Electrical / runnable MCP tool
Run the EV Charger Circuit Calculator in your AI assistant
Through the free Intry MCP server, Claude, ChatGPT, or Cursor runs this exact calculator and hands back a verdict and the cited source, not a guess. Tool name: ev_charger.
What it runs: Wire, breaker, ground and GFCI for a Level 2 EV charger, and whether the existing panel has room for it. The panel check is a real NEC 220.87 calculation when you give it your metered demand. Without one it falls back to a rule of thumb, and the answer says which you got.
What you get back: wire/breaker/ground, charge speed, and a verdict on whether the service takes the charger.
How it computes the answer
Sized from the NEC 625.41 continuous-load rule (125%), NEC Table 310.16 ampacity with the 240.6(A) breaker and Table 250.122 ground.
What it cites
Your assistant gets the same verdict and the same citation a technician gets on the interactive calculator, because both call one engine. These are the sources that engine reads.
- NEC 625.41 and 625.42
- Electric-vehicle charging loads are continuous loads for the purposes of Article 625 (625.42), so the branch OVERCURRENT DEVICE is rated at not less than 125% of the equipment's maximum load (625.41 Overcurrent Protection) and the CONDUCTOR is sized to the same 125% under 210.19(A)(1). NFPA 70-2023, p. 70-557.
- NEC 625.44, 625.54, and 210.21(B)(1)
- Connection and protection. A cord-and-plug NEMA 14-50 is limited to a 50 A receptacle, so above a 40 A continuous charger (a 50 A branch) the tool forces a hardwired connection: a single receptacle on an individual branch circuit must be rated for that circuit (210.21(B)(1)). A cord-and-plug EVSE requires GFCI protection (625.54). A unit over 60 A needs a disconnecting means that is readily accessible AND lockable open in accordance with 110.25, and where it is installed remote from the equipment a plaque on the equipment must state its location (625.43).
- NEC Table 310.16
- Conductor ampacity (75°C column with the 110.14(C) terminal cap). The general ampacity table for conductors in raceway or cable. Fetched from the primary (p.70-187).
- NEC 240.6(A), 240.4(B), 240.4(D), and Table 250.122
- The circuit is sized through the same locked wire-size engine: standard overcurrent-device ratings (240.6(A)) with the next-standard-size-up allowance (240.4(B)), the small-conductor cap on #14/#12/#10 (240.4(D), which governs a small charger), and the equipment grounding conductor sized from the overcurrent device (Table 250.122). Fetched from the primary.
- NEC Chapter 9 (voltage drop) and 210.19(A)
- The voltage-drop reading reuses the voltage-drop engine: conductor circular mils from NEC Chapter 9 Table 8 against the advisory 3% recommendation (210.19 Informational Note, guidance, not an enforceable limit).
- NEC Table 310.15(B)(1)(1) and Table 310.15(C)(1)
- The two corrections that sit between the table ampacity and the conductor this tool names. NEC 310.16(3) and (4) give Table 310.16's conditions of use, a 30 C (86 F) ambient and not more than three current-carrying conductors, and the table's own notes point to 310.15(B) and 310.15(C)(1) for anything else. This branch is sized as THHN, so the ambient correction is taken in the 90 C column of Table 310.15(B)(1)(1): 87 to 95 F takes 0.96, 96 to 104 F takes 0.91, 105 to 113 F takes 0.87, 114 to 122 F takes 0.82, 123 to 131 F takes 0.76, 132 to 140 F takes 0.71, 141 to 149 F takes 0.65, 150 to 158 F takes 0.58, 159 to 167 F takes 0.5, 168 to 176 F takes 0.41, 177 to 185 F takes 0.29. Those are the bands above the table's own basis; the table also prints correction factors BELOW it, which raise ampacity, and this tool does not size a conductor down on a declared temperature. Table 310.15(C)(1) then adjusts for conductor count, at 4-6 conductors at 80 percent, 7-9 conductors at 70 percent, 10-20 conductors at 50 percent, 21-30 conductors at 45 percent, 31-40 conductors at 40 percent, 41+ conductors at 35 percent. Its title is Adjustment Factors for More Than Three Current-Carrying Conductors, so three or fewer is the absence of an adjustment and not a row of the table. The adjustment applies where the count in a raceway or cable exceeds three, or where conductors run without maintaining spacing for longer than 600 mm (24 in.), and 310.15(C)(1)(a) through (d) exempt cable trays, raceways not exceeding 600 mm (24 in.), certain trench entries, and certain Type AC and Type MC cable. Both factors apply to the ampacity at the conductor's own rating, and 310.15(A) then holds the corrected and adjusted result to the termination rating under 110.14(C), which is a cap the corrections cannot lift. Read from the printed primary at folios 70-184, 70-185, 70-186 and 70-187 on 2026-08-23.
- NEC 750.6, 750.30, and 750.50, energy management systems
- What an energy management system must be, and what it is not permitted to do. 750.6 requires the system to be listed, as a complete system, as a kit for field installation in switch or overcurrent-device enclosures, or as listed individual components assembled as a system. 750.30 permits an EMS to monitor and control loads and sources, and then bounds it: under 750.30(A) it may not override the load-shedding controls that hold minimum capacity for fire pumps, emergency systems, legally required standby systems and critical operations power systems, and under 750.30(B) it may not disconnect power to elevators, to positive mechanical ventilation for hazardous locations, to ventilation exhausting hazardous gas, to circuits supplying emergency lighting, or to essential electrical systems in health care facilities. 750.30(C) states plainly that an EMS shall not cause a branch circuit, feeder or service to be overloaded, and where one is used to limit current on a conductor it attaches four conditions: a single current setpoint, which is also the value 220.70 permits in the load calculation; monitoring and controls that cease current flow automatically on malfunction; adjustable settings reachable only behind a sealed cover, a tool-opened door, a locked door, or password-protected access; and field marking of the equipment with the maximum current setting, the date of calculation, the loads and sources involved, and wording that the current-limiting feature is not to be bypassed. 750.50 additionally requires a directory identifying the controlled devices and circuits, posted on the controller, disconnect or branch-circuit overcurrent device. These are site facts about installed equipment, so this tool names them and does not treat any of them as satisfied. Read from the printed primary at folios 70-668 and 70-669 on 2026-08-23.
- NEC 625.42(B) + 750.30(C) + 110.3(B)
- The adjusted-setting route. NEC 625.42 sizes the service and feeder from the product ratings unless the installation's overall rating is limited through controls permitted by 625.42(A) or (B), and of those two only (B) changes what an EVSE's own ampere rating IS, which is the quantity 625.41 sizes the branch overcurrent device from. So an EVSE's restricted-access adjusted current setting is the one route the NEC gives to that unit's own rating being smaller, and this tool never takes it: nothing in this tool is sized from a setting you enter. The conductor, breaker, ground and voltage drop come from the full hardware rating, and the panel check from the greater of that load and NEC 220.57's 7,200 VA minimum. A setting you enter is echoed back with the conditions rather than applied. Those conditions are facts about installed equipment that a calculator cannot check, and there are 4 of them: Where the adjusting means is part of an energy management system, that system uses monitoring and controls to automatically cease current flow if it malfunctions. 750.30(C) applies its subdivisions where an EMS is used to limit the current on a conductor. (NEC 750.30(C)(2)) Access to the ampere adjusting means is restricted by at least one of the five means 750.30(C)(3) names: behind a removable and sealable cover over the adjustment, behind a cover or door that needs a tool to open, behind a locked door accessible only to qualified personnel, password protected with the password held by qualified personnel only, or software whose access to the adjusting means is password protected for qualified personnel only. (NEC 750.30(C)(3)) The equipment supplying the branch circuit is field marked with the maximum current setting, the date of the calculation and setting, identification of the loads and sources associated with the current limiting feature, and the words "The setting for the EMS current limiting feature shall not be bypassed". Those markings meet the requirements in 110.21(B) and are located so they are clearly visible to qualified persons before examination, adjustment, servicing, or maintenance of the equipment. (NEC 750.30(C)(4)) The adjustment was made in accordance with the manufacturer's instructions, and the adjusted rating appears on the rating label with enough durability to withstand the environment involved. (NEC 625.42(B) / 110.3(B)) They are the conditions this tool can name, not a full compliance checklist: 625.40, 625.54 and 750.30's own capacity requirement are untouched by them. NFPA 70-2023, pp. 70-557 (625.42) and 70-669 (750.30(C)).
- NEC 220.60
- Noncoincident loads, NFPA 70-2023, p. 70-96, read from the printed folio: "If it is unlikely that two or more noncoincident loads will be in use simultaneously, using only the largest load(s) that will be used at one time for calculating the total load of a feeder or service shall be permitted." This is the section that reaches an interlocked pair, and it is why a circuit-share switch changes what the service calculation carries while claiming no relaxation under 625.42(A) or 220.70. Its second sentence carries a condition worth knowing: where a motor or air-conditioning load is part of the noncoincident group and is not the largest of them, 125 percent of the motor or air-conditioning load, whichever is larger, is what enters the calculation.
- NEC 230.79 and NEC 230.42(A)(1)
- Two service rules that size DIFFERENT quantities, and this tool keeps them apart on purpose. NFPA 70-2023, p. 70-113: "230.79 Rating of Service Disconnecting Means. The service disconnecting means shall have a rating not less than the calculated load to be carried, determined in accordance with Part III, IV, or V of Article 220, as applicable." That is the SERVICE RATING, set from the Article 220 calculated load at 100 percent, and it is the quantity the panel check in this tool compares against. NFPA 70-2023, p. 70-110: 230.42(A)(1) sizes SERVICE-ENTRANCE CONDUCTORS at "the sum of the noncontinuous loads plus 125 percent of continuous loads". This tool does not size service conductors and never applies that 125 percent to the service rating. Reading 230.42(A)(1) without reading 230.79 beside it is how a continuous designation gets applied to the wrong quantity.
- NEC 230.90 and NEC 240.4
- Overcurrent protection either side of the service point, named where the tool tells you a feeder or service needs it. NFPA 70-2023, p. 70-115, 230.90(A): "Such protection shall be provided by an overcurrent device in series with each ungrounded service conductor that has a rating or setting not higher than the ampacity of the conductor." NEC 240.4 is the general conductor-overcurrent rule on the feeder side, p. 70-122 for the lead-in and (A), with 240.4(D) on p. 70-123. Neither figure is computed by this tool: the tool names the requirement and leaves the sizing to whoever runs the service.
- NEC 210.20(A)
- Branch-circuit overcurrent protection at 125 percent of a continuous load, p. 70-84. It is the section the wire-size engine names when it applies the continuous factor to the charger branch, and it is the branch-side counterpart to 230.42(A)(1)'s service-side 125 percent. That distinction is the one 220.70 turns on: an energy management system limits current to a feeder or service and never to a branch.
These are NEC table and rule values, applied by the engine to the charger and circuit you enter, not measurements. The on-page panel-capacity check runs NEC 220.87 from the metered peak demand you enter, with the charger at its NEC 220.57 value; with no reading entered it falls back to a labelled main-breaker-headroom estimate, which is not an NEC method. A restricted-access adjusted setting under NEC 625.42(B) is echoed and never applied: nothing in this tool is sized from it. The manufacturer's instructions and the AHJ govern the final install; a hardwired unit follows its nameplate under 110.3(B).
The full receipt, with every source and how each is cross-checked, is on the interactive EV Charger Circuit Calculator.
Ask your assistant
The one rule that makes it reliable: name Intry in your question. That is what tells Claude to run the ev_charger tool and answer with the real number, the verdict, and the citation. Leave Intry out and Claude may just guess from memory, which is exactly what you are trying to avoid. Type something like:
“Use Intry to size a 48 A hardwired EV charger: wire, breaker, and ground.”
“Ask Intry if a 200 A panel that's about half loaded can take a 48 A charger.”
Inputs
| Field | Required | Accepts | What it is |
|---|---|---|---|
| amps | yes | number | Charger output current in amps (e.g. 48). This calculator answers for 8 to 80 A, which is a scope of the tool and not a code limit. |
| voltage | optional | number | Circuit voltage (default 240). This calculator answers for 120 to 240 V single-phase premises supply. Outside that the conductor, breaker and ground would still be sized from amps, but the published charge speed and voltage drop would not be answerable, so the call is refused rather than half-answered. |
| distance | optional | number | One-way run length in feet (default 50). 0 to 300, the same run lengths the web tool answers for. |
| material | optional | cu, al | Default cu. |
| mainBreakerAmps | optional | number | Existing main breaker / service size (default 200). |
| existingLoadPercent | optional | number | FALLBACK ONLY. Rough existing panel load as % of main (default 50). Used only when meteredDemandValue is absent; it is a rule of thumb, not an NEC method. |
| meteredDemandValue | optional | number | The home's measured maximum demand. Supplying this runs the real NEC 220.87 existing-loads calculation instead of the rule of thumb. |
| meteredDemandUnit | optional | kw, a | Unit of meteredDemandValue (default kw). |
| demandSource | optional | utility, recording | utility = 12-month utility peak; recording = 30-day recording-ammeter peak (the 220.87 exception). Default utility. |
| batteryKwh | optional | number | EV battery size in kWh, for the hours-to-full estimate (default 75). Ignored when vehicleId is supplied and that vehicle publishes a battery capacity: the roster's sourced figure is used instead, because mixing a sourced charge rate with a caller-supplied capacity produced a hours-to-full figure that was wrong by 89 percent on a published machine surface. |
| plug | optional | NEMA 14-50, hardwired | Connection type (default hardwired). A NEMA 14-50 request is answered as hardwired when the breaker computed for amps exceeds the receptacle's 50 A rating; the effective connection is returned as 'connection' in the result. |
| evemsDeviceType | optional | shed, throttle, circuit-share | NEC 625.42(A): a listed energy management system already installed on this service, by mechanism. shed = a demand-control relay that disconnects the charger before the panel reaches its limit; throttle = a device that lowers the charge current to a setpoint; circuit-share = an automatic interlock time-sharing one existing 240 V branch. Supplying it makes the panel verdict the maximum load that system permits (625.42(A) / 220.70 / 750.30) instead of the raw 220.87 headroom. NEC 625.42(A) sets the maximum equipment load for the service and feeder calculation. This tool applies it to the NEC 220.87 method, so it moves the panel verdict ONLY on a call that also supplies `meteredDemandValue`: without a meter reading there is no 220.87 calculation here to relax, and the verdict is byte-identical to the same call without the device. It changes no circuit: conductor, breaker, ground, voltage drop and parts list are sized from `amps`, the full hardware rating, on every path. This tool has not verified that any device is installed, listed, set or marked; it returns the conditions it can name as a site condition. |
| evemsDeviceRatingAmps | optional | number | The declared device's controlling rating in amps, and it means a different quantity per mechanism: for shed it is the EV pass-through breaker, for circuit-share it is the shared branch's breaker, and the charger is 80% of it (NEC 210.20(A)). A throttle needs none, because what it controls is the charger already given in `amps`. Ignored unless evemsDeviceType is supplied. Declared without evemsDeviceType it declares nothing and changes nothing; supplied with a type that needs it and omitted, the tool says so rather than answering silently. |
| vehicleId | optional | ford-f150-lightning-2025-sr, ford-f150-lightning-2025-er-123, ford-f150-lightning-2025-er-131, nissan-leaf-2025-s, nissan-leaf-2025-sv-plus, kia-ev6-2025-light-standard-range, kia-ev6-2025-light-long-range | The vehicle being charged, from a closed roster of 7 records (Ford, Nissan, Kia) whose onboard AC charger rating or EPA consumption rating was fetched from a primary document this repo holds. Supplying it makes the charge speed the lower of the car's onboard limit and the charger's output, computed on that vehicle's own EPA combined consumption figure, and makes the hours-to-full use that vehicle's own battery. It changes no circuit: conductor, breaker, ground, voltage drop, panel check and parts list are sized from the charger's full rating on every path, because NEC 625.41/625.42 size the branch from the EVSE and NEC 220.57 values the service load at 7,200 VA or the nameplate rating of the equipment, whichever is larger, the equipment being the EVSE and not the car. The roster is small on purpose: A vehicle appears here only when its manufacturer publishes an onboard-charger figure, or the EPA publishes a consumption figure, that this repo fetched and holds. An unsourced trim is dropped, never estimated. A vehicle absent from this list is one this repo either holds no source for, or holds a source for that lacks a field a record requires; it is NEVER one that cannot be charged. GM (Silverado EV, Blazer EV, Equinox EV) were attempted and Intry holds no manufacturer specification document giving an onboard charger rating for them; the pages it did fetch and archive carry none, which is a limit of what those documents say rather than a refutation. Those vehicles can still be chosen from the EPA tier, where the figures EPA itself publishes are shown and no rating is taken from the car. |
| ambientF | optional | 86, 95, 104, 113, 122, 131, 140 | Ambient temperature at the run, in F (default 86, which is the 30 C basis NEC Table 310.15(B)(1)(1) is based on). NEC Table 310.15(B)(1)(1) corrects conductor ampacity above it. Values below the table's basis are refused rather than answered: below 30 C the correction is an uplift, which permits a smaller conductor, and this tool does not size a conductor down on a declared temperature. The listed values are the ones the web tool offers, not a limit on what this accepts. A value between two of them is answered, at the correction factor for the table row that contains it, because NEC Table 310.15(B)(1)(1)'s rows are ranges: 87 F and 94 F both fall in the 87-95 F row and both return 0.96, and 96 F falls in the next row and returns 0.91. Your declared value is echoed back on the result, not replaced. Do not round a measured temperature down to one of the listed values: rounding 94 F to 86 F moves the factor from 0.96 to 1.00, which permits a smaller conductor than the site condition allows. Send what you measured. |
| conductorsInConduit | optional | 1-3, 4-6, 7-9, 10-20, 21-30, 31-40, 41+ | Current-carrying conductors sharing the raceway (default 1-3, which applies no adjustment). NEC Table 310.15(C)(1) prints an adjustment for more than three; its own title is 'Adjustment Factors for More Than Three Current-Carrying Conductors', so 1-3 is the absence of an adjustment rather than a row of it. NOT inferred from `plug`: whether a 14-50's neutral is current-carrying is NEC 310.15(E) and this tool does not decide it. |
| adjustedSettingAmps | optional | number | NEC 625.42(B): a restricted-access adjusted current setting BELOW the unit's rating, when the EVSE is field-adjustable. It is accepted and applied to nothing: the conductor, breaker, ground, voltage drop, panel check and parts list are all sized from the full hardware rating in `amps`, and do not move. It adds a site-condition blocker naming 625.42(B) and 750.30(C), plus the circuit that setting would call for if a qualified person certifies those conditions. Accepted range 8 to 80 A. Outside that, or at or above `amps`, no conditional circuit is returned. The setting must also land on a standard EVSE output: 16, 24, 32, 40, 48 A above 120 V, or 12 A at Level 1, where the unit's own rating cannot exceed 16 A either. A setting between two rungs returns no conditional circuit, because a value no listed unit can actually be set to is not a setting a circuit may be sized from. |
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- (If a field is blank, paste the link below into the URL field.)
- In any chat, tap + then Connectors and switch Intry on. Then name Intry in your question (“use Intry to…”) so Claude runs the tool instead of guessing.
https://www.intrysys.com/api/mcpNo login, no API key, and it works on every Claude plan, right from your phone.
Using ChatGPT, Cursor, or a dev tool? See the developer setup on the main page. The endpoint is https://www.intrysys.com/api/mcp.
Every answer comes with the cited NEC section, so you can check it or show an inspector. The numbers come from the same calculator we run on intrysys.com, and we re-check every one automatically before anything goes live, so the number Claude hands you matches the code.