|>>I was wondering if someone could help me. I have only one 220V plug
|>>(for the oven) in my appartment and I would like to use an oven and a
|>>clothes dryer. Would it be safe to plug the dryer on the oven plug?
|>>Is there any adaptor I could use?
|> The problem is your dryer needs 30a overcurrent protection and the
|> oven circuit is probably 40 or 50a.
| The Op wants to know if he can use smaller current appliance on an
| existing circuit..
| Of course you do that all the time with 110volt devices. Who ever heard
| of having a breaker rated to protect your clock radio.
Breakers are rated to protect the building circuit. Appliances are then
rated to be safe on circuits rated up to what they are permitted to be
plugged in to.
| And it is the norm in 240volt 50 hz countries to plug in anything as
| long as it is not tooo big.
That's the key ... not TOO big.
Circuits in the UK are typically 30 amp ring circuits. They also require
fuses in the plugs. Plugging your clock radio into a 30 amp circuit is
more risky than in a 20 amp circuit. The wire would have to be thicker
to be equally safe, unless there is a fuse. The UK scheme, though quite
inconvenient, is probably a lot safer, since you can, in theory, put in
a 1/4 amp fuse for the clock (I don't know what the legal requirements
actually are for that).
I know this is inconvenient because I have in fact dealt with fused plugs
in the USA. At least at one time, line voltage Christmas light strings
had these. I don't know if it was actually required, then, or not. But
they did periodically blow for no apparent (at the time) reason. Maybe
they were just on for too long at a time.
| Unless this is not allowed by some obscure NEC provision in 240 volt USA
| installations Of course it is OK.
It depends on the actual appliance. All new appliances today need to be
safe on a circuit protected at 20 amps. There are a number of ways to
achieve that. Having every part rated to some percentage of that current
level is one. Having parts that will ensure a higher current flow on a
failure is another, provided that higher current flow is within the range
that will trip the breaker. If the breaker is rated too high, it might
If your clock motor winding shorts out and starts pulling in 30 amps of
current through the remaining part of the winding, is a 30 amp breaker
expected to trip?
| The breakers protect the wiring not the device.
But the device has to be rated for the available un-interrupted current,
or provide its own supplemental protection.
| Phil Howard KA9WGN (ka9wgn.ham.org) / Do not send to the address below |
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