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- Thread starter Dmc16
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Hey iwire.
Dmc16
Member
- Location
- Sparta,nj,United states
Any more thoughts
Any more thoughts
Manufacter said gen will only produce 75 amps since its natural gas. They also said changing breaker in generator may void warranty
Any more thoughts
Hey guys any more thoughts.
Manufacter said gen will only produce 75 amps since its natural gas. They also said changing breaker in generator may void warranty
Sierrasparky
Senior Member
- Location
- USA
- Occupation
- Electrician ,contractor
Since the Gen is the only service when the transfer switch is thrown and any other loads are shed it's a no brainer it carries the entire load of the dwelling as it is now a service.
kwired
Electron manager
- Location
- NE Nebraska
- Occupation
- EC
Sticking with NEC terms, it still is not a service, but is the only source at that time, but if it transfers only to selected circuits it doesn't have the same load diversity as if it were capable of supplying the entire dwelling load - which is why 310.15(B)(7) exists in the first place, the entire dwelling load has a different load diversity then selected portions of it. NEC doesn't let us determine for ourselves what the load diversity might be though.
Sierrasparky
Senior Member
- Location
- USA
- Occupation
- Electrician ,contractor
load diversity or not.
If the dwelling supply source only supplies the whole or less than the whole what difference does it make. The intention of the code states that the wire size need not be larger than the whole. Why in carnation would anyone upsize the wire greater than the service or the supply when it is servicing less than the whole. I can see same size but not larger. You people are making something of nothing and not what the code was meant.
romex jockey
Senior Member
- Location
- Vermont
- Occupation
- electrician
This is a tad confusing. I see nothing in 445 or 705 that requires a demand load calculation for a genny install, although some insist a 'whole house T switch' would qualify as just that, with the 'wrench' of load shed salted in the wound...
So perhaps a pertinent Q would be in design? ...., would there be a difference in placing said T switch before vs. after the main(s) ,ergo it is or is not technically service equipment?
like>>>
~RJ~
So perhaps a pertinent Q would be in design? ...., would there be a difference in placing said T switch before vs. after the main(s) ,ergo it is or is not technically service equipment?
like>>>
~RJ~
RICK NAPIER
Senior Member
- Location
- New Jersey
702.4 requires a load calculation.This is a tad confusing. I see nothing in 445 or 705 that requires a demand load calculation for a genny install, although some insist a 'whole house T switch' would qualify as just that, with the 'wrench' of load shed salted in the wound...
So perhaps a pertinent Q would be in design? ...., would there be a difference in placing said T switch before vs. after the main(s) ,ergo it is or is not technically service equipment?
like>>>
~RJ~
mivey
Senior Member
That hits the nail on the head IMO. Taken to the extreme, suppose we shed all but one load, then it should be clear an "over-amped" conductor would not be appropriate.
That said, I do think there is merit to a diversity case if the remaining loads would meet minimum dwelling requirements. As an extreme: if we shed the ferris wheel out back, we should expect normal dwelling diversity from the remaining loads.
kwired
Electron manager
- Location
- NE Nebraska
- Occupation
- EC
A somewhat common example that has come up before, meter main on exterior of house, only one branch circuit for an air conditioning unit installed in meter main. Rest of the dwelling load is supplied by a feeder connected to the meter main. Can this feeder be sized per 310.15(B)(7) since some of the dwelling load has been dropped off at the meter/main? As NEC is worded, no. From a common sense perspective why not though?
As far as the OP's genset, sounds like it will not produce more then about 85 amps, so the conductor will never be overloaded anyway, not so sure NEC sees it that way though.
As far as the OP's genset, sounds like it will not produce more then about 85 amps, so the conductor will never be overloaded anyway, not so sure NEC sees it that way though.
gadfly56
Senior Member
- Location
- New Jersey
- Occupation
- Professional Engineer, Fire & Life Safety
It would be for my house. When I was looking into generators after Sandy, I calculated that without the A/C a 7.5KW was good for the remainder of the house. A 20KW would easily pick up my A/C load.
- Location
- Massachusetts
Nope. You are using common sense instead of applying the NEC.
Sierrasparky
Senior Member
- Location
- USA
- Occupation
- Electrician ,contractor
Ok ,
Please show us where the language in the NEC disagrees with my opinion as per the 2014 as CA will be on the basic 2014 next year.
I understand if the actual service is a 200 amp and this set up is only a 100 amp or less. However if all is 100 amp then you don't need to be larger than the service wires load diversity or not the load will not be greater just because the load is on one set of wires or another.
romex jockey
Senior Member
- Location
- Vermont
- Occupation
- electrician
702.4(B) System Capacity. The calculations of load on the
standby source shall be made in accordance with Article
220 or by another approved method.
Thank you sir....
~RJ~
- Location
- Massachusetts
Can you clear this up one way or the other?
Will the generator supply everything that the homes service does at the same time?
It absolutely makes a difference, if you shed any load or not.
Does the entire homes load calculation remain under 20KW?
Can you please provide a direct answer to these questions?
- Location
- Massachusetts
Hey kid it is still unanswered
JFletcher
Senior Member
- Location
- Williamsburg, VA
Would #4cu be mfg spec'd because the generator wouldnt be run above 80% capacity? otoh, why not run #3 and be covered? If you can physically install #2 AL, #3 Cu will fit the lugs/terminals... and #1AL would be cheaper, if it will fit.
Dmc16
Member
- Location
- Sparta,nj,United states
Don't have a solid answer.
Don't have a solid answer.
Yes I am aware of this now. Made a error. The #2 al is in the 100 ser we ran through basement.
Looking to understand if we can find a way around this without pulling new. Manufacturer does not support changing breaker. So..... idk
sorry I wire do not have a solid answer on load calc. Customer purchased gen set up, I'm helping install.
At this point should have trusted my gut and said no thanks. But I'm in it now. I'll see it through.
Don't have a solid answer.
Yes I am aware of this now. Made a error. The #2 al is in the 100 ser we ran through basement.
Looking to understand if we can find a way around this without pulling new. Manufacturer does not support changing breaker. So..... idk
sorry I wire do not have a solid answer on load calc. Customer purchased gen set up, I'm helping install.
At this point should have trusted my gut and said no thanks. But I'm in it now. I'll see it through.
Sierrasparky
Senior Member
- Location
- USA
- Occupation
- Electrician ,contractor
What size is the service?
JFletcher
Senior Member
- Location
- Williamsburg, VA
What about a 90A breaker/fused disco between the generator and panel?
kwired
Electron manager
- Location
- NE Nebraska
- Occupation
- EC
Sort of been my thought all through this process. Probably cost less then the unit mount breaker in the generator anyway.
Unless you enter more then 25 feet into the home, the conductor from the generator to said disconnect is likely a legal feeder tap.
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