I have a one (1) inch EMT conduit running from meter mainbreaker to to the termination in exterior wall. I would like to upgrade my garage panel from 60 amp to 100 amp. Can I snake three 2 gauge (2 hot/1 neutral) wires and its 4 gauge ground through this one inch conduit? Right now there is 6 ga. with 8 ga. ground there. Thanks for any replies.
Handyman, painter, wood floor refinisher, property maintenance in Tulsa, OK
“If yer gonna drive fast on the highway why not go as fast as you can? Like… a hundred miles per hour or more lol.”
Replies
I doubt it.
Spheramid Enterprises Architectural Woodworks
Repairs, Remodeling, Restorations.
Making it fit physically isn't the real determining factor. What matters is the conduit fill tables in the NEC. It says that the maximum number of #2 THHN/THWN conductors in a 1" EMT is 3.
But that doesn't include your #4 ground. For that we need to go to the area calculation and table. You have three #2's at 0.1158 sq. in. and a #4 which is 0.0824 sq. in. for a total of 0.4298. For more than two wires, the limit on 1" is 0.346, so you'd need 1 1/4" for a limit of 0.598 sq. in.
As for making it fit physically, going up to the NEC limit isn't usually an easy thing to do. Larger conduit makes for easier pulls. The internal diameter of 1" EMT is 1.049", bare copper solid #2 has a diameter of 0.2576", and #4 is 0.2043". So going over the NEC limit and using the 1" EMT in this case probably wouldn't be physically possible.
-- J.S.
Then I can't do it. No problem. Theres always another way :)
Handyman, painter, wood floor refinisher, property maintenance in Tulsa, OK
"If yer gonna drive fast on the highway why not go as fast as you can? Like... a hundred miles per hour or more lol."
The combination of wires you want to use won't fit in a 1" conduit per the NEC rules. You could go #3 wire with a #6 ground, which is adequate for 100 amps (THHW/THWN wire, 75 degrees C insulation, and assuming your garage is reasonably close to the house and voltage drop is not an issue) but 1" conduit is still too small for that. You'll need 1 1/4" at least.
Your'e right.
Handyman, painter, wood floor refinisher, property maintenance in Tulsa, OK
"If yer gonna drive fast on the highway why not go as fast as you can? Like... a hundred miles per hour or more lol."
Depends. Following the NEC a lot depends on the particular type of insulation the conductors are covered in. Older insulation are thicker and take up substantially more room in the conduit. Finding out what type of insulation the conductors are covered in would help determine your options.
The second consideration is how long a run it is. The NEC allows a much higher fill percentage, 60% versus 40% otherwise, for runs at or under two feet, as per NEC CH9 Table 1 Note #4.
I could run a calculation if I knew what the insulation types of the conductors. A close call can sometimes be tilted in your favor by stripping the insulation from the ground conductor as this effectively reduces the cross-section involved. This is legal but seldom used.
The run is about 20 feet with two 90 degree elbow bends. I think I will replace the conduit with 1½" or 2" EMT . This way I will be above code. That is a nifty solution though. I really enjoy hearing that kind of stuff.
Stuart: I am pretty sure I will need 100 amp service if not 125. The garage is being converted into an apartment with washer/dryer, electric stove, 240 volt water heater (that new H²0 heater, I can get a good deal on it) and possibly even a steam generator for shower. So no, no power tools and the like.
Handyman, painter, wood floor refinisher, property maintenance in Tulsa, OK
"If yer gonna drive fast on the highway why not go as fast as you can? Like... a hundred miles per hour or more lol."
If you go to the main FHB website (link at top of the page) then in the "extras" there is an article about doing an entrance service and you can download a chart for computing the required service load.
Do that independently for the main house and see if you have enough for both.
I suppose another thing to consider is whether you really need to upgrade to the 100 amp circuit -- I assume you want to run large power tools or a welder or something like that, but unless you have everything turned on at the same time 60 amps may well be perfectly adequate. You may have to put additional breakers in the subpanel in the garage, but that doesn't necessarily mean 100 amps is necessary.
If the utility will allow and the conductors are long enough and properly situated it might be worthwhile to mount a fused disconnect fed by the meter and make the existing panel and a panel you will install sub-panels. This can, depending greatly on the particulars of the situation, a great help in future additions or rewiring of existing structure.