Is it a hazard to plug a surge protector into an ungrounded GFI outlet?

CuriousWithQuestions · 01-30-2008, 07:37 PM

Newbie here, hoping for some guidance!

I have an old home that's been ultra-renovated and upgraded. Nearly all plug outlets are grounded, but as luck would have it, the outlet immediately behind my bed is not. I've got an adjustable bed with a 3-prong plug, and felt very nervous about plugging it into an ungrounded outlet, so I had the outlet switched to a GFI (or, as some say, GFCI) outlet, and all's been good. I'd love to use one of my old surge protectors as a power bar in that outlet, but I wonder if that could be risky somehow. Would the voltage mojo in a surge protector go haywire in an ungrounded GFI outlet? Is there any kind of danger, aside from the surge protector not really working as a surge protector?

goose134 · 01-30-2008, 11:12 PM

It should not be a problem. GFCI measures the current imbalance in the neutral, not the ground. In the absence of a neutral (240 Volts) the imbalance is measured on the phases. So the fact that your receptacle wiring provides no ground is not a problem. In fact, replacing with a GFCI is one of the ONLY acceptable methods to solve this problem.
To the surge suppressor: I don't think that it cares what device it is plugged into since a surge condition is a voltage problem, not a current one. The only thing I can see is if there is a gizmo in the surge suppressor that doesn't get along with the GFCI, causing a nuisance trip. I doubt it very much, but it wouldn't be dangerous. So...plug away, you should be fine.

Stubbie · 01-30-2008, 11:42 PM

The gfci will work.. surge suppressor or not.. but the surge suppressor will not be able to do its job without a grounding connection. Just get a power strip. .

CuriousWithQuestions · 01-31-2008, 05:06 AM

Thanks, guys. Since I've already got the surge protector, is there really a reason to buy a power strip?

goose134 · 01-31-2008, 10:27 PM

Quote:

but the surge suppressor will not be able to do its job without a grounding connection.

Stubbie, why is that?

Stubbie · 02-01-2008, 01:06 AM

NO if you already have it doesn't really matter. Most medium priced surge protectors use MOV's connected to the ground wire inside the surge protector. These varistors use a semiconductor gate that opens on surge/spike and dumps the transient voltage to ground. They behave differently when under normal voltage and have high resistance preventing normal voltage from going to ground. When the voltage surges,(this happens in nanoseconds), the resistance of the semiconductor decreases almost instantly allowing a path to ground, hopefully depleting the surge voltage before it does damage to connected equipment.

CuriousWithQuestions · 02-01-2008, 06:34 AM

Thanks. So I can safely use the surge protector as a glorified power strip.

goose134 · 02-01-2008, 10:04 PM

Quote:

These varistors use a semiconductor gate that opens on surge/spike and dumps the transient voltage to ground.

Ah, yes. I do remember that now, thank you.