250w HPS. How do I plug it in?

[Buhdah]

its not the same as a dryer socket. a dryer socket is much bigger. this one is the same size as a standard 120v plug. only difference is the orientation of the prongs.

 

[rives]

Here is a chart of various plug configurations used in the US. As I said, the one that you have is very common, but usually only for large power tools.

http://www.stayonline.com/reference-nema-straight-blade.aspx

Basically all that you have is a hood and socket. The lamp may or may not work, and is a pretty low dollar item anyway. If the hood looks like what you want to run, you can easily source the rest of the gear. If not, buy a whole system.

 

[StankyBeamer]

Look up lumepower ballasts. I have three I've been running for a few months problem free. They're digital, run at 120 or 240, and put off like no noticeable heat. Around $120 with free shipping for a fan cooled thousand watt. Also flip box compatible

 

[magiccannabus]

Given how many fundamental questions you've had to ask in this topic, I would strongly recommend for your own safety that you just buy a new ballast/bulb/hood setup. There are some truly affordable ones out there, and no rewiring would be required. Please bear in mind this stuff can be very dangerous and a fire is never good, especially in a state where its not legal. In a non-legal state even if the fire department puts it out, chances are they will Rico your house and your insurance won't pay you a penny. Its frustrating to struggle for the right equipment when you're poor or unsure of what you need, but playing it safe is a good idea.