MEP Retrofit of an Old Factory: Survey, Priorities and Doing It Without Stopping Production

Retrofit an old factory in this order: survey the live installation, rank the findings by risk to people first and production second, then phase the work so each line is cut over and tested before its old supply is removed. Plan for the approvals the work reopens: electrical inspection, Fire NOC, DISCOM load and pollution consent. The survey, not the shutdown, decides the cost.

What does the condition survey need to find?

An old factory's drawings usually describe what someone intended in a past decade. Start by drawing what is actually there, and test it while it is live where it is safe to do so.

• Single-line diagram as found. Trace incomers, transformers, DG, panels and every sub-main. Mark spare ways, undocumented tappings and loads added informally over the years.
• Load record. A year of bills with maximum demand, plus a week of logged current on the main incomer and the larger feeders, so you design to measured load rather than nameplate sums.
• Protection and fault level. Compare the breaking capacity of existing switchgear with the fault level the transformer can now deliver, and check relay settings and discrimination between stages.
• Earthing and lightning protection. Earth pit records, resistance readings, bonding of structures and continuity of protective conductors.
• Cables and terminations. Insulation condition, overheated lugs and loose connections. A thermal scan of live panels shows these without a shutdown.
• Fire system as installed against the Fire NOC drawing. Pump flow, hydrant pressure, detector coverage, extinguisher stock, and storage or partitions added after the NOC was issued.
• HVAC, compressed air and water. Capacity against today's process, leaks, corroded pipework, pump duty points.
• Roof and structure. Whether sheets, purlins and slabs can take new cable trays, ducts or equipment.

Our checklist for a brownfield MEP site survey expands each item, and the article on the old-factory expansion compliance trap covers what an expansion exposes.

How do you rank what to fix first?

Rank by consequence, not by cost. A panel that can start a fire outranks a chiller that is merely inefficient. The ranking below is a working method for the survey report; the order within a band depends on your plant.

Which approvals does a retrofit reopen?

Check each against your state's rules, because thresholds differ by state.

• Electrical inspection. Under the CEA Safety Regulations, 2023, additions and alterations to an installation must be done by a contractor licensed by the State Government under a supervisor holding a certificate of competency (regulation 31), and work done in breach cannot be energised. Regulation 33 requires testing before a new or additional supply starts. Regulation 34 sends generating units above a state-notified capacity, including solar, to the Electrical Inspector before commissioning. Our page on CEIG approval for factories explains the route.
• Fire NOC. A change of layout, storage, occupancy or the fire system itself can need a revised scheme or renewal. Compare the system with the approved drawing before you design, and read Fire NOC for factories in Punjab, Haryana and UP.
• DISCOM. Added load needs a load enhancement and sometimes a new transformer or line. Check headroom with the sanctioned load calculator first.
• Pollution consent. A change to process or capacity may need a fresh consent; read the conditions on your existing one and see CTE and CTO.
• Factory approval. The PIB explainer on the OSH Code, in force since 21 November 2025, says permission for construction or expansion of a factory has a 30-day limit with deemed permission. Whether your retrofit counts as expansion depends on whether it adds building area or capacity; ask your state's department.

How do you phase the work without stopping production?

1. Build new beside old. Install new panels, trays and risers in parallel with the live system wherever floor space allows.
2. Isolate by line, not by building. Group loads so that one production line moves at a time, ideally in its planned maintenance window.
3. Write a cut-over procedure for each tie-in. Isolation points, lock-out, temporary supply, test steps and a rollback to the old feeder if tests fail. For installations above 650 V, regulation 47 requires supplies not meant to run in parallel to be interlocked against inadvertent paralleling or backfeed, so a temporary DG tie-in needs that interlock proved first.
4. Test before energising. Insulation, continuity, earth resistance and protection trip tests on the new circuit, with results signed by the licensed contractor.
5. Run both until proven, then remove the old. Keep the old feeder available through the first full production cycle.
6. Update the drawings and approvals file before closing, so the next retrofit starts from truth.

The planning detail, including temporary utilities and shutdown windows, is in our guide to MEP retrofit in a running plant.

What surprises should the contingency cover?

Opening up an old plant finds things the survey could not: cables run through trenches that are now under machines, abandoned services still live, sheeting that may contain asbestos and needs a specialist before it is cut, and loads that were never on any drawing. Keep a contingency line in the budget, price survey-dependent items as provisional, and agree a rate for variations before work starts. A fixed lump sum on an unsurveyed old plant moves the risk to whoever guessed lowest.

How Secured Engineers helps

We survey and design in-house, then execute electrical, fire fighting, HVAC and plumbing under one MEPF contract, which keeps cut-over sequencing in one hand. Fire NOC, CEIG and DISCOM filings, including net-metering where solar is added, are prepared by our own team. We work from offices in Noida (Delhi NCR) and Ludhiana, on 535+ projects across 18+ states, with 89.77% repeat clients.

If you already hold a retrofit BOQ or drawings, send them and we will review the scope against the survey findings above and flag gaps in sequencing and approvals. See turnkey MEPF contracting, try the MEPF cost calculator for a first budget, then message us on WhatsApp, call +91 70099 85817 or ask for a free proposal.