Since I am well aware that North American 1000w H34 mercury vapor lamps run at twice the current and half the arc drop of North American 1000w H36 mercury vapor lamps, I am wondering if a 1000w H34 mercury vapor lamp with any 120v autotransformer ballast will trip the breaker on a typical North American 15a circuit. Does this mean that I should have issues running 1000w H34 mercury vapor lamps on a 15a 120v circuit with a proper 120v input autotransformer ballast designed for such lamps?

  U need do some electrical math here

  Remember Volt x Amps = watts

  So a 15 amp breaker and u know voltage is


   120 V x 15A = 1800 watts

     Meaning U dont want any thing else on circuit running at same
 Time.

   Newer houses now days been having 20 amp bedroom circuit.  Due electric portable space heaters or window A/c and computers or TV that would Trip a normal 15 A breaker.

Hello WorldwideHIDCollectorUSA,

basically funkybulb gave you the answer however he took one thing out of consideration. 120x15A = 1800VA, VA being volt amps. You can have a "load" of 1800VA and drawing a current of 15A and still have not a single Watt of power dissipation. Possible is this for example with an (ideal)  inductor or a large capacitor. If you ad inductance or capacitance in an AC Circuit you creat reactive power and blind current. reactive current is an current. This current is flowing thruw you conductors between it sources and the effecting component, it is flowing with all the consequence, and inducing loses and wear on the system, however it cannot be used to do work. Your ballast is also producing reactive current, this is why you put capacitors in parallel to the input (line), to compensate these reactive currents.
So the question is how much reactive current does your ballast produce? Well thats what the power factor says to you, that information is missing.

However i don't think  that the current flowing to the line to your lamp (The geometrical addition of reactive and real power) will reach 15A. But I can't tell.

The second thing, a circuit breaker will not break the circuit immediately if it is slightly overloaded. Every breaker has a time current chart wich shows how long an overload must be present until a trips. If you would draw a few amps over it creating it can still take 30min to several hours according to its exact rating and timecurve. Is it good to overload a cable even for short time? Certainly not. So think carefully what your doing, your responsible for it.


Best regards Alex

And even when the ballast is perfectly compensated with the lamp stabilized, its power factor is not unity. With discharge ballasts there is always quite significant current distortion (series choke yields triangular wave instead of the sine, the CWA will be way more spikey). On top of that the CWA is phase compensated only at one single particular mains voltage (I would expect at the minimum, to prevent current dropping with voltage going up, which could lead to instabilities in larger installations with some accumulated Neutral resistance). Any other and the result is quite significant reactive power.
 So it is very likely a 1500W load will exceed the 1800VA.
Plus the compensation goes through the window when the lamp has not warmed up yet.
All together, the general rule is to size the feed circuit VA rating for 2x the lamp power. So a 1500W lamp need 3000VA rated circuit, so 25A rated breaker and wiring at 120V.

If the lamp is of European vs US spec does not matter (provided the ballast is matching the lamp), as the different voltages and currents get transformed by the ballast to about the same anyway.

Maybe check to see what else is plugged into the circuit. The 1000 watts drawn by the lamp can easily cause an overload if something else like a microwave is plugged into the same circuit as the light and is allowed to run while the light bulb is drawing lots of current as it warms up.
Another thing to check is if an RCD is connected to the circuit. You may have a ballast that's close to EOL and is producing residual current which will trip an RCD protected circuit
Also, check to make sure you didn't accidently wire something backwards