Daisy Chain of Electrical Equipment

[Electriman]

Good morning,

I have faced in some cases that electrical equipmet are daisy chained to be fed. For example in one case I saw two transformers are daisy chained on the primary side and there was only one breaker that feed bothe transformers and in the second case I saw two lighting panels were daisy chained and feed from one breaker.

Does this fulfile the NEC requirements? Is there any part of NEC that talks about this subject?

 

[augie47]

It is permitted.
In the case of the transformers, care should be taken to assure the installation follows Art 450.3 for transformer protection.
For the transformers and panels the "standard" Code rules apply.. 240.4, 240.21,310,16 etc.

 

[kwired]

The panels - consider what differences there are with the following-

200 amp feeder - supplies 2 - 20 space panels each with 200 amp bus.

alternate install- same loads supplied:

Same too amp feeder supplying one 40 space panel with 200 amp bus

Do you see any issue with either from a code compliance perspective.

 

[Electriman]

The panels - consider what differences there are with the following-

200 amp feeder - supplies 2 - 20 space panels each with 200 amp bus.

alternate install- same loads supplied:

Same too amp feeder supplying one 40 space panel with 200 amp bus

Do you see any issue with either from a code compliance perspective.

Part of it is reliability. If you lose one you lose the other one. The feeding cable needs to be sized differenetly.

 

[augie47]

Part of it is reliability. If you lose one you lose the other one. The feeding cable needs to be sized differenetly.

The reliability issue is normally considered a design issue rather than a Code issue. The Code is a minimum standard.

 

[kwired]

Part of it is reliability. If you lose one you lose the other one. The feeding cable needs to be sized differenetly.

Is one feeder and same circuits being fed either way as I described it.

With single panel if you lose one you still lose everything.

Before they did away with the 42 circuit rule in recent years, to get what is equivalent to today's 84 circuit panel you at very least needed 2- 42 circuit panels even though you may tie them both to the same feeder.

Then you sometimes get in a situation where you run a feeder over some distance and make occasional taps to supply localized areas. True that each tap will be able to be isolated from the feeder by opening it's protective device - but you are still all on one common feed with everything.

Totally design issue, if you want more reliability in that last situation I described you can spend extra money for extra feeds to each localized area. But unless there are multiple sources there is still a common point somewhere that can fail.