Starting an oven and have some Q's

[Cancruiser]

I have been reading this forum for a few weeks now and am starting my oven.

The outer dimensions are 4x4x7
The frame is 2" square tubing
Insulation will be 2" mineral wool
Outer covering is 22 gauge sheet metal
Inner covering is 18 gauge metal
Freezer latches to hold door shut

There will be a divider halfway up made up 2" tubing and insulated.
The plan is to be able to just run the top half of the oven except when larger parts need to be baked.

For the electrical, I am most likely getting the digital controller that so many here seem to be using. The TET612 seems like a good unit sold by coldfusionx on ebay.

Now here is where my questions come in. I was trying to determine if 4 1800w elements would suffice for this oven or would I have issues maintaining temperature stability. My main concern is that if I go up to 2500w elements I would have to much draw on my available power (available amps). I would most likely only be running 2 elements 75-80% of the time anyways.

What contactor would best work in this oven?

[hbracing]

I would use the smaller elements and set it up so that you could manually shut what you don't need when you are at half capacity. Use 1 contactor for each element and you will have the control you want. It will add a few more bucks but from what you discribed, sounds like a sweet set up, and is pretty much what I am building. Spend the few extra bucks and have the control you are after and you won't be sorry..................

[hbracing]

To answer the question, The contactors sizes are determined by the element sizes. Be sure your contactor is rated for the use, and a little more certainly will not hurt...................

[mbeaver]

Maybe if you could get your hands on MIL-H-6875 this may provide you with some guide lines. It's a good base specification which I have used in setting up other heat treating shops. Michael

[gourdhedd]

Originally Posted by Cancruiser

Now here is where my questions come in. I was trying to determine if 4 1800w elements would suffice for this oven or would I have issues maintaining temperature stability. My main concern is that if I go up to 2500w elements I would have to much draw on my available power (available amps). I would most likely only be running 2 elements 75-80% of the time anyways.

What contactor would best work in this oven?

The contactor you need is the one which has enough capacity to handle all of your elements ON at one time. Which brings us back to your first question.

Your oven volume is 112CF. Using the 1800 watt elements, you'll have around 65watts/CF. My oven heats up very quickly (7-8 minutes) with around 330 watts/CF, so I think that yours will take a little longer to heat up, hard to say just how long. I suspect my oven is overpowered a bit, also. Using 4ea 1800watt elements, your current draw on a 220v service will be about 33amps or so. You'll need a contactor with a 40amp resistive rating.

If you want to disable two of your elements, you may want to consider having two of the elements fed by a simple plug and outlet. Don't want those elements hot, unplug them.

[chromo]

If the oven is temp controlled does it matter rather some or all the elments are on? Provided you have the power to run them all at once.

I mean 500F is 500F right, rather fast with 4 elements or twice as long with only 2 elements, it's still the same power used to heat and hold the oven at 500F.
Or am I missing something?

New to this and going to try building my own oven soon. My plans are to use parts from junk house stoves, Electric ranges are trashed all the time while still working, I can get them at scrap yards for $10 or less. I would think all theparts are there, I just have to install them into a new cabnit and wire them up.

[JTW37]

I built my first oven and have been using it for a few weeks now. I have a wiring diagram posted with photo's of my oven build. Now I wish i would have used heavier gage steel for the walls, but it works fine, it just makes heating groans Mine is 28 ga. (should have used at least 20) 3x3x6 and is pretty much a good size. I am currently building one half the size, 3x3x3, of the big one. Most of the parts I'm coating are automotive related. Follow the link for a look if you want.
http://s80.photobucket.com/albums/j1...20Coat%20Oven/

[donafams]

your walls seem thin, not the 30ga sheet metal but the wall itself, and where is the insulation?