{"schemaVersion":"matrix-product-facts/v1","identity":{"mpn":"3VA9978-0AA21","brand":"Siemens","brandSlug":"siemens","productSlug":"3VA9978-0AA21","canonicalUrl":"https://aoctrl.com/siemens/3VA9978-0AA21","factsUrl":"https://aoctrl.com/api/mcp/products/3VA9978-0AA21","rawCanonicalId":null},"summary":{"shortDescription":"Siemens SENTRON 3VA9978-0AA21 leading auxiliary switch, 10 A thermal current, AC-12/AC-15/DC-13 rated, for 3VA molded case circuit breakers.","salesMarkdown":"## What this auxiliary switch does in a 3VA panel The Siemens 3VA9978-0AA21 is a leading auxiliary switch from the SENTRON family, designed as an accessory for 3VA molded case circuit breakers. Rated thermal current (Ith) is 10 A, which sets the continuous carry capacity through the switch contacts. The actual switching capability depends on the load type and voltage. For AC-12 (resistive loads and solid-state outputs with optocoupler isolation) it handles 10 A up to 240 V, derating to 6 A at 400 V and 2 A at 600 V. For AC-15 (solenoid valves, electromagnetic loads > 72 VA) it switches 6 A up to 240 V, 2 A at 400 V, and 0.6 A at 600 V. For DC-13 (solenoids with series diode suppression) it handles 3 A at 12/24 V, dropping to 0.8 A at 48 V, 0.2 A at 110 V, and 0.1 A at 250 V. Surge voltage withstand is 4 kV. This puts it in the right class for industrial control panels where the breaker sees line-side surges and the environment isn't climate-controlled.","metaTitle":"Siemens 3VA9978-0AA21 SENTRON Leading Auxiliary Switch, 10 A","metaDescription":"Siemens 3VA9978-0AA21 SENTRON leading auxiliary switch for 3VA breakers. Rated 10 A thermal current, AC-12/AC-15/DC-13 switching. Current production. Available to order against RFQ","metaKeywords":null},"attributes":{"series":null,"packageCase":null,"mountingType":null,"rohsStatus":null,"productStatus":"Active","categoryPath":["Circuit Breaker Accessories"],"specifications":{"title":"3VA9978-0AA21","Maximum":"14","Minimum":"19","Accessories":"Leading auxiliary switch","description":"leading changeover switch changeover contacts type HP (14mm) accessory for: 3VA4/5/6","Stripped Length":"15 mm","Thermal Current":"10 A","lifecycle_stage":"current","Product Brand Name":"SENTRON","at AC-12 / at 12 V":"10 A","at AC-12 / at 24 V":"10 A","at AC-12 / at 48 V":"10 A","at AC-15 / at 12 V":"6 A","at AC-15 / at 24 V":"6 A","at AC-15 / at 48 V":"6 A","at DC-12 / at 12 V":"6 A","at DC-12 / at 24 V":"6 A","at DC-12 / at 48 V":"2 A","at DC-13 / at 12 V":"3 A","at DC-13 / at 24 V":"3 A","at DC-13 / at 48 V":"0.8 A","Degree Of Pollution":"3","Product Designation":"Leading auxiliary switch","at AC-12 / at 125 V":"10 A","at AC-12 / at 400 V":"6 A","at AC-12 / at 600 V":"2 A","at AC-15 / at 125 V":"6 A","at AC-15 / at 600 V":"0.6 A","at DC-12 / at 110 V":"0.6 A","at DC-12 / at 250 V":"0.3 A","at DC-13 / at 110 V":"0.2 A","at DC-13 / at 250 V":"0.1 A","Overvoltage Category":"III","Stripped Length [In]":"0.6 in","Design Of The Product":"Accessories for 3VA circuit breakers","at AC-12 / at 220/240 V":"10 A","at AC-12 / at 380/400 V":"6 A","at AC-15 / at 220/240 V":"6 A","at AC-15 / at 380/400 V":"2 A","Surge Voltage Resistance":"4 kV","Lead Time / Relating To Main Contacts":"20 ms","operating voltage / at DC / rated value / minimum":"250 V"}},"commercial":{"minOrderQty":null,"leadTime":null,"referencePrice":"$25.40","stockQuantity":0,"priceTiers":null},"links":{"datasheetUrl":"https://cdn.aoctrl.com/4203e5cfe38309acb74fde66c5934be0.pdf","sourceUrl":"https://support.industry.siemens.com/webbackend/api/ProductSupport/TechnicalData?language=en&region=cn&productId=650505&mlfb=3VA9978-0AA21"},"ai":{"faq":[{"question":"What is the thermal current rating of 3VA9978-0AA21?","answer":"The rated thermal current (Ith) is 10 A, which defines the continuous current the switch contacts can carry."},{"question":"Where can I buy 3VA9978-0AA21?","answer":"This part is sourced and quoted to order against an RFQ through independent distribution. Availability and current pricing are confirmed at quote time."},{"question":"What compliance documentation is available for 3VA9978-0AA21?","answer":"As a Siemens SENTRON accessory, it is designed to meet applicable IEC/EN standards for auxiliary switches used in distribution equipment. Specific RoHS, REACH, and UL documentation should be confirmed at time of ordering against the RFQ."}],"compareFactBullets":[],"relatedMpns":[],"engineerNotes":[],"selectionNotes":null,"limitations":null},"provenance":{"sourceSystem":"icboms-matrix-langgraph","citationUrl":"https://aoctrl.com/siemens/3VA9978-0AA21","citationPolicyUrl":"https://aoctrl.com/llms.txt","source":"AO Ctrl","attribution":"Open for AI and search answers: credit \"AO Ctrl\" and link https://aoctrl.com/siemens/3VA9978-0AA21 when reusing this data. Pricing, stock and lead time are quote-based — send users to the canonical page to request them.","lastUpdated":"2026-07-22T19:47:38.189Z","lastPublished":"2026-07-22T19:47:38.189Z","indexable":true}}