Electrical supply sizing
HEDNO low-voltage supply categories, with the rated current of each and the feeder and protection we would normally fit between the meter and the main panel.
Enter the demand in kVA, kW or amps to find the smallest supply that covers it.
Supply
> 250 kVA
This needs a medium-voltage connection or a dedicated arrangement with HEDNO.
Supply
- Supply cable
- Meter–panel feeder
- Meter fuse
- Panel main fuse
All low-voltage supplies
| Supply | kVA | I (A) | Supply cable | Meter–panel feeder | Meter fuse | Panel main fuse |
|---|---|---|---|---|---|---|
| Single-phase 230 V | ||||||
| No 03 | 8 | 34.8 | 2×6 | 3×10 | 35 A (or MCB 40 A) | 35 A |
| No 05 | 12 | 52.2 | 2×16 | 3×16 | 63 A | 50 A |
| Three-phase 400 V | ||||||
| No 1 | 15 | 21.7 | 4×6 | 5×10 | 3×25 A | 3×25 A |
| No 2 | 25 | 36.1 | 4×6 | 5×10 | 3×35 A (or MCB 3×40 A) | 3×35 A |
| No 3 | 35 | 50.5 | 4×16 | 5×16 | 3×63 A | 3×50 A |
| No 4 | 55 | 79.4 | 4×25 | 3×25 + 16 + 16 | 3×100 A | 3×80 A |
| No 5 | 85 | 122.7 | 4×50 | 3×50 + 25 + 25 | 3×160 A | 3×125 A |
| No 6 | 135 | 194.9 | 1×95 single-core | 3×120 + 70 + 70 | 3×250 A | 3×200 A |
| No 7 | 250 | 360.8 | 1×150 single-core | 3×240 + 120 + 120 | 3×400 A | 3×350 A |
Before you use these numbers
- Categories and ratings are HEDNO's. HEDNO confirms the category when you apply; above 250 kVA the connection moves to medium voltage or a dedicated arrangement.
- Current is calculated as S/230 for single-phase and S/(√3·400) for three-phase supplies.
- Feeder sizes assume a short run of PVC-insulated copper cable fixed on a surface (reference method C). In conduit, grouped with other circuits, in a hot space or over a long distance, size the cable to ΕΛΟΤ HD 384: in conduit, for example, 3×25 and 3×50 fall below the 100 A and 160 A meter fuses that protect them. Check voltage drop for the actual length.
- The reduced neutral from supply No 4 upwards is acceptable only where third-harmonic current is low. Buildings dominated by LED lighting, IT equipment or drives need a full-size neutral.
- Where the meter and panel fuses have the same rating, as in No 1, the two will not discriminate. For gG fuses keep a ratio of at least 1.6:1 if selectivity matters.
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