I have a question for everyone on GoL. I just tried running a 70 watt HPS lamp in my 100 watt HPS 201SA NEMA head. I only ran it til it warmed up cause I didn't want the lamp to explode or something. Now, I want to try putting a 400 watt HPS lamp in my 100 watt HPS 201SA NEMA head. Is that a bad idea? I just want to see what happens. But if something could go wrong like the lamp exploding or something then I won't do it.
It won't blow up or burn up anything, at least not in the short run. I've run a 400w HPS (and also a 400w mercury) several times on my 100w HPS ballast - the lamp will start and warm up, but obviously not to full brightness. It'll stay in that "low-pressure sodium" monochromatic yellow stage. I've run "improper lamps" on ballasts many times but not more than 15 minutes at a time, and not regularly. Explosions usually result only from extreme overvoltage, short circuits or no current limiting at all (i.e. connecting a lamp directly to mains).