Hey guys, think this fairly straight foward...
We are interested in installing a 20A 220V AC unit in a location where
a 60A 220V welding outlet already exists. A welder will not be used
there. The existing cable is rated for 60A and there is a 60A CB at
the panel for this. There is also an appropriate 60A 220V outlet on
the other end.
The goal is to change the CB to 20A and change the outlet to 20A 220V
while using the existing wire. Is this at all possible? Seems theres
going to be connection issues w/60A rated cable to a smaller 20A CB
Any ideas, tips, hints?
The outlet is going to be a different configuration, it would need
to be changed to match the plug used on the 20A appliance. You're
right, the oversized wiring can stay, no problems there. As soon
as you change the outlet, you are limiting the circuit to a safe
maximum of 20A, so it is a smart move (although possibly not needed
to meet code, I don't know) to downsize the breaker to 20A as well.
Think about it: If something goes wrong in the appliance and it
decides to start pulling 50A, you want the breaker to protect you
and shut it down. That concept doesn't hold much water when it
comes to typical "convenience outlet" circuits in your home where
there might be 4, 5, 6 duplex receptacles on one circuit, but in
this case (one receptacle, one breaker) it makes sense.
I have put in smaller breakers than allowed for exactly that reason; but I
have always thought about lamps with #18 plugged into 20a circuits, and
wondered how many fires result from that.
I have heard in England each outlet has a breaker on it, sized to what is
expected to be plugged in.
The purpose of the breaker is NOT to protect the appliance. The breaker
is there to protect the structure ---- the wires inside the walls. You can
plug a 7 watt nite lite into a 20 A wall outlet, or a 1500 watt heater.
device can cause a fire if it fails or shorts, but NOT in the walls between
the breaker panel and the outlet.
If the appliance needs to be protected to pass the UL safety requirements,
it will be manufactured with internal fuses of some type.
Andy in Fink
Happens countless times every Chrustmas season, idiots wire a tree
with 20 strings of mini-lights, 3 spotlights, 1 motorized tree top,
etc, etc, all running in series through ultra light wire, the first
one of which is carrying the entire load and eventually gets hot
enough to start the carpeting on fire.
That's carrying it a bit too far, IMHO. For the ultra safety minded,
an "extra added safety device" here in the states is a 5.99 power
strip with built-in 15A breaker.
That makes all of the sense in the world for branch circuits with
multiple convenience outlets, 'cause you never know what's going
to be plugged in to any of them, if anything.
But when you have a situation like this, where it's one breaker
protecting one receptacle for an appliance, it's foolish to place
the line cord in a position where it could be carrying 2x or 3x
the intended current flow without tripping the breaker.
Economically speaking, if you're (original situation in this
thread) saving $100-$300 from having a new piece of smaller guage
wire installed, then why not spend $20 of it for the proper sized
Note that it is the plug that is fused. Not the outlet!
However; as I understand it;
Each circuit in a typical UK home does go back to a circuit
breaker or fuse in the main panel, which in the United Kingdom is
often called a CU (Consumer Unit).
1) The voltage over there for almost all appliances is 230 volts
instead of 115. So that for the same amount of wattage the
current will be half of what we see in North America. For example
a 1200 watt electric kettle at 230 volts requires 5.2 amps; at
115 it's 10.4 amps! The lighting circuits etc. are also 230
volts. (Well; except for 'low voltage lighting etc.').
2) Many UK homes have their electrical outlets connected via a
'ring main'. That is to say the house wiring for a run of outlets
leaves the fuse/circuit breaker panel and is wired to each outlet
in turn, same as North American practice; but at the last outlet
is run back to the same circuit breaker/fuse for that circuit at
the main panel. In that way the electricity can flow both ways to
reach any of the outlets on that 'ring'. That means twice the
current can flow in that circuit; twice the current using I
squared etc. = Watts, means that four times the power can be
handled on a certain gauge of wire. (Or thinner wires using less
Taking into consideration that their voltage is also twice that
means that a lot of power and a considerable number of outlets
can be provided on each ring. So much so that one whole floor of
a house can be served by a single ring main circuit. Fewer
circuit breakers? Smaller panels (CUs)!
Each plug is fused to the size of its appliance; a very safe if
more expensive? method. The quality of the plugs and sockets
despite the lower amperages is very good. Also the outlets are
'shuttered'; that is the insertion of the ground pin into an
outlet moves shutters away from the live and neutral pins. Very
unlikely a child could stick a hair pin or something into one of
those outlets; which at 230 volts is probably a good idea.
3) AFIK there is no need in UK homes for two pole/double pole
circuit breakers. There are only two wires, 230 volt live, a
neutral, plus an earth/ground coming into typical UK homes.
In North American practice there are three wires, plus a ground
coming into a typical house. 'Heavy appliances' then use 230
volts, from the two live 115 volt wires, via double pole
breakers/fuses. Outlets and lights being provided with 115 via
single pole breakers from one of the 115 volt live wires and
IMHO the two systems are just different not necessarily one
better than t'other.
Corrections/amendments welcomed. Cheers.
PS. It's 50 Hertz AC in Europe. Also UK light bulbs 'plug in'
using a bayonet socket compared to North American Edison Screw;
at 230 volts of course!
The whole house is wired to 240V. Unlike North America, where
there are two hots and a neutral, with 240V across the hots, and 120V
each to neutral, UK homes (and to an extent the rest of the 230V
world), have 230V phase to neutral, and one phase entering the home
(in some countries 3-phase may be fed to larger homes).
FWIW, ring circuits are fed with 2.5 mm sq wire (approx eqiuv#12AWG) ,
and protected by a 30A fuse or 32A MCB. Radials (outlet circuits in a
straight line, where a ring would be impractical) are run with 4 sq
mm wire (approx eqiuv #10AWG).
But dodgy, with people often instaling the wrong sized fuse, or
not even a fuse at all.
Some circuits/appliances require a double pole break.
Actually, there is no separate ground fed from the supply in NA homes,
the protective ground is derived from the supply neutral and the main
service disconnect. Some UK homes derive earth the same way.
European homes also tend to have what is called an RCD, which is more
or less a master GFCI that protects a number of circuits, rather than
having a GFCI breaker per circuit or outlet where needed.
In my experience the vast majority of fires that result from electrical
shorts involve either substandard wiring, objects cutting through insulation
on wires (i.e. screws, nails, or wires being strung where they shouldn't and
being cut), or shorts in electronic devices. In the 11 years that I've been
in the fire service I don't think I've seen a fire that resulted from a lamp
As another poster mentioned, the breaker is there to protect the permanent
part of the system.
However, how much current a given wire size can take is dependent on
a number of factors, such as temperature ratings. The part of the code
that says "AWG14 for 15 A" or "AWG12 for 20 A" (speaking of copper here)
is not the same part of the code that dictates the rules for things like
power cords for lamps.
Case in point: I will be installing a 3600 Watt built-in oven in the
house we are building. It is powered by a 240V/20A circuit, which
naturally has a 12/3 cable feeding it. The cable that comes out of the
oven that attaches to that 12/3 cable in a junction box near the oven
has 16 gauge wires!
Perfectly acceptable as this falls under a different part of the
"Never ascribe to malice what can equally be explained by incompetence."
The power cord for the AC is not rated for 60A, however. There's a risk of
fire, should something short out in the AC unit.
Doug Miller (alphageek-at-milmac-dot-com)
Save the baby humans - stop partial-birth abortion NOW
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