wyliesdiesels
Well-known member
He literally referenced the NEC tables.
If you dont want to use the NEC tables as your guideline, then no point in even asking questions on here
100A subpanel installation questions
- Thread starter DerStig
- Start date
He literally referenced the NEC tables.
If you dont want to use the NEC tables as your guideline, then no point in even asking questions on here
TRWham
Well-known member
Engineers seem to make the worst electricians.
Some engineers misconstrue optimize as oversize. Any engineer who works with stuff that needs to float, fly, go fast, or sell in a competitive market understands that trade-offs are necessary, and good enough really can be good enough if the problem is correctly defined.
Thanks everyone for help. I have a follow up question.
Assuming in the future I add another 100A subpanel from this subpanel, where the second subpanel is in a detached garage about 60-80 feet from this subpanel, does using #2 vs #3 to this first subpanel matter? Should I use #2 in the first run?
Assuming in the future I add another 100A subpanel from this subpanel, where the second subpanel is in a detached garage about 60-80 feet from this subpanel, does using #2 vs #3 to this first subpanel matter? Should I use #2 in the first run?
Zeke
Well-known member
Wire according to protection — always. Doesn't hurt to go up a size or 2 depending on the run but 60 to 80 feet is not that great. Up the wire temp rating if in doubt when it's a close call (or just use the next size up).
Mainpanel ———— 50 feet or less ———— First Subpanel ———— Second Subpanel
Are you saying go up a size on both runs or first run or second run?
I suppose voltage drop, compounded, can add up. So while say 1% or 2% drop is fine for first run, the same amount of drop from the second run will compound on the first one making a significant amount?
Zeke
Well-known member
So go up a size from the sub to the next sub if you want to consider compounding. I see your point although I think all the answers are already here in this thread.
I have a follow up question.
I have decided to go with #3 Cu for this as I anticipate another 100-150 ft run from this subpanel to another subpanel.
With that said, I want to confirm #6 EGC is appropriate. Its interesting because my main which is 200A has #6 as EGC. So either the main panel should go to #4 or I can use #8?
I have decided to go with #3 Cu for this as I anticipate another 100-150 ft run from this subpanel to another subpanel.
With that said, I want to confirm #6 EGC is appropriate. Its interesting because my main which is 200A has #6 as EGC. So either the main panel should go to #4 or I can use #8?
You can use 8 for a 100A, but then you have to do extra to protect it from damage. A number 6 does not have this requirement so you can just run it.
cderalow
Well-known member
This will be a THHN in a 1 1/2” conduit. What does it mean extra to protect it? Conduit isnt enough?
Sorry I thought we were talking grounding electrode conductor instead of grounding equipment conductor for some reason.
Yes the grounding equipment conductor for a 100A feeder is #8 cu or #6 Al unless you are using oversized conductors.
For #3 Cu, is it more appropriate to use #6 or #8?
Furthermore, does the size of the CCC determine EGC or are they independent?
alfredeneuman
Well-known member
No. The size of the circuit breaker determines the size of the ground wire.
EDIT:
If you oversize the circuit conductors you must increase the size of the ground wire by the same percentage ratio that the circuit conductors are. (That's the purpose of the notes to the table)
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No. The size of the circuit breaker determines the size of the ground wire.
EDIT:
If you oversize the circuit conductors you must increase the size of the ground wire by the same percentage ratio that the circuit conductors are. (That's the purpose of the notes to the table)
Ok so what you are saying contradicts what the previous poster said.
Based on what you are saying I cant use #8 EGC for #3 CCC Copper, it has to be #6.
wyliesdiesels
Well-known member
Huh?
#3 cu is max 100a.
a #8 cu EGC is required for 100a breaker.
Nobody contradicted anyone
The table says #8 for 100A.
The poster also says if one is upsizing the wire, you have to upsize EGC too.
A few posts before (or a page), someone said I dont have to use #3 for 100A, smaller wire is OK since its only 49 ft.
Just connecting all these posts, if all of that is true then #8 EGC needs to be upsized too?
wyliesdiesels
Well-known member
Where was that said? Its incorrect.
#3 cu is the required size for 100a.
You cannot reduce wire size for a given ampacity simply based on footage
So given there will be a second sub panel from this subpanel that itself that is 100 ft away (so 150 ft total from main), I decided to use #2 CU for CCC and #6 EGC in a 1 1/2” PVC. Any comments as far as the wire choice or conduit size? Conduit fill table says 7 wires this size fits, I am going to be using half of that including EGC here.
I chose #2 because of the second subpanel in the future.
I will need siemens QP breakers and looking at the current breakers on my main as well as what I would be buying, I can see they are rated both 60/75 degrees.
https://www.homedepot.com/p/Siemens...lcUDpNtLFKE0KGnjNyhoCb20QAvD_BwE&gclsrc=aw.ds
pattenp
Well-known member
If the total end run to the last panel is 150ft from the main I think you would be fine with using #3Cu for the sub feeds and using the called for #8Cu EGC. You shouldn't be loading the sub feeds to a max of 100A as a common practice, if so, you need a larger sub feed than a 100A.
I think it would be under 150 but very close. Anyhow, is there a huge size difference between 2 vs 3? I’m of the type who would want to play safe and overengineer things than to do bare minimum. At the end of the day, this is my house, its not like its a paid job.
Also siemens does not have a 115a breaker. A size higher is 125a and at that point, I am looking at #1 wire.
Things I would be running on these sub panels are big items such as car lifts, 5 hp table saw, 5hp compressor, press drill, washer/dryer, car dryer (master blaster).
Not all of them will be run at once obviously. Its not very easy to accurately estimate this stuff.
b-boy
Well-known member
Yes. This was in my house, which was built in the late 1800s. The silver stuff is probably tin plating. It confused me at first too.
Can someone help me figure out whether this panel accepts a 125amp breaker? Siemens does have a 125amp QP breaker but I cant tell looking at the panel sheet. I am attaching pictures of relevant parts. I’m thinking maybe I should oversize everything when its easier to do so.
Its Siemens G4040MB1200 Series .C Type 1
Its Siemens G4040MB1200 Series .C Type 1
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Hello guys,
I have not been able to reach out to siemens - potentially due to the virus call centers are overloaded. Is there anyway anyone here can comment on whether my panel can accept a 125A breaker?
Furthermore is a 125A subpanel with a main breaker a common thing to do?
I have not been able to reach out to siemens - potentially due to the virus call centers are overloaded. Is there anyway anyone here can comment on whether my panel can accept a 125A breaker?
Furthermore is a 125A subpanel with a main breaker a common thing to do?
Not really, 100A yes, one reason is that a 100A breaker is considerably cheaper then 125A, need is another in a residential situation the load is actually pretty low.
mike93lx
ALLIANCE MEMBER
I can easily find 125a main breaker panels around me at HD and Lowe's. Never looked for a separate 125a breaker though
mike93lx
ALLIANCE MEMBER
The only way to know for sure is to call Siemens since it isn't listed.
You'll never hit anywhere near that much draw anyway, based on the tools you listed
You'll never hit anywhere near that much draw anyway, based on the tools you listed
The reason for 125A is because I have plans to have a detached garage which will have its own subpanel that is a subpanel to this subpanel. The detached garage will have 2 car lifts and a 5hp compressor (but not any other tools like table saw etc. those stay in this attached garage).
So in reality this 125 subpanel will have a load of 40-50amps. There will be a 60A breaker that feeds the other subpanel.
If I had only 1 subpanel, I would not bother going with 125A.
Assuming a 125A subpanel and #1 Copper THHN in 1-1-1-6 configuration:
The other question is as per NEC I can put 5x#1 wires in a 1 1/2” PVC. There is a substantial size difference between a 2” PVC and 1 1/2”. That being said these past 2 weeks I have been moving/reorganizing all the wires around my main panel and ceiling to make room and as of now I can do a 2” conduit but I dont know if its necessary. The run will be around 35-40 ft. There will be a 3 or so 90 degree bends and 2 or so 45 degree offsets to clear gas pipes. I will put the conduit pull boxes so I will not exceed 360 degrees at any point.
So in reality this 125 subpanel will have a load of 40-50amps. There will be a 60A breaker that feeds the other subpanel.
If I had only 1 subpanel, I would not bother going with 125A.
Assuming a 125A subpanel and #1 Copper THHN in 1-1-1-6 configuration:
The other question is as per NEC I can put 5x#1 wires in a 1 1/2” PVC. There is a substantial size difference between a 2” PVC and 1 1/2”. That being said these past 2 weeks I have been moving/reorganizing all the wires around my main panel and ceiling to make room and as of now I can do a 2” conduit but I dont know if its necessary. The run will be around 35-40 ft. There will be a 3 or so 90 degree bends and 2 or so 45 degree offsets to clear gas pipes. I will put the conduit pull boxes so I will not exceed 360 degrees at any point.