Looking for ideas “how” to run pv wire from rooftop to shed

[Nan_wpg]

Cabin has an accessible attic, and interior walls are paneling (easy access for running conduit). Foundation is pad and post. Lots of room underneath. Shed is about 10’ from cabin. Underground conduit (or other?)

I’m thinking:

1. PV wire into soladeck box > thwn into metal conduit through attic, through interior wall, floor, run under cabin and then underground to shed.

2. Pv wire into combiner box > metal conduit to soladeck box located near roof edge > metal conduit through soffit, along exterior cabin wall, then underground to shed. This way would be easier and faster.

I could also run conduit to the gable end, either on the roof, or through the attic then along the outside wall.
Are there any other ways to do this that I haven’t thought of? I watched a you tube video and the guy used some kind of rubberized wire with that metal Armour stuff along a wall.


Not sure if I should use metal the entire run, or metal where required, and then transition to pvc underground?

 

[timselectric]

Whichever is easier is fine.
Metal conduit is required at the house, but PVC is preferred underground.

 

[Nan_wpg]

Whichever is easier is fine.
Metal conduit is required at the house, but PVC is preferred underground.

Easier (for me) is a metal conduit on the roof, to the eves, and then through the soffit. No crawling in an attic.

Regardless what would you recommend for flexible? I’m Leary of bending conduit and would rather use it for straight runs, and then something flexible where it has to go through studs/plates, etc. in the event the holes drilled don’t (or can’t) line up I’d like to be able to “flex” instead of bend.

 

[timselectric]

Easier (for me) is a metal conduit on the roof, to the eves, and then through the soffit. No crawling in an attic.

Regardless what would you recommend for flexible? I’m Leary of bending conduit and would rather use it for straight runs, and then something flexible where it has to go through studs/plates, etc. in the event the holes drilled don’t (or can’t) line up I’d like to be able to “flex” instead of bend.

MC cable and flexible metal conduit is perfect for inside the house.
It's what I have used for all of the PV circuits.

 

[Nan_wpg]

MC cable and flexible metal conduit is perfect for inside the house.
It's what I have used for all of the PV circuits.

Which do you prefer? Is one “better” for a diy’er ?

 

[timselectric]

Which do you prefer? Is one “better” for a diy’er ?

MC cable for single circuit, and flexible conduit for multiple circuits.
MC, is a cable with conductors in it.
Conduit is empty, until you pull what you want in it.

 

[Nan_wpg]

MC cable for single circuit, and flexible conduit for multiple circuits.
MC, is a cable with conductors in it.
Conduit is empty, until you pull what you want in it.

It a single circuit (pv array). In another thread you helped me decide on 10g to allow for future paralling.

Does MC require any special derating? It’s going in an attic so temperature derate applies. Only 2 current conductors so conduit doesn’t apply BUT mc is in its own conduit and it’s pretty “tight”.

How do electricians figure attic temperature? Highest ambient temp on record + percentage?

Likely buying this: (it’s stranded)

Southwire 10/2 x 25 ft. Solid CU MC (Metal Clad) Armorlite Cable 68581821 - The Home Depot

Beef up your network standards with the help of this excellent Southwire Solid CU MC Armorlite Cable.

www.homedepot.com

 

[timselectric]

Does MC require any special derating?

Not unless you have several grouped together.

It’s going in an attic so temperature derate applies.

Correct, and continuous duty.

How do electricians figure attic temperature? Highest ambient temp on record + percentage?

Truthfully, It's a lot of guess work. Every attic is different, and several factors affect the temperature.
For the most part, we just all have a rule of thumb for our region.

 

[Nan_wpg]

Not unless you have several grouped together.

Correct, and continuous duty.

Truthfully, It's a lot of guess work. Every attic is different, and several factors affect the temperature.
For the most part, we just all have a rule of thumb for our region.

Tim, which colum do I use to derate? Wago/wire nuts are good to 105c. Wire to 90c. The weak link will be the breaker/busbar.

When in doubt it’s 60c, but midnites breakers operate up to 85c and I’m assuming their busbars are the same. (ChatGPT told me 60c for older, and 75c for newer). ChatGPT also told me my attic will be 113-131F and to use 122F as a conservative temp.

So let’s see if I get this right.

10g mc cable (40A) attic temp 140F (hottest day back in 1936)

40 x .58 = 23.2 x .8 = 18.56 max a for my PV run. I can even add a parallel string (maybe). Do I use ISC or IMP for amps?

My panel ISC is 9.58 which x2 would put me over 18.56A.

Or I can bump up to 8g cable

 

[timselectric]

Tim, which colum do I use to derate? Wago/wire nuts are good to 105c. Wire to 90c. The weak link will be the breaker/busbar.

When in doubt it’s 60c, but midnites breakers operate up to 85c and I’m assuming their busbars are the same. (ChatGPT told me 60c for older, and 75c for newer). ChatGPT also told me my attic will be 113-131F and to use 122F as a conservative temp.

So let’s see if I get this right.

10g mc cable (40A) attic temp 140F (hottest day back in 1936)

40 x .58 = 23.2 x .8 = 18.56 max a for my PV run. I can even add a parallel string (maybe). Do I use ISC or IMP for amps?

My panel ISC is 9.58 which x2 would put me over 18.56A.

Or I can bump up to 8g cable

Close enough, #10 would not concern me.
Remember that your production is also going to suffer from the extreme heat.
So, unless you are seriously overpaneling, you won't see extended times of full output.
If you are seriously overpaneling, then I would bump it up to #8.

 

[Nan_wpg]

Close enough, #10 would not concern me.
Remember that your production is also going to suffer from the extreme heat.
So, unless you are seriously overpaneling, you won't see extended times of full output.
If you are seriously overpaneling, then I would bump it up to #8.

10 it is! I didn’t consider reduced output. So moving forward should I use the 75c column? Anything new should be rated for 75?

 

[timselectric]

10 it is! I didn’t consider reduced output. So moving forward should I use the 75c column? Anything new should be rated for 75?

Maybe......but,
You really need to check each components rating. Nothing is for sure, unless verified.

 

[MarkSolar]

Consider aerial cable for such a short distance.

 

[Nan_wpg]

MC cable for single circuit, and flexible conduit for multiple circuits.
MC, is a cable with conductors in it.
Conduit is empty, until you pull what you want in it.

Since I already have the thhn wire I’m gonna attempt conduit. Never used it but I like learning new things. Worst case I need to use mc in the attic to under the cabin. From there it’s just 90 bends so conduit should be easy.

I can always buy mc for that single circuit. I’d need 75 feet. I can only find it in 125’ and 250’ and 25’ rolls. 25 gets me to the bottom of cabin. Conduit from there.

As for conduit do you have any tricks or tips in terms of workflow, or logistics?

More specifically I need to run 2 seperate ac circuits. (All same AMP) I understand I can use 1 ground conductor.
But as for multiple circuits in a conduit I’m assuming you pull all the wire together and then “drop off” each one as you go.

How do you mark or label the wires? Do you use different colors for the seperate line and neutrals?

I was thinking of pulling 1 circuit. Hook it up and then pull the second. Tape the 2nd circuit for identification.

 

[timselectric]

As for conduit do you have any tricks or tips in terms of workflow, or logistics?

Just like building a road, start at one end and work your way to the other.
Which end to start from depends on what is easier.

But as for multiple circuits in a conduit I’m assuming you pull all the wire together and then “drop off” each one as you go.

Correct

I was thinking of pulling 1 circuit. Hook it up and then pull the second.

Don't do this, unless it's a very short distance.
The moving conductors can cut into the stationary ones.

How do you mark or label the wires? Do you use different colors for the seperate line and neutrals?

With only two circuits, I just make a taped set on one.

 

[Bop]

Personally, I would use an aerial lead myself as well, unless there is a particular reason not to... its a lot easier for such a short run...
Very common in the UK and here in Australia for mains feeds... (240vAC 3 core, or 5 core for 415v 3 phase)


5 core SWA rated at 32A 415vAC for example