That depends upon the type of cable feeding the outlets. It would either
have to be steel cable, in which the steel serves as the ground, or a non
metallic cable with an internal grounding conductor. If neither is present,
only non grounding receptacles can be used. You can also run ground wires to
each outlet, or replace the feed cables to them, if it is practical. If you
are concerned about human safety, the circuit can be protected by a GFCI
device, but that won't add grounding to the circuit
Sounds like you have ungrounded circuits. In that case you can't have 3
pronged plugs. The only ground is the polarized two pronged plug. That's
so the wide prong is always tied to neutral which is ground at the panel.
re: Sounds like you have ungrounded circuits. In that case you can't
have 3 pronged plugs.
That is not true. You can't have *grounded* 3 prong plugs without a
ground wire, but you can certainly have 3 prong plugs.
If a GFCI receptacle or breaker is installed in the circuit, all down
stream receptacles can be 3 prong "plugs". This is code-compliant.
The user is protected from a grounding problem by the GFCI, although
the equipment is not.
In addition, the downstream outlets need to be marked as "ungrounded,
GFCI protected" so that the user knows the status.
What is the purpose of the T slots? I thought it was for 20 amps,
but it says 15 amps. I was watching a remodeler and a potential
customer last week and he seemed to say it meant 220 volts. That
didn't seem likely and this one is 125 volts, so what is use of
AFAIK the NEC no longer allows the use of 2 prong outlets in a *new*
installation, but it's still OK to replace an existing 2 pronger with
a new 2 pronger.
When the 2 pronger will no longer hold the 3 prong adaptor that you
have your iron lung plugged into, you are allowed to replace it with
another 2 prong receptacle.
re: It's not code but is consistency.
What's not code?
re: So why do YOU think the electrician removed the 3 prong plugs?
If you back up a few posts, you'll see that I basically asked that
same question to the OP. I'm curious as to why the contractor
replaced the receptacles and didn't offer the other code-compliant
I won't argue the point of mixing receptacles being "confusing", but
in a case where a GFCI is protecting all 3 prong receptacles in a
circuit, there is no mixture, therefore no confusion.
Your comments that "markings can vanish" is valid. However in the
overall scheme of things, I'd live with the chance that a piece of
equipment will get fried as long as the humans are protected.
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