When you guys order HPS cobras, what ballast do you all typically spec, and why when you have the ability to do so?


Me personally HPF reactor when I can (ie 150 watts and under). Its simpler, lighter, more efficient and has a lower current crest factor meaning longer lamp life.


Though I've seen other on here go CWA or magnetic regulator, me being intrigued by it. Also is it true that reactor ballasts are noisier? 

It depends on the anticipated voltage variation/tolerance at the place.
Series reactor usually does not allow more than +/-5% (without exceeding lamp spec tolerances). Usually good enoufgh for most installation unless you are long stretch away from the HV/LV distribution transformer.
CWA uses to tolerate from +/-10..15% variation
Mag-reg may go up to +/-30%, another advantage is the crest factor is about equivalent to series reactor (in fact it is a series reactor with an upstream voltage regulator; although these components are integrated into the common "core&3-coil" and capacitor assembly). The three coils means triple losses with about double mass than series reactor.
But the price to pay for the wider tolerance uses to be higher losses and mass and of course purchase cost (the max-reg being the lossiest, bulkiest and most expensive).

The question is, if it isn't worth to specify LFAC electronic ballast when the mains is expected to vary a lot, because these are able to cover even wider range while retaining their efficiency.
Reliability wise I would not expect the mag-reg to be any better than the electronic: Mainly the capacitor will wear out rather quickly and the ballast is quite sensitive on it.

So if you are close to the pole transformer, so not much voltage variation to be expected, go for the series reactor.
If wider voltage variation is to be expected, I would go for the electronic, of course some reputable brand model, not the cheapest one...

Are you planning on ordering one yourself? If you want something that's going to last a really long time, a reactor ballast will be your best bet. For 200-250w HPS, most manufacturers offer HX-NPF ballasts which are more efficient and should also last a really long time, but they won't be as tolerant of power glitches as a CWA ballast.