Purpose
This document defines the CAD and installation requirements for Daylight residential solar and storage projects. Following these standards reduces review rejections and keeps projects moving on schedule.
All requirements below are written to be consistent with the National Electrical Code (NEC) and with manufacturer installation manuals. For approved equipment models and ratings, refer to the Daylight equipment stack in the support portal.
1. Stringing, MPPT, and Array Layout
Azimuth and roof planes
Do not mix azimuths or roof planes within a single string.
Do not mix North-facing and South-facing arrays on the same MPPT.
Assign one MPPT per azimuth wherever array layout allows.
MPPT utilization
Use all available MPPTs when array size allows:
Sol-Ark 12K-2P → 2 MPPTs, 2 strings per MPPT, minimum 5 panels per string per azimuth
Sol-Ark 15K-2P → 3 MPPTs, 3 strings per MPPT, minimum 5 panels per string per azimuth
Balance the number of panels per MPPT as evenly as possible.
Do not overload one MPPT while leaving another unused.
Minimum string and array requirements
Minimum 5 panels per string per azimuth.
If a roof plane has fewer than 5 panels, either add panels where feasible or redesign the stringing.
ELD requirements
On the ELD, either assign one MPPT per string, or combine only identical (balanced) strings (same module count, orientation/azimuth, Voltage calculations (Vmp and Voc)).
2. AHJ Variations
Where the Authority Having Jurisdiction is stricter than this document, AHJ requirements govern.
Flag any AHJ-driven deviation at the time of submission. Either:
Note the AHJ requirement and the corresponding deviation in the project submission record notes in the portal, or
Flag the project to a Daylight admin before CAD review begins.
Surfacing AHJ exceptions early prevents avoidable rejections during review.
3. Inverter Internal Breaker Values
The grid and load breaker value shown for the inverter must satisfy both of the following:
Cite value published on the inverter's spec sheet (default, on-grid, or off-grid).
Be consistent throughout the plan set - the same value used in the SLD, ELD, equipment schedule, and any narrative callouts.
Pull values directly from the current spec sheet for the model being installed. Do not transcribe from prior plan sets.
4. LST Interconnection and Backup Configuration
Whole-home backup is not permitted on any Daylight project, in any market. All systems must be designed as partial-home backup with a critical loads panel.
Design requirements
• A critical loads panel is required on every system. Only critical loads may be backed up.
• Plan sets must show partial-home backup configuration explicitly. CAD submissions showing whole-home backup will be rejected.
• Wire sizing should follow from the partial-home configuration. Confirm the configuration is correct before sizing conductors.
Why this rule exists
• Future large loads - EVs, hot tubs, and other high-draw additions - can drain the battery and compromise backup performance.
• Whole-home backup creates ongoing liability and asset-management risk for Daylight as the system owner.
• Whole-home configurations add roughly $1.5k-$3k in electrical cost and complexity, primarily from breaker and AFCI work when pulling circuits.
5. Rooftop Wiring and Conduit
Conductor sizing
#10 AWG copper minimum for all rooftop circuits, AC or DC coupled.
Apply NEC 310.15 derating, including rooftop temperature adders for raceways exposed to direct sunlight.
Conduit
¾” Conduit minimum to the roof (subject to local AHJ guidelines). This satisfies conduit fill compliance per NEC Chapter 9.
Conduit fill calculation and de-ration on all rooftop conduit runs
Conduit fill calculations must be included on the single-line diagrams for all rooftop conduit runs, regardless of size.
Rooftop equipment grounding conductor (EGC)
#6 AWG copper is the Daylight standard and should be specified by default.
#10 AWG copper is the minimum acceptable EGC if project conditions require otherwise.
Why #6 is preferred: lower-impedance path for surge and lightning current and reduced voltage drop on the bonding path.
6. AC Tap-Point: Feeder and CTs
Feeder Conductor Sizing
#6 AWG copper from the tap point through the termination on the grid side of the solar / AC combiner box, for circuits up to 60A.
For circuits above 60A, size the conductor per NEC 310.16 and 240.4.
Current Transformers (CTs)
Grid and solar CTs must be included in plans and on all jobs - they are provided by the OEM as standard equipment with the inverter.
Grid CTs: install on the service-entrance conductors (L1 and L2) on the utility side of the AC tap point. Orient per the inverter installation manual (arrow toward the grid).
Solar/generation CTs: install on the AC output of any non-Sol-Ark PV source feeding the same service (e.g., legacy string inverter or microinverter system). Orient per the inverter installation manual.
CTs must appear on the SLD and in the equipment schedule.
7. Battery Conductors (Renon / Deye)
Two sets of 2/0 AWG conductors provided by the OEM for all current Daylight project configurations (one to two batteries per system). If OEM provided length is not adequate, ensure proper crimping per OEM specifications
8. Battery Equipment Grounding Conductor (Renon / Deye)
For consistency, #6 AWG copper for both Renon and Deye batteries; standard across all Daylight markets.
This is an equipment bonding conductor - sizing follows the manufacturer instructions, not the rooftop EGC rule.
9. Outdoor AC Disconnect
Use any UL-listed NEMA 3R fused disconnect at the required amperage rating.
No specific manufacturer is required. Square D and Eaton are commonly used but are not the only acceptable brands.
Fuse sizing must match inverter output current and OCPD requirements per NEC 690.9.
10. NEC Labeling and Placards
Code cycle and applicability
Daylight requires the full set of NEC 2020 or 2023 labels and placards on every job, regardless of local AHJ acceptance or relaxed enforcement.
All required stickers and placards must be in place at installation submission. Missing or incomplete labeling is a rejection trigger.
Format requirements
Yellow background only, subject to AHJ compliance. Red placards are no longer required under NEC 2023 and should not be used as a substitute. Please check the AHJ’s current code cycle prior to CAD design & submission
Machine-printed labels only; P-touch labels or pre-made placards. Handwritten labels are not acceptable.
If required by AHJ, locator placards may be 4x4, 6x6, or 8x8 inches; size is flexible as long as the placard is clearly legible and posted in an accessible location.
Required label categories
Label content must comply with the relevant NEC 2023 article or local AHJ code compliant. Daylight does not specify exact wording - use a compliant pre-made label kit (see vendors below) or labels specified in Appendix A.
At minimum, the install must include labels covering the following categories:
PV system disconnecting means - NEC 690.13, 690.15.
DC PV conductors in metal raceways and enclosures - NEC 690.31.
Point of interconnection / interactive system marking - NEC 690.54.
Rapid shutdown labels and building marking - NEC 690.56.
Service equipment directory and point-of-connection marking - NEC 705.10, 705.12.
ESS disconnecting means and identification - NEC 706.7, 706.15.
AC and DC voltage warning labels at all energized equipment.
Recommended vendors (informational)
FCD - Daylight’s recommended source. Typical 24-48 hour turnaround with FedEx shipping; approximately $35-40 per job at negotiated pricing. Contact a Daylight admin for the introduction.
PV Labels - alternative source.
11. Conductor and Termination Workmanship
DC connections
No exposed copper outside lug terminations. Strip length must match the lug barrel.
Polarity must be clearly identified at every termination. Positive and negative conductors must be marked or color-coded consistently throughout the system.
All barrel and butt connections must be insulated with heat shrink or properly applied tape to minimize exposed DC conductor.
MC4 connections: utilize proper MC4 wrenches to avoid overtorque.
Documentation tie-in
These workmanship items are documented in the install photo package: pre-wired shots (bond bushings, straight-on face shots, connector sealing) and post-wired shots (terminations, torque marks, clean connections). See the Installation Picture Package Requirements for the complete photo list.
Refer to the Daylight equipment stack for approved equipment models and ratings.