ASCO Power Technologies 300 Series power transfer switch, 30-3000 A
Manufacturer: ASCO Power Technologies
ASCO's commercial and light industrial line, and the deepest single bench of used transfer switches on the market
This model is part of SecondWatt’s transfer switche research catalogue. Specifications and price observations are included where supported by sources. Equipment availability and commercial terms require confirmation.
ASCO 300 Series transfer switch dossier: 30-3000 A ratings, Group G controller and retrofit kit, observed used and new pricing, and inspection guidance.
The 300 Series is ASCO's commercial and light industrial transfer switch, sitting one tier above the single-phase 185 Series and one tier below the 4000 and 7000 mission-critical lines. It spans 30 to 3000 A across 15 field-selectable voltage taps from 115 to 600 V, in open transition or delayed transition, automatic or non-automatic, with a service entrance rated catalogue range of its own. The controller is ASCO's Group G, microprocessor-based with an LCD display.
What it does not do is the more important half of the specification. There is no bypass-isolation variant and no closed transition option under the 300 name; both begin at the 4000 and 7000 tier. That single fact places the line outside NFPA 110 Level 1 and mission-critical data center specifications, which require the automatic switch to be serviceable without dropping load, and it explains why 300 Series units turn up so often in the resale channel while 7000 Series bypass units rarely do.
For a used buyer the decisive question is the controller. ASCO sells a Group G retrofit kit under catalogue 955717-001 and an advanced function bundle under catalogue 935147, so a 300 Series power section with a failed or obsolete controller is a repair rather than a write-off. That retrofit path is what puts a floor under used 300 Series pricing, and it is the first thing to verify on any listing.
Why it matters
This is the line that sets the reference price for the whole category. Everything else in the category is priced against it.
Who buys it
Commercial and light industrial facilities, and data center operators buying for house loads, ancillary buildings and spares rather than for the critical bus. Surplus Record carries more ASCO listings than any other transfer switch brand, at 110 of 359 total, and the 300 Series is the bulk of that inventory, which makes it the practical starting point for anyone building a spares pool against a 24 to 40 week new lead time.
Role in the data center
House and ancillary loads, office and support buildings, and spares. The absence of bypass isolation keeps this line off the critical bus in NFPA 110 Level 1 and mission-critical designs, where the automatic switch must be serviceable without dropping load.
Key specifications
| Ampere range | 30 to 3000 A |
|---|---|
| Voltage taps | 15 selectable, 115 to 600 V |
| Poles | 2 and 3 pole published; 4 pole sold in the dealer channel |
| Neutral options | solid neutral (A suffix) or switched neutral (B suffix) |
| Transition types | open (03ATS) and delayed (3ADTS), automatic or non-automatic |
| Withstand and closing rating | 10 to 150 by frame, voltage and upstream device kA |
| Standard | UL 1008 |
| Enclosures | Type 1, 3R, 4, 4X, 12 |
| Controller | Group G, microprocessor with LCD |
| Controller retrofit kit | catalogue 955717-001, plus advanced function bundle 935147 |
| Smallest frame | 30 A at about 18 x 31 x 13 in and 69 lb |
| Largest frame | 2600-3000 A at up to 42 x 95.5 x 74 in and 2,230 lb |
| Bypass isolation | not offered on this line |
| Operating temperature |
Technical summary
Ampere ratings: 30, 70, 104, 150, 200, 230, 260, 400, 600, 800, 1000, 1200, 1600, 2000, 2600, 3000 A. Voltage: 15 field-selectable taps from 115 to 600 V, with lower-voltage limits at the larger frames. Poles: 2-pole and 3-pole in the technical data; 4-pole units appear in the dealer channel. Neutral: solid neutral standard with the A suffix, switched neutral optional with the B suffix. Transition types: automatic open (03ATS), automatic delayed (3ADTS), plus non-automatic equivalents. Bypass isolation and closed transition: not offered on this line. Withstand and closing rating: 10 kA to 150 kA depending on frame, voltage and upstream device. Listing: designed to UL 1008; service entrance rated variants sold as a separate catalogue range. Enclosures: Type 1, 3R, 4, 4X and 12. Controller: Group G, microprocessor-based with LCD display and a published retrofit kit. Dimensions: 30 A at about 18 by 31 by 13 inches and 69 lb; 2600-3000 A at up to 42 by 95.5 by 74 inches and 2,230 lb.
Major variations
Four catalogue forms sit under the 300 name: automatic open transition, automatic delayed transition, and non-automatic versions of each. A separately catalogued service entrance rated range adds the overcurrent and ground-fault protection the Code requires at a service point. Enclosure choice runs Type 1, 3R, 4, 4X and 12.
Configurations and options
The common commercial build is a three-pole solid-neutral open transition switch in a Type 1 enclosure with the Group G controller. Switched-neutral four-wire builds carry the B suffix and are specified where each source must be separately derived. The advanced function bundle retrofit kit adds capability to the Group G controller beyond the base display.
Compatibility and dependencies
The withstand and closing rating must be coordinated with the actual upstream overcurrent device rather than assumed from the nameplate, because a specific-breaker rating does not carry over to a different breaker. Pole count must match the grounding design: a three-pole solid-neutral switch in a separately derived system will produce ground-fault nuisance trips.
Pricing and availability
Published price range: $200 - $21,434 depending on frame and condition. Trend: stable No published price series exists for this line. What the current data shows is an inverted spread: online distributor sale prices for new 300 Series units run 9.67 to 15.98 USD per ampere at 150 to 2000 A, while several new-surplus and small-frame new listings from other channels sit higher, at 16 to 48 USD per ampere. Buying new through a discounting distributor can therefore beat buying new through the surplus channel, which is the opposite of the pattern in generators and transformers. Lead time, new: 24-40 weeks (category benchmark); distributor stock at small frames. Lead time, used or refurbished: Days to 4 weeks from dealer stock.
Lifecycle and maintenance
Manufacturers publish maintenance intervals for this equipment rather than a service life. The pattern across ASCO, Cummins and Kohler literature is consistent: a monthly electrical transfer test, an annual preventive visit covering enclosure cleaning, contact inspection and lug retorquing, and a lithium control battery replaced every two years on the lines that carry one. No manufacturer in this set publishes a mechanical or electrical endurance figure in operations, and ASCO's own manuals state only that the non-replaceable main contacts are designed to last the life of the switch. That absence is why a used unit is priced on evidence of exercise and on controller availability rather than on a cycle count. Arc flash incident energy is calculated under IEEE 1584-2018 and is installation-specific, so NFPA 70E requires an electrically safe work condition before the enclosure is opened.
Thermal and emissions profile
A transfer switch produces no emissions. It is the device that decides when an emitting machine runs, so the environmental accounting belongs to the generator it starts and to the hours that generator accumulates meeting the monthly exercise obligations in NFPA 110. Two facts do belong to the switch itself. Low-voltage transfer equipment is air-insulated, so sulphur hexafluoride is not part of this product class and should never be claimed as a differentiator. The end-of-life recovery case is copper, silver-alloy contacts and a steel enclosure, and the working exposure is arc flash, calculated under IEEE 1584-2018 and managed through the NFPA 70E process.
Common failure points
- Main contacts — Arc erosion pits and can weld the contacts, so the switch fails to transfer or fails to break
- Controller board — Power supply instability or logic fault stops the switch communicating with the generator control
- Voltage sensing drift — Pickup and dropout thresholds drift, so the switch does not register a real source loss
- Actuator and springs — Solenoid or linear actuator failure, capacitor failure or spring fatigue leaves the switch mid-travel
- Terminations — Vibration and moisture loosen lugs and corrode terminals, producing heat at the connection
- Exercise neglect — A switch that has not transferred in months fails on the first real outage
Inspection checklist
Withstand and closing rating: match the nameplate WCR to the actual upstream device, because UL 1008 Edition 9-2022 does not let a specific-breaker rating carry over to a different breaker. Rating convention: establish whether the WCR is specific-breaker or any-breaker time-based, commonly 3-cycle, since the 2 conventions are not interchangeable. Ampere frame and poles: confirm the frame rating and whether the unit is 2, 3 or 4 pole. Neutral configuration: a 3-pole solid-neutral switch dropped into a separately derived system will nuisance-trip ground-fault relays. Transfer test under load: operate normal to alternate and back, the monthly test NFPA 110 requires, and time it against the 10-second Type 10 threshold. Contact condition: inspect for pitting and erosion; discoloration is normal and the manufacturer instruction is to use light emery paper rather than a file.
Procurement channels
Surplus Record and eBay carry the deepest priced inventory, with dealer channels including Depco, Woodstock Power and Worldwide Power Products holding stock but gating price behind an inquiry. Distributor channels including Platt, Norwall, ATI Electrical and Toboa Energy publish new pricing for several frames.
Regional notes
North American product built to UL 1008 with NEMA enclosure types. Neither the California preapproval list nor ASCO literature carries a model-specific seismic preapproval number for this line, so any seismic claim needs verification against the live database rather than a catalogue.