OpenSprinkler › Forums › Hardware Questions › OpenSprinkler Pi (OSPi) › 24 VAC Transformer: will I blow the board?? › Re: Re: 24 VAC Transformer: will I blow the board?? April 28, 2014 at 4:49 pm #26595 frankie75Member @scottsh wrote: Interesting – no I didn’t. I just trusted the 26.5VAC output it listed and ran with it. If you have a tester at home, would you mind measuring yours, in VAC mode, with the terminals disconnected from Ospi board?