1000W 120V lamp in 1500W 240V rated fixture?

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jds10011

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Location
New York State, USA
I have a customer who is looking to replace an outdoor floodlight fixture that uses a 1000W 120V double-ended halogen lamp (10" long). Since they have a number of these fixtures still working, they'd like to stay with the same lamp. The closest they've found is a Cooper Lumark LQL1500WL240, which takes the same size lamp, but is rated 1500W max at 240V. Presumably one could wire this for 120V, but I'm curious if this would mean it would have only a 750W rating, or if the 1500W rating would still stand? Thoughts?

Thanks!
 
P

poeboy

Member
Location
Los Angeles Metro area
what is the actual voltage applied to the fixture? The rating does not always = the Voltage applied to it.

a 120 V lamp with 240 V applied to it will burn real bright for 0.01 seconds.

conversely, a 240 V lamp with 120 V applied to it might glow like a night light, but probably not even that.
 
Dennis Alwon

Dennis Alwon

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Chapel Hill, NC
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Retired Electrical Contractor
If I did my math correctly

Volts Squared/ watts = R

240*240/1500= 57600/1500= 38.4 ohms

120*120/1000= 14400/1000 = 14.4 ohms

Thus a 1500 watt bulb with a 38.4 ohms resistance at 120V would be

V^2/Watts =R

120*120/38.4 = 14400/38.4 = 375 watts

So a 240 volt 1500 watt bulb at 1000 watts would be 375 watts at 120V.

Are you sure they have the same base or length?
 
cadpoint

cadpoint

Senior Member
Location
Durham, NC
...
Thus a 1500 watt bulb with a 38.4 ohms resistance at 120V would be

V^2/Watts =R

120*120/38.4 = 14400/38.4 = 375 watts
Click to expand...

I think you meant V^2/R(ohms) = P for the second line there! :) I only picked it up cause R was already proofed, earlier...
 
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david luchini

david luchini

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Connecticut
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Are you sure they have a 1000W 120V double ended halogen lamp (10" long)?

I've looked at the Philips, Sylvania, and GE Lamp catalogs, and none of them offer that lamp in 120V. They're all 240V. That's not to say that someone else doesn't make it, but I'd think if it was a standard lamp, one of those 3 would make one.
 
W

wireguru

Senior Member
Atlas lighting makes a 1500w floox which they sell 240v and 130v lamps for, so i dont see why you couldnt lamp this one at 1000w 120v....
 
cadpoint

cadpoint

Senior Member
Location
Durham, NC
Respectfully!

I've read a lot of re-fitting luminaries stories here, but in most cases it is a 1 to 1 situation; be it replacing the ballast and lamps, etc.

I don't understand why you not talking to the manufacture about their light and housing and what they have got going with the UL?

It might be dual listed (ok Forum purest your can nail me on the use of that term) to do what you'd like to do, but it might well not be, those this inquiry is dead! Then it will not matter how good or bad the math is here! :)
 
W

winnie

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Location
Springfield, MA, USA
Occupation
Electric motor research
Contact the manufacturer. There are at least three constraints on the lamps that can be fitted to the fixture, and the voltage that can be used:
voltage rating of the insulation
current handling rating of the contacts and wiring
power rating (heat dissipation) of the entire system and housing.

The insulation system is rated higher than 120V, so this is not a problem.
The entire system is rated to handle 1500W, so your 1000W lamps are not a problem.
The only question is how much current the contacts and wiring can handle.

As has been noted, the 1000W 120V lamp will require higher current than the 1500W 240V lamp.

My _guess_ is that since these same R7s contacts are used on standard 500W 120V lamps, that they will have no problem handing the increased current, but only the manufacturer of the floodlight fixture could tell you with certainty. See the note at the bottom of the page: http://www.cooperlighting.com/webDB/documents/lumark/buyersGuide/FL_LQL1500_QRTZFLD.pdf

-Jon
 
Electric-Light

Electric-Light

Senior Member
GE, OSI and Sylvania doesn't offer that lamp. Since he's redoing fixtures, now's a good time to move to standard lamps that are readily available.
 
B

broadgage

Senior Member
Location
London, England
The fixture should be fine fitted with the 120 volt 1000 watt lamp, and supplied with 120 volts.

The voltage is less than the maximum the fixture is rated for, so no problem there.
The wattage is less than the maximum than the fixture is designed for, so no problem there.
The current in the lamp holders is greater with the 120 volt 1000 watt lamp, than with the intended 240 volt 1,500 watt lamp, but should in practice be fine.
The fact that the 120 volt 1,000 watt lamps exist, suggests that suitable lamp holders must be available, and I very much doubt that manufactures bother to make 2 versions of the lampholder, one for 6.25 amps and one for 8.5 amps.
Here in the UK almost all lighting is 240 volt, though 110/120 is used for some purposes.
No one ever worries about useing a 240 volt fixture on 110/120 volts despite the doubleing of the lampholder current.

It might be a better design choice to use a more widely available lamp type, but that is a different issue.
 
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