Timeline for Parallel (2) 20 amp 220 12 ga wires into one 30 amp 220 Breaker OK?
Current License: CC BY-SA 3.0
15 events
| when toggle format | what | by | license | comment | |
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| Feb 15, 2018 at 23:34 | comment | added | Herb G | Thanks Harper,, no mortgage,, and the house will never be sold while I'm alive. The oven is great, and the same as all modern ovens... so you guys have convinced me to pull 10/3 through the attic and install the correct 30 amp breaker. Thanks for your help!! | |
| Feb 15, 2018 at 23:28 | comment | added | Harper - Reinstate Monica | You have several risks. One is of owning a mortgage on a burnt out house when insurance refuses to pay. Another is when the buyer's inspector discovers the shoddy work, discovers all the work was unpermitted, and the AHJ makes you tear it out, pull permits and redo it. I have seen this happen to neighbors. You have but 3 options: get correct ovens, install correct wiring, or get two 10kva transformers to carry the needed power over a single 12/2. I recommend the first one, back to Home Depot it goes. An oven change alone, absent any wire work, doesn't need a permit. Wire changes do. | |
| Feb 15, 2018 at 23:15 | comment | added | Herb G | Hi Harper,, Thanks and apologies for my ignorance. At the oven opening I have 2 sets of 4 wires. (one for each oven) They are red, black, white, and ground. If I join the reds and blacks I think I should have 240v with each leg of 12AWG protected by it's own 20A breaker. The white 12AWG neutrals will also be joined at the oven which should give me enough capacity to carry the 30A max back. In addition, I have 2 grounds that I can connect together. Under this scenario, is my only risk that the unfused white neutrals are actually running in parallel? | |
| Feb 15, 2018 at 22:41 | comment | added | Harper - Reinstate Monica | @herbg because two 12AWG wires feeding a combined 40A into a circuit, can pit 40A on a single neutral wire. Neutrals are not fused. The entire basis for architecting North American service the way we do, is that it's impossible for a neutral to carry more current than its partner hot (hots in MWBC). The same applies to grounds, a 12AWG ground can't be counted on to ground 30-40A of bolted fault, hence the requirements for 10AWG grounds on 30-40A circuits. | |
| Feb 15, 2018 at 22:40 | comment | added | Herb G | Hi Harper,, NO,, I actually mean 4 separate 20 amp breakers. To fully turn off power to each oven, I had to physically turn off 2 for the top oven, and 2 for the bottom oven. I suspect that probably isn't per code as well since if I turned off one breaker and not the other I was supplying the 240v oven with only 120v. | |
| Feb 15, 2018 at 22:37 | comment | added | Herb G | Thanks Tyson,, I'm obviously not a Licensed Electrician, but I can't understand any possible scenario could cause a single 12ga wire that is protected with a 20 amp breaker to exceed it's current draw, (and overheat/fire), without tripping the breaker. I do understand now how connecting both 12ga to a 30amp breaker in parallel "could" cause an unbalanced load if one 12ga wire was broken and the remaining 12ga wire was burdened with the full 30 amp load. | |
| Feb 15, 2018 at 22:36 | comment | added | Harper - Reinstate Monica | When you say "4 breakers" do you actually mean two 2-pole breakers? | |
| Feb 15, 2018 at 22:23 | comment | added | Tyson | Again, think about a worst case example. I know of someone that had a freak accident with a 4 wheeler in a garage that caused damaged to a wall with the oven and hot tub running through it. If you have a LOOP like you suggest, you're going to burn your house down again!. Code exists for a reason, it's the rules, it's the safe way. | |
| Feb 15, 2018 at 21:24 | comment | added | Herb G | Thanks again Tyson... I was hoping that this might work.. Even if it isn't truly per code,, I'm not sure how it could be a hazard if each independent leg is separately protected with it's own appropriately sized breaker. | |
| Feb 15, 2018 at 21:19 | comment | added | Tyson | No, that won’t work either. Sorry but there is only one thing that works: change the wire. | |
| Feb 15, 2018 at 21:15 | comment | added | Herb G | Thank you Tyson,, OK,, I think I understand why paralleling might be bad.. But what about just keeping my (4) 20 amp breakers and just joining the wires at the junction to the oven. Each wire is still protected at it's capacity, and at the oven I should have the 30 amp capacity I need? 2 reds. 2 blacks,2 whites? | |
| Feb 15, 2018 at 21:04 | answer | added | Retired Master Electrician | timeline score: 3 | |
| Feb 15, 2018 at 21:03 | comment | added | Tyson | It makes sense only when dealing with normal currents, in the event of faults and fault current, it’ll burn your house down. The wire needs to be replaced. | |
| Feb 15, 2018 at 20:58 | review | First posts | |||
| Feb 15, 2018 at 21:19 | |||||
| Feb 15, 2018 at 20:55 | history | asked | Herb G | CC BY-SA 3.0 |