Live working on DC -48V systems

[Startinez]

Afternoon all,

Just after a bit of advice and clarification on an issue that was presented to me today. For a bit of background I work in the telecoms industry and today was notified of a manager for a client I work for, advising live working in DC distribution boards. More specifically, isolating the specific MCB which said circuit relates to, removing the relevant equipment, and then removing the relative MCB from the DC board without isolating the whole thing.

As far as I'm aware and in all of my recent teachings, it's simply that live working is not permitted under normal circumstances (regardless of AC/DC and system voltage) and unless it is absolutely unavoidable - which simply isn't this case. This was advised due to wanting to minimise downtime for radio equipment by only isolating the specific circuit which as I've said, is fine, but the removal of the MCB after this shouldn't happen without the whole board being isolated surely?

Thanks in advance.

 

[westward10]

You are quite correct with regards to working live. Why not leave the breaker in place.

 

[Startinez]

You are quite correct with regards to working live. Why not leave the breaker in place.

Exactly, this was the solution I gave to my boss but I just wanted to check that I hadn't missed anything regarding DC. Ultimately, if they want no downtime this is the way it will go.

 

[westward10]

Will you have to remove the circuit from the board because it will be live even with the mcb off.

 

[Startinez]

Will you have to remove the circuit from the board because it will be live even with the mcb off.

I don't quite follow, why would it be live even with the MCB off? I don't have all the details, I'm not involved in this work myself but I was asked for advice by my manager as he'd seen this information handed out and thought it was wrong.

 

[westward10]

If you are going to isolate the mcb at the board to remove the circuit the rest of the board will still be live.

 

[Startinez]

There is a main isolator within the DC board which could be used, but this is exactly what the memo wrongly advised against. Really either the circuit should be isolated by the individual MCB - then the item removed but the cable would remain in place (if their priority is downtime). Or the other option (if their priority is to remove equipment and all redundant cabling) is to isolate the entire DC DB and remove the circuit & MCB.

 

[davesparks]

If you are going to be working inside a live DB then you should be following a documented safe system of work which would usually involve temporary insulation/shielding, PPE, a specific order of operations, supervision etc etc.

As a trainee you should definitely be receiving proper live working training and full supervision if you are to do this.

 

[Startinez]

If you are going to be working inside a live DB then you should be following a documented safe system of work which would usually involve temporary insulation/shielding, PPE, a specific order of operations, supervision etc etc.

As a trainee you should definitely be receiving proper live working training and full supervision if you are to do this.

Absolutely agree, and I wouldn't do that. It rang alarm bells to begin with and that's why I wanted to gather more information here before confirming my state on this!

Like I said, this work does not directly affect me at this moment but it is work that will probably make its way to me eventually. Thanks for all your advice guys.