Al B, you make some valid points, but I also think you need to accept that I've also made some as well.
And yes, you have; but be careful what you think my opinion of digitals is. I think they're great stuff, as I said in my first post on the topic in this thread. I just think they remain exxy and the Lumatek 30% greater brightness claim needs a verification.
Okay, you're the exception here because you're in Australia, your magnetic ballasts appear to be cheaper than anywhere else (probably because you're closer to places like Taiwan where they're made) and your electricity charges also appear to be somewhat cheaper as well.
Cheap Asian ballasts are a big part of it. Power is not that much cheaper, though- AUD12c/kWh vs about USD8c/kWh in the USA (almost the same).
don't forget though, your replacement bulb costs are going to be more than with a digital!
I usually replace my 1000s once every 12-18mos, preferably at 12 mos. They've still got plenty of starts left in them at the end of a year, even running on magnetics, but the tube output will have started to degrade more than I like. A digital can't stop the HPS tube from wearing out, but it does reduce the consumption of mercury on each startup, important for new low-mercury content tubes. Regardless, a digital offers no tube life advantage over a magnetic if tubes are replaced annually, as many makers recommend for horticultural use of HPS.
It's unfortunate that you are in a position that makes it uneconomic to purchase a digital ballast even if you wanted to, but thats not necessarily a valid reason for showing as much scepticism towards digital ballasts as you appear to.
Again, I don't think digitals are a bad thing at all. When the prices come down, as said before, I'll be at the head of the queue.
They are more economic to operate over the short and longer term than Magnetic ballasts, they do output more lumens than equivalent wattage magnetics as evidenced by 1) the manufacturers claims and 2) My own reading of owners reports on digital ballasts ALL claiming that the bulb looks brighter than the previous one. They prolong lamp life and maintain maximum lamp illuminence for longer as well as emitting less heat and noise.
Sorry, but "looking brighter" is not an independently replicatable measure. I would also fully expect a manufacturer to tell me that their product is good stuff and better than anything else; that's why I am looking for an
independent test of a magnetic vs a Lumatek with the same HPS tube,
using a light meter, not a visual estimation of brightness.
An HPS light's lifetime is a mix of wear from startups and running hours. I maintain that a digital ballast will still supply the very same volts and amps to an HPS tube as does a magnetic
while running- and thus can't possibly increase luminous output nor decrease tube wear from running hours.
I'll agree, and have since I started commenting, that you get
more starts out of a given HPS tube with a digital because of the better current control on startups.
I further agree that digitals are more efficient; you said:
The 600w Lumatek runs on 5.1-51.5 amps*, using Ohms law it's pulling (5.1x 120) 612 - (5.15 x 120) 618 watts of electricity. A standard 600w Magnetic core and coil will typically use 5.7 amps on a 120v system so that's pulling 684 watts. The difference is (684-61
= 66 watts.
OK, so accepting your figures of 618W vs 685W for a magnetic and the savings of 66W, we're looking at a (guessing) ~60-70% savings
on the cost of operating the ballast.
However, the
total power saved, 66W, is only about a 9% savings over the magnetic ballast and the HPS tube.
Yes- it's a savings- 9% is 9%.
Yes- the digital ballast will give more starts per tube. If you're a city council running a streetlight for 3-4 years, yes, the digital ballast cuts replacement costs significantly as a streetlight's specific output isn't as important as starting up- and it's on startup that HPS tubes almost always fail. More output degradation is tolerable in streetlights. However, if you replace tubes annually as suggested by the HPS tube output ageing curves, it's not significant.
It's great to have the latest and greatest. But at what cost?
