New oven build.

[sinr98]

Hi guys I am in the process of gathering parts for a new oven I have planned on building. The oven will be 4' x 4' at the base and 8' tall. The frame will be out ouf metal studs, 2" mineral wool insulation, 20 gauge steel that has a high temp coating on them for ovens from a local high end residential oven company. and a fan set-up that I have custom made. As for the controls and heating I am up in the air. I have this controller it's a future design controls fdc-9300-512125. http://www.psi-qc.com/future/Docs/9300_broc.pdf . I might purchase this controller if the one i have won't work. Precision Digital Corporation - Trident Digital Panel Meter . I will run either 3 or 4 of these burners. 240 or 120 vac heating element 5500 watts steel calrod - eBay (item 120298490758 end time Sep-01-08 14:09:02 PDT). I am unsure of what contactors and necessary components are needed to run these with a 65 amp 220 volt main. Or for the matter of working at all. Any help you guys can give me would be greatly appreciated. I am not the most knowledgable electrician but I can wire.

[ed_denu]

Here are a couple of thoughts. First, (3) 5000 watt elements will pull 62.5 amps at 240 volts. A 65 amp breaker in my opinion would be insufficient. Normally you would look at no more than an 80% load, or 52 amp. (4) 5000 elements would surpass the capacity of a 65 amp breaker and circuit.

The controller you have based on the pdf information looks to be custom ordered. If I'm interpreting the model number correctly, it's input is 11-26 vac or vdc. This would be difficult to utilize if your input source is 120 or 240vac.

Your second choice for controllers appear to start at $200 and up. Why do you feel you need this high level of controller to control an oven? You might look at the sticky at the top of this page for Oven Building Material Links.

[sinr98]

I figured that the controller I have wouldn't work. I got that from a friend that has a bunch of misc stuff that he for from a manufacturing plant that closed. The other controller I was wondering about I can get for less than half that price you mentioned and thought that it would serve me well as in the future I would like to make a log sheet with times and temps controlled by my laptop for more precise pcing. I would log in times and temps per test pieces that turned out great, and the colors used and type of material etc. So then I would go into the laptop and pick which settings to use and let her bake. That is the reasoning for the other one. as for the burners I calculated that I would need 10500 watts for the oven with very good insulation. I found this by using a btu calc on some site. Do you think that two of those elements would be sufficient to heat and maintain a 4'x4'x8' internal dimension oven? Thanks for your help. Also my power source has twin 65 amp breakers, as I don't know if this makes a difference.

[ed_denu]

Is 10000 watts sufficient? I think it is a little on the light side for an oven this size. A lot depends on how quick you want the oven to heat. Also if you are in a cold weather climate in an unheated garage then winter start up times will be increased.

When you say you have twin 65 amp breakers I'm assuming that you have a double pole 65 amp, 240 volt circuit(Something like this: http://www.pacificcoastbreaker.com/products/4533 ). This could support safely around 12,500 watts(65 amps * .8 * 240 volts), so you might want to look at different elements to give you a little more heating capacity.

[sinr98]

Actually if I run two of the burners at 240vac I will have 11000 watts. There will be a recirculating fan to help the heat transfer through the oven also. The shop which my friend and I own has 6 different sections with adjustable heating in each location of the shop. The section of the pcing is well insulated and temp controlled.
Yes the breaker is a double pole like you described. Thanks a bunch on all of this btw.
The other ? I have is a contactor. Would I need a 2 pole with say 40amp 240vac contactor and run the elements in parrell. or a 120vac contactor? I know very little about contactors.

[ed_denu]

A 40 amp contactor would probably not be sufficient as 11000 watts would be near 46 amps. Some contactors however have a resistive load rating higher than their rated load. I would look for a 60 amp unit with a 120 vac coil to be safe.

Make sure that the controller you purchase will match the input voltage you have available (120vac) and have relay contact ratings sufficient to support the contactor coil requirements.

[sinr98]

ed_denu.
Thank you for all your help. You clairified most of my thoughts, and gave me a better understanding on where to go from here. I will be making a parts list and supply list soon and will share it with you to see if I still understand and have all the proper parts. I don't want to go boom when I hit the "switch".
BTW... Ed are you an electrical engineer?

[ed_denu]

Originally Posted by sinr98

ed_denu.

BTW... Ed are you an electrical engineer?

No, A lot of my knowledge came from working with EE's and union electricians in the design, build and ongoing maintenance of data centers for a large corporation. My initial entry into the job market was as a systems programmer and manager working with mainframe operating systems software. While I am basically retired now I occasionally still consult on data center construction and management projects.

[sinr98]

I know you know what you are talking about. That is why I asked if you were an electrical engineer. Actually I have my mech eng degree. I worked for Delphi as a test lab engineer and our electrical engineers could never explain the reasoning behind some of their controllers and electrical systems when I had to design tooling and parts around how they would control the tests. But they also never had the hands on experience like you do on the over all functioning and capabilities of the task. It's alot easier talking and working with someone who knows about the whole project than just one part. Thanks a bunch.