The communication/control circuits of the Gateways associated with Tigo Optimizers and Smart Modules system fall under the following NEC Articles:
- NEC Article 300, Wiring Methods and Materials
- Article 690, Solar PV (Photovoltaic) Systems
According to NEC Article 300.3(C) conductors can occupy the same raceway or conduit so long as they have the same insulation rating. Therefore, you may install gateway wire in the same conduit as PV string homeruns as long as the gateway wire has the same insulation voltage rating as the homeruns.
Supplementally, article 690.31(B) allows conductors to occupy the PV array raceway provided they are an associated system. Since gateway communication cables are associated with the rapid shutdown capability of PV arrays using Tigo, they are allowed to share a raceway with PV wire.
The most common wire type that meets these requirements is Instrumentation Tray Cable (ITC). Ensure that the nominal outside diameter is less than .31 inches (7.87 mm).
18 AWG 600V 2P TC (2-Pair Tray Cable)