ERD Buying Guide
Complete specification guide for Emergency Rescue Devices — from 4-person residential lifts to 20-lift centralised systems. Field data from 200+ Indian installations (2017–2024).
Step 1 — Select Your ERD KVA
Match your lift motor capacity to the right ERD size. If you don't know the motor KW, use the formula below or let the calculator do it for you.
| ERD Size | Battery Bank | Batteries in Series | Motor KW Range | Typical Lift | Best For |
|---|---|---|---|---|---|
| 6.5 KVA | 48V | 4 | Up to 4 KW | 4 person (320 kg) | Low-rise residential G+3 |
| 10 KVA | 96V | 8 | Up to 6 KW | 6 person (480 kg) | Standard residential |
| 15 KVA | 120V | 10 | 7–8 KW | 8 person (630 kg) | Mid-rise residential |
| 20 KVA | 180V | 15 | 10–12 KW | 10–13 person (800–1000 kg) | Standard commercial / society |
| 30 KVA | 360V | 30 | 13–18 KW | Multiple or heavy duty | Large societies, malls |
| 50 KVA | 360V | 30 | 28–35 KW | High-speed / cargo | Premium high-rise, hospitals |
| 100 KVA | 480V | 40 | Up to 10 lifts | Centralised | Large society (10 lifts) |
| 200 KVA | 480V | 40 | Up to 20 lifts | Centralised | Large complex (18–20 lifts) |
Data validated against real Indian installations. Full specifications table →
Step 2 — Choose Your Battery Type
The battery bank determines your backup duration, space footprint, and total 10-year cost. ERDs support all three lead acid types and Lithium LiFePO4.
| Type | Cost/Unit | Cycle Life | Usable DoD | Space | Maintenance | Best For |
|---|---|---|---|---|---|---|
| SMF Lead Acid | ₹3,000–₹6,000/unit | 200–300 | ~50% | Large | None | Budget builds, well-ventilated rooms |
| Tubular Lead Acid | ₹5,000–₹9,000/unit | 500–800 | ~60% | Large + ventilation | Water topping every 6 months | Longer backup on budget |
| Lithium LiFePO4 | ₹18,000–₹30,000/unit | 2,000–3,000 | 80–90% | 60% smaller than lead | None — sealed BMS | Premium, limited space, lowest 10yr TCO |
Step 3 — Select Your Backup Duration
Haryana mandates minimum 15 minutes. Most engineers specify 30 minutes. The table below shows battery Ah required for a standard 20 KVA ERD / 11.5 KW lift (the most common size in India).
| Backup Duration | SMF Ah Required | SMF Batteries (100Ah) | Lithium Ah Required | Lithium Batteries (100Ah) | Haryana OK? |
|---|---|---|---|---|---|
| 15 min (Minimum) | 32 Ah | 30 batteries | 16 Ah | 15 batteries | ✓ Yes |
| 30 min (Recommended) | 45 Ah | 30 batteries | 23 Ah | 15 batteries | ✓ Yes |
| 1 hour | 88 Ah | 60 batteries | 44 Ah | 30 batteries | ✓ Yes |
| 2 hours | 125 Ah | 60 batteries | 63 Ah | 30 batteries | ✓ Yes |
| 3 hours | 180 Ah | 90 batteries | 90 Ah | 30 batteries | ✓ Yes |
Note: 20 KVA ERD uses 360V battery bank = 30 batteries in series. Parallel strings add capacity (backup duration). Calculate your exact requirements →
Installation Checklist
8 steps every lift engineer, architect, and PMC team should complete before signing off an ERD installation.
Calculate motor KW
Motor KW = (Load kg × Speed m/s × 9.81) ÷ (1000 × efficiency). Efficiency = 0.85 for gearless, 0.70 for geared.
Size the ERD KVA
ERD KVA = (Total Motor KW ÷ 0.8 PF) × 1.25 safety factor. Round up to nearest standard size.
Choose battery type
SMF for budget. Tubular for longer backup on budget. Lithium for premium or space-constrained locations.
Calculate battery Ah
Use the backup chart. At 30 min: 20 KVA ERD needs 45Ah SMF (30 batteries × 12V in series = 360V bank).
Verify Haryana compliance
Haryana mandates minimum 15 minutes backup + solar capability. Our calculator flags compliance status.
Check BIS certification
Ensure the ERD carries BIS certification for Lift Inverter/Lift UPS/ERD. Ask supplier for the certificate.
Plan battery room space
SMF banks need ventilation (hydrogen off-gassing). Lithium is sealed — smaller and no ventilation requirement.
Consider centralised system
10–20 lifts in a society? One centralised 100–200 KVA ERD is cheaper and easier to maintain than individual units.
Use the Calculator — Get Your Exact Spec in 30 Seconds
Select your lift brand, capacity, speed, number of lifts, and desired backup. Get ERD KVA + exact battery count for SMF, Tubular, and Lithium — compared side by side.
⚡ Open ERD Sizing CalculatorView Full Specifications →