Temp Situation

[Alwayslearningelec]

Situation:

Have 800A distribution board feed from service switchgear switch.

The 800A distribution board feeds (4) panels and 2 xfrmrs.

All the loads must remain active with very limited to no downtime.

The 800A distribution board is being replace with new 800A board IN SAME SPOT.

The way I see it the only way to do this with the least amount of downtime is rent generator to feed a temp board and swing loads from existing 800A board to a temp board.

Then install new work and swing loads over from temp board to new board.

Make sense?

 

[petersonra]

My first question is what do you mean by "very limited to no downtime"?

You will have downtime no matter what you do.

If this is not a 24/7 operation schedule the work for sunday morning at 1:00 am.

 

[infinity]

I've seen zero downtime temp swing overs but it involves tapping the load conductors while energized with "live" taps. Why a generator and not just tap off the existing service switch?

 

[Alwayslearningelec]

My first question is what do you mean by "very limited to no downtime"?

You will have downtime no matter what you do.

If this is not a 24/7 operation schedule the work for sunday morning at 1:00 am.

Its is 24/7 operation . Yes you'll have doen time no matter what but that should just to swing over loads.

 

[petersonra]

Its is 24/7 operation . Yes you'll have doen time no matter what but that should just to swing over loads.

Is there someway to just eliminate the distribution board rather than replacing it?

 

[Alwayslearningelec]

I've seen zero downtime temp swing overs but it involves tapping the load conductors while energized with "live" taps. Why a generator and not just tap off the existing service switch?

That's a good point. See attach showing existing feeders from service switch to board being replaced.
What would the sequence of work be there?
1. Existing conductors could remain and be live when you do a tap?
2. So you could get all your temp in and even the tap feeders while existing is live? Your not increasing the load.
3. Once temp is in you can just swing the loads over to the temp board? Could you have both the temp board and existing board live since the load is not being increased?

 

[Alwayslearningelec]

Is there someway to just eliminate the distribution board rather than replacing it?

How would then feed all the existing loads( panels ad xfrms)? Can't do it from the service switchboard feeding the board.
I'd say no way.

 

[petersonra]

How would then feed all the existing loads( panels ad xfrms)? Can't do it from the service switchboard feeding the board.
I'd say no way.

install enclosed cbs downstream to each load. change out distribution board to be a junction box. just have to watch out for the tap rules.

 

[Alwayslearningelec]

install enclosed cbs downstream to each load. change out distribution board to be a junction box. just have to watch out for the tap rules.

And the enclosed CB's are fed from where?

 

[petersonra]

And the enclosed CB's are fed from where?

The jbox you replaced the old distribution panel with.

 

[Alwayslearningelec]

The jbox you replaced the old distribution panel with.

What would the source of power be? The service switch? That would feed several enclosed circuit breakers?

 

[petersonra]

What would the source of power be? The service switch? That would feed several enclosed circuit breakers?

The same place the distribution board gets it's power. Probably could reuse the existing conductors.

 

[Alwayslearningelec]

Ok sounds like a good idea and informative for me although i dont think the engineer will go for that.

 

[petersonra]

Ok sounds like a good idea and informative for me although i dont think the engineer will go for that.

If the design is already set, why didn't the engineer also design the temp feed.

 

[electrofelon]

I assume they have their reasons, but Does the distribution board really need to be replaced? Unless the breakers are obsolete, why not just replace all the breakers? Other than the breakers, there really isn't much to "go bad" in a panelboard.