megloff11x
Senior Member
It seems to be a tradition that power entry is on top when you come into an enclosure, be it panel or machine. Is there a rule or is it just force of habit?
power in the top?
- Thread starter megloff11x
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petersonra
Senior Member
- Location
- Northern illinois
- Occupation
- Semi-retired engineer
Re: power in the top?
Well, its a lot easier to get the wiring to the line side of the disconnect switch since it is traditionally located towards the top of the cabinet.
I have seen a fair number of specs however that require bottom entry, supposedly this reduces water infiltration in outdoor or hosedown areas.
<added> It also matters where your conduits are run. If they are overhead its a lot easier to bring them in the top. if they are under the floor its easier to come in the bottom.
[ February 09, 2005, 12:17 PM: Message edited by: petersonra ]
Well, its a lot easier to get the wiring to the line side of the disconnect switch since it is traditionally located towards the top of the cabinet.
I have seen a fair number of specs however that require bottom entry, supposedly this reduces water infiltration in outdoor or hosedown areas.
<added> It also matters where your conduits are run. If they are overhead its a lot easier to bring them in the top. if they are under the floor its easier to come in the bottom.
[ February 09, 2005, 12:17 PM: Message edited by: petersonra ]
BAHTAH
Senior Member
- Location
- United States
Re: power in the top?
Check Article 380 Switches. You will see that in general knife switch require the blades to be de-energized when the switch is in the open position, circuit breakers used as switches require the load lugs to be de-energized when in the open position. I especially like fuse clips de-energized when I need to replace a fuse.
Check Article 380 Switches. You will see that in general knife switch require the blades to be de-energized when the switch is in the open position, circuit breakers used as switches require the load lugs to be de-energized when in the open position. I especially like fuse clips de-energized when I need to replace a fuse.
- Location
- Wisconsin
- Occupation
- PE (Retired) - Power Systems
Re: power in the top?
Circuit breakers are not required to have "identified" line and load lugs. Unless there is a specific lable that says "load end" breakers may be fed in either direction.
Circuit breakers are not required to have "identified" line and load lugs. Unless there is a specific lable that says "load end" breakers may be fed in either direction.
jwelectric
Senior Member
- Location
- North Carolina
Re: power in the top?
Mr. Dungar
I agree with your statement but think it wise to add that in the 2002 code;
408.16 (F) Back-Fed Devices. Plug-in-type overcurrent protection devices or plug-in type-main lug assemblies that are backfed and used to terminate field-installed ungrounded supply conductors shall be secured in place by an additional fastener that requires other than a pull to release the device from the mounting means on the panel.
Mr. Dungar
I agree with your statement but think it wise to add that in the 2002 code;
408.16 (F) Back-Fed Devices. Plug-in-type overcurrent protection devices or plug-in type-main lug assemblies that are backfed and used to terminate field-installed ungrounded supply conductors shall be secured in place by an additional fastener that requires other than a pull to release the device from the mounting means on the panel.
BAHTAH
Senior Member
- Location
- United States
Re: power in the top?
With respect to circuit breakers 380-6(c) just a portion of this article " Single-throw knife switches, molded case switches, switches with butt contacts, and CIRCUIT BREAKERS used as switches shall be connected so that the terminals supplying the load are de-energized when the switch is in the open position." So while we know the breakers are generally not required to have line-load identification there are requirements as to the use of the line and load terminals.
With respect to circuit breakers 380-6(c) just a portion of this article " Single-throw knife switches, molded case switches, switches with butt contacts, and CIRCUIT BREAKERS used as switches shall be connected so that the terminals supplying the load are de-energized when the switch is in the open position." So while we know the breakers are generally not required to have line-load identification there are requirements as to the use of the line and load terminals.
- Location
- Massachusetts
Re: power in the top?
Only if breakers are marked line and load is there an issue.
1999 NEC
That would take some fancy wiring.
Note that this section is not talking about terminals marked load, only terminals supplying a load.
Whichever end of the breaker I connect the load to becomes the terminals supplying the load.
I believe that section is redundant to 240-8. Fuses or Circuit Breakers in Parallel, as the only way I can think to have toe load side terminals remain live with the breaker open is to have a second OCPD in parallel with the first.
Grant I do not know what you mean
Only if breakers are marked line and load is there an issue.
1999 NEC
How would it be possible to wire a circuit breaker in a way that the "terminals supplying the load" would still be live with the breaker open?
That would take some fancy wiring.
Note that this section is not talking about terminals marked load, only terminals supplying a load.
Whichever end of the breaker I connect the load to becomes the terminals supplying the load.
I believe that section is redundant to 240-8. Fuses or Circuit Breakers in Parallel, as the only way I can think to have toe load side terminals remain live with the breaker open is to have a second OCPD in parallel with the first.
BAHTAH
Senior Member
- Location
- United States
Re: power in the top?
Bob, we are in total agreement. I guess my point was the breaker is not marked line-load but as in the code article what we would call the load side (either side that goes to the load) must be de-energized when the breaker is in the open position. Once the wire is connected the line and load are determined by use and the load side has a requirement that it be de-energized when the cb is open.
[ February 09, 2005, 06:50 PM: Message edited by: grant ]
Bob, we are in total agreement. I guess my point was the breaker is not marked line-load but as in the code article what we would call the load side (either side that goes to the load) must be de-energized when the breaker is in the open position. Once the wire is connected the line and load are determined by use and the load side has a requirement that it be de-energized when the cb is open.
[ February 09, 2005, 06:50 PM: Message edited by: grant ]
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