Does a fusible safety switch disconnect the neutral wire?


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Old 09-06-18, 03:39 PM
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Does a fusible safety switch disconnect the neutral wire?

I need to replace my 200 amp load center and want to include a 200 amp fusible safety switch with the new hardware. The reason is mainly for the convenience of being able to shut off power to the load center when doing maintanance, add-ons, etc. It would also be fabulous to be able to throw the safety switch to prevent emp damage (natrual or whatever) if possible. My question is do these safety disconnects actually disconnect the neutral as well as the main lines? If not what are the considerations of actually disconnecting the neuitral, as well as the line AC mains power, when disconnecting a home service from the power grid? Are there any safety considerations? Pitfalls? And what about the ground (I'm fairly certain one wouldn't want to disconnect that for any reason...) As always thanks in advance for your advice and input. Best regards...
 
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Old 09-06-18, 03:57 PM
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A fusible safety switch does not disconnect the neutral.
The only possible reason to break the neutral is if you have a whole house manual transfer switch and you needed to isolate the neutral from ground to keep a GFI from tripping on a generator.

Ground is never disconnected.
 
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Old 09-06-18, 04:06 PM
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In the case of an emp wouldn't the neutral be a weakness? I would assume that an emp would induce the same voltages "up" the neutral. My consideration is totally isolating from the grid if necessary, in the event of an emp. A manual transfer switch sounds like a great idea, for the purpose of generators or solar panels in the future... But my main concern is isolating from the grid to prevent an emp from causing damage.
 
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Old 09-06-18, 04:30 PM
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I would assume that an emp would induce the same voltages "up" the neutral.
Neutral is bonded to ground at the main panel or at the pole if older house.
Any induced voltage should flow down into the ground.

If there really is EMP, everything in your house will be fried before you even have a chance to switch the transfer switch.
If you really want to protect your house from EMP, you will have to shield your entire house and run isolated power all the time.
Time to go underground.
 
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Old 09-06-18, 07:15 PM
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The house is shielded with a heavy guage diamond shaped, steel mesh (1/2" holes or they may even be smaller than that) and I've located and resolved any gaps (it was there when I bought it). Any remodeling and insulating has 2 layers of heavy aluminum foil separated by fiberglass insulation (the wire mesh is on the inside and outside of each wall). I'm researching ways to create an isolat(able) power supply. Its not a fanatical concern, but since it was there I thought I would exploit it as much as is possible. I do know that almost all the rooms are shielded now. I've got to work out some small issues in a partially exposed basement. I'm not putting extra money into it, except in projects where it is feasible, such as this load center. I'd like to do any retro's with emp resistance in mind. I've inherited almost 20kw in solar panels so solar is definately in the near future (since it was free) and I'd like to do it without being reliant on the grid for it to function.

PS I do have a working 13kw UPS, although I generally haven't been using it. I paid 15$ for it at a scrap yard, but don't have enough deep cell batteries at present for very much runtime... But it does work, rather nicely.


At any rate is there a specific system for disconnecting the neutral along with the line AC from the grid? I have done very little with regard to solar infrastructure as yet, perhaps something like that is involved, since I'm not interested in relying on the grid for solar to function...
 

Last edited by Solarsails; 09-06-18 at 07:30 PM.
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Old 09-07-18, 05:36 AM
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EMP is traditionally considered to include 3 distinct electrical events, the slowest and longest lasting event is the GIC mode. Here, you have long conductors picking up DC currents inductively coupled from the earth, causing high power transformer concerns. The relatively short distribution lines into your home would not be affected by GIC, but the long transmission lines upstream could be.
The other two modes are faster to occur and to dissipate, but would have no real warning. I would not suggest you envision a scheme to float your home from earth altogether, since these higher voltages may not dissipate well without grounding at a, hopefully, single point connection to earth.
AND, I should add, this is about 80% conjecture.

So, assuming no warning from an actual blast event, the transfer switch has zero hope to operate in time. And, the GIC event would not be destructive to your home, and that one has warning.
 
 

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