zog
Senior Member
- Location
- Charlotte, NC
It is not your job, the engineers should provide you with the fault current data.
What would U Do?
- Thread starter Dennis Alwon
- Start date
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It is not your job, the engineers should provide you with the fault current data.
RETRAINDAILY
Senior Member
- Location
- PHX, arizona
The way I understand it
With the right main feeding your panel you can coordinate a 10k breaker too. like a LA-frame or J-frame.
your Q-frame is not series rated that would be fully rated. more$$
hardworkingstiff
Senior Member
- Location
- Wilmington, NC
Count me in the no camp.
Have you contacted the SQ D local rep? They will put together a series rated package for you. You may find that you can use 10K breakers in the last panel.
- Location
- Chapel Hill, NC
- Occupation
- Retired Electrical Contractor
I believe I can use the 10K in the MLO panel. It's the 1200 amp panel that needs the 65K. At least that's the way I see it based on the calculations.
- Location
- Wisconsin
- Occupation
- PE (Retired) - Power Systems
It is possible to have a series rating with a Q frame breaker, just not the QB's.
- Location
- Chapel Hill, NC
- Occupation
- Retired Electrical Contractor
But mine is a QG and in the table of the link provided it says series rated. ????
- Location
- Wisconsin
- Occupation
- PE (Retired) - Power Systems
Yes it is series rated.
- Location
- Chapel Hill, NC
- Occupation
- Retired Electrical Contractor
Thanks Jim.Yes it is series rated.
I guess it is a bit over due with this code change for 2011. I hope you can read it. Basically it is require the available fault current to be marked on equipment with OCPD in other than dwelling units.
zog
Senior Member
- Location
- Charlotte, NC
Thanks Jim.
I guess it is a bit over due with this code change for 2011. I hope you can read it. Basically it is require the available fault current to be marked on equipment with OCPD in other than dwelling units.
That is a great idea, is that an approved change to come in 2011?
- Location
- Massachusetts
- Location
- Chapel Hill, NC
- Occupation
- Retired Electrical Contractor
That's why the date etc is required. It would certainly be good in the developing stages, like the job I have where no retail shops have opened in this brand new building. Anyway, I think it is a done deal.
- Location
- Massachusetts
The data could 'expire' tomorrow or 30 years from now.
As I understand it every time you add / subtract / change transformers, motors etc it can effect the fault current.
Also as I have read here, listing the fault current higher than it really is can be dangerous as that can result in using less PPE than required. Lower fault current can at times (as I understand it) raise the incident energy.
- Location
- Chapel Hill, NC
- Occupation
- Retired Electrical Contractor
I wish I understood it better to discuss this with you. I would only hope that the transformer would be changed to a similar unit.
If the fault current at the secondaries change every time you add something then the whole concept makes no sense at all. I see the trany with a fault current that remains constant then the wiring gear, etc to the service panel needs another calculation and then from there to the final panel would be yet another right to the end.
If some other retail shop opens up I hope it doesn't change the fault current at the shop I work in otherwise this is worthless. No?
skeshesh
Senior Member
- Location
- Los Angeles, Ca
I have to agree with bob, but Dennis I dont think you need to worry too much about future changes since we're talking about a relatively small system here. The fault current changes that require recalculation are usually at higher voltages and at more sizable facilities with big loads. As suggested by others contact a mfg. and get a series rated quote from them. Finally it does sounds like the engineer didnt deliver due diligence but its not always the engineer's fault. There are some absurdly cheap clients out there that don't want to pay a cent above bare minimums. It is possibly that a short circuit study was not a part of the engineer's design scope.
zog
Senior Member
- Location
- Charlotte, NC
Well if it is required to be updated when system modifications are done or a max of every 5 years like the arc flash analysis requirements then it makes sense.
The more expensive the part is, the more I make so it doesn't really make sense to assume a greater risk for less money....but I still occaisionally do it.
Refurbished = WD40
We have a local small time guy that has a crapload of old stock.
On high end parts like this I will sometimes give the customer the option, especially in an emergency repair/replace situation.
It has to be the right customer though.
Refurbished = WD40
We have a local small time guy that has a crapload of old stock.
On high end parts like this I will sometimes give the customer the option, especially in an emergency repair/replace situation.
It has to be the right customer though.
zog
Senior Member
- Location
- Charlotte, NC
The more expensive the part is, the more I make so it doesn't really make sense to assume a greater risk for less money....but I still occaisionally do it.
Refurbished = WD40
We have a local small time guy that has a crapload of old stock.
Junk dealers like this are bad for everyone. Here is what "reconditioned" means for a MCCB with thermal trip like the one being discussed. http://www.pearl1.org/standards/Low...1 LV MCCB with Thermal Magnetic Trip Rev5.pdf
A properly reconditioned and tested breaker is "safer" than an untested new one. Unless you test your new one you will be taking a risk.
Me too. A poco transformer or other upgrade in their system would increase the AFC and adding load to an existing network or grid would lower it (or raise it with motor contributions).
Does the Code make provisions for annual (or other timetable) re-calculations to ensure the posted data is still correct?
Stupid idea from our friends at the NEC CMPs. :roll:
zog
Senior Member
- Location
- Charlotte, NC
I have to disagree here. besides a major system change the fault current will not change by much, and having something close is better than nothing at all. I see the aftermath of guesses at AIC applications all the time. Something that is close is better than most peoples guess any day.
- Location
- Wisconsin
- Occupation
- PE (Retired) - Power Systems
The new code article is for equipment selection purposes, as written it is not intended to be used for arc flash calculations. In fact, it appears there is no reason it even needs to be anywhere near the actual available amount, as long as it is not less than.
It appears the intent is for the purposes that generated the OP. If the equipment was clearly marked 57KA available, then every electrician should be able to determine which breaker rating must be supplied.
It appears the intent is for the purposes that generated the OP. If the equipment was clearly marked 57KA available, then every electrician should be able to determine which breaker rating must be supplied.
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