flargen
09-09-2021, 11:16 PM
Hey all
I have been reading a lot on this forum, so thanks to you all for your insight. I have been attempting to learn what it will take for me to run secondary to a (sub)panel in my garage, 35ft from the main house (87ft from panel to proposed new panel location). I am a hobbyist woodworker with relatively basic machinery, with some exceptions.
I have recently sat down and written my plan and thoughts down for the sake of getting them out of my head and onto paper. I was hoping someone might have a peek and tell me if I am on the right track or way off base in my understanding.
The very brief version is:
New homeowner and novice looking to run 60a secondary off 125a panel (200a service) from main building/main panel to garage panel, while oversizing things for future upgradeability. Looking for insights and error checking on specific/technicals and theory.
The very long version is:
Our house is brand new to us, but your basic late '40s 2bd/1ba with half-finished basement, a 2+car outbuilding and a mix of gas/elec appliances with an AC. According to city records, the house pulled and completed inspection on a work permit for 200amp service upgrade. There is a newish Eaton panel with 200 amp main breaker, though the panel is rated @ 125amps. So, being the weakest link, the service I am working with is 125amps - as i understand it.
Here is the main:
https://i.imgur.com/qPG0eLs.jpg
https://i.imgur.com/k0g6iHs.jpg
I will safely open the panel this weekend to observe the conductor sizes/ratings, but my assumption is that the previous owner upgraded to 200amp to add AC, but it cost less in material and labor to upgrade the panel to only 125a, which is probably a reasonable load limit for the previous occupants -- is that a reasonable assumption? I ask because I want to make sure I understand the panel setup and the limitations I will have for a secondary service to my garage shop. (hobbyist woodworker, basic shop setup with mostly 1ph, 120v single horse machines, a 240v jointer, and a 3ph 5hp old planer I will run on a 7.5hp 240v RPC. One machine+dust collection+lights at a time. )
My plan, at current, is to occupy the final, top two slots with a 60amp (30/30) breaker protecting adequately rated and sized conductors from panel to basement/foundation wall, out and underground in a PVC raceway to a subpanel in the garage.
I want to install a 100amp subpanel in the garage to give myself space for the future when I have the funds and/or time and knowledge sufficient to upgrade the main panel from 125 to 200a. So for the time being, I will make due with 60a service, which I believe would be plenty for my hobbyist needs right now (again: single machine via RPC+2hp dust collection+led lights at a single time is what I expect to max out at at any given time)
The run from panel to panel is ~86feet, 35' of which will be 18" underground.
I am thinking aluminum for the sake of cost, but I am a little unclear on the pros and cons versus cost with AL and CU. Im considering 4 wire (hot, hot, neutral, ground) romex/NM from main panel to foundation wall junction box to (4 wire, single strand (per code?)) URD in pvc raceway to the subpanel, which will have a main disconnect and non-bonded grounds and neutrals. I will add 2 8ft grounding electrodes, 8ft apart on braided CU.
To make things a little more "futureproof", I am thinking of oversizing the feeder to guarantee a future move to 100a. This is where I get a little hazy. I assume I will be sizing based on the 75℃ column (but will verify all breakers and conductors are appropriately rated), but the actual gauge of things is a bit confusing. If using AL, I've read that I may need to be a size larger than I would if were in CU due to physical limitations. would 2-2-2-4 AL URD be capable of carrying 100amps over 90ft within safe voltage drop parameters? Is that overkill? I probably need to read more.
That pretty much sums up where I am at in my understanding at this particular moment.
Does it sound like I am on the right track?
And to end it all on a question that I should probably ask right at the top?
Is it necessary to run a comprehensive wattage/load audit on our house before I go any further? I also have access to our smart meter basic daily usage data - if that's at all useful.
What else am I missing?
Thanks for reading, if anyone made it this far!
I have been reading a lot on this forum, so thanks to you all for your insight. I have been attempting to learn what it will take for me to run secondary to a (sub)panel in my garage, 35ft from the main house (87ft from panel to proposed new panel location). I am a hobbyist woodworker with relatively basic machinery, with some exceptions.
I have recently sat down and written my plan and thoughts down for the sake of getting them out of my head and onto paper. I was hoping someone might have a peek and tell me if I am on the right track or way off base in my understanding.
The very brief version is:
New homeowner and novice looking to run 60a secondary off 125a panel (200a service) from main building/main panel to garage panel, while oversizing things for future upgradeability. Looking for insights and error checking on specific/technicals and theory.
The very long version is:
Our house is brand new to us, but your basic late '40s 2bd/1ba with half-finished basement, a 2+car outbuilding and a mix of gas/elec appliances with an AC. According to city records, the house pulled and completed inspection on a work permit for 200amp service upgrade. There is a newish Eaton panel with 200 amp main breaker, though the panel is rated @ 125amps. So, being the weakest link, the service I am working with is 125amps - as i understand it.
Here is the main:
https://i.imgur.com/qPG0eLs.jpg
https://i.imgur.com/k0g6iHs.jpg
I will safely open the panel this weekend to observe the conductor sizes/ratings, but my assumption is that the previous owner upgraded to 200amp to add AC, but it cost less in material and labor to upgrade the panel to only 125a, which is probably a reasonable load limit for the previous occupants -- is that a reasonable assumption? I ask because I want to make sure I understand the panel setup and the limitations I will have for a secondary service to my garage shop. (hobbyist woodworker, basic shop setup with mostly 1ph, 120v single horse machines, a 240v jointer, and a 3ph 5hp old planer I will run on a 7.5hp 240v RPC. One machine+dust collection+lights at a time. )
My plan, at current, is to occupy the final, top two slots with a 60amp (30/30) breaker protecting adequately rated and sized conductors from panel to basement/foundation wall, out and underground in a PVC raceway to a subpanel in the garage.
I want to install a 100amp subpanel in the garage to give myself space for the future when I have the funds and/or time and knowledge sufficient to upgrade the main panel from 125 to 200a. So for the time being, I will make due with 60a service, which I believe would be plenty for my hobbyist needs right now (again: single machine via RPC+2hp dust collection+led lights at a single time is what I expect to max out at at any given time)
The run from panel to panel is ~86feet, 35' of which will be 18" underground.
I am thinking aluminum for the sake of cost, but I am a little unclear on the pros and cons versus cost with AL and CU. Im considering 4 wire (hot, hot, neutral, ground) romex/NM from main panel to foundation wall junction box to (4 wire, single strand (per code?)) URD in pvc raceway to the subpanel, which will have a main disconnect and non-bonded grounds and neutrals. I will add 2 8ft grounding electrodes, 8ft apart on braided CU.
To make things a little more "futureproof", I am thinking of oversizing the feeder to guarantee a future move to 100a. This is where I get a little hazy. I assume I will be sizing based on the 75℃ column (but will verify all breakers and conductors are appropriately rated), but the actual gauge of things is a bit confusing. If using AL, I've read that I may need to be a size larger than I would if were in CU due to physical limitations. would 2-2-2-4 AL URD be capable of carrying 100amps over 90ft within safe voltage drop parameters? Is that overkill? I probably need to read more.
That pretty much sums up where I am at in my understanding at this particular moment.
Does it sound like I am on the right track?
And to end it all on a question that I should probably ask right at the top?
Is it necessary to run a comprehensive wattage/load audit on our house before I go any further? I also have access to our smart meter basic daily usage data - if that's at all useful.
What else am I missing?
Thanks for reading, if anyone made it this far!