Yet another wiring question...

[97Dually]

Long time lurker, first post. Great board, I`ve read nearly the first 10 of 24 pages here, but please bear with me as I`m no electrician.

I have a household oven that I`m using right now, but, like everyone else I`ve learned its just not big enough. I acquired another household oven( freebie) last week. I was looking at doing the pregnant oven thing for awhile, but figured I have 2 working ovens, why not join the two together for the time being until I can afford to build one to my liking.

What I have done so far is disassemble the second oven; which was an oven unit only, no stove top, cut the back out of it, and joined the two together. I want to run the elements in both ovens to cut down on heat up time and hot/cold spots. Can I wire both elements to work off the existing controller of the first oven, or would I be better off going ahead and upgrading whats there with a PID such as this one http://cgi.ebay.com/ws/eBayISAPI.dll...tchlink:top:us which would allow me to use it later when I build my oven ? I have no money in either of these ovens, so spending a little isn`t out of the question, but if I do need to upgrade, I want to buy something that I will be able to use later. I think I want to upgrade anyway, but need to make sure what I but will work on both setups


Thanks in advance and sorry for the long post.

[ed_denu]

Without knowing the rated capacity of the oven controller it would be difficult to say if you could wire both elements together without a problem. It would depend on the wattage of the two elements and the amp capacity of the controller.

The pid you are looking at would work in any future oven you may build. You would also likely need a contactor or SSR to drive the elements.

[97Dually]

Thanks for the reply. After doing more research, I`m pretty sure the single controller won`t work. The second element is a 3200 watt unit, which should draw 13 amps, the controller is only rated for 21 amps and I`m 99% sure the first element will draw more than 7 amps.

So, guess I`ll be upgrading to a PID and SSR unit for this oven and that will allow me to use those new units when I get my bigger oven built.

Next question is gonna be this, I only have a 50 amp circuit available for my oven. If I plan to run 3 2500-3200 watt elements, what will be needed to wire this correctly so as not to overload the circuit ? Meaning, I see alot of ppl using 2 or 3 SSR`s to keep the current draw down ?

[ed_denu]

If you have a 50 amp circuit you could safely draw about 80% of that or 40 amps. (3) 3200 watt elements would draw about 40 amps at 240 volts which should be ok for your 50 amp circuit.

You could use multiple ssr's, or a single 50 or 75 amp ssr. Either would work if wired correctly.

Using multiple ssr's would only reduce the amp draw within the oven element wiring, it would not reduce the current draw on the circuit. Your 50 amp circuit should be using #6 wire, the same as you would need for your service cord to connect the oven to the receptacle.

[97Dually]

Ok, so if I`m following correctly, I can use this PID :
http://cgi.ebay.com/Dual-Digital-F-C...QQcmdZViewItem

...along with 2 of these :
http://cgi.ebay.com/New-25A-SSR-Sold...QQcmdZViewItem

and be safe to upgrade to an oven with up to 3 3200 watt elements ?

Along with the 6 ga wire, what else would I need ?

Thanks for the help ed

[ed_denu]

The pid is ok

(2) of the 25A ssr's you are looking at will not work with (3) 3200 watt elements. With two ssr's you would need to place 2 of the elements on one ssr. Each element draws around 13+ amps, so 2 would draw near 27 amps, to much for the 25A ssr. I would personally go with one ssr rated at a higher amp capacity.

Here is a list of things you may need depending on your design:

Hi-temp Fan
Heat sink for SSR
Screws
rivets
Hi-heat mortar or RTV sealant
Door rope seal
ceramic light socket
hi temp wire(for wiring to elements)
on/off switches(for lights, controller, fan)
terminal block(to keep wiring orderly)
wire for controller(gauge dependent on capacity)
plug & receptacle
Service cable
vent pipe
Conduit/Electrical boxes

[97Dually]

Thanks Ed. I "think" I got a pretty good handle on what I need and how to do it. Thinking I`ll go with an SSR rated at 60 amps to be on the safe side. I`d rather over build now than have to go back later and change things.

[CarWiz]

Check the specs on your SSR. For resistance loads (heating elements), most need to be run at less than or equal to 75% of it rating. And that's with it mounted on a heat sink. That means that an SSR rated 60A should not be loaded to more than 45A.

What's good about using SSRs over electromechanical relays is that they can handle faster cycling that is common in PIDs for better temperature control. The SSRs will also turn on at the Zero boundary of an ac cycle and ramp up to the load rather than slamming your circuits with the full load.

[97Dually]

Yes, I was keeping the 75%-80% loading of the SSR in mind when I figured on a 60 amp unit. If I use 3 3200 watt elements, that should be a load of around 40 amps, well within the 60 amp SSR`s "safety" zone, right ?

I do like the PID/SSR setup alot more now that I understand the differances (thanks entirely to this board) between the two. I can see nothing but positives by using this setup over a mechanical setup. I`ve only had a regular household oven so far, and see the temp`s swing quite a bit in it. Looking forward to eliminating that problem.