How we found the root cause in a leased warehouse, why the cheapest repair quote would only have reset the clock, and how a line-item estimate helped the safety officer get the right fix approved.
- Site: leased warehouse with 4 loading gates and one DB near the dock shutters
- Symptoms: 2 ELCBs tripping frequently; some MCBs burnt twice in 12 months
- Load growth: DB designed for about 12 sockets, now feeding more than 36
- Drawings: SLD showed the original lines only; a decade of changes not recorded
- Quotes: parts-replacement quote about 90% cheaper than our root-cause fix (about ₹1.5 lakh)
- Outcome: the line-item estimate and RCA won management approval for the permanent fix
What happened at this warehouse?
A few years ago, the landlord handed the warehouse over to the tenant with one distribution board near the dock shutters. It fed about 12 sockets. Since then, operations grew. New equipment arrived, and every time someone needed power near a loading gate, a local electrician added a switchboard and connected it to the same DB, because it was the nearest one.
By the time we visited, that DB was feeding more than 36 sockets: battery chargers for pallet trucks, stretch-wrapping machines, fans, coolers, scanners, laptop and mobile chargers, and extension boards plugged into extension boards. In peak hours, when trucks are loading at every gate, almost every socket is in use at the same time.
The symptoms were classic distribution board overloading. ELCB tripping happened frequently on two devices, stopping work at the docks. Several MCBs had burnt out, some of them twice in the last year. Each time, the burnt part was replaced, power came back, and the problem returned a few weeks later.
ELCB tripping frequently and MCB burning: two different warnings
Many sites treat both problems as “the DB is faulty”. They are actually two different warnings, and each points to a different part of the root cause.
| Device | What it protects against | What frequent operation or damage tells you |
|---|---|---|
| ELCB / RCCB (residual current device) | Electric shock and fire from current leaking to earth | Too much leakage on one device: many loads grouped together, damp or damaged cables and plugs, faulty equipment, or neutral wiring errors |
| MCB (miniature circuit breaker) | Overload and short circuit | Tripping means overload or a fault. Burning means heat at the terminals: loose connections, undersized cable, long-term overload or poor-quality breakers |
Terminology: most Indian sites still say “ELCB”. Modern panels almost always have an RCCB or RCBO, which detects the difference between the current going out and the current coming back. In this post, ELCB and RCCB mean the same thing.
Why the ELCB trips: leakage adds up
Electronic equipment such as chargers, computers and anything with a switch-mode power supply normally leaks a small current to earth through its filters, often around 0.5 to 1 mA per device. Product standards allow up to 3.5 mA for some plug-in IT equipment. One device is harmless. Thirty devices on one RCCB are not.
A 30 mA RCCB is also allowed by its product standard to trip anywhere between 50% and 100% of its rating, so between 15 mA and 30 mA. A widely used design rule is to keep the normal standing leakage on one RCCB below about 30% of its rating, which is around 9 mA for a 30 mA device.
25 electronic loads × about 0.5 mA = about 12.5 mA of normal leakage. Add a damp extension board at the dock or one damaged charger cable, and leakage crosses 15 mA. The RCCB trips, as it is designed to. The RCCB is not faulty: the circuit design is.
Why the MCB burns: heat, not just current
An MCB that trips is doing its job. An MCB that burns has been running hot for a long time. In this warehouse, the outgoing circuits and the cable from the main panel had been sized for 12 sockets. With 36 or more sockets loaded together, the cables and terminals ran close to or above their rating for hours every day. Heat loosens terminals, loose terminals create more heat, and the plastic body of the MCB starts to char. The same heat is also happening inside the cable insulation behind the wall, where nobody can see it.
What does thermography show inside an overloaded panel?
Thermography (an infrared thermal scan) shows heat that the eye cannot see. A loose or overloaded connection looks normal in a photo but glows bright yellow on the thermal camera. The images below are from our recent thermography surveys at warehouse and industrial sites. Site details are withheld.
1. Small DB, hot taped joint: the thick cable beside the MCB has been joined and wrapped in tape. That joint is the hottest point in the box at 81.9 °C, while other measured points sit at 35–40 °C. A taped joint has higher resistance than a proper termination, so it heats up under load. This is what “just add one more socket” looks like after a few years.
2. Terminal block: in the photo, every terminal looks the same. On the thermal image, one connection reads 73.0 °C against 46–55 °C for the others: a loose or overloaded termination that will keep getting worse.
3. Busbar terminal links: 103.7 °C on the hottest link, against 53–58 °C at other measured points. Heat at this level damages insulation and can start a fire inside the panel.
How hot is too hot? The NETA hot-spot guide
Thermographers usually judge a hot spot by its temperature difference (ΔT) from a similar component carrying a similar load. The table follows ANSI/NETA MTS Table 100.18, the most widely used guide:
| ΔT vs similar component | ΔT vs ambient air | Suggested action |
|---|---|---|
| 1–3 °C | 1–10 °C | Possible deficiency: investigate |
| 4–15 °C | 11–20 °C | Probable deficiency: repair as time permits |
| – | 21–40 °C | Monitor until corrected |
| More than 15 °C | More than 40 °C | Major discrepancy: repair immediately |
Why was the single line diagram (SLD) useless?
A single line diagram (SLD) is a simplified drawing of how power flows from the incoming supply through panels, breakers and cables to each distribution board and load. It is the map an electrician, an auditor or a fire officer needs to understand the installation.
The SLD we received for this warehouse showed the original lines only. None of the changes made over the last decade had been recorded. Without an accurate SLD you cannot calculate the load on each circuit, check that breakers and cables are matched, isolate equipment safely for maintenance, or tell the fire brigade which supply to cut.
This is not unusual. In Himaya's own electrical audits:
These figures are from Himaya Prevention's own audit experience, not a published survey. For reference, NFPA 70B (2023 edition) has a full chapter on single line diagrams and system studies and expects SLDs to be kept current.
Why are warehouses at higher electrical risk than factories?
- No electrical engineer on site. Most factories have an electrical engineer or a licensed supervisor. Most warehouses are smaller and depend on a local electrician called when something stops working.
- Landlord-tenant gap. The landlord built the installation; the tenant keeps adding to it. Nobody owns the SLD, the load calculation or the periodic testing.
- Load grows at the docks. Pallet truck and forklift battery charging, stretch wrappers, dock levellers, fans and coolers all cluster near the loading gates, usually on the nearest existing DB.
- High fire load. Cartons, plastic, stretch film and stored goods sit close to dock-area panels, so an overheated cable has fuel nearby.
- Few people at night. Chargers and equipment often run overnight with nobody around to notice a burning smell early.
Electrical faults are already a leading named cause of fires in India: in NCRB's 2023 fire accident data, electrical short circuits were recorded for more fire accidents (1,780) than cooking gas cylinder or stove bursts (1,533). A warehouse fire also destroys stock, delays customer orders and can lead to disputes over the insurance claim if the installation was knowingly overloaded.
Cheap electrical repair vs root-cause fix: comparing the two quotes
We submitted an estimate of about ₹1.5 lakh. Another contractor quoted to replace the damaged RCCBs, ELCBs and MCBs and clean the old box, at a price almost 90% lower. On paper, the choice looked obvious. This is where most companies go with the L1 quote and the root cause stays in the wall.
| Quote A: replace parts (L1) | Quote B: root-cause fix | |
|---|---|---|
| Approximate cost | About one-tenth of Quote B | About ₹1.5 lakh |
| Fixes | The burnt and tripping devices | Why they burn and trip |
| Load calculation | No | Yes, socket by socket and phase by phase |
| Thermography (hot spots) | No | Yes, before and after the work |
| SLD revision | No | Yes, as-built drawing handed over |
| Old damaged cable | Left in place | Replaced |
| Load per DB | Still 36+ sockets on one DB | 4 new DBs, one per loading gate, each with its own feeder from the main panel |
| Likely result | Trips and burnt MCBs return; hidden cable heating continues | Stable supply, smaller fault zones, records ready for audits and insurers |
How a line-item estimate and RCA won the approval
The customer's safety officer understood the problem. He did not ask us to reduce the price. He asked for two things he could take to management:
- A line-item estimate with quantities instead of one project cost, so management could see exactly what each rupee buys.
- A root cause analysis (RCA) explaining why the problem keeps coming back.
Those two documents changed the conversation from “why is this ten times more expensive?” to “which of these items can we safely skip?”. The answer was none, and we got the contract.
The root cause analysis (5 Whys)
| Why? | Finding |
|---|---|
| 1. Why do the ELCBs trip and the MCBs burn? | Leakage and load on the dock DB are far above what its circuits and cables were designed for. |
| 2. Why is the load so high? | More than 36 sockets now run from a DB designed for about 12, often all at once in peak hours. |
| 3. Why were all new sockets connected to this DB? | It was the nearest board; additions were made on request, without a load check. |
| 4. Why was there no load check? | The SLD was never updated, so nobody knew the existing load or spare capacity. |
| 5. Why was the SLD never updated? | No one owned electrical changes: no management of change (MOC) for electrical additions and no periodic electrical audit. |
Root cause: uncontrolled electrical additions without load calculation, documentation or ownership. The burnt MCBs were the symptom.
Sample line-item scope (structure we submitted)
| # | Item | Unit | Qty in this case | Why it is needed |
|---|---|---|---|---|
| 1 | Load survey and connected-load register (every socket, charger and machine) | Lot | 1 | Know what is actually connected |
| 2 | Load distribution calculation and phase balancing | Lot | 1 | Size each new circuit, cable and breaker correctly |
| 3 | Infrared thermography of main panel and dock DB at normal load, with report | Panel | 2 | Find hot spots before they become fires |
| 4 | As-built SLD survey and revision (CAD) | Drawing | 1 | Accurate map for maintenance, isolation and audits |
| 5 | New sub-DB with incomer, 30 mA RCCB and outgoing MCBs, one per loading gate | Nos | 4 | Fewer sockets per RCCB, smaller fault zones |
| 6 | New armoured cable feeder from main panel to each new DB (size per load calculation) | Metre | As measured, 4 runs | Take load off the old overloaded cable |
| 7 | Replacement of damaged and undersized old cable | Metre | As measured | Remove hidden heat damage |
| 8 | Regrouping of socket circuits to the new DBs | Point | 36+ | Balance load across gates and phases |
| 9 | Earth continuity, earth pit resistance, insulation resistance and RCD trip tests | Lot | 1 | Prove the new installation is safe |
| 10 | Circuit labelling and DB circuit schedule | DB | 4 | Safe isolation and faster fault finding |
| 11 | Post-work thermography, handover report and RCA | Lot | 1 | Evidence that the fix worked |
Quantities shown are for this case. Cable sizes, lengths and DB ratings depend on the load calculation for each site. Electrical work must be carried out by a licensed electrical contractor.
Tip for safety officers: how to justify the higher quote
- Ask every bidder for line items with quantities, not a lump sum. Compare scope first, price second.
- Attach the RCA and the thermography images. A thermal image of a 103 °C busbar link is easier to approve than a paragraph.
- Show the cost of doing nothing: repeat repair visits, dock downtime in peak hours, stock at risk and a possible insurance dispute.
- Make the SLD and the test report deliverables, so the next audit starts from facts.
10 warning signs your warehouse DB is overloaded
- The ELCB or RCCB trips in peak hours or when several chargers are on together
- MCBs show brown or black marks, melted edges or a burning smell
- The DB cover or the MCBs feel warm to the touch
- Extension boards are plugged into other extension boards near the docks
- New sockets have been added in the last few years with no load check
- Your SLD does not show the switchboards that exist today
- Nobody can say how many sockets each DB feeds
- The same breaker has been replaced more than once in a year
- No thermography has been done on panels in the last 12 months
- Battery charging, wrapping machines and fans all share one board
If you tick three or more, schedule an electrical safety audit before the next peak season. Our free warehouse safety audit checklist covers the rest of the site.
What does a proper fix look like?
- 1. MeasureSurvey every connected load and record it in a load register.
- 2. ScanInfrared thermography of panels and DBs at normal operating load to find hot spots.
- 3. MapRevise the SLD to show the installation as it really is today.
- 4. RedesignSplit the load into new DBs and circuits, each with the right cable, MCB and 30 mA RCCB.
- 5. TestEarth continuity, earth resistance, insulation resistance and RCD trip tests, recorded.
- 6. Control changeNo new socket or machine without a load check and an SLD update, plus thermography every year.
For annual inspection, NFPA 70B (2023) requires electrical equipment to be inspected at least every 12 months, with infrared thermography carried out at normal circuit loading, and more often for equipment in poor condition. Indian sites commonly adopt the same yearly cycle as good practice. For electricians who work on these panels, safe isolation matters as much as good design: see our lockout/tagout (LOTO) training.
Electrical Safety Services from Himaya Prevention
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Related guides
- IS 14489 third-party safety audit
- Fire extinguisher calculator (IS 2190:2024 and NFPA 10)
- Visitor and contractor induction system
- HSE and fire training programmes
- Contact our offices
Frequently asked questions
Why does my ELCB keep tripping frequently?
An ELCB or RCCB trips when current leaks to earth above its trip level. Frequent tripping usually means too many loads share one RCCB, so their small normal leakages add up, or there is a damp, damaged or faulty cable, plug or appliance. Find the cause by splitting circuits and testing; never bypass the device.
What is the reason for an MCB burning?
An MCB burns because of long-term heat at its terminals, caused by overload, loose connections, undersized cables or poor-quality breakers. Replacing the MCB alone does not remove the heat source. The circuit load and connections must be checked, ideally with thermography.
Can I replace a 30 mA RCCB with a 100 mA one to stop tripping?
No. A 30 mA RCCB is used for protection against electric shock. Raising the sensitivity to 100 mA or 300 mA removes that protection and hides the real fault. Reduce the number of loads per RCCB and fix leaking equipment instead.
What is a single line diagram, and when should it be updated?
A single line diagram (SLD) is a simplified drawing showing how power flows from the supply through panels, breakers and cables to each load. It should be updated after every addition or change, and reviewed during every electrical safety audit.
How often should thermography of electrical panels be done?
At least once every 12 months, at normal operating load, and more often for equipment in poor condition. This follows NFPA 70B (2023), which many Indian sites use as good practice.
What temperature difference in thermography needs immediate repair?
Under the ANSI/NETA MTS guide, a hot spot more than 15 °C hotter than a similar component under similar load, or more than 40 °C above ambient air, is a major discrepancy that should be repaired immediately.
Who is responsible for electrical safety in a leased warehouse, the landlord or the tenant?
It depends on the lease, but the occupier who adds loads and uses the installation is responsible for using it safely. Agree in writing who owns the SLD, testing and changes, and keep the records on site.
Why is an electrical safety audit quote higher than a repair quote?
A repair quote replaces failed parts. An audit-based quote includes load calculation, thermography, SLD revision, new circuits and testing, which remove the cause. Ask every bidder for line items with quantities so you compare the same scope.
Disclaimer: This case study is anonymised. Audit percentages are from our own field experience, not a published survey. Leakage values are illustrative. This page summarises general good practice as of November 2026 and is not legal advice; electrical work must be carried out by a licensed electrical contractor in line with the CEA regulations, applicable Indian Standards and your state's electrical inspectorate requirements.
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