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  • my oven build

    Hi everyone! I could use some advice to make sure I do this right the first time around. I have my oven 2/3 of the way built. Inside dimensions are about 4 Ft x 4-1/2 Ft x 7 Ft high. I plan to use 4 elements (probably 3000 watt). I have been looking at PIDs on ebay. This is where I could use advise. I need to stay on the lower end of the price scale. Also, do I just need to the PID, ssr, and thermocouple? (aside from aux switches,...) I've seen others post about heat sinks and contactors,... are these necessary for every setup or just with certain types of setups? I plan to run a 240v power line, something around a 30 Ft run for it. Thanks for your help!

  • #2
    Re: my oven build

    Welcome to the forum. IMO the one thing most people do wrong is to start with the easy part, that is building the physical oven enclosure without giving consideration to supplying the btu needs. While 12k watts 'may' be sufficient for this sized oven I believe it's going to be very slow to heat. That said if you continue with 12k watts you are going to need a 70 amp circuit so hopefully your electrical service panel can accommodate this. If not you will either need to have it upgraded, or look to a gas fired solution.

    Heatsinks are required for ssrs. I would look for (2) 40A models and place 2 elements on each. Contractors are electromechanical relays that do not require heatsinks but cannot switch as rapidly as ssr's and have a much shorter lifespan. Either will work, but you only need one or the other, not both.

    That sized oven will most probably benefit from some sort of heat circulation system to move the hot air back to the bottom.

    As for pid's I never recommend the cheap Asian offerings. Spend a few extra dollars and look for a used Watlow. The model 93's, Sd31's and the newer EZ-Zone controllers are all top of the line offerings that can often be found on ebay at reasonable prices.
    Last edited by ed_denu; 05-01-2014, 10:20 AM.

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    • #3
      Re: my oven build

      Thanks for the info. I am looking into better pids. Was gonna go the cheap route for now but I probably should just spend a little more now.
      So, you're suggesting one pid then 2 ssrs? Will the pid have 2 outputs or will I have to hook them both to 1 output?

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      • #4
        Re: my oven build

        One pid is all that's required. Most pid's can support multiple relays. The number of relays depends on their rated capacity versus your expected wattage load.

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        • #5
          Re: my oven build

          Alright. I bought the Auber SYL-2362 pid. I know some people don't like Auber but the budget isn't allowing for better right now. Easy upgrade down the road. I got an 80 amp sir, heat sink cooling fan,... I bought 4 new 3000 watt elements and some terminal strips and stuff. So, its all coming together. Waiting for some of these items to come in and wrapping up the construction of the box currently. Picked up some yellow r11 insulation and have 3/4 of it in place. How much heat transfer are most of you seeing through the walls?

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          • #6
            Re: my oven build

            I decided to go a little different route than most of the oven builds I have seen. I am mounting my heating elements on the floor of my oven. I'm building a frame so that I can roll my rack into the oven over the elements. The frame will be square tubing. This way too, my oven wont support any weight, just the steel frame that has legs going down to the concrete slab.
            Now, id like some help as far as my wiring goes. I bought a roll of this wire Supco Its rated at 36A. Is that each wire or the 3 together will carry 36A? I'm not the best electrician, I know the basics but obviously theres a lot I don't know.
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            This is what I've got. Will be (2) 120v lines coming in to the terminal strips and distributing to the elements from there. The elements are 3000 watts @240v. Will this be sufficient or will I need to drop two more 120v lines to the terminal strips to carry the load?

            Edit: so the pic isnt real clear. There is 1 ed and 1 black wire coming in from the right side of the box (coming from the control box). The red goes to one terminal strip. He black goes to the other terminal strip. One red and one black ( each 120v) goes to the two elements on the right. Another red and another black goes to the two elements on the left.
            Last edited by AlanMc; 05-19-2014, 10:32 PM.

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            • #7
              Re: my oven build

              I'm sorry to be the bearer of bad news here but from the photo and accompanying dialog I see several problems. The wire you've purchased isn't sufficiently temperature rated for a powder coat oven. It's only rated for 392F and most cure temps for powder are around 400°. The correct wire is MG type wire which is rated near 800°.

              Your elements should be mounted into junction boxes so all wiring and element terminals are protected and not exposed. Having them exposed would present a severe shock/electrocution safety hazard.

              It also appears from your photo that you have chosen to mount terminal strips under/within the oven floor. I've never seen a terminal strip that is rated above 30 amp nor have I seen any that are temp rated. These should be mounted in the control box, isolated from the oven heat source with standoffs.
              Last edited by ed_denu; 05-20-2014, 01:00 AM.

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              • #8
                Re: my oven build

                Are those terminal blocks & wiring under the floor? I'm no expert but from what I've learned from these forums so far is that all wiring inside the oven should be high-temp wiring. If you're thinking that by being under the elements it won't be affected remember that only hot air rises, but heat radiates in all directions. From what I can see I the picture it appears to be normal wiring & blocks just under the floor?

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                • #9
                  Re: my oven build

                  Thank you for the concerns. The element connections will not be left exposed. I'm obviously still working on things. These terminal strips are rated at 45 amps. I posted the picture of how the wires are run in hopes of getting some help on the electrical questions that I'm not quite sure of.

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                  • #10
                    Re: my oven build

                    You still have multiple problems here. The wiring you're using isn't rated for the temps a powder coat oven will see. That and your 4 elements are going to draw 50A and your terminal strips are only rated at 45A and are placed inside the oven walls. My recommendation before you go any further is to spend a little time viewing some of the oven builds documented here.

                    As for correcting these problems, get a small section of hi-temp MG wire. Run this wire from the elements to a junction box outside the oven walls. From that location back to your control box you can use the wire you have, or any multi-strand thhn type wire. Ditch these terminal strips that are rated at 45A and get a decent power block for wiring distribution. The power block will accept the larger gauge wire that will be required for your service feed.

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                    • #11
                      Re: my oven build

                      i can t really see on the picture and you don t mention but if you are using your 36 amp wire from control panel to your terminal strip and then supply the four elements from the strips that won t be good you will need larger wire from control box to your terminal strip
                      http://www.peintureenpoudrepb.com
                      http://www.polissagepb.com
                      http://www.powdercoatpb.com
                      baz

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