Easy question for you....
- Thread starter 220/221
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K8MHZ
Senior Member
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- Electrician
Huh?
They would be nearly identical, the meter doesn't care which voltage you get your watts from.
zog
Senior Member
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- Charlotte, NC
KWH's are billed at the same rate, you pay about 10 cents per KWH regardless of how you apply it.
K8MHZ
Senior Member
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- Electrician
I wonder if he meant amps instead of watts.
There isn't much that only draws a 1/2 or 1/3 of a watt and even if there was, the cost would be minimal.
At 10 cents a KWh, a 1/2 amp load would cost 1/4 of a cent to run 24 hours continuously.
Now, if we had a .41 AMP current at 240 volts, that would be 98.4 watts which would cost 23.6 cents to run for 24 hours.
.36 amps at 120 volts would be 43.2 watts, a bit less than half of the 98.4 watt load, above.
(Anyone else having problems with this site loading slow today???
)Uhhh...I'm an idiot. :roll: I did indeed mean amps.
The spefics.
I retrofitted a bunch of bollard lights from 50W, 240V metal halide to 18W, 120V compact fluorescent and someone was insisting that I increased the load.
I have a side by side amp meter testing thing but it is only set up for 120V.
I connected the 18W lamp to the ampmeter and it drew .36 amps.
I changed the tap on the MH ballast to 120V, connected it to the ampmeter and it drew 8.2 amps.
I'll rephrase the question.
Does my retrofit (240V, 50W MH to 18W, 120V CFL) change the load significantly?
My logic says, .36A x 120V = 43.2W and .82A x 120V = 98.4W, therefore the watts and operating costs are substantially reduced. Am I missing something because I tested the MH @ 120V rather than the 240V they were originally operating at?
Pardon my ignorance but I am more adept at the mechanical end of this trade.
- Location
- Chapel Hill, NC
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Don't you mean .82 amps not 8.2? You probably have not changed the wattage much but it is hard to tell since we don't know the PF of the ballast.
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- Location
- Massachusetts
There is no doubt in my mind the 18 watt CFLs will cost less to run than the the 50 watt MH lamps.
Of course the CFLs only produce about 1/3 the lumens as the MHs.
Yes but that wasn't an issue in this case. It was a louvered bollard and most of the light was blocked anyway. There are some still installed side by side and I can't really see the difference.
I just want to confidentally be able to tell this clown that he was talking out of his astrisk.
gar
Senior Member
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- Ann Arbor, Michigan
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- EE
101129-2254 EST
220/221:
Forget about the voltage it has nothing to do with your question, nor does the current.
If the wattage ratings of the bulbs are correct and you have an equal number of bulbs in each group, then the set of CFLs will consumer 15/50 = 30% of the MH devices.
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220/221:
Forget about the voltage it has nothing to do with your question, nor does the current.
If the wattage ratings of the bulbs are correct and you have an equal number of bulbs in each group, then the set of CFLs will consumer 15/50 = 30% of the MH devices.
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- Massachusetts
That does not make any sense.
mivey
Senior Member
Assuming the MH were old, dirty, color-shifted, lumen depreciated and other things that would lead to a higher net loss factor. It is within reason to figure that the old fixtures might have a net lamp lumen depreciation factor easily below 70%, maybe even approaching 50% or below. The new CFL ballast might be better than the old MH ballast as well.
In that case, you might not notice a big difference in a brand new CFL and the tired old MH that had a higher initial lumen output.
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- Massachusetts
If the light is putting out less it will be dimmer.
Thank you capt obvious. :grin:
Thank you capt obvious. :grin:
mivey
Senior Member
Well, it don't sound quite as elegant when you put it that way. :grin:
You can't really see any more light from them MH's compared to the CFL's, mostly because they are buried behind the louvers 3' off the ground.
Even on the bench, in the open, the MH didn't appear much brighter.
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