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Benefit of grounded outlet for 2 prong devices?


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Hi,

What are the benefits/up sides of having a grounded 3 prong wall plug, specifically for 2 prong devices? I understand a 3 prong device benefits greatly from having the ground however my question is specifically pertaining to plugging a 2 prong device into either a 2 prong outlet OR an non-GFCI 3 prong outlet that has not been grounded.

I am wondering if my newer speakers (a wireless speaker set) or my laptop computer with its 2 prong cable will be okay to plug into a home I am purchasing or if I should absolutely not plug the speakers (or anything i value) into a 2 prong outlet/3prong ungrounded.

Backstory:

Purchasing a small (800ftish) Seattle, WA area 1950's built rambler (with decent attic and crawl space).

The home inspector noted the wall plugs were not grounded in the home but someone had installed the cheating way 3 prong outlets without grounding them. The home seems to be in well maintained condition and I am not seeing anything to suggest crazy electrical modding done - even though additions like AC unit were added and kitchen was remodeled - appears to have been all done by professionals.

Now given the inspectors report I see that I need to have the home electrical system rewired - according to some folks who had similar project in another home recently in the area the absolute whole rewiring of that home cost $8,500 including permitting and taxes done by a local electrician company (no circuits were reused, new wire everywhere). This is something I would like to do as soon as funds allow (20% downpayment on the home is killing me but a good place to start from).

My main concern now is while I live in the home and save up to get it rewired to not blow my expensive electronic toys (which I would very much not want). For my one or two 3 prong devices I would like to somehow get one or two outlets fully grounded to be on the safe side and dont use the rest of the outlets until the big rewire.

many thanks in advance,

~v

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A simple, cost effective solution is to put 2-prong receptacles back onto the 2-wire circuits. Having a grounded circuit does nothing to protect your fancy gizmos. The house will be just as safe as the day it was built.

However...

If you have anything with a 3-prong cord (like a surge arrester - hint, hint) then it needs a GROUNDED 3-prong receptacle. It may be easy or difficult to upgrade an individual receptacle, depending on many things. Get an estimate from an electrician.

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I've never seen a computer power cord that had only 2 prongs.

Home inspectors cannot require anything. That's the domain of the muni code inspector.

If a house was originally wired without grounds but has many circuits updated to three wire, I sometimes recommend a whole-house surge protector and local GFCI's instead of a re-wire. Most cases, my report recommends the re-wire and yes, it is expensive, especially after you pay the drywallers and painters to fix all the holes in the walls. High repair costs don't hinder me from serving my client.

Rewiring just a few choice circuits at first so you can break the repair into stages is fine.

Marc

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Sorry must of worded that wrong. The Home Inspector simply advised me on conditions of the outlets and things that could be done to bring the electrical system up to code.

The really big question I have is what gain will a grounded 3 prong outlet bring to a device that was only designed to be a two prong connection, if any? I know my computers will require 3 prong outlets and I will be looking into getting at least a couple properly grounded outlets for the time being.

Thank you,

~v

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Most things we use in a house have two-prong plugs and going back to two-prong receptacles would be fine. Some exceptions would be refrig. microwave, window ACs, washer, surge protector. If some updating has been done along the way it is likely that some areas have grounded receptacles. Adding a few new circuits with grounded receptacles is much less expensive then rewiring. Down the road you can still rewire as needed or as you remodel.

Back to your original question-Nothing really gained by the ground with a two-prong appliance, other than metal boxes would be grounded.

Also, in my area I find most houses built after about 1950 have grounded wire, even with two-prong receptacles. If the wiring was done with Romex (non-metallic cable) they often bent the ground wire back, ran it through the box connector clamp, and wrapped it around a box connector screw. It is easy to miss that at the receptacle box and often at the panel too because they did the same thing there.

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Also, in my area I find most houses built after about 1950 have grounded wire, even with two-prong receptacles. If the wiring was done with Romex (non-metallic cable) they often bent the ground wire back, ran it through the box connector clamp, and wrapped it around a box connector screw. It is easy to miss that at the receptacle box and often at the panel too because they did the same thing there.
Where would I check for that possible wire? turn off all the breakers, pull out the outlet and then most likely pull out the outlet box and it it would somewhere in that vicinity?

Also thank you all for clarifying the situation surrounding two prong outlets.

thank you,

~v

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I've never seen a computer power cord that had only 2 prongs.. . .

My laptop has only two prongs. No idea why.

Usually the laptop power supply has a grounded power cord, 3 prongs. But the primary side of the transformer probably has only two leads and most of the circuitry is on the secondary side, converting low voltage AC to DC.

The cable from the power supply/battery charger to the laptop is only two conductors, so the laptop itself is never grounded. Doesn't seem to need it.

I use a long two-conductor extension cord to run my laptop power supply. It's handier to pull one end of a light gauge cord, like lamp cord, out of my briefcase and leave the bulky power supply in the case. So I haven't grounded this laptop's power supply in 3 or 4 years.

A reference to ground is a good thing for desktops computers, printers, monitors, etc because for one thing it provides a path for stray voltages or static charges that can otherwise blow circuit components.

Surge protectors need grounding. Good idea from Marc, to put a grounded surge protector in the circuit in the panel or near the panel so everything downstream is protected. Even if there are only 2 conductors the surge protector at the panel can protect your expensive electronics.

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Hi,

What are the benefits/up sides of having a grounded 3 prong wall plug, specifically for 2 prong devices? I understand a 3 prong device benefits greatly from having the ground however my question is specifically pertaining to plugging a 2 prong device into either a 2 prong outlet OR an non-GFCI 3 prong outlet that has not been grounded.

I am wondering if my newer speakers (a wireless speaker set) or my laptop computer with its 2 prong cable will be okay to plug into a home I am purchasing or if I should absolutely not plug the speakers (or anything i value) into a 2 prong outlet/3prong ungrounded.

Backstory:

Purchasing a small (800ftish) Seattle, WA area 1950's built rambler (with decent attic and crawl space).

The home inspector noted the wall plugs were not grounded in the home but someone had installed the cheating way 3 prong outlets without grounding them. The home seems to be in well maintained condition and I am not seeing anything to suggest crazy electrical modding done - even though additions like AC unit were added and kitchen was remodeled - appears to have been all done by professionals.

Now given the inspectors report I see that I need to have the home electrical system rewired - according to some folks who had similar project in another home recently in the area the absolute whole rewiring of that home cost $8,500 including permitting and taxes done by a local electrician company (no circuits were reused, new wire everywhere). This is something I would like to do as soon as funds allow (20% downpayment on the home is killing me but a good place to start from).

My main concern now is while I live in the home and save up to get it rewired to not blow my expensive electronic toys (which I would very much not want). For my one or two 3 prong devices I would like to somehow get one or two outlets fully grounded to be on the safe side and dont use the rest of the outlets until the big rewire.

many thanks in advance,

~v

QUICK ANSWER: NONE

However, the real question here 'is a 120V circuit with an equipment ground better than an old 2-wire system"? Absolutely!!

"It would be best me lad.. you'd be best having equipment grounds within ye circuitry running around your wood box filled with water and pipes and metal things and such and electrical toys.and concrete floors and all. . ya know?" We need a way to catch stray electricity to bring it back to the gate keeper who can then kill it.. " There is no way to bring it back with the old style... :)

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Also, in my area I find most houses built after about 1950 have grounded wire, even with two-prong receptacles. If the wiring was done with Romex (non-metallic cable) they often bent the ground wire back, ran it through the box connector clamp, and wrapped it around a box connector screw. It is easy to miss that at the receptacle box and often at the panel too because they did the same thing there.
Where would I check for that possible wire? turn off all the breakers, pull out the outlet and then most likely pull out the outlet box and it it would somewhere in that vicinity?

Also thank you all for clarifying the situation surrounding two prong outlets.

thank you,

~v

The ground wires are easy to see if they are wired to the neutral/ground terminal in the panel or to the box connectors at the panel (unless the panel is in a finished wall). If you are looking into a receptacle box then look closely where the NM cable passes through the box connector. Also, if you can read the labeling on the cable it would typically read "two conductors with ground" if a ground wire is present. I suppose you could also cut a little drywall out at the end of a receptacle box and see if a ground wire is wrapped around the box connector screw or is otherwise visible.

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