What are the potential risks of plugging a computer into an ungrounded receptacle? Is replacing an ungrounded receptacle with a GFCI a viable option to protect people and equipment? Also could GFCI circuit breakers be installed, wouldn't they provide better protection all the way around in an old house with ungrounded circuits. I wonder if this wouldn't be an option until which time the house could be rewired. I'd like to get others thoughts on this because I have many customers who can't afford to rewire their houses right now.
Ungrounded circuits
- Thread starter Jan
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- Windsor, CO NEC: 2017
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Re: Ungrounded circuits
Jan, welcome to the forum.
It is not as good as a current-code-compliant installation, but it is an option for older existing installations.
Cost effectiveness varies from case to case. Sometimes it is most effective to install both receptacle and circuit breaker-type GFCI protection.
Edit: Current, Voltage, same difference.
[ September 02, 2005, 07:57 AM: Message edited by: georgestolz ]
Jan, welcome to the forum.
The most specific problem in this case is that the surge protector the computer is plugged into is ineffective without a ground to shunt surges and overvoltage to. There are other hazards to non-grounding receptacles and what-not, but that is the stigma behind computers and old houses.
It is an option, see 406.3 and 250.130.
It is not as good as a current-code-compliant installation, but it is an option for older existing installations.
Yes, they can be installed, but there can be limitations due to the distances from the panel in many cases.
Cost effectiveness varies from case to case. Sometimes it is most effective to install both receptacle and circuit breaker-type GFCI protection.
Edit: Current, Voltage, same difference.
[ September 02, 2005, 07:57 AM: Message edited by: georgestolz ]
jimwalker
Senior Member
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- TAMPA FLORIDA
Re: Ungrounded circuits
I would try to run a dedicated circuit if possable for this computer.To do otherwise leaves your computer to risk.Whats its value compared to the cost of fixing the wiring ?
I would try to run a dedicated circuit if possable for this computer.To do otherwise leaves your computer to risk.Whats its value compared to the cost of fixing the wiring ?
petersonra
Senior Member
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- Northern illinois
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- engineer
Re: Ungrounded circuits
surge protectors do not rely on the ground wire to "shunt" off anything. the ground wire is there for protection of people, and nothing else.
if there are only two wires coming to the computer, a surge suppressor across those two lines will suppress whatever "surges" come down those two lines quite nicely.
<added>
I am sort of guessing that what you mean by ungrounded is that the outlets do not have the third hole for the ground plug. That is completely different from having an ungrounded (i.e.-no neutral) electrical system.
A GFCI will provide substantial protection for persons from electrical shock on such a circuit.
Think of it like this. Your typical bathroom circuit does have a third (ground) wire, yet we add a GFCI to provide a higher level of protection from electrical shock. The ground wire only provides protection for direct ground faults (a fault from a hot wire to a grounded part). The GFCI provides additional protection in that if there is even a tiny amount of current flow to ground (like 5 milliamperes) the GFCI trips and opens up the circuit. The CB on a typical 20A circuit breaker will not open immediately unless it sees perhaps 200A of current flow.
[ September 02, 2005, 09:07 AM: Message edited by: petersonra ]
surge protectors do not rely on the ground wire to "shunt" off anything. the ground wire is there for protection of people, and nothing else.
if there are only two wires coming to the computer, a surge suppressor across those two lines will suppress whatever "surges" come down those two lines quite nicely.
<added>
I am sort of guessing that what you mean by ungrounded is that the outlets do not have the third hole for the ground plug. That is completely different from having an ungrounded (i.e.-no neutral) electrical system.
A GFCI will provide substantial protection for persons from electrical shock on such a circuit.
Think of it like this. Your typical bathroom circuit does have a third (ground) wire, yet we add a GFCI to provide a higher level of protection from electrical shock. The ground wire only provides protection for direct ground faults (a fault from a hot wire to a grounded part). The GFCI provides additional protection in that if there is even a tiny amount of current flow to ground (like 5 milliamperes) the GFCI trips and opens up the circuit. The CB on a typical 20A circuit breaker will not open immediately unless it sees perhaps 200A of current flow.
[ September 02, 2005, 09:07 AM: Message edited by: petersonra ]
Re: Ungrounded circuits
Bob I totally disagree with you on the function of the surge supressor. Metal Oxide Varistor (MOV) type surge supressors have the MOV connected between the hot leg and the equipment ground, shunting surges to the equipment ground. If there is no equipment ground, where can the surge go? Most surge supressors use MOV's, mainly because they are cheap. The only type of surge supressor that will work on a 2 wire system is an inductive type which will choke the surge down. They are usually $200.00 and more.
Even with an equipment ground, I don't like MOV's because if you shunt a surge to ground it can come back in thru the cable connection, which is grounded.
Anyway this is my belief after much research. Maybe I'm all wet, if you can prove me wrong I'm all ears.
Bob I totally disagree with you on the function of the surge supressor. Metal Oxide Varistor (MOV) type surge supressors have the MOV connected between the hot leg and the equipment ground, shunting surges to the equipment ground. If there is no equipment ground, where can the surge go? Most surge supressors use MOV's, mainly because they are cheap. The only type of surge supressor that will work on a 2 wire system is an inductive type which will choke the surge down. They are usually $200.00 and more.
Even with an equipment ground, I don't like MOV's because if you shunt a surge to ground it can come back in thru the cable connection, which is grounded.
Anyway this is my belief after much research. Maybe I'm all wet, if you can prove me wrong I'm all ears.
petersonra
Senior Member
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- Northern illinois
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- engineer
Re: Ungrounded circuits
to my knowledge, surge strips typically have the MOVs wired H-N, N-G, and H-G.
That covers all three possible cases where there could be a "surge".
If the MOV was wired only H-G, there would be little or no protection from a H-N or N-G "surge".
These transients are typically high frequency and at the typical transient frequency, there is a lot of impedence back to the N-G bond point, so it would not be effective.
to my knowledge, surge strips typically have the MOVs wired H-N, N-G, and H-G.
That covers all three possible cases where there could be a "surge".
If the MOV was wired only H-G, there would be little or no protection from a H-N or N-G "surge".
These transients are typically high frequency and at the typical transient frequency, there is a lot of impedence back to the N-G bond point, so it would not be effective.
stud696981
Senior Member
Re: Ungrounded circuits
Some of the surge protectors I have seen have three MOVs, they are connected H to N, N to G, and H to G. If there is a rise in voltage, the MOV will short the H and N on a two wire circuit and it should result in suppressing the surge.
Some of the surge protectors I have seen have three MOVs, they are connected H to N, N to G, and H to G. If there is a rise in voltage, the MOV will short the H and N on a two wire circuit and it should result in suppressing the surge.
petersonra
Senior Member
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- Northern illinois
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- engineer
Re: Ungrounded circuits
the ground wire does absolutely nothing to prevent electrical noise.
why would any of these matter?
the ground wire does absolutely nothing to prevent electrical noise.
hurk27
Senior Member
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- Portage, Indiana NEC: 2008
Re: Ungrounded circuits
If a surge was to happen between a hot and ground or neutral and ground, What load would be protecting? There should not be any loads other than the normal hot/neutral loads.
I agree with Bob If you only have a two wire circuit surge suppression on only these two wires will work but keep in mind that any part of a computer system fed from more than one circuit with common grounding pathways between then, can get surges on these path ways. Even a entertainment system can get surges when a remote powered sub woofer is fed from a different circuit because it has a common grounded shield on the audio cable between the two systems.
If a surge was to happen between a hot and ground or neutral and ground, What load would be protecting? There should not be any loads other than the normal hot/neutral loads.
I agree with Bob If you only have a two wire circuit surge suppression on only these two wires will work but keep in mind that any part of a computer system fed from more than one circuit with common grounding pathways between then, can get surges on these path ways. Even a entertainment system can get surges when a remote powered sub woofer is fed from a different circuit because it has a common grounded shield on the audio cable between the two systems.
hurk27
Senior Member
- Location
- Portage, Indiana NEC: 2008
Re: Ungrounded circuits
I should add to the above that a plug in surge suppressor would not help in the above common grounding pathways even if it does provide hot to ground TVSS protection.
I should add to the above that a plug in surge suppressor would not help in the above common grounding pathways even if it does provide hot to ground TVSS protection.
Re: Ungrounded circuits
Bob...I stand corrected. After learning how MOV type surge supressors can backfeed a spike into the modem etc via the grounding conductor I somehow assumed that the MOVs were linked to the grounding conductor only. That's what I like about the forums, there is always something to learn. Thanks.......Brian
Bob...I stand corrected. After learning how MOV type surge supressors can backfeed a spike into the modem etc via the grounding conductor I somehow assumed that the MOVs were linked to the grounding conductor only. That's what I like about the forums, there is always something to learn. Thanks.......Brian
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