Conduit for Input and Output wires

S

SKSolar

Member
Location
Los Angeles
Occupation
Engineer
Good morning experts,

I am designing a Solar Voltaic System with Enphase equipment from my garage to connect my solar input to the 200A Main Service Panel (MSP) which is 25 feet away.

I have a 60A sub panel in the garage fed by an underground 1” conduit and a double pole 70A breaker from the MSP. If I have all my solar panels install near the garage, I would have my Combiner Box there and have the AC disconnect near/next to the MSP.

Since I cannot run another underground conduit between my garage and the MSP because the surface is paved. I would like to use the existing feeder to my garage to connect my solar input from the combiner Box to the MSP via the AC Disconnect. By doing that, I lost my utility supply source to the garage.

As I only need to feed my MSP with 40A (#8 wires) from the solar source (Combiner Box), and in order to maintain/keep the utility supply source to my garage, I would like to replace/downsize the feeder with #8 wires (40A). That means my underground feeder conduit will have input and output 7 #8 wires (reduced one Ground wire ). Also I need to add 4 #18 wires for Consumption CTs , the total conduit fill is still under 40%.

Just wonder whether it is ok per NEC to run the input and output wires in the same conduit? Also it is hard to put all the wires through the 1" underground conduit - the only bend is the two ends where they daylight? I will check with my electrician, just want to make sure it is workable.
 
S

SKSolar

Member
Location
Los Angeles
Occupation
Engineer
jaggedben said:
Why can't you backfeed the garage sub?
Click to expand...
I have a 1" 70A feeder but adding a grid-tie solar requires another underground conduit/wires which is not possible. Downgrade the 70A to 40A so that I could use 7 #6 + 4 #18 wires is viable, pulling those wires through is tough , may not be possible.
 
J

jaggedben

Senior Member
Location
Northern California
Occupation
Solar and Energy Storage Installer
SKSolar said:
I have a 1" 70A feeder but adding a grid-tie solar requires another underground conduit/wires which is not possible. Downgrade the 70A to 40A so that I could use 7 #6 + 4 #18 wires is viable, pulling those wires through is tough , may not be possible.
Click to expand...
You didn't answer the question. Why can't you backfeed the subpanel?

There is no code reason you can't put your solar breaker in the garage subpanel. Is there a utility requirement that's a problem?
 
S

solarken

NABCEP PVIP
Location
Hudson, OH, USA
Occupation
Solar Design and Installation Professional
jaggedben said:
You didn't answer the question. Why can't you backfeed the subpanel?

There is no code reason you can't put your solar breaker in the garage subpanel. Is there a utility requirement that's a problem?
Click to expand...
You can't put a 40A backfed solar breaker in a 60A-rated subpanel - 705.12(B). You can tap the feeder though in the subpanel if the 70A breaker in the Main loadcenter is moved to the bottom position/opposite main breaker. But still have to resolve the CT extension wire issue.
 
Last edited:
J

jaggedben

Senior Member
Location
Northern California
Occupation
Solar and Energy Storage Installer
solarken said:
You can't put a 40A backfed solar breaker in a 60A-rated subpanel - 705.12(B). You can tap the feeder though in the subpanel if the 70A breaker in the Main loadcenter is moved to the bottom position/opposite main breaker. But still have to resolve the CT extension wire issue.
Click to expand...
Sorry, I missed those details.
I imagine the 60A panel could be replaced with a 125 more easily than doing a new conduit and/or wire. What's that doing on a 70A breaker anyway?

CT extension is another issue, but then I wonder if that's really necessary.
 
S

solarken

NABCEP PVIP
Location
Hudson, OH, USA
Occupation
Solar Design and Installation Professional
SKSolar said:
Good morning experts,

I am designing a Solar Voltaic System with Enphase equipment from my garage to connect my solar input to the 200A Main Service Panel (MSP) which is 25 feet away.

I have a 60A sub panel in the garage fed by an underground 1” conduit and a double pole 70A breaker from the MSP. If I have all my solar panels install near the garage, I would have my Combiner Box there and have the AC disconnect near/next to the MSP.

Since I cannot run another underground conduit between my garage and the MSP because the surface is paved. I would like to use the existing feeder to my garage to connect my solar input from the combiner Box to the MSP via the AC Disconnect. By doing that, I lost my utility supply source to the garage.

As I only need to feed my MSP with 40A (#8 wires) from the solar source (Combiner Box), and in order to maintain/keep the utility supply source to my garage, I would like to replace/downsize the feeder with #8 wires (40A). That means my underground feeder conduit will have input and output 7 #8 wires (reduced one Ground wire ). Also I need to add 4 #18 wires for Consumption CTs , the total conduit fill is still under 40%.

Just wonder whether it is ok per NEC to run the input and output wires in the same conduit? Also it is hard to put all the wires through the 1" underground conduit - the only bend is the two ends where they daylight? I will check with my electrician, just want to make sure it is workable
SKSolar said:
Good morning experts,

I am designing a Solar Voltaic System with Enphase equipment from my garage to connect my solar input to the 200A Main Service Panel (MSP) which is 25 feet away.

I have a 60A sub panel in the garage fed by an underground 1” conduit and a double pole 70A breaker from the MSP. If I have all my solar panels install near the garage, I would have my Combiner Box there and have the AC disconnect near/next to the MSP.

Since I cannot run another underground conduit between my garage and the MSP because the surface is paved. I would like to use the existing feeder to my garage to connect my solar input from the combiner Box to the MSP via the AC Disconnect. By doing that, I lost my utility supply source to the garage.

As I only need to feed my MSP with 40A (#8 wires) from the solar source (Combiner Box), and in order to maintain/keep the utility supply source to my garage, I would like to replace/downsize the feeder with #8 wires (40A). That means my underground feeder conduit will have input and output 7 #8 wires (reduced one Ground wire ). Also I need to add 4 #18 wires for Consumption CTs , the total conduit fill is still under 40%.

Just wonder whether it is ok per NEC to run the input and output wires in the same conduit? Also it is hard to put all the wires through the 1" underground conduit - the only bend is the two ends where they daylight? I will check with my electrician, just want to make sure it is workable.
Click to expand...
Are you thinking about an EV charger in the near future? If there is another path to get from the MSP in house to the garage, like trenching around the pavement, I would think about future needs before you do anything. A 60A sub in the garage is not sufficient if EV in your future. Coupled with the other challenges you have with the PV arrangement you describe, it might be best to just trench around and install 1.5-in or 2-inch conduit for an upgraded feeder to garage subpanel, and the solar inverter/combiner output back to MSP, along with a 1-inch conduit for CT wiring + an extra cat6, and another 1-inch conduit for future/spare. You could either backfeed the subpanel right in the garage with the solar or run it back to the main in the house. You can size everything as needed and solve all your issues this way. Also, if you are running CT extension wires, they really need to be in twisted, shielded cable while they run with any power powers in conduit, you can't just run #18 THHN with power wires and expect it will work.
Click to expand...
 
S

SKSolar

Member
Location
Los Angeles
Occupation
Engineer
Thanks you solarken.

As you said going around and thinking about future upgrade make more sense to me now.
Initially, I am just trying to be cheap . Going around for me only add additional 30 feet of wires and that isn't bad at all. Yes, I would go for that option and also since I just have to trenching once, I would add 1" conduit for the CT wires with CAT 6 wires go with it.
 
S

SKSolar

Member
Location
Los Angeles
Occupation
Engineer
jaggedben said:
Sorry, I missed those details.
I imagine the 60A panel could be replaced with a 125 more easily than doing a new conduit and/or wire. What's that doing on a 70A breaker anyway?

CT extension is another issue, but then I wonder if that's really necessary.
Click to expand...
Thank you for reviewing and participating. Solarken has nailed and gave me the solution.
 
S

SKSolar

Member
Location
Los Angeles
Occupation
Engineer
Thanks solarken for sharing your expertise.
As I am planning to use Enphase IQ8+ and combiner 4 and Solar only for now. I plan eventually to add the System Controller 2 and IQ Battery as upgrade. As my solar panels are at the garage area, 25 feet apart and away from the Main Service Panel. Need to put underground conduits as suggested. The Combiner Box 4 would definitely be placed near the garage area. Where should the System Controller 2, and IQ 8 battery be placed best? Near MSP or near the garage?
 
S

solarken

NABCEP PVIP
Location
Hudson, OH, USA
Occupation
Solar Design and Installation Professional
SKSolar said:
Thanks solarken for sharing your expertise.
As I am planning to use Enphase IQ8+ and combiner 4 and Solar only for now. I plan eventually to add the System Controller 2 and IQ Battery as upgrade. As my solar panels are at the garage area, 25 feet apart and away from the Main Service Panel. Need to put underground conduits as suggested. The Combiner Box 4 would definitely be placed near the garage area. Where should the System Controller 2, and IQ 8 battery be placed best? Near MSP or near the garage?
Click to expand...
Sorry, I am not up to speed on Enphase energy storage or their controller.
 
J

jaggedben

Senior Member
Location
Northern California
Occupation
Solar and Energy Storage Installer
SKSolar said:
Thanks solarken for sharing your expertise.
As I am planning to use Enphase IQ8+ and combiner 4 and Solar only for now. I plan eventually to add the System Controller 2 and IQ Battery as upgrade. As my solar panels are at the garage area, 25 feet apart and away from the Main Service Panel. Need to put underground conduits as suggested. The Combiner Box 4 would definitely be placed near the garage area. Where should the System Controller 2, and IQ 8 battery be placed best? Near MSP or near the garage?
Click to expand...
The System Controller should go near where you want your backup subpanel, which I would assume is the house. The battery can go most anywhere, closer is better with the IQ Battery 3/10 , due to wireless comms. Less code restrictions on the garage, but then you'll need another spare conduit.
 
S

SKSolar

Member
Location
Los Angeles
Occupation
Engineer
Electrical Geek said:
If you can wait a little bit, Enphase is coming out with a battery with hardwired comms. I don't know when but it is coming.
Click to expand...
Thanks. You are right to wait for the 3rd Gen ESS. They have the equipment: system controller 3 & IQ battery & Combiner 5 but don't have the installation details.
 
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