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metal halide ballasts

> From: "Michael A. Bateman" <spine at stlnet_com>
> Date: Sat, 15 Mar 1997 10:50:14 -0600
> Subject: New IceCap MH Ballasts

> For those of you using MH lighting or are considering it, IceCap
> Industries has a new Electronic Metal Halide ballast.  They make some
> pretty amazing claims and after talking to them on the phone about
> it, they have me convinced to give the new product a try.  I know my
> current MH ballasts run quite hot and as a user of their VHO ballast
> (which lives up to all of its claims) I'm excited about this new
> product.  Aqualink Direct is selling them for $169 for a single lamp
> ballast.  The following is a list of their claims.  

It is unlikely that high frequency operation increases the efficiency of 
a metal halide lamp.  The arc tube is too short.  Therefore, most of the 
gains are probably in ballast efficiency.  Let's assume that the icecap 
ballast is 100% efficient, and the ballast losses for a 175 watt metal 
halide are 20% of the nominal power of the lamp (which is about right.)

Cost to run a traditional 175 watt metal halide for a year, total
energy consumption 210 watts, 10 hours per day

.21 kW * 0.12 dollars/kWhr * 3650 hours per year = $91.98
Cost to run a 100% efficient ballast + 175 watt lamp, total energy 
consumption 175 watts, 10 hours per day

0.175 kW * 0.12 dollars/kW hr * 3650 hours per year = $76.65

for a whopping savings of:  $15.33 per year.

Advertized cost per ballast is $169.  Time to pay back ballast cost, 
11.0 years.  Equivalent interest rate, 9.1%.  You will do a lot better in 
the stock market.

It looks a little better on a new installation, where you don't have to 
discard an old core and coil or potted ballast.  Assuming a traditional 
ballast cost of $50, the payback time on a new installation is 7.7 
years.  Equivalent interest rate, 12.9%.

If they can show real increases in lamp life, the ballasts will look a 
lot better.  The reason that I'm dubious about that is that part of the 
decay of a metal halide lamp has to to with high temperature chemistry, 
and it isn't immediately obvious to me how high frequency operation is 
going to affect that.