Can you ground an electrical system on an old two wire system without putting in new wire?

Answer 1

Answers for USA, Canada and countries using similar 60Hz mains suppliesAssuming you are talking about house or business wiring, no, you need the third wire.

(LIFE SAFETY WARNING! [disclaimer]

Electricity is dangerous!

You can be injured or killed!

Improper installations can cause fire, injury and death!

Should you be doing this yourself?)

• It is not possible, per se, to "ground" an entire old two wire electrical system.
• It is possible, however - and allowed - to provide a ground at an individual receptacle by installing a grounding conductor according to strict limitations.
• Many simple devices are "double insulated" and designed to be used without any protective ground connection. But some are not so you have to be sure of the differences between them.
• It is recommended to install a new grounded circuit for point of use service wherever a protective ground connection is required.
• The best advice anyone should give here is to call a licensed electrician!

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The answers above are correct, you cannot ground a two wire system without running new wires, however, you can make your circuit as safe as a grounded one by using a GFCI. A GFCI does not have to be grounded to operate as it measures the current flow in both legs. It ensures the live current is equal in value (amperage) to the neutral current. In the case that the currents are not balanced, that is when you are in a hazardous situation.

In a grounded circuit, the fault current is supposed to flow to the ground, keeping you safe. The GFCI on the other hand will trip and give you as good if not better protection.

If you wish to use a GFCI receptacle to protect your circuit, you may install it at the first receptacle of your circuit and tie the remainder of the circuit to the load side of the GFCI so that it will protect the whole circuit. This is legal in Canada, I am not familiar with the American laws, but I would think it is acceptable there too. I do advise to hire a qualified electrical contractor, he should know the laws.

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Using a GFCI with no ground to the load connections is compliant with code in the US as well. The receptacles with the floating ground (protected by a GFCI) must be labeled "No Equipment Ground." However, not sure if local inspectors in all states and/or localities will accept this, especially in some big cities - e.g. New York, which have very strict wiring codes, so it's best to check with a local expert.

DO NOT connect the ground to the neutral! Unfortunately I have seen this done and it creates a very dangerous situation.

ALWAYS CHECK WITH YOUR LOCAL WIRING SAFETY OFFICE BEFORE YOU ATTEMPT TO CHANGE ANYTHING ON POWER MAINS OUTLETS

IF YOU ARE NOT ALREADY SURE YOU CAN DO THIS JOB

SAFELY AND COMPETENTLY

REFER THIS WORK TO QUALIFIED PROFESSIONALS.

If you do this work yourself, always turn off the power

at the breaker box/fuse panel BEFORE you attempt to do any work

AND

always use an electricians test meter having metal-tipped probes

(not a simple proximity voltage indicator)

to insure the circuit is, in fact, de-energized.