Provisions for future roof solar

[designer82]

What would you show on the drawings in terms of future solar provisions for a 2,500 sq.ft single family house?

Would you show a 1" conduit going from the garage to the roof? (I would think the solar installer would just provide this when installing the solar system)
Would you show a 40 Amp circuit breaker on the opposite side of the bus from the main breaker? (I would think the solar installer would just do this)

So really nothing?

I'm confused because the owner asked for provisions for the future roof solar.


Thanks

 

[tthh]

Not a solar guy, but this is my what I've leared from my recent venture into considering solar.

A conduit up into the attic space would be nice. I'd go bigger than 1".

Leave space near the main panel for a another panel for the solar.

The main panel needs to be able to be back-fed by a large enough breaker for solar installtion desired. There are several ways to size it, but the safest for future proofing is to size using the 120% rule. That says that the combination of the service and back-fed from solar cannot exceed 120% of the panel bus rating. So, if you had a 200A panel outfitted with a 200A main breaker and the panel bus was unrated or rated for 200A, then you are limited to a 40A back-fed breaker for solar. In my opinion that is too low for the future, but it depends on how much solar could be added. At minimun, get a panel that has a 225A rated bus even though it has only a 200A breaker. That gets you 70A solar back-fed breaker. That should be good for a higher end solar installtion. If you want to go up from there, a 320A panel that is probably advertised as solar-ready would be the next step.

 

[ggunn]

That says that the combination of the service and back-fed from solar cannot exceed 120% of the panel bus rating.

Not exactly. Assuming that the AHJ is not using a very old version of the NEC, the 120% rule says that the sum of 125% of the PV inverter current and the rating of the main breaker cannot exceed 120% of the bus rating. For a 200A/200A panel the max inverter current is 32A. It sometimes makes a difference.

 

[tthh]

Not exactly. Assuming that the AHJ is not using a very old version of the NEC, the 120% rule says that the sum of 125% of the PV inverter current and the rating of the main breaker cannot exceed 120% of the bus rating. For a 200A/200A panel the max inverter current is 32A. It sometimes makes a difference.

Thanks for point that out...

So a 200A with 200A bus rating gets you a 32A max inverter current.
And a 200A with 225A bus rating gets you 56A max inverter current.

 

[MyCleveland]

I asked this Q about 3 years ago and I believe the consensus was 2-1"c. When I had my EC add a panel for a kitchen remodel I made a path to the attic and had him put in two 1" FMC. Doubtful I will every use them, but they are sitting for the next the guy/gal.

 

[jaggedben]

What would you show on the drawings in terms of future solar provisions for a 2,500 sq.ft single family house?

Design the largest roof plane to be south facing, a single plane, with no vents or other obstructions. Put the kitchen, bathrooms, and any chimney on the north side of the house to help all this.

Would you show a 1" conduit going from the garage to the roof? (I would think the solar installer would just provide this when installing the solar system)

It's much more aesthetic if it's run inside the building when the walls are open during construction.

Would you show a 40 Amp circuit breaker on the opposite side of the bus from the main breaker? (I would think the solar installer would just do this)

It would help to specify some type of solar ready panel. There are different types, but they generally have a 225A bus for a 200A service, or an additional connection to the meter for solar (or 'parallel energy').

You don't need to specify the breaker amperage or location if someone else is going to dial that in later.

So really nothing?

I'm confused because the owner asked for provisions for the future roof solar.

Depends how much you want to take the request seriously or be a burden-shifter. What is your role in the project? Architect? GC? Electrician?

 

[electrofelon]

Standing seam metal roof....

 

[ggunn]

What would you show on the drawings in terms of future solar provisions for a 2,500 sq.ft single family house?

Would you show a 1" conduit going from the garage to the roof? (I would think the solar installer would just provide this when installing the solar system)
Would you show a 40 Amp circuit breaker on the opposite side of the bus from the main breaker? (I would think the solar installer would just do this)

So really nothing?

I'm confused because the owner asked for provisions for the future roof solar.

It makes a difference whether the PV inverter(s) will be string inverters or microinverters. For string inverters, which bring DC conductors down from the roof, the wiring must be in metal conduit. For microinverters the conductors from the roof are simply AC branch circuits.

 

[jaggedben]

It makes a difference whether the PV inverter(s) will be string inverters or microinverters. For string inverters, which bring DC conductors down from the roof, the wiring must be in metal conduit. For microinverters the conductors from the roof are simply AC branch circuits.

And to be clear, the installed solar conduit should be metal so that in the future the solar installer can do whatever they want.

 

[solarken]

What would you show on the drawings in terms of future solar provisions for a 2,500 sq.ft single family house?

Would you show a 1" conduit going from the garage to the roof? (I would think the solar installer would just provide this when installing the solar system)
Would you show a 40 Amp circuit breaker on the opposite side of the bus from the main breaker? (I would think the solar installer would just do this)

So really nothing?

I'm confused because the owner asked for provisions for the future roof solar.


Thanks

Consider allocating space for batteries and a transfer switch near the service entrance, or including a sub panel with all the critical circuits they may want backed up.