Fluorescent shop lites: HD strikes again

I see that you have been proctologically violated. Please consult a psychologist.

I did--and an especially memorable PV it was...

Please accept my deepest sympathies

I was doing the same thing too a while back. The last couple I bought were the $27 ones (T-8, electronic ballast, but a bigger reflector) although I think at the time of my gushing this same model was much cheaper.

Most residential customers still pay for watts, not amps, don't they?

Even though you are measuring amps, I believe the electronic ballast will have the same watts.

Power factor may matter if you've got a whole field full of these. (I think some others posted in my gushing thread.) I believe that it's still true that Watts = Amps * Volts * PowerFactor.

Tim.

I also accept donations--a 1 lb jar of Prep H would do me fine.

You might try a .5 mf cap across the ballast. That will improve the powerfactor issue. Be sure to use one designed for 250 ac. Steve

Yeah, but what's the *real* power being drawn? You can't measure that without a proper wattmeter (your clampon does NOT do the trick). Cheap electronic ballasts probably have a bad power factor, but if you're residential you don't pay for that.

Best regards, Spehro Pefhany

Hum, are you sure an electronic ballest has an inductive PF? It might not be.

It's a bridge rectifier into a capacitor filter, at least in the last one I took apart. It draws current in chunky spikes near the peak of the AC line.

Best regards, Spehro Pefhany

everygoddamthing in sight....

Here's a copy of a post I made in 1998 regarding shop lights. All of them are still working....Paul

"I recently built a shop and purchased 24 fixtures from Sears. I got a really good deal(I thought!). They were on sale for $7.99 plus I got a 10% volume discount. I had bought these before and was satisfied. They were

40 watt and had real ballasts. Well I put up first one and worked great. Second one was DOA. Third one buzzed my AM radio something terrible. Went downhill from there. Ended up returning the lot. Turns out that the old fixtures had USA ballasts, while these were Mexico. Very poor quality. Ended up paying $16.95 at Home Depot and getting bulbs at Costco. Cost was a lot more than budgetted, but these work and no radio buzz."

The Prep H especially because of the "deepest sympathies"? ERS

Sure, but twice the amps at the same voltage equals twice the watts. Greg

Not if it's only on half the time... Solid state power supplies might be very confusing to simple ammeters. The real answer is to hook up abunch of them and let you electric company's meter tell you what they're drawing, since what they read is what counts...

Not true. Twice the amps at the same voltage equals twice the VA. VA times power factor = watts. This is why they always rate cheap UPSs in VA. They assume a 50% power factor so a 500 Watt UPS suddenly becomes a 1000 VA UPS (read the small print). It just sounds better to the uninitiated.

Vaughn

You can measure it with this:

Vaughn

There's a fundamental way to remove all energetic ambiguity. Delightfully simple in theory, miserable in practice:

Perform calorimetry: Immerse sed fixtures completely in a water bath (!!) in a big-assed styrofoam picnic cooler, calculate E = m x c x delta Temp. An unambiguous "Voila". The higher T loses! :) (other variables normalized out, factored for lumens, etc.)

The other issue here, w/ electric meters: Are *they* being fooled by power factors, wave forms, pulses, etc. etc.??? Could the loser in the above calorimetry test (the gold standard), *win*, according to an electric meter?

Ain't nuthin simple anymore, it seems.

Residential kWH meters use two coils, one producing a field proportional to voltage and another producing a field proportional current. The fields are perpendicular to each other; one induces eddy currents in the circular disk that spins around, and the other actually moves the disk. It's the product of the two fields - true power - that causes the disk to rotate. They're very fine devices, and the legal specification requires them to be accurate to better than 0.1%.

The commercial ones that rack up charges based on power factor etc. are more complicated.

Tim.

Sounds like someone in Meter Engineering earned their salary that week! Wow...

Having done metering work on power station performance tests I can say that

0.1% is at the limit of achievability for rotating kWh meters and not achievable over a wide rage of loads or power factors without correcting for errors. Domestic meters also do not have sufficient frequency stability or power factor stability to be within the 0.1% meter class. These are both a side effect of the thick disks required to generate sufficient torque to drive the meter dials.

Domestic meters in the UK are required by law to be within +2.5% -3.5% error. Electronic meters can be much more accurate than rotating meters for a similar cost and will eventually completely replace electro dynamic ones.

I was very amused in 1988 when I was required by the customer to have my site meters verified by the Indian NPL prior to a performance test at an Indian power station. I brought my (Norma 5155 power analyzer) electronic Whr meters to be checked at the Indian NPL with their fresh calibration certificates from the British NPL. The chap at the Indian NPL in Delhi thanked me for the opportunity to check his standards with my (better) ones.

Having said all of that. what your meter says is what you pay for whether its right or wrong, so it pays to look at what it says :-)

regards Mark Rand RTFM