Pad-mount, substation, dry-type or cast-coil — describe the unit and the engine checks DOE efficiency, NEC 450 siting, insulation level and fusing by citation, prices Good / Better / Best, and shows the fault current your switchboard must handle. Every number comes from the rules, never from a guess.
Pad-mounted liquid-filled (three- and single-phase), substation units, dry-type general purpose and cast-coil — 15 to 10,000 kVA, primaries from 480 V to 34.5 kV, mineral oil, natural ester, silicone or dry.
DOE efficiency (10 CFR 431.196) at the current level and the 2029 level; NEC 450 siting — oil indoors needs a vault, with ester, silicone and dry-type as the ways out; BIL by voltage class (IEEE C57.12), fusing, K-factor harmonic loads and solar step-up (IEEE C57.159).
The secondary fault current the downstream switchboard must handle — shown with its arithmetic (rated current over impedance) — plus the site responsibilities an engineer expects, stated rather than buried.
Cited rules decide what may be built and where it may sit — and every size, price and refusal shows its source.
Free to use — Nteli is paid only when an order is won through it.
A transformer quote built in a spreadsheet goes stale the day one of these shifts. The engine doesn’t watch for changes — people teach it: a change comes in with its source, gets replayed against past quotes to show what it touches, is approved by a second person, and ships in a versioned pack. Your quotes cite the rule that priced them.
The April 2024 final rule raises efficiency levels for units made from April 23, 2029 — and DOE’s 2026 review of those levels is open now.
The steel duty reaches transformers (HTS 8504), and the allowance on a quote has to be stated, not hidden in the margin.
Article 450 decides where each liquid and dry-type may sit — vaults, clearances, less-flammable fluids — and it moves on the code cycle.
At 30–60 weeks, a quote priced on last year’s rules is delivered under next year’s — the compliance date belongs on the quote.
The engine is a full MCP server — connect it to Claude and your team quotes distribution transformers in plain conversation: describe the unit, answer the question card, pick Good / Better / Best. The starter rule pack ships with the line; override it with your own rules, governed and audited — and you're onboarded.
Connect the engine as a custom connector (two steps, shown here), then paste any of these. They were run on the live engine; prices are illustrative until your price book loads.
What you’ll see: Mineral oil indoors without a vault is refused under NEC 450.26 — with four ways out, each priced: natural ester from about $127,000 (the usual choice), a vault from about $120,000, silicone from about $137,000, or a dry-type unit.
What you’ll see: A 99.51% minimum-efficiency build (10 CFR 431.196, 2029 level) at about $128,000 — and the fault-current arithmetic in the open: about 31.4 kA at the standard 5.75% impedance, 36.1 kA if you go low impedance, so the switchboard rating is decided before the order, not after.
What you’ll see: A step-up design to IEEE C57.159 — electrostatic shield, built for no-load nights and inverter harmonics — at about $182,000. And a detail estimators catch: no bayonet fuse is published at 34.5 kV, so the primary is protected upstream per NEC 450.3, stated on the quote.
The four manufacturing levers · Estimate your leak ledger · The benchmark rates, with the math · The Leak Ledger Workshop
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