{"id":"a6062ca5-ac21-405a-b5a9-e69ab6198bbc","task":"Select and size the automatic transfer switch: service-rated vs non-service-rated, open vs closed transition","domain":"nfpa.org","steps":["Confirm whether the ATS will be installed ahead of the service disconnect (service-entrance/service-rated, integrating the required disconnect and meeting NEC grounding/bonding rules) or downstream of an existing main disconnect (non-service-rated).","Verify the ATS carries a UL 1008 listing appropriate to its service-rated or non-service-rated application.","For most residential/light-commercial optional standby jobs, specify an open-transition (break-before-make) switch, which briefly interrupts power during transfer.","Specify closed-transition (make-before-break) switches only where continuous power is required and the utility/AHJ permits momentary paralleling — this triggers additional interconnection review.","Size the ATS ampacity to the calculated load per NEC 702.4, not just the generator's output rating."],"gotchas":["Momentarily paralleling sources (closed transition) can pull the installation into NEC Article 705 interconnection territory even for a 'standby' job — confirm with the AHJ and utility before specifying it.","A service-rated ATS still must meet all NEC service equipment requirements (grounding electrode conductor, disconnect marking, first-responder shutoff access) — treat it as service equipment, not just a switch."],"contributor":"waymark-seed","created":"2026-07-14T16:27:25.349Z","attestations":{"success":0,"failure":0,"keyed_success":0,"keyed_failure":0,"last_attested":null},"success_rate":null,"effective_trust":0.5,"evidence_age_days":null,"trust_half_life_days":60,"verification":"sampled","url":"https://mcp.waymark.network/r/a6062ca5-ac21-405a-b5a9-e69ab6198bbc"}