Solar Photovoltaic Design- 2013 California Energy Code Section 130.5 (c)

[Jordan King]

I am designing a solar photovoltaic system for an existing building in Arcata, CA. The building department's plan check agency is requiring a design load of less than 2% from the pv panelboard to the AC disconnect/meter main service, siting compliance with the 2013 California Energy Code Section 130.5 (c). Seems like this section of the Code is for new construction lighting systems and not solar PV addition. Are the recommended voltage drop limits of the NEC (2% feeders and 3% branch circuits) now mandatory based on this section of the Energy Code? Also, is this now a requirement for all solar PV installations on existing buildings?

 

[ggunn]

I am designing a solar photovoltaic system for an existing building in Arcata, CA. The building department's plan check agency is requiring a design load of less than 2% from the pv panelboard to the AC disconnect/meter main service, siting compliance with the 2013 California Energy Code Section 130.5 (c). Seems like this section of the Code is for new construction lighting systems and not solar PV addition. Are the recommended voltage drop limits of the NEC (2% feeders and 3% branch circuits) now mandatory based on this section of the Energy Code? Also, is this now a requirement for all solar PV installations on existing buildings?

It's not required by the NEC but AHJ's may require a maximum voltage drop. I have run into it before.

 

[jaggedben]

Are the recommended voltage drop limits of the NEC (2% feeders and 3% branch circuits) now mandatory based on this section of the Energy Code?

Apparently yes.

They are feeders and branch circuits so even if they were only intended to apply to loads I don't know what argument you can make.

I've not had an AHJ make an issue of it, but then I think we're pretty much always within those limits.

 

[SolarPro]

If an AHJ tries to enforce this, you may need to model the voltage drop as described in this article "Reassessing DC Voltage Drop Conventions." If you calculate it based on Vmp and Imp, which are STC ratings, you will overestimate the effective voltage drop on an annual basis. The effective voltage drop is typically 70% to 50% of the value calculated based on STC conditions, depending on the average annual irradiance at the site.

 

[GoldDigger]

It is interesting that we normally calculate VD based on worst case current, since we are worried about the effects of low voltage on other equipment.
But in the case of energy codes it does seem justified to look at average VD instead. (Do not average over 24 hours though!)

 

[jaggedben]

If an AHJ tries to enforce this, you may need to model the voltage drop as described in this article "Reassessing DC Voltage Drop Conventions." If you calculate it based on Vmp and Imp, which are STC ratings, you will overestimate the effective voltage drop on an annual basis. The effective voltage drop is typically 70% to 50% of the value calculated based on STC conditions, depending on the average annual irradiance at the site.

I don't think the AHJ will try to enforce this for DC circuits. At least I hope not.