would a typical surge protector protect from a floating neutral?

[Red Squirrel]

Basically as title says, would it protect?

See this:

http://gal.redsquirrel.me/imag...ng_neutral_diagram.JPG

Just something I've thought of, as I've seen the damage a floating neutral can do, and while rare, it's possible. (ex: someone deliberately cutting the cable outside as an act of vandalism, or some natural effect etc)

The diagram assumes a fault at the main line but this could easily happen internally too on a double pole breaker (bad connection, etc). So say a PC is plugged on split plug and a lamp is plugged into it as well, if the neutral is in floating condition both the pc and the lamp are in series at 240v. I don't know the technicality behind it but it will not be 50/50, one could take more voltage then the other.

 

[PM650]

I think what you're describing is basically impossible unless the main neutral line was cut - I fail to see how a double-pole breaker (which in my understanding has nothing to do with the neutral) would cause this. I would guess that the resulting voltage difference would cause some devices to eventually or immediately fail/shutoff, until the load was 'balanced' enough to not cause anymore device failure/shutoffs - that or everything would eventually shut down. Basically everything in the house would be in either series or parallel with every other device, so some interesting things might happen.

A simple surge protector is for high-voltage spikes only, and even then it's not terribly effective - so no, it would not protect from an over/under-voltage event.

 

[Red Squirrel]

With a double pole breaker assuming there is a load on both legs (and not just a 240v item) if that neutral were to be at fault it would cause issues on the two 120v legs. Of course, a floating neutral in the house is very rare and would be the result of a VERY shoddy wiring job. But the main line getting cut, could happen durring a storm I suppose.

 

[Modelworks]

It would be rare, but it does happen. Ground rod is also attached to the neutral bus in the breaker box so that is an alternate path to ground which is another reason to have a properly grounded box. If the neutral bus were not tied to ground rod and the neutral from the step down transformer were disconnected you could have a situation where any grounded appliance in the home would use someone touching it as a path for the current to flow to ground through them. Breakers would not likely ever trip because the current being used would be less than the amount they normally pass since the appliances are now using 240V would cause less current flow. GFCI breakers would trip but not all homes use those except on bathrooms/kitchens. A UPS could block the voltage since some can adapt voltage from 108~240vac. And some pc power supplies can auto switch when the voltage goes to 240vac.


MOV for protection in most power supplies and surge strips are usually the 300V + type so they would not clamp the voltage either. You would need a strip with 180V type and even then the MOV would eventually burn out.
There are circuits that can protect from this, but not normally found in low end surge protectors. Something like a crowbar circuit with high current capacity and a fuse blow when circuit fails.

They do make crowbars big enough for a whole house, but I doubt many people have one .

A cheaper alternative would be to use a circuit where the homes power passes through a relay connected to a device that measures the homes power. If the power exceeds a preset limit the relay would disengage power.