Removing a Meridian Mail column.

[hached]

Hi Folks,

I have to remove a Meridian Mail column from a working Option 61.

The MerMail is on it's own pedestal and is DC powered, the system is already decommissioned; I just need to physically remove it.

My question is how to I remove the DC power without killing myself? This system has rectifiers and batteries.

Any guidance would be appreciated.

Regards.

DH

 

[KCFLHRC]

There should be separate breakers for that column in the rectifier. You will also need to re option your system monitor to tell it to reduce the number of slaves.

 

[janaya]

Turn the breakers off at the DC Power plant.
Turn the breakersoff at the base of the column
Take the power cables off the pedestal one at a time, capping the end with electrical tape after you remove. Use enough so the copper doesn't break through
Once removed from the column, you can do the same on the DC Power plant.

DC power - don't touch the negative to either the positive or the logical return. It will arc on you if you haven't turned off the breakers. Other than that, just take it slow and you won't have any issues. I have been inside a live DC plant pulling in cable and as long as you don't touch the negative to the either the positive or the logical return you will be fine.

One last thing. Don't touch the negative to either the positive or logical return.
DON'T TOUCH THE NEGATIVE TO EITHER THE POSITIVE OR LOGICAL RETURN

 

[hached]

Thanks for the feedback guys.

One last question, I have a multimeter, I would like to check at the PDU to make sure that there is no power before I start unplugging the DC leads. Is it as simple as Red lead on Positive and Black on Negative or will that kill me? lol

Once I kill the breaker at the rectifier and the PDU).

I'm a software guy, can you tell!.

 

[Reusser]

DC voltage so one is neg and one is Pos - we can not verify color with out looking in rectifier.
Multimeter will read it eitherway so yes use your multimeter to check if power after flipping breaker off on Rectifier.

Remember though that even with all breaker off on recifier, as long as batteries are connected it is live

repeated from janaya:

Don't touch the negative to either the positive or logical return.
DON'T TOUCH THE NEGATIVE TO EITHER THE POSITIVE OR LOGICAL RETURN

 

[KCFLHRC]

Reusser, I'm not sure I follow your logic when you say "Remember though that even with all breaker off on recifier, as long as batteries are connected it is live" , If the breaker is off then the -48v DC is no longer at the PDU, that is the reason for the breaker in the recifier. Just like a light switch, you interrupt the hot side. Keep in mind this is DC power, the negative is really the hot and typically is a red wire with black being the + and green usually being the personal safety ground wired to the column frame under the PDU. However, some people tend to use what ever color wire they have available and may only put phase tape on it to denote it's purpose.

 

[Reusser]

Sorry was refering to the Rectifier as always having live power not the PDU. Once he removes cables from the PDU he will have to remove other end from rectifier.

 

[janaya]

And don't forget the lovely Logical Return. Never understood this as it goes back to the + bus bar. Guess it has something to do with the PDU unit. Once you do a couple of these hot, you get used to it.

 

[Raycons]

BREAKERSOFF