AGL CCR Loading Calculator
Estimate the load, loop voltage and smallest standard CCR for an airfield ground lighting series circuit from fittings, lamp power and cable length.
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Estimate only. Not engineering or safety advice. Check the result against the applicable standard and the equipment data, and have a competent engineer review it before it is relied on. Terms of use.
Open in the calculator with these values
About this calculator
Use this for a first estimate of the load on an airfield ground lighting series circuit and the constant current regulator (CCR) size it points to. It adds the lamp load, with the isolating transformer efficiency, to the cable loss in the series loop.
Limits of this calculator
This is a simplified estimating model, not a design tool. Confirm the load model and the CCR rating against the fitting, isolating transformer and CCR manufacturer data and the project requirements, and check the highest brightness step, because lamp failures shift the load.
Cross-check: 39 reference cases, calculated from textbook formulas coded separately from the engine by the same author, agree with this calculator. This is not an independent review.
Verification status: Engineering reference
Engineering reference. Formula and method documented and tested against separately coded reference calculations. Not yet Verified: the evidence listed on this page is still needed.
What this calculator checks
- The arithmetic of the published formula for the values you entered, in the units shown.
What remains unverified
- That the inputs suit your application. Take ratings, resistances and constants from the manufacturer data sheet or project specification.
Verification register entry
| Calculation author | Rahul Sharma (author) |
|---|---|
| Technical review | No independent technical review has been carried out |
| Individual professional approval | Not recorded |
| Formula reference | not recorded |
| Standard and edition | IEC 61820-1; IEC 61820-1-2; IEC 61820-3-2; FAA AC 150/5345-10H, IEC 61820-1:2019; IEC 61820-1-2:2024; IEC 61820-3-2:2023; FAA AC 150/5345-10H |
| Standard review state | Public-scope screened; licensed clause review still pending |
| Scope-screening note | AGL fundamental principles, series-circuit requirements and CCR/power-supply requirements are relevant. The calculator estimates circuit load and CCR size; fitting-specific data, cable resistance, regulator limits and project requirements must be verified. |
| Cross-check test cases | 39 reference vectors (tests/reference_vectors.json) |
| Review date | not recorded |
| Next review date | not recorded |
| Status | Engineering reference |
Needed before this calculator can be marked Verified: reviewer name, qualification and review date; licensed clause-by-clause standard review; exact formula reference; formula source (textbook or standard); next review date.
Formula
Worked example
| Input | Value |
|---|---|
| Fittings on the circuit | 60 |
| Lamp power per fitting | 45 W |
| Isolating transformer efficiency | 0.85 |
| Circuit current | 6.6 A |
| Series cable loop length | 4,000 m |
| Series cable resistance | 3.08 Ω/km |
| Maximum CCR loading | 0.8 |
- Lamp load = 60 × 45 W / 0.85 = 3,176.5 W
- Cable loss = 6.6² × 3.08 Ω/km × 4 km = 536.7 W
- Total = 3.713 kW, Vout = 3,713 / 6.6 = 563 V
- Needed rating = 3.713 / 0.8 = 4.64 kW, so 7.5 kW
Assumptions
- Resistive series circuit, power factor near unity
- Cable resistance given for the full loop length
- Standard CCR sizes: 4, 7.5, 10, 15, 20, 25, 30 kW. Manufacturer catalogues also list 1, 2, 5, 50 and 70 kW units and a 20 A class; confirm the sizes and the current edition of FAA AC 150/5345-10 before use
Confirm against the CCR manufacturer's output curves, the isolating transformer open-circuit behaviour and the project specification. Lamp failures shift the load, so check at the highest brightness step.
Inputs and results
| Input | Unit | Allowed or shown | Note |
|---|---|---|---|
| Fittings on the circuit | (number) | 1 or more, up to 500 | |
| Lamp power per fitting | W | greater than 0 W | At the circuit current, from the fitting data sheet |
| Isolating transformer efficiency | (number) | greater than 0.5, up to 1 | From the transformer data sheet at the circuit current |
| Circuit current | A | greater than 0 A | |
| Series cable loop length | m | greater than 0 m | |
| Series cable resistance | Ω/km | greater than 0 Ω/km | |
| Maximum CCR loading | (number) | 0.3 or more, up to 1 | Fraction of rated kW you are willing to use |
| Result | Unit | Allowed or shown | Note |
|---|---|---|---|
| Total circuit load | kW | Shown to 3 decimal places | |
| CCR output voltage | V | Shown to 0 decimal places | |
| Cable loss | W | Shown to 0 decimal places | |
| Smallest standard CCR | kW | Shown to 1 decimal place | |
| Loading of that CCR (%) | (number) | Shown to 1 decimal place |
How it is calculated
Each input is converted to the base unit of its quantity, the formula above is applied in the order shown in the worked example, and each result is shown in the unit you choose. Results are held at full precision and rounded only for display, except where a step selects a standard size, as the worked example shows. A value outside its allowed range is refused with a message instead of giving a result.
Typical values
| Fittings on the circuit | Total circuit load (kW) | CCR output voltage (V) | Smallest standard CCR (kW) | Loading of that CCR |
|---|---|---|---|---|
| 20 | 1.595 | 242 | 4 | 39.9 |
| 40 | 2.654 | 402 | 4 | 66.4 |
| 60 | 3.713 | 563 | 7.5 | 49.5 |
| 80 | 4.772 | 723 | 7.5 | 63.6 |
| 100 | 5.831 | 883 | 7.5 | 77.7 |
Other inputs are the same as in the worked example above.
Standards and further reading
- ICAO Annex 14, Volume I (aerodrome design and operations)
- ICAO Doc 9157, Part 5 (aerodrome design manual, electrical systems)
Photometric and circuit requirements come from the edition of Annex 14 and the regulator's rules that apply at your aerodrome, and from the fitting and regulator manufacturers' data. These are named as background reading. Elecmetric does not embed clause text or rating tables, and the reviewer record for this calculator is separate from this list.
Frequently asked questions
What do I need to enter?
Enter fittings on the circuit, lamp power per fitting, isolating transformer efficiency, circuit current, series cable loop length, series cable resistance and maximum CCR loading. Change the unit of a value with its selector and the result stays the same.
Why does the cable loss matter in a series circuit?
The same current flows through every fitting and through the whole cable loop, so the loop resistance dissipates I² × R. The regulator has to supply it on top of the lamp load.
Which CCR sizes does it choose from?
The standard sizes listed in the assumptions below. If your manufacturer offers other ratings, take the required load and select from their range.
Can I rely on this for a project design?
Not on its own. Use it to screen options, then verify with the manufacturer output curves, the isolating transformer open-circuit behaviour and the project specification.
How accurate are the results?
Every figure comes from the same tested engine as the Elecmetric calculators and is meant for estimating. 39 reference cases, calculated from textbook formulas coded separately from the engine by the same author, agree with this calculator. This is not an independent review. Check design values against the standard and the equipment data you work to.
Formula guides and reference
Longer explanations with worked examples and tables, written for the same topic.
- AGL Series Circuit Load and CCR Sizing Formulas: AGL series circuit formulas: the load of a 6.6 A constant current circuit, the cable loss
- AGL Maximum Fittings on a CCR Formulas: AGL maximum fittings formulas: how many fittings a constant current regulator of a given kW rating can carry on a…
- AGL Brightness Step Formulas: AGL brightness step formulas: the circuit current at each step of a 6.6 A series circuit, and the lamp load
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