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Home Electric Service Entrance Box Question

08/27/2007 9:16 AM

Just curious, what would happen if a circuit from one side of a standard 200 amp entrance box found it's way back to the other side (hot to hot and common to common)? On the same side?

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#1

Re: Home Electric Service Entrance Box Question

08/27/2007 1:10 PM

As long as there's no difference of potential nothing will happen. If by "hot to hot" you mean L1 - L1 (A phase) nothing will occur because its the same phase. Usually hot to hot means L1 to L2 and this results in smoke, fire, and damage if there's no load device in between.

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#2
In reply to #1

Re: Home Electric Service Entrance Box Question

08/27/2007 2:30 PM

Totally agree. Also, may I hasten to add, your circuit would be fed from both sides like a ring (on the phase side only) therefore the circuit breaker would just cut the ring but not isolate the phase from the circuit, this phase having only the protection of the next in line protective device, be it a 240A line fuse or a 40A house fuse! Both are very capable of killing anybody unfortunate enough to touch or fall foul of the beast!

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#3

Re: Home Electric Service Entrance Box Question

08/27/2007 3:07 PM

So breaker on right side connected to breaker on left side = death?

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#4
In reply to #3

Re: Home Electric Service Entrance Box Question

08/27/2007 3:43 PM

It means that you play without a safety net! A circuit will have a line fuse to protect the line (out in the street somewhere), a Main house fuse to protect the tails, a max current trip to limit your current draw, after this the protection is for the user, ie, an RCD to cut the current if there is short to earth, and a breaker for the circuit! The last two are designed to trip as quick as possible if a fault occurs on the consumer side, If you miss these out there is nothing stopping you from getting well and truly fried, and I do mean fried!

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#5

Re: Home Electric Service Entrance Box Question

08/27/2007 4:36 PM

A visual aid to help satify your curiosity. My 1200a main as I found it 2 weeks ago on startup. I'm still on a generator.

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#9
In reply to #5

Re: Home Electric Service Entrance Box Question

08/28/2007 5:05 AM
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#14
In reply to #5

Re: Home Electric Service Entrance Box Question

08/28/2007 11:37 AM

Ouch

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#6

Re: Home Electric Service Entrance Box Question

08/27/2007 5:25 PM

Hopefully it does find it's way back to the neutral (120V) or to the other hot wire 208Volt or 240Volt through a load of some kind.

The only problem is when the load is missing and there is nothing there of resistance.

If the resistance or impedence is gone, you have a short circuit condition and then it will arc, crash, and burn.

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#7

Re: Home Electric Service Entrance Box Question

08/28/2007 12:46 AM

If I'm not reading this wrong, he is talking about bypassing the meter. If that were to happen the power company would probably have you in jail before night fall.

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#8
In reply to #7

Re: Home Electric Service Entrance Box Question

08/28/2007 5:05 AM

...if the poster survives the experience that is. (S)He might like to look at the picture above and ask whether it is worth the risk...

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#10
In reply to #8

Re: Home Electric Service Entrance Box Question

08/28/2007 9:15 AM

No, I do not have larcenous intent. I have a camp in the mountains that sometimes loses power during storms. I purchased a 3000 watt generator this summer and put together a double male extension cord that allows me to plug into one of 5 outlets that ring the building (after turning off the main breaker of course). I also flip off all 220 breakers (stove, pump, water and baseboard heater.) All that's left are outlets, lights, and the refrigerator, which is key and the reason for purchasing the generator in the first place. Problem is that the refrigerator is on the "opposite side" as the outdoor outlets so I'm trying to come up with solutions. One of them is using empty breaker slots to build a simple bridge across the two sides to power all of the outlets in the house with the generator. This bridge would be closed only after the main breaker was turned off.

If for some reason the main breaker was on when the power comes back on when you have a generator "backfeeding", the generator breaker will kick so we that scenario is covered. I needed to address the scenario of what would happen if by chance the main power was applied without breaking the bridge circuit first. I didn't know if the two breakers connected in the bridge would trip and severe the circuit.

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#11
In reply to #10

Re: Home Electric Service Entrance Box Question

08/28/2007 9:55 AM

Ah, why didn't you say ealier! Why not use a rotary switch made for this purpose, then you can have one or the other but not the two at the same time! If you split your board so that you have all your high drain on the mains and all your low drain switchable between the two? Do you follow me?

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#15
In reply to #10

Re: Home Electric Service Entrance Box Question

08/28/2007 2:47 PM

Take this from an idiot who got away with this n-1 times. Never, ever, ever, make a double male cord. No matter for what. They sell generator disconnects for about $200 USD; that's a lot cheaper than a fire.

If you don't want to do that, buy a 50' 12AWG extension cord for the fridge.

Tom

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#16
In reply to #15

Re: Home Electric Service Entrance Box Question

08/28/2007 3:18 PM

I've used a double male 4 prong 230v cord to plug my home standby generator into my house system for the past 4 years, 20+ power outages. What happened to you on the nth time?

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#17
In reply to #16

Re: Home Electric Service Entrance Box Question

08/30/2007 12:39 PM

Hello Paddy, Check out this for an idea of what you need! The solution is very easy if you know what you are doing, if not, leave it to an electrician! Hope it helps!

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#12

Re: Home Electric Service Entrance Box Question

08/28/2007 10:13 AM

We get to the real issue. Paddy, if you make the mistake you are about to you very well could end up with a mess that looks like my switchgear. Or worse...you could cause a bad fire which your insurance would never cover due to significant code violations. NEC 702.6 states that you must design and install so that inadvertant interconnection of sources is not possible.

If at all possible you should have a licensed electrician do this work. If not possible you must install a proper setup to minimize hazard to life and property. The cheapest way would be to install interlocked breakers. There are a couple of methods out there...the easiest is a kirk key that only allows one breaker to be closed and the key is captive. I have a couple of references here somewhere and if all stays quiet I'll chase it a bit.

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#13

Re: Home Electric Service Entrance Box Question

08/28/2007 10:35 AM
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Desert Rat (1); hilltopper (1); Mr. Truman Brain (4); Paddy O'Flanigan (3); Pepper (1); PWSlack (2); Switchman (4); TVP45 (1)

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