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Thread: PC Oven Build

  1. #1
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    Default PC Oven Build

    Got the oven finished a few weeks ago but haven't had a chance to do a writeup so here goes.

    I needed to build this oven with two space requirements in mind, first I needed to be able to fit the oven in a space in my garage near the available 50a 240v outlet.

    The household oven that I was using was sitting there for the time being. I initially planned on using the electronics from this oven to run the new oven but decided on going in a different direction. You can see the sheets of galv steel aside the oven in this pic. The other size requirement was the interior dimension. I wanted to be able to fit a normal M/C frame and/or have multiple shelves for batch work.

    I took the measurements and figured out what I would need for materials and ordered cut to size galv sheet (26ga) and bought some metal framing studs from Home Depot. I also picked up 2 bundles of rock wool insulation.

    Doing the pre-plan on the size and ordering the galv sheet was key in making the assembly as straightforward as possible. Basically you just cut the studs to the required length and pop rivet a frame or wall together and then skin it with the sheet. The framing studs fit into each other if you cut notches in the lip on the interior of the "C" at the corners and where a cross stud will be. I didn't take pictures of that step but I'm sure you can figure it out. Just be sure to use only one rivet at each joint on each side, that way you can wiggle the frame to be square with the sheet. After that it's just drill/rivet/drill/rivet......


    I did the floor with a hand riveter. If you want forearms like this:

    Build the whole thing with one of these, it makes interesting to say the least. After the first wall with the hand riveter I smartened up and went to HF and got one of these:

    Thing works tits and is a buttload easier. As with any HF tool it has slight drawbacks. The top mechanism needs to be lubricated with dry graphite lube. Definitely do not lube it with oil, WD-40, or KY-Jelly. The gripping mechanism creates little aluminum shards that will collect in the nose and cause jamming requiring disassembly and clearing the jam after every 3rd rivet.....not fun.

    The floor and the ceiling you insulate and close up both sides with the galv sheet. The Walls you skin only one side.


    The rock wool works awesome and is easy to cut/fit. Use a bread knife to cut it to shape and then fit it in the spaces. Be sure to fill the area inside the studs.

    I put casters on the floor to ease movement around. HF has cheap casters.

    After the floor and ceiling are finished put them aside and enjoy the happiness of drilling and riveting until you have nightmares about the task. It's mind-numbing work and is sure to drive you crazy around the 1000th rivet. I spaced the rivets @3-4 inches apart. The OCD side of me was going to measure every rivet placement to be uniform but OCD side and rational side got in a fight about it. Rational kicked OCD's ass and so it became a "that looks about right" exercise in drilling and riveting.

    Build the three walls and then fit them together.


    I held the walls up with clamps and magnets (science) after they're basically situated tap them around with a rubber mallet, your boot, dead cat, whatever until they are square. You can see how the exterior of the walls are open at the moment. That is so you can pop-rivet each wall to each other and to the floor and ceiling.

    You want to be generous with the rivets in this area for two reasons: One is that the studs are thin (@28ga) and two its an area for heat to escape.
    Once it's all riveted together it's pretty structurally sound.


    Now it's time to install all the electrical bits. As I mentioned earlier I was going to re-use the electronics from the household oven but after some research realized that for various reasons that wouldn't have been safe or efficient. Since this thing is going in my garage which is attached to the house I didn't think I'd earn any brownie points with the wife if I burned the house down.
    I opted to use a PID from Auberins. It has all kinds of fancy who-ha capabilities that I will probably never use. Basically it's a thermostat. You set a value (SV) and it reads a process value (PV) via a thermocouple wired to the inside of the oven. I has alarms, safeties, ramp/soak functions...bla..bla..bla. The instructions are written in geek-speak, so it took me about .234 seconds to just plug it in and figure it out on my own. You set the SV to the temp you want, the thermocouple informs the PID of the PV and it sends a 24v signal to a solid state relay (SSR) to either energize the heating elements or not.....simple.
    Here's what the control box looks like:

    On the top left is the PID, top right is the SSR, bottom right is a distribution block for trafficking the legs of the 220v feed to the PID, fan, lights, SSR and elements.


    One of the other things I chose to add was a circulation fan. This draws hot air from the top of the oven and circulates it to the bottom via a channel in the back wall of the oven. This keeps the temperature consistent top to bottom. The fan is a Dayco 76cfm high temp fan rated to @550deg. The interior of the oven is approximately 76sqft so it should recirc the entire capacity 1/min.

    The lights are held in ceramic household fixtures mounted to 4x4 electrical boxes, normal 40w appliance bulbs shine the light.

    The elements are 3400w GE oven elements, also mounted in 4x4 boxes. All the wiring from the inside boxes to the outside boxes is high temperature 18ga wiring, exactly like a household oven.

    Once outside the oven the wiring can be normal 12ga THHN protected by 1/2"EMT.


    Quote Originally Posted by JHawley View Post
    everybody wants to be black till the cops show up.

  2. #2
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    Insanity! Looks awesome!

  3. #3
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    Cooking for Thanksgiving just got easier

  4. #4
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    Obviously I skipped over the step of insulating the walls. Once the interior electrical components are in, you can lay the oven on it's sides and insulate and skin the exterior with the galv sheet.

    I used the window from the household oven for the door and mounted it sideways. You can see in this pic how the studs are fit together by cutting the little lip and bending it out of the way allowing one stud to nest into another. The door is also completely insulated.

    I used a continuous "piano" hinge for the door. Since the studs are so thin this is better than 2 or 3 regular door hinges (stronger). Laying this thing down and and standing it back up after it was basically complete was interesting, it's pretty heavy.

    So here's where it sits. It takes up about 4" more room than I had planned because of the junction boxes on each side and the fan motor sticking out of the back. The first run was interesting as it smoked like a motherfucker burning off all the mfg oils, fingerprints, etc. It makes all kinds of creepy noises when heating up. I was actually nervous that the window would explode due to the metal contracting/expanding with the heat but everything was fine. It gets to 420deg in just under 20 min and holds the heat well. The SSR is only triggered @every 4 minutes after reaching set temp....pretty efficient.

    The first thing I PC'd was a 4.5' pole to gauge the uniformity of the heat top to bottom. Happy to say that I observed the powder flow out consistently top to bottom with no hot spot issues. I was concerned that the elements may need a shield to protect against burning the powder in close(er) proximity to the elements. I have one shelf/hanging rack near the top of the oven as well as an eye bolt through the ceiling. Plan on adding additional shelves as needed. Since the first run I've done a handful of parts and it works as expected. The only thing I would have done differently is used thicker gauge sheet metal for the interior walls. The 26ga warps slightly but nothing serious.

    A note on doing it over.....No, I would never build another one. The work was tedious, killed my back, and took forever. My workbench in the garage is usually very organized.

    The amount of bullshit involved in building, the itching from the insulation, it was just a mess.....I haven't added up all the parts but my best estimate is loads better than the quote that I originally got for PC'ing all the parts I needed done on the interceptor.

    Quote Originally Posted by JHawley View Post
    everybody wants to be black till the cops show up.

  5. #5
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    Quote Originally Posted by yzedf View Post
    Cooking for Thanksgiving just got easier
    Yeah, or if I need to dispose of any.....bodies.....

    Quote Originally Posted by JHawley View Post
    everybody wants to be black till the cops show up.

  6. #6
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    Even though you say you wouldn't do it over again, you did some nice work there. Thanks for taking some pictures to show how much was involved. Nice setup on the temp controller too. Pretty similar to what we use on our heated platens for presses, only we run 3 phase SSR's and heater wiring.
    "Live your life one day at a time because
    tomorrow may never come."

  7. #7
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    Why did you put the RTV into the corners rather than on the mating surfaces? Also are you going to insulate the outside surface of your recirc channel?
    For the Kids...

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  8. #8
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    that's a damn nice job you did.
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  9. #9
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    Quote Originally Posted by mhenry600 View Post
    Even though you say you wouldn't do it over again, you did some nice work there. Thanks for taking some pictures to show how much was involved. Nice setup on the temp controller too. Pretty similar to what we use on our heated platens for presses, only we run 3 phase SSR's and heater wiring.
    Thanks, I did a ton of research before embarking on the build. I saw tons of guys that used gutted refrigerators, file cabinets, stuff like that. Most didn't look too safe and were ugly as hell to boot. I do have the option of adding another (up to 5) SSR's with that PID, but I don't see the need in heating the oven any faster.

    I actually read a bit where a guy built a diesel fired oven made from two shipping containers welded together! He can drive an entire truck inside!

    Quote Originally Posted by JHawley View Post
    everybody wants to be black till the cops show up.

  10. #10
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    Quote Originally Posted by SVnunook View Post
    Why did you put the RTV into the corners rather than on the mating surfaces? Also are you going to insulate the outside surface of your recirc channel?
    Lol. I forgot about that. It's not RTV, it's this caulk called "fire stop".....it didn't work as intended. I have some proper high temp stuff coming to replace that. I guess I could have put the caulk on the mating surfaces And yeah, the recirc channel gets @150 deg. while running. Not hot enough to be concerned about, but I plan on using the rest of the scrap that I have to add an insulating channel outside to protect that area/aid in some more heat retention.

    Quote Originally Posted by JHawley View Post
    everybody wants to be black till the cops show up.

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