It is true that 20 amp circuits typically have 15 amp receptacles
installed.
The difference is that 15 amp receptacles have two plain straight slots
(plus the round ground opening) and the 20 amp receptacle has a neutral
slot (right hand slot) with an additional horizontal slit added to
accommodate a 20 amp only plug.
You can go to the panel and simply check the breaker to determine if the
circuit is 15 or 20 amps. They are required to be labeled as to "garage"
or "bedrooms" etc. Plug a light into the outlet and test if you can
switch it off with the corresponding breaker.
Aside from the extra horizontal slot, I have not noticed a significant
difference in 20 amp and 15 amp receptacles. I have plugged in chargers,
heaters, welders, compressors, air conditioners, and other heavy loads
into 15 amp receptacles on 20 amp circuits with no noticeable ill
effects for decades. They seem to take the full 20 amps without harm. It
may be that the only difference is the additional horizontal slot, but I
haven't fully investigated. I would think that if there were any danger
of over heating, etc. that the standard practice of installing 15 amp
120V receptacles on a 20 amp circuit would not be allowed, or at least
strongly discouraged at least in in some localities, but it is not.
Fires and the like tend to get the electrical regulation board's attention.
If you are planning on plugging in an EV daily into a 120 volt outlet,
you would likely want to eventually change it out for a "hospital grade"
type receptacle. These are really designed to take constant, daily,
disconnection and reconnection use and are constructed of _far_ better
materials than a standard receptacle. They cost at least 5 times as much
as a standard receptacle, of course.
Bill D.
On 1/20/2016 7:20 AM, Mike Nickerson wrote:
While the circuit in the garage is probably 20A, it may be wired with 15A
outlets. They are pretty easy to change, though.
If I were going to charge an EV on a 120V outlet regularly, I would probably
change it anyway. Most home construction uses light duty outlets that aren't
built to take the load for hours per day. Change it to a good heavy duty
outlet and it will work much better.
Mike
On January 20, 2016 1:28:43 AM MST, Bill Dube via EV <ev@lists.evdl.org> wrote:
Paul,
There are a number of places in your home that are _required_ by the
national electrical code to have dedicated 20 amp circuits for the 120V
receptacles.
There are at a minimum five (5) 20 amp 120V receptacle circuits in a
modern house:
https://dbs.idaho.gov/programs/electrical/publications/2014_Homeowner_guide_brochure.pdf
Sometimes, in a low-cost tract house without a garage there are less,
(and in older homes there could be fewer) but typically there are quite
a few more. The places that you will find additional dedicated 20 amp
receptacles for; the microwave, the garbage disposal, occasionally the
dishwasher, etc. Often, the savvy custom home builder will call for
upgrades on 20 amp 120V receptacles for the patio, pool, workshop area,
green house, deck, workout area, home entertainment area, basement,
etc.
You will notice that the code requires a 20 amp circuit for the garage,
were your EV is likely to be parked.
In commercial buildings, typically _all_ of the 120V receptacles are 20
amp.
I used to be an electrician, many years ago. I wired (and rewired)
_countless_ houses. :-)
Bill D.
On 1/19/2016 2:56 PM, dovepa via EV wrote:
A 120volt outlet is usually only rated for 15 amps.
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