Just curious, can the 250w HPS run MH lamps or vice versa? USA versions please as I'm in Canada. I know I asked recently in someones thread but I can't find it in the sea of new topics..

In most cases, 250w HPS and MH are not interchangeable. This is because 250w S50 HPS runs at 100v 3.0a while 250w M58 MH and M138/M153 pulse start MH bulbs run at 130v 2.15a. However, there are some European 250w and a few US 250w pulse start MH bulbs that actually can run at 100v 3.0a and can work directly on 250w S50 HPS ballasts while some HPS retrofit lamps for MV ballasts such as Philips Retrolux 250w HPS lamps and Iwasaki Sunlux Ultra Ace 250w HPS lamps will run at 130v 2.15a and will work just fine on 250w M58 MH ballasts or 250w M138/M153 pulse start MH ballasts without the ignitor in the circuit.