I see enclousures with a single circuit breaker mounted in them and the handle operates left to right instead of up and down. There are no markings in the panel to indicate line and load. If the contractor installs the load conductors on the top side of the breaker and the line conductors on the bottom of the circuit breaker is this a violation? Manufacturer is silent on this matter. I asked the contractor to use a magic marker to label line and load and he agreed.

Sounds like a good example of cooperation between inspector and contractor.
I don't know what you could cite as a violation

Check 408.16(F) back fed devices.
Switches and breakers used as switches must also be indicating, i.e. off /on if not verticle. 404.7
I think these references are the ones you need.
Alan--
Just reread the question...same references plus UL listing.
Is he using a double pole breaker with line on one terminal and load connected to the other half ?????
When the breaker is off it is still energized. Why does he use an enclosure instead of just wrapping tape around the bomb he has made.
Alan--

Alan I don't think that you have in your mind what George is describing.

I do not think we are talking about a breaker in a panel.

I believe he asking about a single breaker enclosure that is sometimes used in place of a fused disconnect.

George If I am correct about the installation the EC can feed bottom or top unless the breaker is marked line and load.

If you had asked me I would have written line and load on it but I really do not believe you could require me to.

On the job I was at today I have a 1600 amp single breaker in a large enclosure, I fed the bottom of the breaker as the feed is coming from a transformer (The supply conductors where down low already)

In this case I specified bottom feed when we ordered it. The only change that I can see from the top feed one I have is the direction the current sensor is facing on the neutral for the GFP.

Bob

Alan- Bob is correct, the CB is being used like you'd use a safety switch. There were no Line/Load designations. The terminals were on the top and bottom of the CB and the handle operated horizontally. I asked the contractor to label Line/Load with a marker, which he did. If I were the installer, I'd mark it for my own benefit because you'd probable not remember Line/Load when you went back to it in the future. The panel was flush in the wall and there was no way of knowing which way the conductors were coming from. As it turned out the top side of the breaker was being used as the Load and usually the top side is the Line.

Great point, honestly the 1600 I described above is not readily apparent either by looking at the conduits or by the construction of the unit.

I have to order phenolic labels for the job, may be I will have a couple of line and load ones made to mark it.

Bob

I've seen this discussion somewhere else, possibly in the IAEI magazine. The consensus of the discussion was that if there were no markings on the breaker or the enclosure, the line could be connected to either end. This is in agreement with what is in the UL White Book (DIVQ) last sentence of the Installation paragraph "Line and load markings on a circuit breaker are intended to limit connections thereto as marked."

Asking the installer to identify which end is the line connection is an excellant idea and sounds to me like a possible proposal for the 2011 NEC.

Tom

If you are going to work on it, shut it off and put a tester on it. If you are not working on it, when would knowing line or load be critical?