I put in the album. You can see the fan mounted high back top center of the wall. This is controlled by a 3 speed 110v house fan switch found at home depot.

Hope this helps,
Drew Young

[viper56]

chicagorich,


If you purchased the same temp. control that I did, it comes with a wiring diagram showing how to wire in a contactor if you are planning a larger draw than 30 amps.

Jim

[chicagorich]

oh yeah

Thanks viper i just looked at the directions and your right, awsome maybe i could build my larger oven now.