Saftey first

[jjust61]

Be careful out there people, I just ran across a 3 phase rooftop unit with a single phase disconnect installed on it. Third leg was hot all the way from breaker down stairs right to 1 leg on compressor. Volts were everywhere and I was lucky I checked with meter before touching. Even more confusing was that unit used a single phase contactor which made it appear even more like a single phase that a 3 phase. Unit is wired correctly with new disconnect.

[frank26601]

always check with meter i learned the hard way

[karsthuntr]

I had a new install I was working on where an electrician did that to me. I was working late on a sat. to start the equipment up. I called the electrician right there and made them fix it, I wasn't waiting until Monday. He had to drive an hour to get to me.

[ZiLLaCooL]

Be careful out there people, I just ran across a 3 phase rooftop unit with a single phase disconnect installed on it. Third leg was hot all the way from breaker down stairs right to 1 leg on compressor. Volts were everywhere and I was lucky I checked with meter before touching. Even more confusing was that unit used a single phase contactor which made it appear even more like a single phase that a 3 phase. Unit is wired correctly with new disconnect.

I always check each leg to ground,AT THE UNIT!,not only this,always Verify your meter is working at a known voltage soure.Not only will this save you the hassel of melted fillings,it just may save your life.Point being if your meter is having a bad day,odds are you will too!

[Tool-Slinger]

I always lift the lid and visually verify the contact arms pull out. I have seen about 6 or 8 over the years that are broken and do not actually disconnect all 3 of the legs.

[Adnshel]

Verifying your meter on a known voltage source is important. Low batteries can KILL.

[flange]

a buddy of mine teaches for one of the locals, and also teaches the osha thirty course.......he jst cut off his thumb on a powersaw. oops.

[y7turbo]

I always lift the lid and visually verify the contact arms pull out. I have seen about 6 or 8 over the years that are broken and do not actually disconnect all 3 of the legs.

I just had a brand new disconnect that had failed to open all 3 legs..

Always check each leg to ground before touching any wires.. I also keep a lock in my tool bag to lockout a power source if needed.

[gruntly]

A few years ago a competitor jumped one leg in an outdoor disconnect because it failed... Then they lost the contract to us.

Found it before it killed anyone, but I never found the guy that booby trapped that one or else it may have caused a fatality afterall...

[Ammonianite]

Don't forget your hardhat, faceshield, gloves, and flame-retardant clothing. You need to put those on before you shut the disconnect off. Then verify that all three legs are dead. Once dead, lock out the unit before servicing. And if you must troubleshoot with live electicity present, you must have all the gear on.