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Electrical heat gain - Page 10

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Posted by Tim Jackson on April 17, 2009, 9:18 am
daestrom wrote:

The power rating of domestic appliances is *supposed* to be the line
power consumption, I'm not saying it is necessarily *accurate*, but it
should draw no more than the nominal wattage.  Rating lamps in anything
else is pretty meaningless, and useless except for comparing like with
like.  By law (UK/EU) power input must be specified for any piece of
equipment, for the purpose of sizing and fusing of cables.

If a lamp were rated as say 10W light output, that would be a very
different thing, and could to some extent be used for choosing between
different types of lamp for the same lighting effect (but would ignore
the effect of reflectors). In practice it requires a little effort to
obtain that information.

Motors are different.  A motor is not an appliance to be connected to
the mains and used, it is a component of a machine, and its power
consumption can only be determined with reference to the mechanical load
applied.  While a motor may be sold under the tag of 2hp(US) or
1.5kW(EU) it will carry a rating plate detailing such things as
full-load current and power factor, rpm and shaft torque, which the
machine builder uses to determine the power input rating plate he puts
on his machine.  This is a legal requirement on the machine builder.

Tim Jackson

Posted by Eeyore on April 17, 2009, 6:47 pm

daestrom wrote:

Appliances are always rated at the input power to the device ( not sub-part ).


Posted by daestrom on April 18, 2009, 2:08 pm

Maybe on your side of the pond.

But here the nominal rating for fluorescent lamps is *not* the power going
into the fixture.  The nominal rating (e.g. 40 watt) is the nominal power
rating of the fluorescent lamp sans ballast.  (see definition 1.11 under App
Q of the reference)



Posted by Jim Wilkins on April 18, 2009, 2:17 pm
"Advance" shop light ballast label:
120 Volts,  60 Hertz, Line Current .80 amp.
For 2-40W 430 MA RS lamps or 2-F-40-4FT "34W" or "35W" RS lamps 460 MA


Posted by Eeyore on April 18, 2009, 3:59 pm

Jim Wilkins wrote:

I hope you know the difference between VA and Watts.


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